Methods of Analysis by the U.S. Geological Survey

National Water Quality Laboratory—Determination 

of Elements in Whole-Water Digests Using Inductively

Coupled Plasma–Optical Emission Spectrometry and 

Inductively Coupled Plasma–Mass Spectrometry

Open-File Report 98–165 

 

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 
ERRATA FOR OFR 98-165 

Methods of Analysis by the U.S. Geological Survey National Water Quality

Laboratory—Determination of Elements in Whole-Water Digests Using Inductively

Coupled Plasma–Optical Emission Spectrometry and Inductively Coupled Plasma–

Mass Spectrometry

The following method number was added on July 17, 2003, to page 3 of the Analytical Methods 

section of the report: 

Inorganic Constituents and Parameter Code:

Metals, Acid Digestion, Whole-Water Recoverable, I-4472-97 

Inductively coupled plasma–mass spectrometry
Methods of Analysis by the U.S. Geological Survey National 

Water Quality Laboratory—Determination 

of Elements in Whole-Water Digests Using Inductively

Coupled Plasma–Optical Emission Spectrometry and 

Inductively Coupled Plasma–Mass Spectrometry

By John R. Garbarino and Tedmund M. Struzeski 

_______________________________________________________

U.S. GEOLOGICAL SURVEY

Open-File Report 98–165 

Denver, Colorado 

1998 
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

The use of trade, product, or firm names in this report is for descriptive 

purposes only and does not imply endorsement by the U.S. Government. 

For additional information write to: Copies of this report can be purchased from: 

Chief, National Water Quality Laboratory U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

Box 25046, Mail Stop 407 Box 25286 

Federal Center Federal Center

Denver, CO 80225-0046 Denver, CO 80225-0286 
CONTENTS 

Abstract ............................................................................................................................ 1 

Introduction ............................................................................................................................ 1 

Analytical methods ................................................................................................................. 3 

Inductively coupled plasma–optical emission spectrometry............................................. 3 

 1A. Application......................................................................................................... 3 

2A. Summary of method........................................................................................... 3 

 3A. Interferences....................................................................................................... 4 

 4A. Apparatus, instrumentation, and operating conditions....................................... 6 

 5A. Reagents and calibration standards.................................................................... 9 

 6A. Analytical procedure .......................................................................................... 10 

 7A. Calculations........................................................................................................ 12 

8A. Reporting of results............................................................................................ 12 

Inductively coupled plasma–mass spectrometry............................................................... 13 

 1B. Application......................................................................................................... 13 

 2B. Summary of method........................................................................................... 13 

 3B. Interferences....................................................................................................... 13 

 4B. Apparatus, instrumentation, and operating conditions....................................... 17 

5B. Reagents and calibration standards.................................................................... 19 

 6B. Analytical procedure .......................................................................................... 21 

 7B. Calculations........................................................................................................ 22 

 8B. Reporting of results............................................................................................ 22 

Discussion of results............................................................................................................... 23 

Accuracy and variability ................................................................................................... 23

Results for digested standard reference water samples............................................... 23 

Spike recoveries in natural whole-water digests......................................................... 25 

Comparison of inductively coupled plasma–optical emission 

spectrometry and inductively coupled plasma–mass spectrometry 

to former methods in the analysis of natural whole-water digests..................... 26 

Aluminum ................................................................................................................... 28 

Antimony .................................................................................................................... 28

Barium......................................................................................................................... 28 

Beryllium .................................................................................................................... 29 

Boron........................................................................................................................... 29 

Cadmium..................................................................................................................... 29

Calcium....................................................................................................................... 29 

Chromium ................................................................................................................... 30 

Cobalt.......................................................................................................................... 30 

Copper......................................................................................................................... 30 

Iron ............................................................................................................................ 30 

Lead ............................................................................................................................ 31 

Lithium........................................................................................................................ 31 

Magnesium.................................................................................................................. 31 

Manganese .................................................................................................................. 31 

CONTENTS III 
CONTENTS—Continued 

Molybdenum............................................................................................................... 32 

Nickel.......................................................................................................................... 32 

Selenium ..................................................................................................................... 32 

Silver........................................................................................................................... 32 

Sodium........................................................................................................................ 32 

Strontium .................................................................................................................... 33 

Zinc ............................................................................................................................ 33 

Conclusions ............................................................................................................................ 33 

Summary of test results for inductively coupled plasma–optical emission 

spectrometry (ICP–OES) ............................................................................................... 33 

Summary of test results for inductively coupled plasma–mass spectrometry (ICP–MS).... 34 

References cited ...................................................................................................................... 36 

Appendix—Illustrations and tables......................................................................................... 37 

FIGURES 

1. Schematics showing:

1a. Sample introduction manifold for inductively coupled plasma–optical 

emission spectrometric method............................................................................. 39 

1b. Sample introduction manifold for inductively coupled plasma–mass 

spectrometric method............................................................................................ 39 

2–30. Graphs showing:

2a. Sulfate interference on copper determinations by inductively coupled 

plasma–mass spectrometry ................................................................................... 40 

2b. Sulfate interference on zinc determinations by inductively 

coupled plasma–mass spectrometry...................................................................... 40 

3. Accuracy of inductively coupled plasma–mass spectrometric 

sulfate determinations using 32S16O+

 response ..................................................... 41 

4a. Accuracy of sulfate interference corrections on copper determinations by

inductively coupled plasma–mass spectrometry................................................... 41 

4b. Accuracy of sulfate interference corrections on zinc determinations by

inductively coupled plasma–mass spectrometry................................................... 42 

5a. Short-term inductively coupled plasma–optical emission spectrometric 

(ICP–OES) results in relation to the most probable value (MPV) 

for Standard Reference Water Sample T107 ........................................................ 43 

5b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) 

results in relation to the most probable value (MPV) for Standard 

Reference Water Sample T107 ............................................................................. 46 

CONTENTS IV 
FIGURES—Continued 

6a. Short-term inductively coupled plasma–optical emission spectrometric 

(ICP–OES) results in relation to the most probable value (MPV) for 

Standard Reference Water Sample T119.............................................................. 48 

6b. Long-term inductively coupled plasma–mass spectrometric 

(ICP–MS) results in relation to the most probable value (MPV) 

for Standard Reference Water Sample T119 ........................................................ 51 

7a. Short-term inductively coupled plasma–optical emission spectrometric 

(ICP–OES) results in relation to the most probable value (MPV) 

for Standard Reference Water Sample T133 ........................................................ 53 

7b. Long-term inductively coupled plasma–mass spectrometric 

(ICP–MS) results in relation to the most probable value 

(MPV) for Standard Reference Water Sample T133 ............................................ 56 

8. Short-term inductively coupled plasma–optical emission spectrometric 

(ICP–OES) results in relation to the most probable value (MPV) 

for Standard Reference Water Sample T135 ........................................................ 58 

9. Long-term inductively coupled plasma–optical emission spectrometric 

(ICP–OES) and inductively coupled plasma–mass spectrometric 

(ICP–MS) results in relation to the most probable value (MPV) for 

Standard Reference Water Sample WW-1............................................................ 61 

10a. Scattergrams and regression analyses showing aluminum whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former direct current plasma– 

atomic emission spectrometric (DCP–AES) method............................................ 65 

10b. Box plots and Kruskal-Wallis Test results showing aluminum 

data from the former direct current plasma–atomic emission 

spectrometric (DCP–AES) method (group 3), inductively coupled 

plasma–optical emission spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry (ICP–MS, group 2) 

for whole-water digests......................................................................................... 65 

11. Scattergram, box plots, Paired t-Test results, and regression coefficients 

showing antimony data from the former graphite furnace–atomic 

absorption spectrophotometric (GF–AAS) method and inductively 

coupled plasma–mass spectrometry (ICP–MS) for whole-water digests.............. 66 

12a. Scattergrams and regression analyses showing barium whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method................................................. 66 

12b. Box plots and Kruskal-Wallis Test results showing barium data from 

the former flame–atomic absorption spectrophotometric (F–AAS) 

method (group 3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and inductively coupled plasma– 

mass spectrometry (ICP–MS, group 2) for whole-water digests.......................... 67 

CONTENTS V 
FIGURES—Continued 

12c. Scattergram, box plots, One-sample Sign Test, and regression 

coefficients showing barium data from inductively coupled plasma– 

optical emission spectrometry (ICP–OES) and inductively coupled 

plasma–mass spectrometry (ICP–MS) for whole-water digests........................... 67 

13. Scattergram, box plots, Paired t-Test results, and regression coefficients 

showing beryllium data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and inductively coupled plasma– 

mass spectrometry (ICP–MS) for whole-water digests......................................... 68 

14a. Scattergrams and regression analyses showing boron whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former direct current plasma– 

atomic emission spectrometric (DCP–AES) method............................................ 68 

14b. Box plots and Kruskal-Wallis Test results showing boron data from 

the former direct current plasma–atomic emission spectrometric 

(DCP–AES) method (group 3), inductively coupled plasma–optical 

emission spectrometry (ICP–OES, group 1), and inductively coupled 

plasma–mass spectrometry (ICP–MS, group 2) for whole-water digests............. 69 

14c. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing boron data from the former direct current plasma– 

atomic emission spectrometric (DCP–AES) method and inductively 

coupled plasma–optical emission spectrometry (ICP–OES) for wholewater digests.......................................................................................................... 69 

14d. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing boron data from the former direct current plasma– 

atomic emission spectrometric (DCP–AES) method and inductively 

coupled plasma–mass spectrometry (ICP–MS) for whole-water digests.............. 70 

15. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing cadmium data from the former graphite furnace–

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 70 

16. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing calcium data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method and inductively 

coupled plasma–optical emission spectrometry (ICP–OES) for wholewater digests.......................................................................................................... 71 

17a. Scattergrams and regression analyses showing chromium whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former graphite furnace– 

atomic absorption spectrophotometric (GF–AAS) method .................................. 71 

CONTENTS VI 
FIGURES—Continued 

17b. Box plots and Kruskal-Wallis Test results showing chromium data 

from the former graphite furnace–atomic absorption spectrophotometric 

(GF–AAS) method (group 3), inductively coupled plasma–optical 

emission spectrometry (ICP–OES, group 1), and inductively coupled 

plasma–mass spectrometry (ICP–MS, group 2) for whole-water 

digests ................................................................................................................... 72 

17c. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing chromium data from the former graphite furnace–

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–optical emission spectrometry (ICP–OES) 

for whole-water digests......................................................................................... 72 

17d. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing chromium data from the former graphite furnace–

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 73 

18a. Scattergrams and regression analyses showing cobalt whole-water digest 

data from inductively coupled plasma–optical emission spectrometry 

(ICP–OES) and inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former graphite furnace–atomic 

absorption spectrophotometric (GF–AAS) method .............................................. 73 

18b. Box plots and Kruskal-Wallis Test results showing cobalt data from 

the former graphite furnace–atomic absorption spectrophotometric 

(GF–AAS) method (group 3), inductively coupled plasma–optical 

emission spectrometry (ICP–OES, group 1), and inductively coupled 

plasma–mass spectrometry (ICP–MS, group 2) for whole-water digests............. 74 

18c. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing cobalt data from the former graphite furnace– 

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 74 

19a. Scattergrams and regression analyses showing copper whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former graphite furnace– 

atomic absorption spectrophotometric (GF–AAS) method .................................. 75 

19b. Box plots and Kruskal-Wallis Test results showing copper data from 

the former graphite furnace–atomic absorption spectrophotometric 

(GF–AAS) method (group 3), inductively coupled plasma–optical 

emission spectrometry (ICP–OES, group 1), and inductively coupled 

plasma–mass spectrometry (ICP–MS, group 2) for whole-water digests............. 75 

CONTENTS VII 
FIGURES—Continued 

19c. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing copper data from the former graphite furnace– 

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 76 

20. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing iron data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method and inductively 

coupled plasma–optical emission spectrometry (ICP–OES) for 

whole-water digests............................................................................................... 76 

21. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing lead data from the former graphite furnace–atomic 

absorption spectrophotometric (GF–AAS) method and inductively 

coupled plasma–mass spectrometry (ICP–MS) for whole-water digests.............. 77 

22a. Scattergrams and regression analyses showing lithium whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method................................................. 77 

22b. Box plots and Kruskal-Wallis Test results showing lithium data from 

the former flame–atomic absorption spectrophotometric (F–AAS) 

method (group 3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and inductively coupled plasma– 

mass spectrometry (ICP–MS, group 2) for whole-water digests.......................... 78 

23. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing magnesium data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method and inductively 

coupled plasma–optical emission spectrometry (ICP–OES) for wholewater digests.......................................................................................................... 78 

24a. Scattergrams and regression analyses showing manganese wholewater digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method................................................. 79 

24b. Box plots and Kruskal-Wallis Test results showing manganese data 

from the former flame–atomic absorption spectrophotometric (F–AAS) 

method (group 3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and inductively coupled plasma– 

mass spectrometry (ICP–MS, group 2) for whole-water digests.......................... 79 

25. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing molybdenum data from the former graphite 

furnace–atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 80 

CONTENTS VIII 
FIGURES—Continued 

26. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing nickel data from the former graphite furnace– 

atomic absorption spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry (ICP–MS) for wholewater digests.......................................................................................................... 80 

27. Scattergram, box plots, Paired t-Test results, and regression coefficients 

showing selenium data from the former graphite furnace–atomic 

absorption spectrophotometric (GF–AAS) method and inductively 

coupled plasma–mass spectrometry (ICP–MS) for whole-water digests.............. 81 

28. Scattergram, box plots, One-sample Sign Test results, and 

regression coefficients showing sodium data from the former flame– 

atomic absorption spectrophotometric (F–AAS) method and 

inductively coupled plasma–optical emission spectrometry (ICP–OES) 

for whole-water digests......................................................................................... 81 

29a. Scattergrams and regression analyses showing strontium whole-water 

digest data from inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method................................................. 82 

29b. Box plots and Kruskal-Wallis Test results showing strontium data from 

the former flame–atomic absorption spectrophotometric (F–AAS) 

method (group 3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and inductively coupled plasma– 

mass spectrometry (ICP–MS, group 2) for whole-water digests.......................... 82 

30a. Scattergrams and regression analyses showing zinc whole-water digest 

data from inductively coupled plasma–optical emission spectrometry 

(ICP–OES) and inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic absorption 

spectrophotometric (F–AAS) method................................................................... 83 

30b. Box plots and Kruskal-Wallis Test results showing zinc data from the 

former flame–atomic absorption spectrophotometric (F–AAS) method 

(group 3), inductively coupled plasma–optical emission spectrometry 

(ICP–OES, group 1), and inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests......................................................... 83 

30c. Scattergram, box plots, One-sample Sign Test results, and regression 

coefficients showing zinc data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method and inductively 

coupled plasma–mass spectrometry (ICP–MS) for whole-water digests.............. 84 

CONTENTS IX 
TABLES 

1. Former methods, ICP–OES, and ICP–MS method detection limits and 

calibration limits for elements determined in whole-water digests ...................... 4 

2. Spectral interferences that affect elements determined by ICP–OES 

in natural whole-water digests .............................................................................. 6 

3. Analytical wavelengths and background correction points used for 

the determination of elements in whole-water digests by ICP–OES .................... 7 

4. Upper and lower concentration limit and concentration overlap region 

for ICP–OES elements having dual emission wavelengths.................................. 8 

5. Molecular ion interferences for elements determined in whole-water 

digests by ICP–MS................................................................................................ 16 

6. Doubly charged ion interferences for elements determined in wholewater digests by ICP–MS...................................................................................... 17 

7. Isotopes used to quantify elements determined in whole-water 

digests by ICP–MS................................................................................................ 18 

8. Statistical analysis of short-term ICP–OES results for U.S. Geological 

Survey’s Standard Reference Water Sample T107............................................... 85 

9. Statistical analysis of short-term ICP–OES results for U.S. Geological 

Survey’s Standard Reference Water Sample T119............................................... 86 

10. Statistical analysis of short-term ICP–OES results for U.S. Geological 

Survey’s Standard Reference Water Sample T133............................................... 87 

11. Statistical analysis of short-term ICP–OES results for U.S. Geological 

Survey’s Standard Reference Water Sample T135............................................... 88 

12. Statistical analysis of long-term ICP–MS results for U.S. Geological 

Survey’s Standard Reference Water Sample T107............................................... 89 

13. Statistical analysis of long-term ICP–MS results for U.S. Geological 

Survey’s Standard Reference Water Sample T119............................................... 90 

14. Statistical analysis of long-term ICP–MS results for U.S. Geological 

Survey’s Standard Reference Water Sample T133............................................... 91 

15. Statistical analysis of long-term ICP–OES and ICP–MS results for 

U.S. Geological Survey’s Standard Reference Water Sample WW-1.................. 92 

16. Analytical variability of ICP–OES and ICP–MS results for Standard 

Reference Water Sample WW-1........................................................................... 94 

17. Analytical variability of ICP–OES and ICP–MS over an extended 

concentration range ............................................................................................... 95 

18. Spike recovery results for whole-water digests........................................................... 97 

19. Chemical characteristics of natural whole-water samples.......................................... 100 

20. Statistical analysis summary of ICP–OES and ICP–MS results for 

natural whole-water digests .................................................................................. 101 

CONTENTS X 
CONVERSION FACTORS, ABBREVIATED WATER-QUALITY UNITS, ADDITIONAL

ABBREVIATIONS, AND DEFINITIONS

Multiply By To obtain

liter (L) 2.64 X 10-1 gallon 

meter (m) 3.94 X 101 inch

microgram (μg) 3.53 X 10-8 ounce, avoirdupois 

millibar 1.93 X 10-2 pounds per square inch 

milligram (mg) 3.53 X 10-5 ounce, avoirdupois 

milliliter (mL) 2.64 X 10-4 gallon

millimeter (mm) 3.94 X 10-2 inch

nanometer (nm) 3.94 X 10-8 inch

Degree Celsius (oC) may be converted to degree Fahrenheit (oF) by using the 

following equation: 

oF = 9/5 (oC) + 32

Abbreviated water-quality units used in this report:

L/min liter per minute

mL/min milliliters per minute

mg/L milligram per liter

mg/mL milligram per milliliter

μg/L microgram per liter

μL microliter

μS/cm microsiemens per centimeter at 25oC 

Other abbreviations used in this report: 

amu atomic mass unit 

ASTM American Society for Testing and Materials 

CAS Chemical Abstract Service 

DCP–AES direct current plasma–atomic emission spectrometry

F–AAS flame–atomic absorption spectrophotometry

FEP fluorinated ethylene propylene (Teflon) 

GF–AAS graphite furnace–atomic absorption spectrophotometry

ICP–MS inductively coupled plasma–mass spectrometry

ICP–OES inductively coupled plasma–optical emission spectrometry, also known as 

inductively coupled plasma–atomic emission spectrometry (ICP–AES) 

kW kilowatt 

lb/in2 pound per square inch 

CONTENTS XI 
MDL(s) method detection limit(s) 

MHz megahertz 

MPV(s) most probable value(s) 

NIST National Institute of Standards and Technology

NWQL National Water Quality Laboratory

QA/QC quality assurance/quality control 

SRWS(s) U.S. Geological Survey Standard Reference Water Sample(s) 

SOP standard operating procedure 

W watt 

~ approximate 

> greater than 

< less than

 plus or minus 

Glossary 

MDL The method detection limit (MDL) is defined as the minimum concentration 

of an element that can be measured and reported with 99-percent confidence 

that the elemental concentration is greater than zero and is determined from

analysis of a sample in a given matrix containing the element of interest 

(U.S. Environmental Protection Agency, 1994). 

MPV The most probable value (MPV) is equal to the mean value for numerous 

interlaboratory analyses using multiple analytical methods. 

Spectrum shifter step One step equals about 0.008 nm. 

CONTENTS XII 
Methods of Analysis by the U.S. Geological Survey 

National Water Quality Laboratory—Determination of 

Elements in Whole-Water Digests Using Inductively 

Coupled Plasma–Optical Emission Spectrometry and 

Inductively Coupled Plasma–Mass Spectrometry 

By John R. Garbarino and Tedmund M. Struzeski

ABSTRACT

Inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry

(ICP–MS) can be used to determine 26 elements 

in whole-water digests. Both methods have distinct advantages and disadvantages—ICP–OES 

is capable of analyzing samples with higher

elemental concentrations without dilution, however, ICP–MS is more sensitive and capable of

determining much lower elemental concentrations. Both techniques gave accurate results for 

spike recoveries, digested standard referencewater samples, and whole-water digests. 

Average spike recoveries in whole-water digests 

were 10010 percent, although recoveries for 

digests with high dissolved-solid concentrations 

were lower for selected elements by ICP–MS. 

Results for standard reference-water samples 

were generally within 1 standard deviation of the 

most probable values. Statistical analysis of the 

results from 43 whole-water digests indicated 

that there was no significant difference among

ICP–OES, ICP–MS, and former official 

methods of analysis for 24 of the 26 elements 

evaluated. 

INTRODUCTION

Elements associated with water-suspended 

particulate material are an important fraction of 

the total elemental composition of natural water. 

Elements adsorbed to the surface of the 

particulate material are solubilized by using a

mineral acid medium at low temperature and 

filtered to produce the whole-water digest 

(Hoffman and others, 1996). The U.S. 

Geological Survey’s National Water Quality

Laboratory (NWQL) offers several methods for 

the determination of elements in whole-water

digests. Former methods use single-element 

quantification that is based on either atomic 

absorption or atomic emission spectrophotometry. Alternative methods by use of 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES) and inductively

coupled plasma–mass spectrometry (ICP–MS) 

technology provide simultaneous multielement 

determinations that reduce analytical costs while

maintaining or exceeding the analytical

performance of earlier methods. The elements 

determined by ICP–OES and ICP–MS methods 

are listed as follows: 

INTRODUCTION 1
Element ICP–OES ICP–MS Element ICP–OES ICP–MS

Aluminum   Magnesium 

Antimony  Manganese  

Barium   Molybdenum  

Beryllium   Nickel  

Boron  Selenium 

Cadmium   Silicon 

Calcium  Silver  

Chromium  Sodium 

Cobalt   Strontium  

Copper   Thallium 

Iron  Uranium 

Lead   Vanadium 

Lithium   Zinc  

The objectives of this report are to: 

 Provide a detailed description of new ICP–

OES and ICP–MS methods for wholewater digest analysis. Detailed 

descriptions of operating conditions and 

procedures are concisely outlined in 

sections 1A-8A and 1B-8B, respectively.

 Compare the accuracy of ICP–OES and 

ICP–MS methods to former methods of 

analysis. Multiple strategies are used in 

the statistical analysis of the 

experimental data to provide a practical 

estimate of the expected accuracy. 

 Compare the variability of ICP–OES and 

ICP–MS methods to former methods of 

analysis. 

 Compare the analytical performance of 

ICP–OES and ICP–MS methods. 

 Estimate potential effects on long-term 

water-quality studies. 

 Provide guidance for selecting the most 

appropriate method of analysis. 

Whole-water recoverable elements at present

determined by flame–atomic absorption 

spectrophotometry and by direct current 

plasma–atomic emission spectrometry will be

determined by ICP–OES effective December 1, 

1998. The ICP–MS method described in this 

report will be implemented at a date to be

announced. The methods were developed by the 

U.S. Geological Survey (USGS) for use at the 

NWQL. These methods supplement other 

methods of the USGS that are described by

Fishman and Friedman (1989) and by Fishman 

(1993).

ANALYTICAL METHODS 2
ANALYTICAL METHODS 3

ANALYTICAL METHODS 

Inorganic Constituents and Parameter Codes: 

Metals, Acid Digestion, Whole-Water Recoverable, I-4471-97

Inductively coupled plasma–optical emission spectrometry 

Paramétrer Lab 

code Parameter Lab code Parameter Lab code 

Aluminum, g/L 2351 Copper, g/L 2358 Nickel, g/L 2365 

Barium, g/L 2352 Iron, g/L 2359 Silica (SiO2), mg/L 2366 

Beryllium, g/L 2353 Lead, g/L 2360 Silver, g/L 2367 

Boron, g/L 2354 Lithium, g/L 2361 Sodium, mg/L 2368 

Cadmium, g/L 2355 Magnesium, mg/L 2362 Strontium, g/L 2369 

Calcium, mg/L 2356 Manganese, g/L 2363 Vanadium, g/L 2370 

Cobalt, g/L 2391* Molybdenum, g/L 2364 Zinc, g/L 2371 

*Changed April 8, 1999.

Metals, Acid Digestion, Whole-Water Recoverable, I-4472-97 (Added July 17, 2003)

Inductively coupled plasma–mass spectrometry 

Parameter Lab 

code Parameter Lab code Parameter Lab code 

Aluminum, g/L 2372 Copper, g/L 2379 Silver, g/L 2386 

Antimony, g/L 2373 Lead, g/L 2380 Strontium, g/L 2387 

Barium, g/L 2374 Lithium, g/L 2381 Thallium, g/L 2388 

Beryllium, g/L 2375 Manganese, g/L 2382 Uranium, g/L 2389 

Cadmium, g/L 2376 Molybdenum, g/L 2383 Zinc, g/L 2390 

Chromium, g/L 2377 Nickel, g/L 2384 

Cobalt, g/L 2378 Selenium, g/L 2385 

Inductively Coupled Plasma–Optical 

Emission Spectrometry 

1A. Application 

This method is used to determine 

aluminum, barium, beryllium, boron, cadmium, 

calcium, cobalt, copper, iron, lead, lithium, 

magnesium, manganese, molybdenum, nickel, 

silicon (reported as silica, SiO2), silver, sodium, 

strontium, vanadium, and zinc in natural wholewater digested by using the in-bottle procedure 

described by Hoffman and others (1996). The 

method detection limits (MDLs) and analytical 

concentration ranges are listed in table 1. 

MDLs were calculated by using U.S. Environmental Protection Agency’s (1994) definition 

and represent pooled averages on the basis of 

four MDLs determined on different days over 

several weeks. 

2A. Summary of Method 

Whole-water recoverable elements are 

determined simultaneously on a single sample 

using inductively coupled plasma–optical 

emission spectrometry. Sample solution is 

pumped into a high dissolved-solids tolerant 

nebulizer to produce an aerosol. The aerosol is 

subsequently transported by argon gas through a 

spray chamber and torch assembly into an 

inductively coupled plasma source where the 
Table 1. Former methods, ICP–OES, and ICP–MS method detection limits and calibration limits for

elements determined in whole-water digests

[All results are in micrograms per liter; MDL, method detection limit; ICP–OES, inductively coupled plasma–optical 

emission spectrometry; ICP–MS, inductively coupled plasma–mass spectrometry; DCP–AES, direct current plasma–

atomic emission spectrometry; GF–AAS, stabilized temperature graphite furnace–atomic absorption

spectrophotometry; F–AAS, flame–atomic absorption spectrophotometry; na, not available; nd, not determined] 

Former methods ICP–OES ICP–MS

Element Technique MDL

Upper limit 

(without 

dilution) 

MDL

Upper limit 

(without 

dilution) 

MDL

Upper limit 

(without 

dilution) 

Aluminum DCP–AES 1 10 10,000 14 500,000 1 1,000 

Antimony GF–AAS 0.8 25 nd nd 0.7 500

Barium F–AAS 1

 100 5,000 0.5 10,000 0.08 1,000

Beryllium F–AAS 1 10 200 2 10,000 0.07 500

Boron DCP–AES 1 10 10,000 13 10,000 nd nd

Cadmium GF–AAS 0.06 5 5 10,000 0.05 500

Calcium F–AAS 1 100 60,000 5 1,000,000 nd nd

Chromium GF–AAS 0.3 20 nd nd 2 500

Cobalt GF–AAS 0.4 25 7 10,000 0.04 500

Copper GF–AAS 0.4 25 5 10,000 0.3 500

Iron F–AAS 8 1,000 6 200,000 nd nd

Lead GF–AAS 0.4 25 60 10,000 0.05 500

Lithium F–AAS 5 1,000 8 10,000 0.04 500 

Magnesium F–AAS 1 100 10,000 3 500,000 nd nd

Manganese F–AAS 4 1,000 2 25,000 0.06 1,000 

Molybdenum GF–AAS 0.9 50 34 10,000 0.4 500

Nickel GF–AAS 0.5 25 35 10,000 0.3 500

Selenium GF–AAS 0.8 50 nd nd 2 500

Silicon (as SiO2) na na na 70 100,000 nd nd

Silver GF–AAS 0.1 10 4 1,000 0.7 25

Sodium F–AAS 1 100 80,000 70 500,000 nd nd

Strontium F–AAS 1 10 5,000 0.5 10,000 0.04 500

Thallium na na na nd nd 0.3 500

Uranium na na na nd nd 0.2 500

Vanadium na na na 5 10,000 nd nd

Zinc F–AAS 6 500 20 25,000 0.5 1,000 1

Method reporting level, no method detection limit has been established.

sample is desolvated, atomized, and the 

resultant atoms or ions excited. The 

intensity of light emission that results when

the excited-state atoms or ions relax to their 

ground state is directly proportional to the 

concentration of the emitting species in 

solution. Mean concentrations of elements 

are reported from three replicate 

determinations. 

3A. Interferences 

Corrective action must be taken to 

minimize interferences that might lead to 

inaccuracies in ICP–OES results, including

physical and spectral interferences. 

3A.1 Physical interferences: Physical

interferences are generally considered to be 

effects associated with sample transport and 

ANALYTICAL METHODS 4
nebulization processes. Sample matrices

that are significantly different than the 

calibration standards, such as those having

high dissolved-solid concentrations (or high

specific conductance), might cause changes 

in the transport and nebulization process 

leading to significant inaccuracy in the final

result. Physical interference effects can be 

overcome by using dilution or internal 

standards, or both. Simple dilution reduces 

the viscosity of the sample solution and the

concentration of matrix salts. Addition of a 

surfactant to the samples and calibration 

standards also tends to stabilize sample

transport. 

The use of an internal standard can 

reduce the effects associated with changing

sample transport properties as well as

instrument drift. Yttrium (371.029 nm) is 

commonly used as an internal standard for 

ICP–OES analyses. The accuracy of internal

standardization relies on the absence of 

yttrium in the sample. If yttrium is present, 

results will be negatively biased. Therefore,

it is important to verify the absence of 

yttrium in the samples being analyzed. 

There are several methods that can be used 

by the analyst to verify its absence. The best 

procedure requires a rapid spectral scan of 

each sample to determine if yttrium is

present. An alternate method would be to 

monitor the yttrium intensity in each sample

during the analyses. Whenever the yttrium

intensity is 10 percent greater than the

yttrium intensity for a preceding yttrium-free 

Standard Reference Water Sample (SRWS), 

an unacceptable level of yttrium is indicated. 

In such cases, a different internal standard 

element must be used. 

3A.2 Spectral interferences: Spectral

interferences occur when constituents in a

sample emit radiation at wavelengths close to 

the analytical wavelength being measured. 

Unresolved spectral emission at the analytical

wavelength can result in significant positive bias

in the results. In some instances, the high

concentration of an interferent can suppress the 

emission from an element and result in a

negative bias. Relating the apparent elemental 

concentration to the concentration of the 

interfering element (see table 2) is used to 

minimize this type of interference. This relation 

is a linear function of concentration that must be

calibrated daily. Other spectral interferences can 

result from stray light, molecular broadband 

emission, and spectral-line broadening that 

contribute to the background or offset in the 

element signal. By measuring the background 

emission at one or two positions adjacent to the 

analytical wavelength, this offset can be 

subtracted from the signal (see table 3 for 

background measurement positions). 

Experiments were conducted to evaluate 

spectral interferences by measuring element

responses from 10- to 100-mg/L concentrations 

of numerous inorganic constituents, including

major cations (calcium, magnesium, potassium, 

silica, and sodium), major anions (carbonate, 

chloride, nitrate, phosphate, and sulfate), and 

other minor elements. Elements that have 

significant spectral interferences are listed in 

table 2 with the interferent and the approximate

degree of the interference. 

Specific conductance is used to identify

filtered, acidified samples that can exhibit 

physical interference effects because of high

dissolved-solid concentrations. Since the 

specific conductance for a whole-water digest 

is inherently high but generally unknown, a 

nebulizer that can tolerate high dissolved solids 

must be used. A Noordemeer V-groove 

maximum dissolved-solids nebulizer was used

to obtain the data presented in this report. Other 

nebulizer designs can be used, but they must be 

resistant to clogging and capable of providing

ANALYTICAL METHODS 5
Table 2. Spectral interferences that affect elements determined by ICP–OES in natural 

whole-water digests

[ICP–OES, inductively coupled plasma–optical emission spectrometry; nm, nanometer; 

μg/L, microgram per liter] 

Affected 

element

Affected 

elements’ 

analytical 

wavelength 1 

(nm) 

Interferent Interferent 

concentration

(μg/L) 

Apparent 

concentration of 

affected element

(μg/L) 

Aluminum 2 167.081 Iron 100,000 250

Boron 2 249.773 Iron 100,000 20

Beryllium 313.042 Vanadium 10,000 70

Cadmium 214.438 Iron 100,000 20

Cadmium 214.438 Aluminum 100,000 15

Cobalt 238.892 Iron 5,000 350

Copper 324.754 Manganese 25,000 -8

Iron 259.940 Manganese 25,000 10

Iron 259.940 Sodium 500,000 35

Lead 220.353 Aluminum 100,000 75

Manganese 257.610 Aluminum 100,000 -30

Manganese 257.610 Iron 100,000 -30

Manganese 257.610 Magnesium 500,000 15

Sodium 330.223 Zinc 25,000 -60

Vanadium 292.402 Iron 100,000 -10

Vanadium 292.402 Molybdenum 500 -8

Zinc 2 206.200 Iron 100,000 20 1

Interferent effects are wavelength specific. 2

Wavelength is second order. 

method detection limits within a factor of two 

of those listed in table 1. 

4A. Apparatus, Instrumentation, and 

Operating Conditions 

4A.1 Labware: Use clean Type A glass 

volumetric flasks to prepare all solutions. Store 

solutions in fluorinated ethylene propylene 

(FEP Teflon) bottles to maintain stable

elemental concentrations. Regularly verify

accuracy of all pipets and volumetric flasks 

used to prepare standard solutions with either 

an analytical balance or an automatic

calibrating spectrophotometer. 

4A.2 Instrumentation: A Thermo 

Jarrell-Ash (TJA) argon or nitrogen purged 

spectrometer with a 0.75-m focal length and 

spectrum shifter background correction was 

used in this method. The argon plasma was 

generated using 27.12 MHz energy. 

Accessories included a TJA Model AS300 

autosampler, Gilson peristaltic pump, TJA 

internal standards kit (Part #13670800), and 

computer data system. A Noordemeer Vgroove nebulizer was used because of its 

ability to resist clogging when analyzing

samples with high dissolved-solid 

concentrations. 

ANALYTICAL METHODS 6
Table 3. Analytical wavelengths and background correction points used for the 

determination of elements in whole-water digests by ICP–OES

[ICP–OES, inductively coupled plasma–optical emission spectrometry; nm, nanometer; one spectrum

shifter step equals about 0.008 nm] 

Element Wavelength 1

(nm) 

Background 

correction point 3

(spectrum shifter steps)

Aluminum (1) 2 167.081 12

Aluminum (2) 308.215 12 

Barium 455.403 -11

Beryllium 313.042 -11

Boron 2 249.773 12

Cadmium 214.438 -11

Calcium (1) 396.847 -11 

Calcium (2) 315.887 12 

Chromium 267.716 -11

Cobalt 238.892 12

Copper 324.754 12

Iron 259.940 12

Lead 220.353 -11

Lithium 670.784 none

Magnesium (1) 279.553 12 

Magnesium (2) 383.231 -11 

Manganese 257.610 -11

Molybdenum 203.844 12

Nickel 2 231.604 -11

Silicon, as SiO2 288.158 12

Silver 328.068 -11

Sodium (1) 588.995 none

Sodium (2) 330.223 -11 

Strontium 421.552 -11

Vanadium 292.402 -11

Yttrium 371.029 -11

Zinc 2 206.200 12 1

Wavelengths are instrument and method specific. 2

Wavelength is second order. 3

Shift relative to indicated wavelength; a shift to a lower wavelength is identified by the minus sign.

The wavelengths used to measure 

elemental concentrations are listed in table 3. 

Two analytical wavelengths are listed for 

aluminum, calcium, magnesium, and sodium. 

These wavelengths are listed in order of the 

emission intensity; therefore, the first wavelength is the more sensitive. There is some

overlap in the calibration curves for the two 

wavelengths; hence a range of concentrations 

can be quantified with either wavelength. 

Upper and lower concentration limits for both 

wavelengths are determined by the linearity of

their response. These concentration limits and 

overlap regions are listed in table 4. The analyst 

or data system determines which emission line

results should be reported on the basis of 

elemental concentration, quality-control results, 

and the presence of interferences.

ANALYTICAL METHODS 7
Table 4. Upper and lower concentration limit and concentration overlap region for 

ICP–OES elements having dual emission wavelengths

[ICP–OES, inductively coupled plasma–optical emission spectrometry; all concentrations are in

milligrams per liter, except for aluminum, which is in micrograms per liter; the overlap region is the 

concentration range where results from either emission wavelength can be reported; MDL, method 

detection limit (see table 1)] 

Concentration limits 

Element 1 Lower Upper Overlap region (use

wavelength 1 or 2)

Aluminum (1)

Aluminum (2)

MDL

300 

75,000 

500,000 300 to 75,000 

Calcium (1) 

Calcium (2) 

MDL

 6 

25 

1,000 6 to 25 

Magnesium (1)

Magnesium (2)

MDL

 6 

100 

500 6 to 100 

Sodium (1) 

Sodium (2) 

MDL

 50 

125 

500 50 to 125 

1

Corresponding wavelengths are listed in table 3.

4A.3 Operating conditions:

 Inductively coupled plasma operating 

conditions— 

Optimized operating conditions are 

listed as follows. These settings are based 

on experiments that maximize the signal to 

noise ratio for several atomic emission and 

ionic emission wavelengths that have different 

ionization potentials as a function of incident 

power, horizontal observation position, and 

sample delivery rate. 

Incident radio frequency power ~ 0.95 kW

Reflected radio frequency power ~ 0 W

Torch gas flow rate ~ 14 L/min (high)

Auxiliary flow rate ~ 1.0 L/min

Nebulizer pressure ~ 45 lb/in2 (~3.2 

 kilograms/square

 centimeter) 

Sample flow rate (to nebulizer) ~ 2.9 mL/min

Horizontal observation position ~ 15 mm above 

 load coil 

Vertical observation position Center 

 Internal standard manifold—

Yttrium is used as the internal standard. 

Other elements may be substituted if needed; 

however, the choices are limited to the

elemental wavelengths present on the

instrument. The internal standard introduction 

system is based on a modified TJA internal 

standard kit (TJA item # 13670800). The 

peristaltic pump tubing provided in the kit was 

modified to achieve the overall lowest possible 

MDLs using the Noordemeer V-groove 

nebulizer. The manifold system is shown in 

figure 1a (see Appendix). 

 Data acquisition—

Two measurements are made for every

element, one at the analytical wavelength

maximum and one adjacent to the analytical

wavelength (background correction). Both

measurements consist of three 5-second 

integrations. 

ANALYTICAL METHODS 8
 Interelement correction factors— 

Interelement correction factors are used 

to adjust for apparent increases or decreases in

a signal because of unresolved spectral interferences (see section 3A.2 and table 2).

 Background correction protocol—

The background adjacent to the 

analytical wavelengths is measured to 

minimize spectral background interferences. 

Background correction points are listed in 

table 3. 

 Optimization of primary refractor plate 

position (profile)— 

Instrument profile is adjusted to within 

0.1 spectrum shifter steps of the maximum peak

intensity for mercury at 435.835 nm. 

 Autosampler cycles—

Specified cycle times have been shown 

to minimize memory effects from samples 

containing all elements up to the upper 

calibration standard (see table 1) and boron up 

to 5,000 g/L. The length of the cycle times is 

dependent on the sample introduction system 

being used. If the sample introduction system 

described in this method is modified, these 

times likely will require adjustment. 

Rinse cycle ~ 25 seconds 

Flush cycle ~ 90 seconds 

5A. Reagents and Calibration Standards 

ASTM Type I reagent water (American 

Society for Testing and Materials, 1995, p. 

122–124), spectroscopic grade commercial 

standards, and ultrapure acids must be used to 

prepare all solutions. All percentages represent

volume-to-volume ratios. All concentrated 

acids and commercial standards must be verified 

to contain concentrations of concomitant 

elements that are less than the MDLs after the 

prescribed dilution. Every solution must be 

stored in a designated clean FEP Teflon bottle; 

solutions that contain silver must be stored in a 

designated clean opaque FEP Teflon bottle. 

5A.1 Nitric acid (HNO3): Concentrated, 

specific gravity 1.41. 

5A.2 Hydrochloric acid (HCl): Concentrated, specific gravity 1.196. 

5A.3 Calibration blank and rinse 

solution, ASTM Type I reagent water acidified 

to 0.4 percent nitric acid and 2 percent 

hydrochloric acid. 

5A.4 Commercial single-element

standard solutions, 1.00 mL = 10 mg preserved 

in nitric acid for each of the following: Al, Ag, 

Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Na, 

Ni, Pb, Sr, and Zn. 

5A.5 Commercial single-element

standard solution, 1.00 mL = 5 mg vanadium 

preserved in nitric acid. 

5A.6 Commercial single-element

standard solution, 1.00 mL = 10 mg

molybdenum preserved in hydrochloric acid. 

5A.7 Commercial single-element

standard solution, 1.00 mL = 5 mg boron in 

water. 

5A.8 Commercial single-element

standard solution, 1.00 mL = 10 mg silicon in 

water. 

5A.9 Commercial single-element

standard solution, 1.00 mL = 10 mg yttrium 

preserved in nitric acid. 

5A.10 Brij-35 (CAS 9002-92-0), 30 

percent solution of polyoxyethylene lauryl ether. 

ANALYTICAL METHODS 9
5A.11 Multielement calibration standard 

I, 1.00 mL = 5.0 g of Cd, Cr, Pb, and Zn; 1.00 

mL = 50.0 g Fe. Dilute 0.5 mL (except for Fe, 

use 5.0 mL) of each commercial single-element 

standard to 1,000 mL in a volumetric flask with 

calibration blank. 

5A.12 Multielement calibration standard 

II, 1.00 mL = 5.0 g of Ba, Be, Co, Cu, Ni, Sr, 

and V. Dilute 0.5 mL of each commercial 

single-element standard to 1,000 mL in a 

volumetric flask with calibration blank. 

5A.13 Multielement calibration standard 

III, 1.00 mL = 4.0 g of Ag; 1.00 mL = 5.0 g 

of Li and Mo; 1.00 mL = 10.0 g of Ca. Dilute 

0.4 mL of the commercial Ag standard, 0.5 mL

of the commercial Li and Mo standard, and 1.0 

mL of the commercial Ca standard to 1,000 mL

in a volumetric flask with calibration blank. 

5A.14 Multielement calibration standard 

IV, 1.00 mL = 5.0 g of Mn; 1.00 mL = 50 g 

of Ca and Na. Dilute 5.0 mL (except for Mn, 

use 0.5 mL) of each commercial single-element 

standard to 1,000 mL in a volumetric flask with 

calibration blank. 

5A.15 Multielement calibration standard 

V, 1.00 mL = 10.0 g of Mg and Na; 1.00 mL = 

50.0 g of Al. Dilute 1.0 mL of the 

commercial single-element standard (except for

Al, use 5.0 mL) to 1,000 mL in a volumetric 

flask with calibration blank. 

5A.16 Multielement calibration standard 

VI, 1.00 mL = 5.0 g of B and Si. Dilute 0.5 

mL of each commercial single-element

standard to 1,000 mL in a volumetric flask with 

calibration blank. 

5A.17 Performance check solution, 1.00 

mL = 5.0 g of Ag, Al, B, Ba, Be, Ca, Cd, Co, 

Cu, Fe, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sr, V, 

and Zn. Dilute 0.5 mL of each commercial 

single-element standard, except dilute B and V 

using 1.0 mL, to 1,000 mL in a volumetric flask 

with calibration blank. 

5A.18 Spectral interference check 

solution I, 1.00 mL = 100 g of Fe. Dilute 10.0 

mL of the commercial single-element standard

to 1,000 mL in a volumetric flask with 

calibration blank. 

5A.19 Spectral interference check 

solution II, 1.00 mL = 5.0 g of Fe and V; 1.00 

mL = 500 g of Mg. Dilute 0.5 mL of the 

commercial Fe standard, 50 mL of the 

commercial Mg standard, and 1.0 mL of the 

commercial V standard to 1,000 mL in a 

volumetric flask with calibration blank. 

5A.20 Spectral interference check 

solution III, 1.00 mL = 500 g of Al and Na; 

1.00 mL = 5.0 g of Mo. Dilute 50 mL of each 

commercial single-element standard (except for

Mo, use 0.5 mL) to 1,000 mL in a volumetric 

flask with calibration blank. 

5A.21 Spectral interference check 

solution IV, 1.00 mL = 25 g of Mn; 1.00 mL = 

5.0 g of Zn. Dilute 2.5 mL of the commercial 

Mn standard and 0.5 mL of the commercial Zn

standard to 1,000 mL in a volumetric flask with 

calibration blank. 

5A.22 Internal standard working 

solution, 1 mL = 5 g Y. Dilute 0.5 mL of 

commercial single-element standard for Y and 

200 L Brij-35 solution to 1,000 mL in a 

volumetric flask with calibration blank. 

6A. Analytical Procedure 

Refer to Thermo Jarrell-Ash (1991) for 

details of procedures outlined in the following

paragraphs. 

6A.1 Set up the instrument using the 

operating conditions described in section 4A.3 

ANALYTICAL METHODS 10
and ignite the plasma. Allow the instrument to 

warm up for at least 30 minutes prior to 

optimization. 

6A.2 Start the ThermoSPEC software. 

6A.3 Edit an autosampler table with the

unknown sample identifiers. Load the 

autosampler with calibration blank, 

multielement calibration standards, quality

assurance/quality control (QA/QC) samples, 

and unknown samples. 

6A.4 Turn on the instrument-mounted 

mercury pen lamp, move it in front of the 

entrance slit, and execute the profile option in 

the ThermoSPEC software. Adjust the mercury

profile until the peak position is within ± 0.1 

spectrum shifter steps. Start calibrating the

instrument. 

6A.5 Verify the accuracy of the 

calibration by using the results from the

instrument performance check solution (see 

section 5A.17) and calibration blank. 

Instrument performance check solution 

concentrations must not deviate from the 

theoretical concentrations by more than ±5 

percent, and the relative standard deviation of 

the replicate integrations must be less than 4 

percent. If the error exceeds ±5 percent,

reanalyze the instrument performance check 

solution. If error still exceeds the criterion, the 

instrument must be recalibrated. Relative

standard deviations greater than 4 percent for 

the instrument performance check solution 

most likely indicate problems with sample

introduction. Whenever the variability is poor, 

the nebulizer, peristaltic pump, and 

transmission tubing must be checked and the 

instrument re-calibrated. 

Calibration blank concentrations must be 

within ±12 percent of the current MDLs. If any

result is outside this limit, reanalyze the

calibration blank. If a result is still outside the 

limit, use another calibration blank solution and 

recalibrate the instrument. 

6A.6 Verify that interelement correction 

factors are accurate by using results from the 

spectral interference check solutions (see 

sections 5A.18–21). If the concentration for any

element that is affected by spectral interference 

deviates by more than ±12 percent from the 

current MDLs, a new interelement correction 

factor for that element must be established 

before continuing sample analyses. A “UDELETE” (unable to analyze) code will be 

reported instead of cobalt concentrations for

samples that have iron concentration greater 

than or equal to 2,000 g/L because of the large 

spectral interference from iron emission on the

cobalt analytical wavelength. Whenever iron 

concentrations exceed 2,000 g/L, the accuracy

of the interelement correction becomes 

unacceptable. 

6A.7 The QA/QC plan requires analysis of 

at least one of the following solutions at a 

frequency of at least 1 in every 10 unknown 

samples: SRWS, calibration blank, duplicate 

sample, diluted sample, or matrix spike. If

SRWSs are used, the analyst must ensure that

results fall within the established quality-control 

limits. Selection of a suitable SRWS should be 

based on the expected sample concentration range. 

6A.8 If all data-acceptance criteria are 

satisfied, then the analytical results are

acceptable. If any one criterion is not satisfied, 

then the analyst must reanalyze the sample in 

question. If the results remain outside the 

criteria, the instrument must be recalibrated and 

all samples following the last acceptable

QA/QC check reanalyzed. For selected 

elements, the upper calibration limit does not 

represent the endpoint of the linear range but 

rather a concentration limit more appropriate for

the majority of samples analyzed. Nevertheless, 

if an elemental result is greater than the upper 

calibration limit, the sample must be diluted 

ANALYTICAL METHODS 11
(with the calibration blank), so that the

elemental result will be less than the upper 

calibration limit, and reanalyzed. 

7A. Calculations

7A.1 Concentrations are automatically

calculated by the instrument’s computer 

software. Headings identify the results. 

7A.2 If samples were diluted, multiply

results by appropriate dilution factor using the

computer software. 

7A.3 Formulas used to calculate percent 

spike recovery for the matrix spike and percent 

difference for duplicates are provided in the 

standard operating procedure (SOP; T.M. 

Struzeski, U.S. Geological Survey, written 

commun., 1998). 

8A. Reporting of Results 

The number of significant figures reported 

in the results varies with element and is a

function of concentration. Whenever the 

elemental concentration is less than the MDL,

the result is reported as less than the MDL (<

MDL). All other elemental results for wholewater digests are reported by use of the criteria 

listed below. These criteria are based on the 

uncertainty indicated in table 17. Alternatively,

the variability associated with the mean

concentration (reported with the mean by each 

instrument) measured in each sample could be 

used to establish the appropriate number of 

significant figures to report. The use of such a 

procedure would provide the most accurate

estimate of the uncertainty associated with each 

unique sample matrix. 

For barium and strontium— 

 If the concentration is greater than or 

equal to the MDL, but less than 100 g/L, then

report result to the nearest 0.1 g/L. 

 If the concentration is greater than 100 

g/L, but less than 1,000 g/L, then report result to 

the nearest 1 g/L.

 If the concentration is greater than 1,000 

g/L, then report result to the nearest 10 g/L.

For aluminum, beryllium, boron, 

cadmium, cobalt, copper, lithium, 

manganese, molybdenum, nickel, 

silver, vanadium, and zinc— 

 If the concentration is greater than or 

equal to the MDL, but less than 100 g/L, then

report result to the nearest 1 g/L.

 If the concentration is greater than 100 

g/L, then report result to the nearest 10 g/L.

NOTE: Whenever the concentration of iron is 

greater than or equal to 2,000 g/L, an “UDELETE” (unable to analyze) code will be 

reported for cobalt (see section 6A.6). 

For lead— 

 If the concentration is greater than or 

equal to the MDL, then report result to the nearest 

10 g/L.

For calcium, iron, magnesium, and 

sodium— 

 If the concentration is greater than or 

equal to the MDL, but less than 1 mg/L, then

report result to the nearest 0.001 mg/L. 

 If the concentration is greater than or 

equal to 1 mg/L, but less than 10 mg/L, then report 

result to the nearest 0.01 mg/L.

 If the concentration is greater than or 

equal to 10 mg/L, but less than 100 mg/L, then 

report result to the nearest 0.1 mg/L. 

ANALYTICAL METHODS 12
 If the concentration is greater than or 

equal to 100 mg/L, then report result to the 

nearest 1 mg/L.

For silicon (reported as SiO2)—

 If the concentration is greater than or 

equal to the MDL, but less than 1 mg/L, then

report result to the nearest 0.01 mg/L.

 If the concentration is greater than or 

equal to 1 mg/L, but less than 10 mg/L, then 

report result to the nearest 0.1 mg/L.

 If the concentration is greater than or 

equal to 10 mg/L, but less than 100 mg/L, then 

report result to the nearest 1 mg/L.

Inductively Coupled Plasma–Mass 

Spectrometry

1B. Application 

This method is used to determine 

recoverable aluminum, antimony, barium, 

beryllium, cadmium, chromium, cobalt, copper, 

lead, lithium, manganese, molybdenum, nickel, 

selenium, silver, strontium, thallium, uranium, 

and zinc in natural whole-water samples 

digested by using the in-bottle procedure that is 

described by Hoffman and others (1996). The 

MDLs and analytical concentration ranges are 

listed in table 1. The method calibration ranges 

were optimized for elemental concentrations 

normally found in natural water, however, the 

dynamic range for ICP-MS is linear to a 

maximum of about 1 mg/L for elements that are 

monoisotopic, and somewhat greater than 1 

mg/L for elements that have multiple isotopes. 

MDLs were calculated by using U.S. 

Environmental Protection Agency’s (1994) 

definition and represent pooled averages on the 

basis of four MDLs that were determined on 

different days over several weeks. 

2B. Summary of Method 

Whole-water recoverable elements are 

determined simultaneously on a single sample

by using inductively coupled plasma–mass 

spectrometry. An aerosol of the sample solution 

is produced by using a high dissolved-solids 

tolerant nebulizer. The aerosol is introduced 

into the argon plasma where it undergoes 

desolvation, atomization, and ionization. Ions 

are sampled through multiple orifices into the

quadrupole mass spectrometer where they are 

separated on the basis of their mass-to-charge

ratios. An electron multiplier detects the ions by

generating an electrical current that is directly

proportional to the concentration of the element 

present in the sample. A more detailed 

description of ICP–MS theory and application is 

described in Montaser and Golightly (1992) and 

Boumans (1987a and 1987b). 

3B. Interferences 

Several types of physical and spectral

interference are recognized and documented for 

ICP–MS techniques. Physical interferences are

associated primarily with sample introduction 

and are minimized by using the internal

standardization technique. Isotopes measured in 

this procedure have been selected specifically to

minimize spectral interferences from isobaric,

doubly charged, and molecular ions. Multiple 

isotopes can be measured for selected elements

that have potential isobaric or molecular ion 

interferences. Data from multiple isotopes can

indicate the presence and magnitude of 

interferences. The analyst must be conscious of 

these interferences because they might occur 

with certain types of sample matrices. 

3B.1 Physical interferences: The effects 

of sample transport, instrumental drift, and 

matrix-induced fluctuations in plasma

characteristics are reduced by using the ratio of 

elemental ion intensity to the internal standard

element ion intensity for calibration. Accurate 

ANALYTICAL METHODS 13
results depend on having a constant internal 

standard ion intensity throughout the analysis of 

all standards and samples. Constant internal

standard ion intensity requires that any

interferences associated with the internal

standard element can be corrected and that the 

internal standard element is not naturally

present in the samples being analyzed. 

Three isotopes that extend the mass range 

from 6 to 240 atomic mass units (amu) are used 

as internal standards—in this method 45Sc+

, 115In+

, and 209Bi+ are routinely used. 

Alternative isotopes may be substituted after

ensuring that there are no spectral interferences 

associated with the new selections. Analytical

isotopes less than 45 amu are normalized to 

45Sc+

, and those greater than 209 amu are 

normalized to 209Bi+

. Analytical isotopes 

between 45 and 115 amu are normalized by

using a response obtained from the linear 

interpolation of the responses for 45Sc+

 and 

115In+

. Similarly, isotopes between 115 and 209 

amu are normalized by using an interpolated 

response based on 115In+

 and 209Bi+. 

Memory effects that are related to sample

transport are negligible for most elements 

normally present in natural whole-water

digests. Carryover from samples that have 

elemental concentrations less than 1,000 g/L

is negligible for all elements except antimony. 

Antimony concentrations greater than 50 g/L

can produce substantial carryover in subsequent 

samples. Analyses following samples that have

elemental concentrations greater than 1,000 

g/L must be reanalyzed to verify that 

carryover was negligible. 

3B.2 Spectral interferences: Whenever 

possible, the isotope used for quantitation has 

no spectral interferences or has a small number 

of potential spectral interferences that is 

unlikely to occur in whole-water digests or can 

easily be corrected. Spectral interferences can 

originate from isobaric ions, molecular ions, or 

doubly charged ions. The analyst must be aware 

of these potential spectral interferences when 

reviewing analytical results. Spectral overlap 

contributions caused by insufficient abundance 

sensitivity are negligible and can be minimized

by measuring each isotope at three points that

transect the peak maximum, which is centered at

the nominal mass. The known interferences for 

the elements that are determined in this method 

are listed below. 

3B.2.1 Isobaric interferences: There are 

only three isobaric interferences for isotopes 

measured in this method—82Kr+

 on 82Se+, 114Sn+

on 114Cd+

, and 115Sn+ on 115In+. Krypton can be 

a minor contaminant found in argon gas used to 

support the plasma, however, its concentration 

will remain constant for both the standards and 

samples, and, therefore, usually does not require 

correction. 

The most abundant cadmium isotope 

114Cd+

 is used as a secondary isotope and is 

subject to isobaric overlap from 114Sn+

. The 

following equation must be used to calculate the 

ion intensity corresponding to only 114Cd+

: 

114Cd+

 = I114 – [I118 X (114Sn/118Sn)] (1) 

or 

114Cd+

 = I114 – (I118 X 0.02707) , (2) 

where I114 and I118 are the ion intensities 

measured at 114 and 118 amu, respectively,

and 114Sn/118Sn is the ratio of the natural 

abundance of the two tin isotopes (this ratio is 

based on the assumption of natural abundance). This isobaric correction is acceptable 

for tin concentrations less than or equal to 2 

mg/L. If tin concentrations exceed 2 mg/L, 

then only 111Cd+

 results can be considered. 

Indium is routinely used as an internal 

standard. Whenever tin is present in a sample, 

its isobaric interference on 115In+

 isotope is 

eliminated by using the following equation: 

ANALYTICAL METHODS 14
115In+

 = I115 – [I118 X (115Sn/118Sn)] (3) 

or 

115In+

 = I115 – (I118 X 0.01416) , (4) 

where I115 and I118 are the ion intensities 

measured at 115 and 118 amu, respectively,

and 115Sn/118Sn is the ratio of the natural 

abundance for the given tin isotopes. This 

isobaric correction is acceptable for tin

concentrations less than or equal to 2 mg/L. 

If tin concentrations exceed 2 mg/L, an 

alternate internal standard element, such as 

rhodium (103Rh+

), can be used. 

3B.2.2 Molecular ion interferences: 

There are several known molecular ion 

interferences associated with elements determined in this method. Molecular ions, for 

example, CeO+

, ClO+, and NaAr+, are produced 

within the expansion zone behind the interface. 

Molecular ion spectral interferences are listed 

in table 5 as apparent elemental concentrations 

corresponding to a given concentration of 

interferent with the ionic species responsible 

for the interference. 

Molecular ion interferences on 52Cr+

 and 

53Cr+

 from 40Ar12C+ and 40Ar13C+, respectively,

have been found to be negligible. The interference on 53Cr+

 from 38Ar15N+ also is 

negligible because of the low natural abundance of the argon and nitrogen isotopes. 

Interferences on chromium that are associated 

with chloro-oxygen species are minimized by

matrix-matching the calibration standards to 

the same percentage of hydrochloric acid as the 

in-bottle digests, however, the matrix matching

must be accurate. 

Sulfur and oxygen isotopes form 

molecular ions of S2

+

, SO+, and SO2

+

 that

interfere with chromium, copper, selenium, and 

zinc determinations. Sulfur molecular ions 

arise from sulfide, sulfite, or sulfate, although in 

whole-water digests, sulfate is the primary form. 

The interference on selenium and chromium is 

negligible for sulfate concentrations less than

1,000 mg/L. However, sulfur molecular ion 

interferences can significantly affect copper and 

zinc results. Errors associated with these 

interferences are corrected by calibrating the 

apparent copper and zinc concentrations to 

sulfate concentration. Apparent 65Cu+

and 66Zn+

concentrations are linear through 1,000 mg/L

sulfate based on the instrument response at 

32S16O+

 (see figs. 2a–b in Appendix). 

Instrument response at 32S16O+

 as a function of 

sulfate concentration is represented best by a 

polynomial equation for concentrations less than

1,000 mg/L (see fig. 3 in Appendix), however, 

the response is linear at less than 600 mg/L. 

Using 32S16O+

 to quantitate sulfate interferences

requires correction for unresolved contributions 

from 48Ca+

 (0.19 percent abundance) and 48Ti+

(73.8 percent abundance). These contributions 

are determined by measuring 43Ca+

 and 47Ti+

and calculating the corresponding effect at 48 

amu using the following equations: 

48Ca+

 = I43 X (

48Ca/43Ca) = I43 X 1.36 (5) 

48Ti+

 = I47 X (

48Ti/47Ti) = I47 X 10.1 (6) 

32S16O+

 = I48 – 48Ca+ – 48Ti+ , (7) 

where I43, I47, and I48 are the ion intensities 

measured at 43, 47, and 48 amu, respectively, and 

48Ca/43Ca and 48Ti/47Ti are the ratios of the natural 

abundance for the given isotopes. This correction 

method is problematic because calcium concentration can be relatively high in whole-water 

digests. In the absence of calcium or titanium, 

subtracting the apparent concentration from the

original concentration (25 g/L copper and zinc) 

gives a corrected concentration of acceptable 

accuracy (see figs. 4a–b in Appendix).

ANALYTICAL METHODS 15
Table 5. Molecular ion interferences for elements determined in whole-water digests by ICP–MS 

[ICP–MS, inductively coupled plasma–mass spectrometry; g/L, microgram per liter; mg/L, milligram per 

liter; ~, approximate; <, less than; MDL, method detection limit; >, greater than] 

Isotope 1 Primary 

interferent

Interferent 

ion or ions

Interferent 

concentration

Approximate

apparent 

element 

concentration

(μg/L) 52Cr Chloride 35Cl16OH+ 100 mg/L Cl ~0.2 52Cr Sulfate 36S16O+ 1,000 mg/L SO4

2 ~2 53Cr Chloride 37Cl16O+, 35Cl18O+ 100 mg/L Cl ~0.2 53Cr Sulfate 36S16O+ 1,000 mg/L SO4

2 ~2 59Co Calcium 43Ca16O+, 42Ca16OH+ 250 mg/L Ca <MDL 60Ni Silicon as SiO2 28Si16O2

+ 40 mg/L SiO2 ~0.2

60Ni Calcium 44Ca16O+ 250 mg/L Ca <MDL 63Cu Sodium 40Ar23Na+ 500 mg/L Na ~10 65Cu Titanium 49Ti16O+ 1 mg/L Ti ~0.5 65Cu Sulfate 33S16O2

+

, 32,33S2

+ 1,000 mg/L SO42 ~20 66Zn Barium 132Ba2+ 100 mg/L Ba ~5 66Zn Chromium 50Cr16O+ 1 mg/L Cr ~0.1 66Zn Sulfate 34S16O2

+

, 32,34S2

+

, 33S2

+ 1,000 mg/L SO42 ~10 66Zn Titanium 50Ti16O+ 1 mg/L Ti ~0.3 66Zn Vanadium 50V16O+ 1 mg/L V ~0.1 67Zn Barium 134Ba2+, 135Ba2+ 100 mg/L Ba >50 82Se Sulfate 34S16O3

+ 1,000 mg/L SO4

2 ~9 107Ag Zirconium 91Zr16O+ 1 mg/L Zr ~1 109Ag Niobium 93Nb16O+ not determined not determined 111Cd Molybdenum 95Mo16O+ 1 mg/L Mo ~0.4 114Cd Molybdenum 98Mo16O+ 1 mg/L Mo ~0.6 

1

Isotopes that are routinely used as secondary isotopes are listed in italic. 

Errors ranged from 0.5 to 1 g/L copper or 

zinc for sulfate concentrations from 0 to 

1,000 mg/L. 

An alternative correction method 

determines the linear regression equations 

for apparent 65Cu+

 and 66Zn+ as a function 

of sulfate concentration by analyzing two 

sulfate standards (see sections 5B.21 and 22) 

with each batch of samples. After the 

analyses have been completed, these 

equations and the sulfate concentrations 

obtained for each sample by using another 

analytical method are used to determine the 

fraction of 65Cu and 66Zn concentrations that 

result from sulfate. The regression 

equations and interference corrections are 

calculated by using a software program that 

is executed following the analyses. The 

accuracy of this method of interference 

correction is equivalent to the method 

described in the preceding paragraph, 

however, it is likely to be more accurate as 

calcium concentrations increase. 

ANALYTICAL METHODS 16
Oxides of chromium, molybdenum, 

niobium, silicon, titanium, vanadium, and 

zirconium generally are negligible because of 

the low ambient concentration levels for these

elements in whole-water digests. Interferences 

on 111Cd+

 (from 95Mo16O+) and 66Zn+ (from

50Cr16O+

) are not routinely determined because 

the interferences are negligible at molybdenum 

and chromium concentrations that are usually

present in natural whole-water digests. 

Comparing results for primary and secondary

isotopes may identify other possible oxide 

interferences. For example, comparing 107Ag+

to 109Ag+

 results could indicate the degree of 

zirconium or niobium interference on silver. 

If concentration levels of interferentcausing elements exceed those listed in 

tables 5 and 6, the sample must be diluted 

by an appropriate factor and reanalyzed. 

Dilution must be made by using the calibration 

blank (see section 5B.3). 

3B.2.3 Doubly charged ion interferences: 

A doubly charged ion is created in the plasma for 

any element that has a second ionization 

potential that is less than the ionization potential 

for argon. Under normal operating conditions, 

the ICP–MS generates less than 0.2 percent 

doubly charged barium ion (see table 6). 

Apparent copper and zinc concentrations will 

exceed MDL concentration levels whenever 

barium concentrations exceed 1,000 g/L. 

Lutetium and ytterbium (176 amu) doubly

charged ions will interfere with strontium. 

Similarly, dysprosium, europium, and holmium 

(163, 164, and 165 amu) doubly charged ions 

interfere with selenium. These rare earth 

isotopes, however, are usually found at negligible 

concentrations in whole-water digests. 

Table 6. Doubly charged ion interferences for elements determined in whole-water digests by ICP–MS 

[ICP–MS, inductively coupled plasma–mass spectrometry; g/L, microgram per liter; mg/L, milligram per liter; 

~, approximate] 

Isotope Interferent Interferent 

ion 

Interferent 

concentration

Apparent element 

concentration

(μg/L) 

65Cu Barium 130Ba2+ 1 mg/L Ba ~0.1 66Zn Barium 132Ba2+ 1 mg/L Ba ~0.4 67Zn Barium 134Ba2+ 1 mg/L Ba ~10 

4B. Apparatus, Instrumentation, and 

Operating Conditions 

4B.1 Labware: See section 4A.1 

4B.2 Instrumentation: VG Elemental

PlasmaQuad I ICP–MS system, which consists 

of a Gilson 222 automatic sampler, high-solids 

pneumatic nebulizer, Gilson peristaltic pump, 

internal standard introduction manifold, 

computer system, and printer. The high-solids 

nebulizer used for sample introduction was a 

parallel-path design that was entirely

constructed of tetrafluoroethylene monomer 

(CPI Inc., Model 50, P/N 4060-69). This 

nebulizer design resists clogging and is 

chemically inert. Other nebulizer designs can 

be used, however, they must be resistant to 

clogging and capable of providing MDLs that 

are within a factor of two of those listed in 

ANALYTICAL METHODS 17
table 1. More state-of-the-art (circa 1997) ICP–

MS instruments will provide MDLs that are a

factor of 4–50 times lower than levels reported 

in this study. Instrument software must be 

capable of providing automatic interference

correction (for example, PQVision Version 

4.1.2). 

4B.3 Operating conditions:

 Isotopes—

Isotopes used to quantify elements, 

which are determined in whole-water digests by

inductively coupled plasma–mass spectrometry,

are listed in table 7. Secondary isotopes are in 

italic. In addition, the use of the sum of all four 

lead isotopes for quantitation is highly

recommended because the lead isotopic 

abundance in a sample may deviate from natural 

abundance. 

 Internal standards—

45Sc, 115In, and 208Bi are used as internal

standards in the interpolated mode. Other 

interference-free isotopes may be substituted 

if needed. 

 Inductively coupled plasma—

Incident radio frequency power: ~ 1.3 kW

Reflected radio frequency power < 5 W 

Coolant flow rate ~ 13 L/min 

Auxiliary flow rate ~ 0.5 L/min 

Nebulizer flow rate ~ 0.7 L/min 

 Vacuum system, in millibar— 

Section Static 

pressure 

Operating 

pressure 

Analyzer ~ 1 X 10-8 ~ 5 X 10-6

Intermediate ~ 10-4 ~ 10-4

Expansion atmosphere ~ 1.5

 Ion sampling position—

Signal response on the rate meter for 115In is

maximized while adjusting the x, y, and z 

positioning on the torch box. 

Table 7. Isotopes used to quantify elements determined in whole-water digests by ICP–MS 

[ICP–MS, inductively coupled plasma–mass spectrometry]

Element Isotope 1 Element Isotope 1 Element Isotope 1

Aluminum 27 Copper 65, 63 Silver 107, 109

Antimony 121 Lead 2 208 Strontium 88

Barium 137 Lithium 7 Thallium 203

Beryllium 9 Manganese 55 Uranium 238

Cadmium 111, 114 Molybdenum 95 Zinc 66, 67

Chromium 3 52 Nickel 60

Cobalt 59 Selenium 82

1

Secondary isotopes are shown in italic. 2

The sum of all lead isotopes (204, 206, 207, and 208) for quantitation is highly recommended (see section 4B.3). 3

Quantification can be problematic because of molecular ion interferences. 

ANALYTICAL METHODS 18
 Ion optics—

The potentials applied to the ion optics 

are optimized to give the maximum reading on 

the rate meter for 115In. Nominal vernier 

settings for each ion lens are listed below. 

Lens Vernier 

setting 

Lens Vernier

setting 

Collector ~ 8 L4 ~ 2 

Extraction ~ 0.5 Differential

aperture 

~ 1 

L1 ~ 8 Front plate ~ 5 

L2 ~ 6 Pole bias ~ 5 

L3 ~ 5 Prefilter ~ 4

 Peristaltic pump—

Pump rate is adjusted to approximately 

1 mL/min.

 Internal standard manifold—

The internal standard introduction 

system uses a 12-turn microbore mixing coil 

(Alpkem 303-0310), microbore double 

injection fitting (Alpkem 303-107-00), 

microbore debubbler (Alpkem 303-0103-00), 

and the peristaltic pump tubing that is listed in 

figure 1b (see Appendix). 

 Detector potential—

The potential applied to the electron 

multiplier must be optimized by using

manufacturer’s guidelines (Galileo ElectroOptic Corporation, 1991). This potential will 

increase over the life of the multiplier.

 Data acquisition—

Data are acquired using the peakhopping mode to collect three points per peak 

per isotope. Three 40-second integrations are 

averaged for the reported result.

 Mass calibration and resolution—

Mass calibration is verified at 4 to 6 

masses that extend throughout the full mass 

range. The calibration must be within 0.1 amu 

of the theoretical value for each mass. 

The valleys between Mg and Pb isotopes 

must be about 10 percent of the maximum 

peak height. 

 Oxide molecular ion and doubly 

charged ion levels—

Oxide and doubly charged ion intensities 

should be less than the following upper limits: 

BaO+

 / Ba

+ < 0.5 percent 

Ba2+ / Ba

+ < 3 percent 

 Autosampler cycles—

Autosampler cycle times listed below 

minimize carryover in the sample introduction 

configuration shown in figure 1b (see 

Appendix). 

Rinse cycle ~ 60 seconds 

Flush cycle ~ 75 seconds 

5B. Reagents and Calibration 

 Standards 

ASTM Type I reagent water (American 

Society for Testing and Materials, 1995, p. 

122–124), spectroscopic grade commercial 

standards, and ultrapure acids must be used to 

prepare all solutions. All percentages 

represent volume-to-volume ratios. All 

concentrated acids and commercial standards 

must be verified to contain concentrations of 

concomitant elements that are less than the

MDLs after the prescribed dilution. Every

solution must be stored in a designated clean 

FEP Teflon bottle; solutions that contain silver

must be stored in a designated clean opaque 

FEP Teflon bottle. 

ANALYTICAL METHODS 19
ANALYTICAL METHODS 20

5B.1 Nitric acid (HNO3): Concentrated, 

specific gravity 1.41. 

5B.2 Hydrochloric acid (HCl): 

Concentrated, specific gravity 1.196. 

5B.3 Calibration blank: Reagent water 

acidified to 0.4 percent nitric acid and 2 

percent hydrochloric acid. 

5B.4 Commercial single-element 

standard solutions, 1.00 mL = 10 mg 

preserved in nitric acid for each of the 

following: Al, Ag, Ba, Bi, Be, Cd, Co, Cr, 

Cu, In, Li, Mn, Mo, Ni, Pb, Se, Sb, Sc, Sn 

(may include a low percentage of hydrofluoric 

acid), Sr, Tl, U, and Zn. 

5B.5 Commercial sulfate standard, 1.00 

mL = 10 mg sulfate in water (from sodium 

sulfate). 

5B.6 Multielement stock solution I, 1.00 

mL = 0.010 mg of Be, Cd, Co, Cr, Cu, Mo, 

Ni, and Pb: Dilute 1.0 mL of each 

commercial single-element standard to 1,000 

mL in a volumetric flask with 1 percent nitric 

acid. 

5B.7 Multielement stock solution II, 

1.00 mL = 0.010 mg of Se, Sb, Sr, Tl, and U: 

Dilute 1.0 mL of each commercial singleelement standard to 1,000 mL in a volumetric 

flask with 1 percent nitric acid. 

5B.8 Multielement stock solution III, 

1.00 mL = 0.010 mg of Al, Ba, Mn, and Zn: 

Dilute 1.0 mL of each commercial singleelement standard to 1,000 mL in a volumetric 

flask with 1 percent nitric acid. 

5B.9 Lithium stock solution IV, 1.00 mL 

=0.010 mg of Li: Dilute 1.0 mL lithium 

commercial single-element standard to 1,000 

mL in a volumetric flask with 1 percent nitric 

acid. 

5B.10 Silver stock solution V, 1.00 mL 

= 0.010 mg of Ag: Dilute 1.0 mL silver 

commercial single-element standard to 1,000 

mL in a volumetric flask with 1 percent nitric 

acid. 

5B.11 Multielement calibration 

standard I, 1.00 mL = 0.025 g Al, Ag, Ba, 

Be, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Se, 

Sb, Sr, Tl, U, and Zn: Dilute 0.250 mL of 

multielement stock solutions I, II, and III, 

lithium stock solution IV and silver stock 

solution V to 100 mL in a volumetric flask 

with calibration blank. 

5B.12 Multielement calibration 

standard II, 1.00 mL = 0.100 g Al, Ba, Be, 

Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Se, Sb, 

Sr, Tl, U, and Zn: Dilute 1.0 mL of 

multielement stock solutions I, II, and III and 

lithium stock solution IV to 100 mL in a 

volumetric flask with calibration blank. 

5B.13 Multielement calibration 

standard III, 1.00 mL = 0.500 g Be, Cd, Co, 

Cr, Cu, Li, Mo, Ni, Pb, Se, Sb, Sr, Tl, and U: 

Dilute 5.0 mL of multielement stock solutions 

I, II, and III and lithium stock solution IV to 

100 mL in a volumetric flask with calibration 

blank. 

5B.14 Multielement calibration 

standard IV, 1.00 mL = 1.00 g Al, Ba, Mn, 

and Zn: Dilute 1.0 mL of multielement stock 

solution III to 100 mL in a volumetric flask 

with calibration blank. 

5B.15 Internal standard stock solution, 

1 mL = 0.1 mg Sc, In, and Bi: Dilute about 10 

mL of each commercial single-element 

standard for Sc, In, and Bi and 10 mL 

ultrapure nitric acid to 1,000 mL in a 

volumetric flask with reagent water. 
5B.16 Brij-35 (CAS 9002-92-0), 30 

percent solution of polyoxyethylene lauryl

ether. 

5B.17 Internal standard working 

solution, 1 mL = 0.5 g Sc, In, and Bi: Dilute 

5 mL of internal standard stock solution and 

100 L of Brij-35 solution to 1,000 mL in a 

volumetric flask with calibration blank. 

5B.18 Performance check standard, 

1.00 mL = 0.010 g of Ag, Al, Ba, Be, Cd, Cr, 

Co, Cu, Li, Mn, Mo, Ni, Pb, Sb, Se, Sr, Tl, U, 

and Zn. Dilute 4.0 mL of multielement 

calibration standard I to 10 mL with 

calibration blank. 

5B.19 Interference check stock solution, 

1.00 mL = 0.010 mg Sn: Dilute 1.0 mL of the 

tin commercial single-element standard to 

1,000 mL in a volumetric flask with 1 percent 

nitric acid. 

5B.20 Interference check standard, 1.00 

mL = 0.100 g of Sn. Dilute 1.0 mL of 

interference check stock solution to 100 mL in 

a volumetric flask with calibration blank. 

5B.21 Sulfate interference calibration 

standard I, 1 mL = 100 g of sulfate. Dilute

0.1 mL of sulfate standard to 10 mL with 

calibration blank. 

5B.22 Sulfate interference calibration 

standard II, 1 mL = 500 g of sulfate. Dilute

0.5 mL of sulfate standard to 10 mL with 

calibration blank. 

5B.23 Tuning solution, 1 mL = 0.1 g 

Be, Co, In, Mg, Pb, U: Dilute about 10 L of 

each commercial single-element standard for 

Be, Co, In, Mg, Pb, and U and 10 mL reagent 

grade nitric acid to 1,000 mL in a volumetric 

flask with reagent water. 

6B. Analytical Procedure 

Refer to VG Elemental (1988, 1994) and 

NWQL Standard Operating Procedure 

IM0011.0 (J.R. Garbarino and M.R. Hill, U.S. 

Geological Survey, written commun., 1994) 

for details of procedures outlined in the

following paragraphs. 

6B.1. Ignite plasma. Ensure that 

inductively coupled plasma and vacuum 

conditions are set correctly (see section 4B.3). 

Allow at least 30 minutes prior to 

optimization. Use the tuning solution (see 

section 5B.23) for procedures outlined in 

sections 6B.2–4. 

6B.2. Optimize plasma-sampling

position and ion optics. 

6B.3. Adjust the electron multiplier 

voltage to provide about 2,000 counts per 

second for 1 g/L 115In. 

6B.4. Verify mass resolution and mass 

calibration. 

6B.5. Assemble an analytical procedure 

having the calibration blank, multielement 

calibration standards, QA/QC samples, and 

unknown samples. In addition, include sulfate 

interference calibration solutions if external

calibration is being used. 

6B.6 Load the autosampler with 

calibration blank, multielement calibration 

standards, QA/QC samples, and unknown 

samples. Execute the analytical procedure. 

6B.7 Verify the accuracy of the 

calibration using the results from the

performance check solution. Concentrations 

must not deviate from the theoretical

concentrations by more than ±5 percent 

(except for selenium at ±30 percent). 

Elemental relative standard deviations for the

performance check solution must be within 

ANALYTICAL METHODS 21
±0.5 percent of the variability listed in table 17 

for 12.5 g/L. The instrument must be recalibrated for failure in either criterion for any

element.

6B.8 Verify the accuracy of interference 

correction equations by analyzing the 

interference check standard (see section 

5B.20). If either the indium intensity exceeds 

that of the calibration blank by more than 5 

percent, or the secondary cadmium isotope 

(

114Cd) concentration exceeds the MDL, then 

the instrument must be recalibrated or the

interference equations must be reestablished 

before continuing sample analyses. 

6B.9 The QA/QC plan requires analysis 

of at least one of the following at a frequency

of at least 1 in every 10 unknown samples: 

SRWS, calibration blank, duplicate sample, 

diluted sample, or matrix spike. If SRWSs are

used, the analyst must ensure that results fall 

within the established quality-control limits. 

Selection of a suitable SRWS should be based 

on the expected sample concentration range. 

6B.10 Acceptance criteria for 

duplicates, dilutions, and matrix spikes are 

fully outlined in the SOP. If all dataacceptance criteria are met, then the analytical

results are acceptable. If any one criterion is

not satisfied, then the analyst must reanalyze 

the sample in question. If the results remain 

outside the criteria, the instrument must be 

recalibrated and all samples following the last 

acceptable QA/QC check reanalyzed. The 

upper calibration limits do not represent the 

endpoint of the linear analytical range but 

rather a concentration limit more appropriate

for the majority of samples analyzed. 

Nevertheless, if an elemental result is greater

than the upper calibration limit, the sample 

must be diluted (with the calibration blank)

and reanalyzed so that the concentration will 

be less than the upper calibration limit. 

7B. Calculations

Correct the copper and zinc results from 

sulfate interference after the analyses have 

been completed if external sulfate calibration 

was used. This operation can easily be done 

by using a spreadsheet program. All other 

calculations are performed automatically by

the operating system. If a sample was diluted, 

the appropriate dilution factor must be 

included in the analytical procedure before the 

automatic calculation is performed. Linear 

regression coefficients and standard and 

sample concentrations for every element are 

printed out immediately after the analyses. 

VG Elemental (1994) describes the formulas 

that are used in the calculations. 

8B. Reporting of Results 

The number of significant figures 

reported in the results varies with element and 

is a function of concentration. Whenever the 

concentration is less than the MDL for an

element, the result is reported as less than the

MDL (< MDL). All other elemental results 

for whole-water digests are reported by using

the criteria listed below. These criteria are

based on the uncertainty indicated in table 17. 

Alternatively, the variability that is associated

with the mean concentration (reported with the

mean by each instrument) measured in each 

sample could be used to establish the appropriate number of significant figures to report. 

The use of such a procedure would provide the 

most accurate estimate of the uncertainty that 

is associated with each unique sample matrix. 

For antimony, barium, beryllium, 

cadmium, copper, lithium, manganese, 

molybdenum, nickel, and zinc—

ANALYTICAL METHODS 22
 If the concentration is greater than 

or equal to the MDL, but less than 100 g/L,

then report result to the nearest 0.1 g/L. 

 If the concentration is greater than 

100 g/L, but less than 500 g/L, then report 

result to the nearest 1 g/L. 

 If the concentration is greater than 

500 g/L, then report result to the nearest 10 

g/L. 

For cobalt, lead, silver, strontium, 

thallium, and uranium— 

 If the concentration is greater than 

or equal to the MDL, but less than 10 g/L,

then report result to the nearest 0.01 g/L. 

 If the concentration is greater than 

100 g/L, but less than 500 g/L, then report 

result to the nearest 1 g/L. 

 If the concentration is greater than 

500 g/L, then report result to the nearest 10 

g/L. 

For aluminum, chromium, and 

selenium— 

 If the concentration is greater than 

or equal to the MDL, but less than 500 g/L,

then report result to the nearest 1 g/L. 

 If the concentration is greater than 

500 g/L, then report result to the nearest 10 

g/L.

DISCUSSION OF RESULTS 

Accuracy and Variability

The accuracy and variability for the 

analysis of whole-water digests are evaluated 

by comparing results obtained by ICP–OES 

and ICP–MS to results obtained by former 

USGS methods of analysis. Results from the 

analysis of digested SRWS, spiked natural 

whole-water digests, and 43 natural wholewater digests are used to identify elements that

can be determined by using ICP–OES or ICP–

MS, while maintaining or exceeding the 

performance of the former methods. Former 

USGS methods include U.S. Geological 

Survey approved methods (Fishman and 

Friedman, 1989; Fishman, 1993) and U.S. 

Environmental Protection Agency methods of 

analysis (U.S. Environmental Protection 

Agency, 1992) that have been adapted for use 

at the NWQL. 

It is either not practical or instrumentally

impossible to determine all elements by both 

ICP–OES and ICP–MS. Antimony is not 

determined by ICP–OES because the 

instrument currently (1998) does not support 

it, and the determination of selenium is not 

feasible because of poor sensitivity. Calcium, 

iron, magnesium, silicon, sodium, and 

vanadium are not determined by ICP–MS 

either because the concentration level

normally present in whole-water digests 

exceeds the working range of the technique or 

because substantial molecular ion interferences are present.

Results for Digested Standard Reference Water 

Samples 

U.S. Geological Survey SRWS T107, 

T119, T133, T135, and WW-1 were analyzed 

to determine the accuracy and variability of 

the ICP–OES and ICP–MS methods. Only

WW-1 approximates a natural whole-water

sample that has suspended sediment, although 

the amount of sediment exceeds the level 

routinely present in such samples that are 

submitted to the NWQL. Other SRWSs are

filtered, acidified natural-water matrices. 

SRWS T135 was only analyzed by ICP–OES 

because selected elements are present at

concentrations better suited to evaluate the 

DISCUSSION OF RESULTS 23
accuracy for less sensitive elements (for 

example, lead and molybdenum). Ten bottles 

of SRWS T107, T119, T133, and T135 and 

five bottles of WW-1 were digested on 

different days by using the in-bottle digestion 

procedure (Hoffman and others, 1996). 

In general, results for SRWS digests 

from ICP–OES and ICP–MS were obtained 

within different time domains. Data for

SRWS T107, T119, T133, and T135 by ICP–

OES represent short-term (about 1-hour) 

results obtained by analyzing each of 10 inbottle SRWS digests within a single

calibration period. In contrast, all the SRWS

data from ICP–MS correspond to long-term 

results obtained by analyzing all the standard 

solutions over a 2-week period using different 

calibrations. However, long-term accuracy

and variability of the two methods are directly

comparable using results from SRWS WW-1. 

All five bottles of SRWS WW-1 were

analyzed four times over a 2-week period. 

The analytical variability of the two 

techniques is compared by using the variance 

from determinations of standards that have a 

wide range of concentrations. Three 

determinations were performed sequentially

on a single aliquot in less than 1 minute. A 

WW-1 digest, or another SRWS that has more 

suitable concentration levels for ICP–OES, 

and a series of standards are used for comparing the data. 

The accuracy of the SRWS results is

examined by comparing the experimental

mean to the published most probable value 

(MPV) by use of two methods. First, the 

experimental mean is compared to the 1 (68 

percent) confidence interval about the 

published MPV. Then the Student t-Test or 

the Wilcoxon Signed Rank Test, depending on 

whether the data set was normally distributed 

and showed equal variance, is used to test 

whether the experimental mean is significantly 

different from the MPV at the 95-percent 

confidence level (a p-value less than 0.05). 

Frequently the p-value indicates that the 

experimental mean is significantly different 

from the MPV, even though the result is 

within the confidence interval of the MPV. In

most of these cases, failure is related to the

variability in the experimental data, and the

difference between the experimental mean and 

the MPV is analytically insignificant. 

Short-term ICP–OES results for SRWS

T107, T119, T133, and T135 are listed in 

tables 8 through 11. The confidence intervals 

about the MPV and the experimental ICP–

OES mean are shown in figures 5a, 6a, and 7a 

and in figure 8 (see Appendix). The experimental means for elements determined by

ICP–OES were inside the 1-confidence 

interval of the MPV for all SRWS except for

calcium, magnesium, manganese, nickel, 

silver, vanadium, and zinc. Calcium, 

magnesium, manganese, and vanadium means, 

however, are within the 1.5-confidence 

interval that is acceptable by the NWQL. 

Silver is only slightly outside the interval in 

SRWS T135. All zinc data are acceptable 

except for T133, which is negatively biased. 

Nickel results are outside the 1-confidence 

interval in 75 percent of the SRWSs and 

greater than 1.5 for T107 and T119. 

All long-term experimental means for

SRWS T107, T119, and T133 by ICP–MS 

(see tables 12 through 14 and figures 5a, 6b, 

and 7b in Appendix) are within the 1-

confidence interval of the MPV except for 

beryllium, boron, chromium, lithium, and 

silver. The mean beryllium and lithium 

concentrations measured in T107 are outside 

the 1.5-confidence interval of the MPV. 

Boron and chromium results for T107 and 

silver in T119 are inside the 1.5-confidence 

interval for the MPV. 

DISCUSSION OF RESULTS 24
DISCUSSION OF RESULTS 25

The 1-confidence interval about the 

MPV, the long-term experimental mean and 

standard deviation, the statistical test used, the 

test statistic value, and the p-value for SRWS 

WW-1 are listed in table 15. The MPV 

confidence interval and the experimental 

results from ICP–OES and ICP–MS are shown 

in figure 9 (see Appendix). Elemental results 

from both methods are within the 1-

confidence interval of the MPV except for 

ICP–OES cadmium and nickel results; 

however, both elements are well within the 

1.5 -confidence interval, so the data are 

acceptable. For selected elements, one 

method can be seen to have greater long-term 

accuracy and variability than the other. For 

example, the experimental mean for 

beryllium, cadmium, and nickel by ICP–MS 

are somewhat more accurate than for ICP–

OES; results for the other elements are 

equivalent. Less variability is indicated in the 

ICP–OES data for some of the lighter 

elements (those less than 60 amu, for example, 

beryllium, chromium, lithium, and 

manganese). Increase in variability for some 

of the ICP–MS results may be the consequence of shifting spectral background that is 

not entirely offset by the internal standard. 

Cadmium, molybdenum, nickel, and silver 

concentrations are at or less than the ICP–OES 

MDLs and the aluminum concentration is 

much greater than the 1,000-μg/L calibration 

limit for ICP–MS.

The analytical variability in ICP–OES 

and ICP–MS data from WW-1 (except for 

aluminum, cobalt, lead, molybdenum, and 

silver which used other reference standards) 

is listed in table 16. The analytical 

variability should represent only the 

component associated with each method 

because using a single WW-1 digest 

eliminates the variability from the in-bottle 

digestion procedure and the homogeneity of 

WW-1. SRWS T107 data were used for 

aluminum (220 μg/L), cobalt (11 μg/L), 

and silver (12 μg/L) and SRWS T117 was 

spiked with about 100 μg/L lead and 50 

μg/L molybdenum to provide concentration 

levels measurable by ICP–OES. The 

median analytical variability for elements 

common to both methods is about a factor 

of two to three better by ICP–MS. The 

variability in elemental results is lower for 

ICP–MS than for ICP–OES when 

concentrations are less than 100 g/L, a 

decrease most likely a consequence of its 

higher sensitivity. In contrast, ICP–OES 

provides lower variability in elemental 

results for concentrations greater than 100 

g/L (for example, barium, manganese, and 

strontium). 

The analytical variability that can be 

expected over an extended range of concentrations is listed in table 17. In contrast to the 

variability presented for WW-1, these data were 

obtained for a calibration blank matrix and 

therefore correspond to optimal matrix 

conditions. The variability (in terms of percent 

relative standard deviation) generally increases as 

the concentration approaches the MDL. 

Elements with similar MDLs for ICP–OES and 

ICP–MS show about the same variability. 

Results for ICP–MS show much lower variability 

for elements, such as chromium, cobalt, lead, 

molybdenum, nickel, and zinc, because the 

corresponding MDLs are lower. Nevertheless, 

the variability of both methods approaches each 

other as the concentrations increase. As with the 

WW-1 data, these data indicate that the 

variability of ICP–OES is somewhat lower for 

selected elements at higher concentrations (for 

example, barium and strontium in table 17). 

Spike Recoveries in Natural Whole-Water 

Digests 

The percentage of spike recoveries for all 

elements was determined in six natural wholewater digests. Two ground-water and four 

surface-water samples that have specific 

conductance that are representative of the range 
DISCUSSION OF RESULTS 26

of whole-water samples submitted to the 

laboratory for analysis were spiked. The predigestion specific conductances for the groundwater samples were 519 and 1,600 S/cm and 

103, 230, 683, and 1,900 S/cm for the 

surface-water samples. The spike 

concentration level was determined 

individually for each sample and element. 

First, the original concentration of every 

element was determined in each sample digest. 

If the original concentration was found to be 

less than the MDL, the concentration of the 

spike was ten times the MDL, otherwise the 

sample was spiked at two times the original 

concentration. 

Spike recovery results for the wholewater digest samples are listed in table 18. The 

average percent recovery for the six samples 

was used as an indicator for the overall 

accuracy of each method for every element. 

The average percent recovery is within 10010 

for all elements determined by ICP–OES. All 

elements determined by ICP–MS were also 

within this range except for beryllium, 

cadmium, chromium, manganese, and silver. 

The average percent recoveries for these 

elements are only marginally outside the 10-

percent interval. Nevertheless, the recoveries 

are acceptable, considering that beryllium, 

cadmium, chromium, and silver were spiked at 

low concentrations. The mean recovery for 

manganese should have been expected to be 

within 10 percent, however, the mean recovery 

was influenced by the spike recovery for one 

digest. Low spike recoveries in the groundwater sample that have high specific 

conductance indicate high concentrations of 

dissolved solids may affect the accuracy of 

ICP–MS determinations (see table 18, for 

example, boron, cobalt, copper, lithium, 

manganese, nickel, and zinc). For this 

particular sample, the percentage recovery for 

selected elements was invariably low, however, 

never by more than 25 percent. 

Comparison of Inductively Coupled Plasma–

Optical Emission Spectrometry and Inductively 

Coupled Plasma–PMass Spectrometry to 

Former Methods in the Analysis of Natural 

Whole-Water Digests 

Forty-three acidified, whole-water 

samples that had been digested by using the 

in-bottle procedure were selected from the 

population of such samples that were 

submitted to the NWQL. Selected digested 

whole-water samples have a wide range of 

element concentrations and specific 

conductance. Both surface-water and groundwater samples are included in the sample set; 

the number of each type is approximately 

proportional to its fraction of the total 

submitted for analysis during an average year. 

Other chemical characteristics that often 

influence the performance of analytical 

methods, such as sulfate concentration, 

chloride concentration, and alkalinity, were 

also considered in the selection process (see 

table 19 for sample characteristics). 

Every sample digest was analyzed by 

ICP–OES, ICP–MS, and one former method. 

The former method was either stabilized 

temperature graphite furnace–atomic 

absorption spectrophotometry (GF–AAS), 

flame–atomic absorption spectrophotometry 

(F–AAS), or direct current plasma–atomic 

emission spectrometry (DCP–AES), 

depending on the element being determined. 

The presence or absence of significant 

bias (bias relative to the former method as 

opposed to method analytical bias) in ICP–

OES and ICP–MS results was determined 

using a combination of statistical treatments. 

ICP–OES and ICP–MS results were compared 

to former method results by constructing 
scattergrams and box plots to show the bias 

and variance of the data set, by determining

linear regression coefficients to identify

systematic errors, and by using statistical 

analysis techniques to test whether ICP–OES 

and ICP–MS results differed significantly

from former method results. Before an 

appropriate method of statistical analysis 

could be selected, all data sets were tested for

normality and equal variance. If the data set 

was normally distributed with equal variance, 

a parametric test was used, otherwise, a 

nonparametric test was used. 

A realistic statistical evaluation of the

sample results was provided by only

comparing results that were greater than the 

MDLs and within the calibration range of the

methods being compared. The only exception 

to this approach was for comparisons made to 

GF–AAS. A high percentage of whole-water 

digests analyzed by GF–AAS required dilution 

because of its narrow linear calibration range. 

If these samples were omitted, the data set 

would have been too small for statistical 

analysis. In contrast, only a small number of 

digests required dilution for the other 

methods. Statistical analysis was impractical 

for some elements because the number of 

samples having results greater than the MDL

was small. For example, cadmium, cobalt,

lead, and molybdenum have only a small 

number of samples with concentrations greater 

than the MDLs for ICP–OES, therefore, only

ICP–MS results could be compared with GF–

AAS results. Aluminum, calcium, 

magnesium, and sodium concentrations 

exceed the calibration range for some samples 

and for some methods. Selected elements 

could not be determined by both ICP–OES 

and ICP–MS, hence, only one method was 

compared to the former method. 

Nonparametric test procedures generally

were used to compare methods because all the 

element concentrations extended several 

orders of magnitude. The Kruskal-Wallis Test 

was used whenever sufficient sample results

were available for all three methods. The test 

was used to determine if there was any

significant difference in the medians from 

each method at the 95-percent confidence 

level. Test results include the test statistic, pvalue, and mean rank for each method. The 

mean rank is useful for relating individual 

methods to one another; the closer the mean 

ranks are to each other the better the overall 

correspondence. In all instances, the group-1 

mean rank corresponds to ICP–OES data, 

group-2 corresponds to the ICP–MS, and 

group-3 corresponds to the former method. 

For selected elements, ICP–OES and ICP–MS

also are compared individually to the former 

method using the One-sample Sign Test to 

determine if there is any difference between

the medians at the 95-percent confidence 

level. The One-sample Sign Test was applied 

whenever one of the three methods was 

omitted because of its limited data set or 

whenever only two methods were available for 

comparison. 

Linear regression analysis was used to 

calculate the slope and y-intercept coefficients

of the equation describing the relation between 

ICP–OES or ICP–MS to the former method. 

The reliability of such a treatment was 

improved by always using the more precise, or 

equally precise, method as the independent 

variable (the x-axis variable). The regression 

coefficients (the slope, labeled with the former

method’s acronym and the y-intercept) and 

their 95-percent confidence intervals are 

provided (for example, see fig. 10a in 

Appendix). 

The range of element concentrations 

composing the sample set is listed in table 19. 

The 25th percentile, 50th percentile (median), 

75th percentile, and maximum concentration 

for every element demonstrate the broad 

concentration range of the sample set. The 

DISCUSSION OF RESULTS 27
fraction of samples having concentrations less 

than the MDL provides insight into the

suitability of each method for the analysis of a 

representative subset of the whole-water 

digests submitted to the NWQL. Results of

the Kruskal-Wallis Test and One-sample Sign

Test for each element are listed in table 20. 

Scattergrams, box plots, and regression 

coefficients for the same data set also are 

provided to augment the statistical results (see

figs.10 through 30 in Appendix). There are no 

U.S. Geological Survey approved methods for 

the determination of silicon, thallium, 

uranium, and vanadium in whole-water 

digests, therefore, no comparisons could be 

made to ICP–OES and ICP–MS. The 

conclusions drawn from all statistical

treatments are summarized for each of the 

following elements. Illustrations showing

results of the statistical treatments are

provided in the Appendix (see figs. 10–30). 

(0.880.02, see fig. 10a) indicates there is a 

slight negative bias (about 10 percent) in the 

ICP–OES results; the large y-intercept is 

negligible at the 95-percent confidence level 

(62108). No systematic errors are indicated 

by the regression coefficients for ICP–MS in

relation to DCP–AES (slope=1.040.02, yintercept= –3.8104). 

Antimony

Only nine sample results could be 

compared because over 70 percent of the 

samples had antimony concentrations less than

the MDL. Antimony concentration in the

sample data set ranged from about 0.8 to 5 

g/L. Since the limited data set was normally

distributed with equal variance, the Student tTest was used to determine if there was a

significant difference between the means from

ICP–MS and GF–AAS. A p-value of 0.3061 

suggests that any difference between the 

means is statistically insignificant, however, 

the scattergram and box plots indicate 

considerable variation in the results and show 

that ICP–MS results are negatively biased by

about 30 percent (see fig. 11). 

Aluminum 

Seventeen sample results were omitted 

from the data set used in the statistical analysis 

because the upper calibration limit for 

aluminum by DCP–AES is 10,000 g/L and 

by ICP–MS is 1,000 g/L; ICP–OES has an

upper limit of 500,000 g/L. However, the 

data set included two samples having the 

aluminum concentrations greater than 1,000 

g/L that were diluted and analyzed by ICP–

MS. Only one sample was omitted because 

the aluminum concentration was less than an 

MDL. Using data having aluminum 

concentrations from 13 to greater than 13,000 

g/L, the Kruskal-Wallis Test indicated that

there was no significant difference among

results obtained using DCP–AES (the former 

method), ICP–OES, and ICP–MS (for n=25, 

the p-value=0.9750, see fig. 10b). 

Nevertheless, the mean rank for ICP–MS is 

somewhat closer to the mean rank for DCP–

AES than is ICP–OES. The slope of the 

relation of ICP–OES to DCP–AES 

Barium 

The size of the data set used in the comparison 

of ICP–OES and ICP–MS to the former F–

AAS method was limited because of the high

F–AAS method reporting limit of 100 g/L

(no MDL has been established); therefore, 

only 20 samples were used in the statistical

analysis. The scattergrams show that there is

considerable nonlinearity between F–AAS and 

ICP–OES results and between F–AAS and 

ICP–MS results (see fig. 12a). The box plots 

show a significantly larger variability in the F–

AAS results. Nevertheless, the Kruskal-Wallis 

Test indicates that there is no significant

difference between results for the three 

methods (p-value=0.3754). The mean ranks 

for ICP–OES and ICP–MS results were 

DISCUSSION OF RESULTS 28
fig. 14d). The slope of the regression 

(2.00.7, see fig. 14a) also indicates that ICP–

MS results are about two times greater than 

DCP–AES results. This difference can easily

be seen in the box plot (see fig. 14d). 

However, the slope of 1.000.03 for ICP–OES 

indicates close agreement with DCP–AES (see 

fig. 14c). In addition, the average difference 

between DCP–AES and ICP–OES over the 

entire concentration range of the samples was 

approximately 8 g/L, a concentration that is

less than the method reporting limit for DCP–

AES.

nearly equal although slightly greater than 

F–AAS, indicating that F–AAS results may be

biased low (also shown in the box plots for 

ICP–OES and ICP–MS in fig. 12b). A 

comparison of regression analysis coefficients

for ICP–MS and ICP–OES results shows close 

agreement (see fig. 12c showing a slope of 

1.130.04). 

Beryllium 

All the samples have beryllium 

concentrations less than the F–AAS MDL, and 

only five are greater than the ICP–OES MDL

of 0.7 g/L. ICP–OES and ICP–MS results 

for these five samples were normally distributed with similar variance, so the Student 

t-Test was used to compare the results. The 

test indicated that there is no significant

difference in the data (p-value=0.0974) and a 

slope of 1.00.1 indicated negligible bias (see 

fig. 13). 

Cadmium 

The accuracy of the ICP–OES method 

could not be determined because only one 

sample out of 43 had a cadmium concentration 

greater than its MDL of 6 g/L. Statistical

analysis indicated that there is no significant

difference in results from ICP–MS and GF–

AAS (p-value=0.0522, n=27, see fig. 15) for 

samples with cadmium concentrations ranging

from less than 0.1 to 6 g/L. Also, the slope 

(1.000.02) and y-intercept (0.030.03) 

indicate there is no significant bias or method 

offset. 

Boron 

Fifteen data points (seven samples 

having boron concentrations less than the 

MDLs and eight samples having boron 

concentrations greater than the ICP–MS upper 

calibration limit of 100 g/L) were omitted so 

that the data set would have boron concentrations that ranged from 13 to 82 g/L. The

scattergrams, box plots, and regression 

coefficients indicate considerable differences 

among the DCP–AES, ICP–OES, and ICP–

MS results, a finding also supported by the 

Kruskal-Wallis Test (p-value=0.0021, see fig.

14b). The mean rank for ICP–OES was about 

30 percent lower than the DCP–AES mean 

rank; ICP–MS was about 20 percent higher. 

In treating the methods separately by using the 

One-sample Sign Test, there is still a

significant difference (p-value=0.0288, n=36, 

see fig. 14c) between DCP–AES and ICP–

OES results and between DCP–AES and ICP–

MS results (p-value=0.0009, n=28, see 

Calcium 

Thirty-two samples have calcium 

concentrations less than the calibration limit 

(60 mg/L) of the former method (F–AAS). 

Statistical analysis of the data set using the

One-sample Sign Test indicated a substantial 

difference between ICP–OES and F–AAS 

results (p-value=<0.0001, see fig. 16). This 

difference is based on the fact that 29 out of 

32 ICP–OES results were greater than F–

AAS; the median difference for the data set is 

approximately 1 mg/L for samples having

from 1 to 60 mg/L calcium. However, the 

slope coefficient of the regression 1.030.03 

suggests that the bias between F–AAS and 

DISCUSSION OF RESULTS 29
unsatisfactory when iron concentrations 

exceed 2 mg/L. ICP–MS and GF–AAS results

from 31 samples having cobalt concentrations 

ranging from 0.5 to 86 g/L showed 

significant differences (p-value 

=0.0033, see fig. 18c). The slope of 0.870.04 

suggests about 14 percent negative bias in the 

ICP–MS data, however, the median difference 

between the methods was only about 0.3 g/L

(fig. 18b). When data from three samples 

having the largest deviation from the former 

method are omitted, the bias in the ICP–MS 

data was reduced to about 3 percent. 

ICP–OES results is negligible. The box plots 

(see fig. 16) also support this conclusion. 

Chromium 

Because the MDLs for ICP–OES (4 g/L)

and ICP–MS (2 g/L) are greater than GF–

AAS, the data set is reduced to only 15 samples 

having between 6 to 160 g/L chromium. 

Using this data set, the Kruskal-Wallis test 

showed there is a high probability that GF–

AAS, ICP–OES, and ICP–MS results are 

statistically different (p-value=0.0078), an 

outcome supported by the box plots in figure 

17b. When comparing the methods individually to GF–AAS, the One-sample Sign Test 

indicated significant differences between ICP–

OES and GF–AAS (p-value=<0.0001, n=15, 

see fig. 17c) and between ICP–MS and GF–

AAS (p-value=<0.0001, n=26, see fig. 17d). 

ICP–OES results were always less than GF–

AAS (by a median of 13 g/L) and ICP–MS 

results were always greater than GF–AAS (by a 

median of 3 g/L). The slope of the regression 

equation for ICP–OES in relation to GF–AAS 

(0.520.05) also shows a 50 percent negative 

bias in the ICP–OES results (fig. 17a). 

However, the slope (1.040.05) for the 

regression of ICP–MS in relation to GF–AAS 

suggests no significant bias, although there is 

perhaps a slight offset in the results 

(y-intercept=32). 

Copper

Due to the relatively high copper 

concentrations, 28 samples could be used to 

compare ICP–OES, ICP–MS, and GF–AAS 

methods; 15 samples were omitted because 

copper concentrations were less than the MDL

by ICP–OES. Copper concentrations ranged 

from 3 to 370 g/L. Statistical analysis of the 

data set using the Kruskal-Wallis Test 

indicated that the results from the three

methods were not significantly different 

(p-value=0.5285, see fig. 19b). Scattergrams 

in figure 19a show a pattern of nonlinearity in 

GF–AAS for cooper concentrations greater 

than 100 g/L that is possibly a result of 

dilution error. The ICP–OES mean rank of 38 

is slightly less than the former method 

probably because about half the sample 

concentrations were near the MDL (see fig.

19b). In contrast, the mean rank for ICP–MS 

equals that of GF–AAS and there is no 

significant difference indicated by the Onesample Sign Test (p-value=0.6440, n=42, see 

fig. 19c) for the extended data set. 

Cobalt 

Cobalt concentrations were greater than 

the relatively high ICP–OES MDL of 10 g/L

in only six samples. ICP–OES gave high

results for four of these samples when compared to GF–AAS (see fig. 18a). This 

inaccuracy is related to the direct spectral

overlap from a nearby iron wavelength; the 

four samples had iron concentrations ranging

from 2 to 50 mg/L. The accuracy of the 

algorithm used to correct iron emission 

contributions to cobalt is apparently 

Iron 

Thirty-eight sample results were

included in the sample set, two samples with 

iron concentrations greater than 50,000 g/L,

one sample with iron concentration less than 

DISCUSSION OF RESULTS 30
Lithium the MDL, and two samples were not analyzed 

because of the lack of sample. The Onesample Sign Test implies that substantial 

differences exist between ICP–OES and 

F–AAS results for the samples having iron 

concentrations between 40 and 19,000 g/L

(p-value=0.0002, n=38, see fig. 20). Over 80 

percent of the ICP–OES results were less than

the former method (a median difference of 

only 80 g/L) probably because of its lower 

MDL. The slope of the regression equation 

(0.870.03) shows a negative bias of more 

than 10 percent in ICP–OES results, a level 

that is acceptable considering the wide 

concentration range of the samples analyzed. 

When the concentration range is narrowed to 

include samples with concentrations from 440 

to 4,500 g/L iron (the concentration 

boundaries where 50 percent of the iron 

results occur), there is no significant difference between the two methods. 

Sixteen samples having lithium 

concentrations less than 10 g/L, the methodreporting limit for the former method F–AAS, 

were omitted from the data set. The differences between analytical results for F–AAS, 

ICP–OES, and ICP–MS were found to be 

statistically insignificant using the KruskalWallis Test (p-value=0.9191, see fig. 22b). 

The scattergram of ICP–OES in relation to 

F–AAS data indicate slight nonlinearity, 

however, the slope interval of 0.900.09 

indicates the negative bias is insignificant (see 

fig. 22a). The slight positive bias (slope

interval 1.10.1) between F–AAS and ICP–

MS is also negligible. 

Magnesium 

The upper calibration limit for 

magnesium by the F–AAS method is 50 mg/L. 

This limitation reduced the data set to 41 

samples for which no statistically significant 

difference between ICP–OES and F–AAS 

results was indicated (p-value=0.6440, see 

fig. 23). Regression analysis indicated only a 

minor 7 percent negative bias in the ICP–OES 

results (slope=0.930.03) probably because of 

the lower variability in the ICP–OES data set 

(see the box plot in fig. 23). 

Lead

Because of the insensitivity of the lead 

emission wavelength, only four samples had 

lead concentrations that are measurable using

ICP–OES. Nonetheless, ICP–OES results for

these samples were inexact because the 

concentrations were less than a factor of two 

greater than the MDL of 50 g/L. The number 

of results comparing ICP–MS to GF–AAS 

was reduced to 31 by eliminating nine samples 

having lead concentrations less than the GF–

AAS MDL and three samples having lead 

concentrations greater than the upper 

calibration limit of 100 g/L for ICP–MS. 

The One-sample Sign Test suggested that 

there was no significant difference between 

ICP–MS and GF–AAS results (p-value 

=0.2810, see fig. 21). This result is supported 

by linear regression coefficients that show no 

systematic errors or offset (slope=0.980.06 

and y-intercept=0.121.3, for n=31). 

Manganese 

The sample set was reduced to 36 by

eliminating one sample having manganese

concentration less than the reporting limit by

F–AAS and six samples having manganese 

concentrations greater than 1,000 g/L, the

ICP–MS upper calibration limit. Results of 

the Kruskal-Wallis Test suggest that there are

no significant differences among the former 

F–AAS method, ICP–OES, and ICP–MS 

(p-value=0.8669, see fig. 24b) for samples 

having manganese concentrations ranging

from 6 to 870 g/L. However, ICP–OES

provided somewhat more accurate results for 

DISCUSSION OF RESULTS 31
the sample set when compared to F–AAS, as

indicated by its mean rank, than did ICP–MS. 

Both proposed methods gave marginally lower 

results than the former F–AAS method. 

However, the slopes for ICP–OES (0.990.04, 

n=36) and ICP–MS (0.940.05, n=36) in 

relation to F–AAS showed no bias (see 

fig. 24a). 

0.2 g/L. The slope of the regression suggests 

that the ICP–MS data are negatively biased by

about 10 percent when compared to GF–AAS. 

This bias would represent from 0.2 to 0.8 g/L

for 50 percent of the samples. 

Selenium 

Only four samples have selenium 

concentrations greater than 0.8 g/L, the MDL 

for the former method GF–AAS. Using this 

limited, normally distributed data set, the

Student t-Test indicated that there were no 

significant differences between ICP–MS and 

GF–AAS results (p-value=0.3670). Although 

not presented in figure 27, the One-sample 

Sign Test also indicated no significant 

difference (p-value=0.62). Close examination 

of the data shows that ICP–MS measured 

levels up to two times its MDL (2 g/L) in 4 

of the 40 samples in which GF–AAS detected 

less than 0.8 g/L. However, this apparent 

discrepancy is not unusual because of the 

inherent limitations of measuring samples near

the MDL.

Molybdenum 

All the samples had molybdenum 

concentrations less than the ICP–OES MDL

(about 20 g/L), therefore, only ICP–MS 

could be compared to the GF–AAS. Only 28 

samples composed the data set; 15 samples 

had molybdenum concentrations less than

either the ICP–MS or GF–AAS MDLs. The 

One-sample Sign Test suggested that there 

was no significant difference between ICP–

MS and GF–AAS results (p-value=0.5716, see 

fig. 25) for the sample set having molybdenum concentrations from about 0.4 to 13 

g/L. In addition, no bias was indicated by

the regression analysis (slope=1.00.2). 

Nickel Silver 

Eighty percent of the samples have

nickel concentrations less than the ICP–OES

MDL. Of the seven remaining samples, five

were only two times greater than the MDL of

20 g/L. Two samples having greater than 

100 g/L nickel compared favorably (within 2 

to 20 percent) to the ICP–MS and GF–AAS 

results. The data set used for comparing ICP–

MS to GF–AAS was composed of 34 samples; 

six samples were omitted because the nickel 

concentration was less than the GF–AAS or 

ICP–MS MDL and three because the nickel

concentration exceeded the upper calibration 

limit for ICP–MS. Statistical analysis of the

data set indicates there is a significant

difference between ICP–MS and GF–AAS 

results (p-value=0.0243, see fig. 26) even 

though the median difference was only 

Only one sample had silver at 

concentration levels greater than the GF–AAS

MDL of 0.1 g/L; all the samples were less 

than the ICP–OES MDL. The single GF–

AAS result (2.0 g/L) compared favorably to

the ICP–MS result of 2.1 g/L.

Sodium 

Significant differences between ICP–

OES and F–AAS results (p-value=0.0046, 

n=33, see fig. 28) are suggested by the Onesample Sign Test. Seventy-five percent of the 

ICP–OES results were greater than the 

corresponding F–AAS measurements. The 

median difference was only about 0.7 mg/L

for sodium concentrations ranging from 0.7 to 

38 mg/L. A slight positive bias in the ICP–

DISCUSSION OF RESULTS 32
are provided separately for ICP–OES and 

ICP–MS in the following paragraphs. 

Poor performance in any of the evaluation 

processes for an element is specifically

addressed for each method. 

OES results (slope=1.080.02) might be 

related to differences in calibration standards. 

Strontium 

Thirty-seven samples composed the data

set used to compare the methods; six samples 

were not analyzed because of the lack of 

sample volume. Statistical analysis indicated 

there was no significant difference between 

the method results (p-value=0.9369, see fig.

29b) and no significant bias was implied in the 

regression coefficients. 

Summary of Test Results for 

Inductively Coupled Plasma–Optical 

Emission Spectrometry (ICP–OES)

Most results from Standard Reference 

Water Sample (SRWS) analyses, spike

recoveries for six natural whole-water 

digests, and the analysis of 43 natural 

whole-water digests show that aluminum, 

barium, beryllium, boron, cadmium, 

calcium, copper, iron, lead, lithium, 

magnesium, manganese, molybdenum, 

nickel, silicon, silver, sodium, strontium, 

vanadium, and zinc can be accurately

determined using ICP–OES. Some

calcium, magnesium, manganese, and 

vanadium SRWS data are outside the 1

interval about the most probable value 

(MPV) but within the 1.5 interval that is 

acceptable by National Water Quality

Laboratory (NWQL) criteria. Zinc and 

silver concentrations in one SRWS and 

nickel in two SRWSs are greater than the 

1.5 interval of the MPV. Spike recoveries 

in two ground-water and four surface-water 

sample digests ranged from 90 to 110 

percent for all elements. Elemental results

for a large number of digested natural 

whole-water samples agree with former

methods of analysis for most elements. 

Evaluation of these results for beryllium, 

cadmium, lead, molybdenum, nickel, and 

silver are constrained by a small number of 

sample results because concentrations are 

less than the ICP–OES method detection 

limits (MDLs). All other data indicate that

samples having concentrations greater than

MDL for these elements can be accurately

analyzed. The vanadium and silicon 

evaluations were based only on SRWS and 

Zinc

Twenty-six samples were not included in 

the comparison of ICP–OES, ICP–MS, and 

the former method F–AAS because either the 

zinc concentration was less than ICP–OES or

F–AAS MDLs or the zinc concentration was 

greater than the upper calibration limit for F–

AAS. Statistical analysis of the remaining 17 

samples indicated that there were no significant differences in the results obtained by the 

three methods (p-value=0.8097, see fig. 30b) 

although the mean rank for ICP–OES is 

slightly higher than for F–AAS. The Onesample Sign Test suggested that there was no 

significant difference between ICP–MS and 

F–AAS (p-value=0.8388, n=26, see fig. 30c) 

for the extended data set. However, the slopes 

indicated about a 10-percent negative bias in 

the ICP–MS results compared to only 4 

percent for ICP–OES (fig. 30a). 

CONCLUSIONS

Results from SRWS, spike recoveries

for six natural whole-water digests, and the 

analysis of 43 natural whole-water digests 

were used to evaluate the overall accuracy and 

variability of ICP–OES and ICP–MS. The

conclusions derived from all these test results 

provide an accurate estimate of the expected 

analytical performance of the new methods. 

Summaries of results of the evaluation process 

CONCLUSIONS 33
spike recovery data because former methods 

are not available at NWQL. molybdenum, nickel, selenium, silver, 

strontium, thallium, uranium, and zinc can

be determined accurately by using ICP–

MS. All elemental results were within 

1.5 of the MPV for all SRWSs except

for beryllium and lithium in one SRWS. 

Spike recovery results were 10010 

percent except for beryllium, cadmium, 

chromium, and silver. These elements are 

only marginally outside the 10 percent 

acceptance limit. The spike 

concentrations, however, were generally

less than 10 g/L except for chromium. 

Because of the low spike levels and 

acceptable accuracy for SRWSs and 

whole-water digests, these four elements

can most likely be determined accurately

by ICP–MS. The accuracy achieved in the 

SRWS and spike recovery data for 

antimony, selenium, and silver is not 

strongly supported with whole-water 

digest results because of the small number 

of samples with detectable concentrations. 

Nevertheless, the probability is high that

accurate determination of these elements

can be achieved. 

Only chromium and cobalt exhibited 

unacceptable performance in selected tests. 

Chromium results for whole-water digests 

were consistently more than 50 percent lower

than the former method results even though 

the concentrations were greater than the MDL. 

The suppression of the chromium emission for 

the whole-water digests is apparently not 

being adequately controlled by the yttrium 

internal standard. This suppression is not 

apparent in the SRWS or spike-recovery data 

and could possibly be related to the dissolvedsolid concentration in the digests or an 

unidentified spectral interference. Therefore, 

the determination of chromium by ICP–OES 

is not recommended without further 

investigations. 

The evaluation of the accuracy of cobalt

results for the whole-water digests was 

difficult because of the limited number of 

samples; more than 90 percent of the

measurements were less than the MDL. The 

severe direct-spectral overlap, however, 

prevented accurate cobalt determinations 

whenever the iron concentration exceeded 

2,000 g/L. Because natural whole-water 

digests likely contain substantial amounts of 

iron, the determination of cobalt will always

be problematic. Therefore, the determination 

of cobalt by ICP–OES is recommended only

when samples have less than 2,000 g Fe/L.

Thallium and uranium accuracy is 

based only on SRWS and spike recovery

data because former methods for 

determination of these elements in wholewater digests are not available at NWQL. 

Subsequent to conducting this evaluation, 

a new SRWS (T139) became available that 

has MPV for thallium (3.10.8 g/L) and 

uranium (5.00.2 g/L). ICP–MS results 

for thallium and uranium are within the

1-confidence intervals of the MPVs. 

These elements also are generally

unaffected by spectral interferences 

because of their high masses. 

Summary of Test Results for 

Inductively Coupled Plasma–Mass 

Spectrometry (ICP–MS)

Most results from SRWS analyses, spike 

recoveries for six natural whole-water digests, 

and the analysis of 43 natural whole-water 

digests show that aluminum, antimony, 

barium, beryllium, cadmium, chromium, 

cobalt, copper, lead, lithium, manganese, 

Whole-water digest results for boron 

show considerable deviation from the 

former direct current plasma–atomic 

emission spectrometry (DCP–AES)

CONCLUSIONS 34
method. The slope of the regression indicates 

that ICP–MS results are consistently two times 

greater than the former method. Box plots and 

scattergrams also show considerable variation 

throughout the concentration range. Even 

though SRWS and spike recovery data do not 

indicate any problem for the determination of

boron, apparently some form of interference is 

affecting the accuracy of results. Consequently, the determination of boron by ICP–

MS is not recommended without additional 

investigations. 

Accurate determination of chromium by

ICP–MS has been shown to be acceptable by

the data presented here. Correction for 

chlorine-based molecular ion interference,

however, has been based on matrix matching

the calibration standards to the in-bottle

digests. This method of correction can 

become problematic. In a small number of 

instances, the degree of accuracy has been 

found to be unacceptable. 

The bulleted list below provides a 

succinct outline of the major conclusions of

this report. In addition to analytical 

performance comparisons, suggestions are 

provided for selecting appropriate methodology and the potential effect of the ICP–

OES and ICP–MS methods on long-term trend 

analysis in water-quality studies. 

 MDLs for ICP–MS are between 5 

and 1,000 times lower than ICP–OES. ICP–

MS MDLs are similar in magnitude to former

graphite furnace–atomic absorption spectrophotometry (GF–AAS) methods and MDLs

for both ICP–MS and ICP–OES are much 

lower than former flame–atomic absorption 

spectrophotometry (F–AAS) methods. 

 The short- and long-term accuracy of 

ICP–OES and ICP–MS was acceptable for the 

reference materials studied. Greater than 90 

percent of the elements were within 1 of 

the most probable value. 

 For most elements, ICP–MS is

the method of choice whenever 

concentrations are less than 100 g/L. 

Conversely, ICP–OES performs better at 

concentrations greater than 1,000 g/L.

 The median long-term variability

in elemental results from a simulated wholewater sample (SRWS WW-1) was 2 to 3 

times lower for ICP–MS than for ICP–OES. 

Nevertheless, there was somewhat less 

variability in results from ICP–OES for

lighter elements (< 60 amu) and whenever 

elemental concentrations were greater than 

100 g/L.

 Short-term analytical variability

decreased with method sensitivity; therefore, 

there is less variability in results from ICP–

MS, especially at lower concentration levels.

 Matrix interferences affected the 

determination of lighter elements (< 60 amu) 

in selected samples by ICP–MS; however, 

the maximum error was 25 percent.

 Data from 43 surface- and groundwater samples indicated there was no 

significant method bias for 90 percent of the 

elements tested. Only chromium (by ICP–

OES) and boron (by ICP–MS) results were 

unacceptably biased.

 Data from ICP–MS will have the

highest probability of affecting long-term 

trends in water-quality studies. For

example, more than 50 percent of the wholewater digests analyzed had cadmium,

chromium, lead, molybdenum, nickel, and 

zinc concentrations less than the ICP–OES 

MDLs. The level of accuracy and variability

for concentrations less than 100 g/L 

will be substantially different than for

CONCLUSIONS 35
handbook for mass spectrometry

applications: Sturbridge, Mass., 

64 p. 

most former methods. Data from ICP–OES will 

have somewhat less of an effect.

 ICP–OES and ICP–MS are state-ofthe-art multielement techniques that are more

efficient and cost effective than former USGS 

single-element methods such as F–AAS, GF–

AAS, or DCP–AES. For these reasons they are 

the methods of choice. 

Hoffman, G.L., Fishman, M.J., and 

Garbarino, J.R., 1996, Methods of 

analysis by the U.S. Geological 

Survey National Water Quality

Laboratory—In-bottle acid digestion 

of whole-water samples: U.S. 

Geological Survey Open-File Report 

96-225, 28 p. 

REFERENCES CITED 

American Society for Testing and Materials, 

1995, Annual book of ASTM standards, 

Section 11, Water (D1193, Standard 

specification for reagent water): 

Philadelphia, v. 11.01, p. 122–124. 

Montaser, Akbar, and Golightly, D.W., 

eds., 1992, Inductively coupled 

plasmas in analytical atomic

spectrometry: New York, VCH 

Publishers, Inc., 2nd Edition, 1017 p. 

Boumans, P.W.J.M., ed., 1987a, Inductively

coupled plasma emission spectroscopy—

Part I, Methodology, instrumentation, 

and performance: New York, John 

Wiley & Sons, 584 p. 

Thermo Jarrell-Ash, 1991, Operator’s 

manual: Franklin, Mass. 

U.S. Environmental Protection Agency, 

1992, Methods for the determination 

of metals in environmental samples: 

Boca Raton, CRC Press, Inc., 339 p. ______1987b, Inductively coupled plasma 

emission spectroscopy—Part II,

Applications and fundamentals: New 

York, John Wiley & Sons, 486 p. ______1994, Guidelines establishing test 

procedures for the analysis of 

pollutants (Part 136, Appendix B. 

Definition and Procedure for the 

Determination of the Method 

Detection Limit—Revision 1.11): 

U.S. Code of Federal Regulations, 

Title 40, Revised as of July 1, 1994, 

p. 635–637. 

Fishman, M.J., and Friedman, L.C., 1989, 

Methods for determination of inorganic 

substances in water and fluvial 

sediments: U.S. Geological Survey

Techniques of Water-Resources 

Investigations, book 5, chap. A1, 545 p. 

Fishman, M.J., ed., 1993, Methods of analysis 

by the U.S. Geological Survey National 

Water Quality Laboratory—

Determination of inorganic and organic 

constituents in water and fluvial

sediments: U.S. Geological Survey

Open-File Report 93-125, 217 p. 

VG Elemental, 1988, PlasmaQuad 

operators manual: Beverly, Mass., 

164 p. 

______1994, PlasmaQuad PQVision 

software manual, 335 p. 

Galileo Electro-Optic Corporation, 1991, 

Channeltron electron multiplier 

CONCLUSIONS 36
APPENDIX 

Figures 1 – 30 

Tables 8 – 20 

CONCLUSIONS 37
Internal standard,

surfactant

Sample

4-turn coil Peristaltic

pump

0.80 mL/min

0.16 mL/min

nebulizer

To

Peristaltic pump tubing color code

0.16 mL/min orange/yellow

0.80 mL/min red

 mL/min, milliliters per minute

Figure 1a. Sample introduction manifold for inductively coupled plasma–optical 

emission spectrometric method. 

Wa Debubbler ste

Internal standard,

surfactant

Air

Sample

12-turn coil Peristaltic

pump

1 mL/min

0.05 mL/min

0.10 mL/min

0.32 mL/min

nebulizer

To

Peristaltic pump tubing color code

0.32 mL/min black

0.10 mL/min orange/green

0.05 mL/min orange/blue

1 mL/min gray

 mL/min, milliliters per minute

Figure 1b. Sample introduction manifold for inductively coupled plasma–mass spectrometric

method.

APPENDIX 39
0 200 400 600 800

0

2

4

6

8

10

AP

P

ARE

N

T 65Cu C

O

N

C

E

NTRATION,

IN MICROGRA

MS PER LIT

ER [

Y] SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER [X]

Figure 2a. Sulfate interference on copper determinations by inductively coupled plasma–mass

spectrometry. The linear regression equation is y = 0.021 + 0.013x (R2

 = 0.9999). 

0 200 400 600 800

0

1

2

3

4

5

6

APPAR

E

N

T 66Zn C

O

N

C

E

NTR

A

TIO

N,

IN MICROG

R

AMS

P

E

R LITER [Y]

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER [X]

Figure 2b. Sulfate interference on zinc determinations by inductively coupled plasma–mass

spectrometry. The linear regression equation is y = 0.48 + 0.0068x (R2

 = 0.9977). 

APPENDIX 40
0 200 400 600 800 1000

0

200

400

600

800

E

XPERIM

ENTAL S

ULFATE CON

C

E

NTRATION,

IN 

MIL

LIGRAM

S P

ER LITER [Y]

THEORETICAL SULFATE CONCENTRATION,

IN MILLIGRAMS PER LITER [X]

Figure 3. Accuracy of inductively coupled plasma–mass spectrometric sulfate determinations

using 32S16O+

 response. The polynomial regression equation is y = –7.9 + 1.2x – 0.0004x2 

(R2

 = 0.9998). Error bars represent 1 standard deviation. 

0 100 200 300 400 500 600

24

26

28

30

32

34

36 Uncorrected

 Corrected

65Cu CON

C

E

N

T

RATIO

N,

IN MICR

O

GRAM

S PER LIT

E

R

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 4a. Accuracy of sulfate interference corrections on copper determinations by inductively

coupled plasma–mass spectrometry. 

APPENDIX 41
0 100 200 300 400 500 600

24

26

28

30

32

34

Uncorrected

Corrected

66Zn C

ONCE

N

T

RATION,

IN MIC

R

O

G

R

AMS P

E

R LITER

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 4b. Accuracy of sulfate interference corrections on zinc determinations by inductively

coupled plasma–mass spectrometry. 

APPENDIX 42
150

175

200

225

250

275

300

ALUMINUM

180

190

200

210

BARIUM

9

10

11

12

13

BERYLLIUM

100

110

120

130

140

150

160 BORON

10

12

14

16

18

CADMIUM

10

11

12

13

14

CALCIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

8

10

12

14

16

18

CHROMIUM

MPV ICP-OES

9

10

11

12

13

14

15 COBALT

MPV ICP-OES

27

28

29

30

31

32

33

CONCENTRATION, IN MICROGRAMS PER LITER

COPPER

Figure 5a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T107. Error bars represent 1 standard deviation from the mean. 

APPENDIX 43
40

45

50

55

60

IRON

170

180

190

200

210

LITHIUM

1.75

2.00

2.25

2.50

MAGNESIUM,

IN MILLIGRAMS PER LITER

35

40

45

50

55

MANGANESE

10

15

20

25

30

35

NICKEL

7.0

7.5

8.0

8.5

SILICA,

IN MILLIGRAMS PER LITER

MPV ICP-OES

4

6

8

10

12

14

16

18

20

SILVER

MPV ICP-OES

18

19

20

21

22

23

SODIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

50

55

60

65

70

CONCEN

T

RATION, I

N MIC

R

O

G

RAM

S PER LI

T

E

R

STRONTIUM

Figure 5a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T107—Continued. 

APPENDIX 44
MPV ICP-OES

10

12

14

16

18

CON

C

ENTRATION, IN MI

CROGRAMS P

E

R LITE

R

VANADIUM

MPV ICP-OES

60

65

70

75

80

85

90 ZINC

Figure 5a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T107—Continued. 

APPENDIX 45
150

175

200

225

250

275

300

ALUMINUM

5

7

9

11

13

15

ANTIMONY BARIUM

180

185

190

195

200

205

210

BERYLLIUM

9

10

11

12

13

14

15

16

BORON

100

110

120

130

140

150

160

170

180

CADMIUM

11

12

13

14

15

16

17

MPV ICP-MS

10

12

14

16

18

20

CHROMIUM

MPV ICP-MS

9

10

11

12

13

14

COBALT

MPV ICP-MS

27

28

29

30

31

32

33

CONCENTRATION, I

N MIC

ROGRAMS P

ER 

LIT

E

R

COPPER

Figure 5b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T107. Error

bars represent 1 standard deviation from the mean. 

APPENDIX 46
20

22

24

26

28

30

32

LEAD

175

185

195

205

215

225

235

245

LITHIUM

35

40

45

50

55

MANGANESE

12

13

14

15

16

17

18

MOLYBDENUM

22

24

26

28

30

32

34

NICKEL

8

9

10

11

12

13

14 SELENIUM

MPV ICP-MS

9

10

11

12

13

14

15

SILVER

MPV ICP-MS

56

58

60

62

64

66

STRONTIUM

MPV ICP-MS

60

65

70

75

80

85

90

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

ZINC

Figure 5b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T107—

Continued. 

APPENDIX 47
125

150

175

200

225

ALUMINUM

40

42

44

46

48

BARIUM

11

12

13

14

15

16

BERYLLIUM

15

20

25

30

35

40

BORON

0

2

4

6

CADMIUM

10

11

12

13

CALCIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

16

18

20

22

CHROMIUM

MPV ICP-OES

2

4

6

8 COBALT

MPV ICP-OES

35

40

45

50

55

C

ONC

E

NTRATION, I

N MI

C

R

OGRAM

S P

E

R LITE

R

IRON

Figure 6a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T119. Error bars represent 1 standard deviation from the mean. 

APPENDIX 48
55

57

59

61

63

65

LITHIUM

2.8

2.9

3.0

3.1

3.2

3.3

3.4

MAGNESIUM,

IN MILLIGRAMS PER LITER

30

32

34

36

38

40

MANGANESE

0

5

10

15

20

25

MOLYBDENUM

5

10

15

20

25

30

NICKEL

8.4

8.6

8.8

9.0

9.2

9.4

9.6

SILICA,

IN MILLIGRAMS PER LITER

MPV ICP-OES

0

2

4

6

SILVER

MPV ICP-OES

19

20

21

22

SODIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

66

68

70

72

74

76

78

80

CONCENT

RATION, I

N MICROG

RAMS PER LI

T

E

R

STRONTIUM

Figure 6a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T119—Continued. 

APPENDIX 49
MPV ICP-OES

2

3

4

5

6

7

CONCENTRATION, I

N MIC

R

O

GRA

M

S

PER LIT

E

R

VANADIUM

MPV ICP-OES

15

20

25

30

35 ZINC

Figure 6a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T119—Continued. 

APPENDIX 50
130

140

150

160

170

180

190

200

210

ALUMINUM

6

7

8

9

10

11

ANTIMONY BARIUM

40

42

44

46

48

50

BERYLLIUM

11

12

13

14

15

16

17

BORON

10

20

30

40

50

CADMIUM

2.25

2.50

2.75

3.00

3.25

MPV ICP-MS

16

17

18

19

20

21

22

CHROMIUM

MPV ICP-MS

4.0

4.5

5.0

5.5

6.0

6.5

COBALT

MPV ICP-MS

0.5

1.0

1.5

2.0

2.5

3.0

3.5

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

COPPER

Figure 6b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T119. Error

bars represent 1 standard deviation from the mean. 

APPENDIX 51
5.0

5.5

6.0

6.5

7.0

7.5

8.0

LEAD

50

55

60

65

70

LITHIUM

30

32

34

36

38

40

MANGANESE

9

10

11

12

13

14

15

MOLYBDENUM

17

19

21

23

25

NICKEL

8

9

10

11

12 SELENIUM

MPV ICP-MS

1

2

3

4

5

6

SILVER

MPV ICP-MS

60

65

70

75

80

STRONTIUM

MPV ICP-MS

18

21

24

27

30

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

ZINC

Figure 6b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T119—

Continued. 

APPENDIX 52
40

45

50

55

60

65

70

ALUMINUM

130

135

140

145

150

155

160

BARIUM

32

34

36

38

BERYLLIUM

270

280

290

300

310

320 BORON

22

24

26

CADMIUM

6.50

6.75

7.00

7.25

7.50

CALCIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

30

35

40

45

50

CHROMIUM

MPV ICP-OES

10

15

20

25

30 COBALT

MPV ICP-OES

80

82

84

86

88

90

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

COPPER

Figure 7a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T133. Error bars represent 1 standard deviation from the mean. 

APPENDIX 53
20

25

30

35

40

IRON

45

47

49

51

53

55

LITHIUM

5.25

5.50

5.75

6.00

6.25

MAGNESIUM,

IN MILLIGRAMS PER LITER

110

115

120

125

130

MANGANSE

25

35

45

55

65

MOLYBDENUM

10

15

20

25

30

35

40

NICKEL

MPV ICP-OES

9.0

9.5

10.0

10.5

11.0

SILICA,

IN MILLIGRAMS PER LITER

MPV ICP-OES

5.5

6.0

6.5

7.0

7.5

8.0

8.5

SILVER

MPV ICP-OES

28

29

30

31

CONCEN

T

RATION, I

N MICROGRAMS PER LIT

E

R

SODIUM,

IN MILLIGRAMS PER LITER

Figure 7a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T133—Continued. 

APPENDIX 54
MPV ICP-OES

115

120

125

130

135

STRONTIUM

MPV ICP-OES

8

10

12

14

16

VANADIUM

MPV ICP-OES

30

40

50

60

ZINC

CONCENTRATION, I

N MICRO

G

RA

M

S PE

R LI

T

E

R

Figure 7a. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T133—Continued. 

APPENDIX 55
40

45

50

55

60

65

70

ALUMINUM

9

11

13

15

17

19 ANTIMONY BARIUM

130

135

140

145

150

155

160

BERYLLIUM

30

32

34

36

38

40

BORON

270

280

290

300

310

320

330

CADMIUM

20

21

22

23

24

25

26

MPV ICP-MS

34

36

38

40

42

44

CHROMIUM

MPV ICP-MS

18

19

20

21

22

COBALT

MPV ICP-MS

80

82

84

86

88

90

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

COPPER

Figure 7b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T133. Error

bars represent 1 standard deviation from the mean. 

APPENDIX 56
24

26

28

30

32

34

LEAD

48

50

52

54

56 LITHIUM

110

115

120

125

130

MANGANESE

35

40

45

50

55

MOLYBDENUM

23

25

27

29

31

NICKEL

16

18

20

22

24

26 SELENIUM

MPV ICP-MS

6

7

8

9

SILVER

MPV ICP-MS

115

120

125

130

STRONTIUM

MPV ICP-MS

45

50

55

60

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

ZINC

Figure 7b. Long-term inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample T133—

Continued. 

APPENDIX 57
0

5

10

15

20

ALUMINUM

60

65

70

75

80

BARIUM

55

57

59

61

63

65

BERYLLIUM

0

5

10

15

20

25 BORON

45

47

49

51

53

55

CADMIUM

9.5

10.0

10.5

11.0

11.5

CALCIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

70

75

80

85

90

CHROMIUM

MPV ICP-OES

35

37

39

41

43

45 COBALT

MPV ICP-OES

50

55

60

65

70

CONCENTRATION, I

N MICROGRAMS PER LIT

E

R

COPPER

Figure 8. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T135. Error bars represent 1 standard deviation from the mean. 

APPENDIX 58
210

220

230

240

250

IRON

80

90

100

110

120

130

LEAD

65

70

75

80

85

LITHIUM

1.85

1.90

1.95

2.00

2.05

2.10

2.15

MAGNESIUM,

IN MILLIGRAMS PER LITER

390

400

410

420

430

440

450

MANGANESE

50

55

60

65

70

75

80

MOLYBDENUM

MPV ICP-OES

45

50

55

60

65

70

75

NICKEL

MPV ICP-OES

3.9

4.1

4.3

4.5

4.7

4.9

SILICA,

IN MILLIGRAMS PER LITER

MPV ICP-OES

8

9

10

11

12

13

14

CONCENTRATION, I

N MICROGRAMS PER LITER

SILVER

Figure 8. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T135—Continued. 

APPENDIX 59
28

29

30

31

32

33

SODIUM,

IN MILLIGRAMS PER LITER

MPV ICP-OES

42

44

46

48

50

STRONTIUM

MPV ICP-OES

48

50

52

54

56

58

VANADIUM

MPV ICP-OES

35

40

45

50

55

ZINC

CONCEN

T

RATION, I

N MI

C

ROGRAMS

P

E

R LI

T

E

R

Figure 8. Short-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

results in relation to the most probable value (MPV) for Standard Reference Water Sample 

T135—Continued. 

APPENDIX 60
0

5,000

10,000

15,000

ALUMINUM

0

2

4

6

8

ANTIMONY

100

120

140

160

180

200

BARIUM

7

8

9

10

11

BERYLLIUM

MPV ICP-OES ICP-MS

-15

0

15

30

45

60

75

BORON

MPV ICP-OES ICP-MS

3

4

5

6

7

8

9

C

O

N

C

E

N

T

RATIO

N, IN MIC

R

O

G

RA

M

S P

E

R LIT

E

R

CADMIUM

Figure 9. Long-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

and inductively coupled plasma–mass spectrometric (ICP–MS) results in relation to the most

probable value (MPV) for Standard Reference Water Sample WW-1. Error bars represent 1 

standard deviation from the mean. 

APPENDIX 61
16

17

18

19

20

CALCIUM,

IN MILLIGRAMS PER LITER

15

20

25

30

35

CHROMIUM

10

12

14

16

18

20

COBALT

20

24

28

32

36

40

COPPER

MPV ICP-OES ICP-MS

8,000

10,000

12,000

14,000

16,000

18,000

20,000

IRON

MPV ICP-OES ICP-MS

15

20

25

30

35

CON

CENTRATIO

N, I

N MICROGRA

M

S P

ER LITER

LEAD

Figure 9. Long-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

and inductively coupled plasma–mass spectrometric (ICP–MS) results in relation to the most

probable value (MPV) for Standard Reference Water Sample WW-1—Continued. 

APPENDIX 62
10

15

20

25

LITHIUM

5

6

7

8

9

MAGNESIUM,

IN MILLIGRAMS PER LITER

500

520

540

560

580

600

620

640

660

MANGANESE

2

3

4

5

6

7

8

MOLYBDENUM

MPV ICP-OES ICP-MS

10

20

30

40

50

NICKEL

MPV ICP-OES ICP-MS

3

4

5

6

7

8

CONCENTRATION, IN MICROG

RA

MS PER LIT

E

R

SELENIUM

Figure 9. Long-term inductively coupled plasma–optical emission spectrometric (ICP–OES)

and inductively coupled plasma–mass spectrometric (ICP–MS) results in relation to the most

probable value (MPV) for Standard Reference Water Sample WW-1—Continued. 

APPENDIX 63
10

20

30

40

50

SILICA,

IN MILLIGRAMS PER LITER

0

1

2

3

4

5

SILVER

16

18

20

22

SODIUM,

IN MILLIGRAMS PER LITER

75

80

85

90

95

STRONTIUM

MPV ICP-OES ICP-MS

10

15

20

25

30

35

VANADIUM

MPV ICP-OES ICP-MS

50

60

70

80

90

100

110

CON

CENTRATION, I

N MICROGRA

MS PER LITER

ZINC

Figure 9. Long-term inductively coupled plasma–optical emission spectrometric

(ICP–OES) and inductively coupled plasma–mass spectrometric (ICP–MS) results in 

relation to the most probable value (MPV) for Standard Reference Water Sample 

WW-1—Continued. 

APPENDIX 64
APPENDIX 65 

Figure 10a. Scattergrams and regression 

analyses showing aluminum whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former direct current 

plasma–atomic emission spectrometric (DCP–

AES) method. Concentrations are in 

micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 10b. Box plots and Kruskal-Wallis Test 

results showing aluminum data from the former 

direct current plasma–atomic emission 

spectrometric (DCP–AES) method (group 3), 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

-5000

0

5000

10000

15000

20000

25000

DCP-AES, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

0

0.05

0.9750

0.05

0.9750

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

25 931.00 37.24

25 954.00 38.16

25 965.00 38.60

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method

-5000

0

5000

10000

15000

20000

ICP-OES, in μg/L

-5000 0 5000 10000 15000 20000 25000

DCP-AES, in μg/L

Scattergram

62.58 -45.25 170.40

0.88 0.86 0.90

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. DCP-AES, in μg/L

-5000

0

5000

10000

15000

20000

25000

ICP-MS, in μg/L

-5000 0 5000 10000 15000 20000 25000

DCP-AES, in μg/L

Scattergram

-3.85 -108.17 100.47

1.04 1.03 1.06

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. DCP-AES, in μg/L
APPENDIX 66

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 11. Scattergram, box plots, Paired t-Test 

results, and regression coefficients showing 

antimony data from the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method and inductively coupled 

plasma–mass spectrometry (ICP–MS) for wholewater digests. Concentrations are in 

micrograms per liter (g/L). 

Figure 12a. Scattergrams and regression 

analyses showing barium whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method. 

Concentrations are in micrograms per liter 

(g/L). 

-2

0

2

4

6

8

ICP-MS, in μg/L

-2 0 2 4 6 8

GF-AAS, in μg/L

Scattergram

-2

0

2

4

6

8

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

-0.14 -2.77 2.49

1.35 0.31 2.38

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

0.62 8 1.09 0.3061

Mean Diff. DF t-Value P-Value

ICP-MS, in μg/L, GF-AAS, ...

Paired t-test

Hypothesized Difference = 0

-100

0

100

200

300

400

500

600

700

800

ICP-OES, in μg/L

-100 0 100 200 300 400 500 600 700 800

F-AAS, in μg/L

Scattergram

69.55 11.60 127.50

0.63 0.42 0.84

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-100

0

100

200

300

400

500

600

700

800

ICP-MS, in μg/L

-100 0 100 200 300 400 500 600 700 800

F-AAS, in μg/L

Scattergram

53.08 -8.49 114.64

0.78 0.56 1.01

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L
APPENDIX 67

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 12b. Box plots and Kruskal-Wallis Test 

results showing barium data from the former 

flame–atomic absorption spectrophotometric (F–

AAS) method (group 3), inductively coupled 

plasma–optical emission spectrometry (ICP–

OES, group 1), and inductively coupled plasma–

mass spectrometry (ICP–MS, group 2) for 

whole-water digests. Concentrations are in 

micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 12c. Scattergram, box plots, Onesample Sign Test, and regression coefficients 

showing barium data from inductively coupled 

plasma–optical emission spectrometry (ICP–

OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

-100

0

100

200

300

400

500

600

700

800

ICP-MS, in μg/L

-100 0 100 200 300 400 500 600 700 800

ICP-OES, in μg/L

Scattergram

-7.55 -14.77 -0.34

1.13 1.09 1.17

Coefficient 95% Low er 95% Upper

Intercept

ICP-OES, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. ICP-OES, in μg/L

-100

0

100

200

300

400

500

600

700

800

ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

13

30

0

0.0137

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

0

100

200

300

400

500

600

700

800

F-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

4

1.96

0.3754

1.96

0.3749

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

20 667.00 33.35

20 641.00 32.05

20 522.00 26.10

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method
APPENDIX 68

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 13. Scattergram, box plots, Paired t-Test 

results, and regression coefficients showing 

beryllium data from inductively coupled 

plasma–optical emission spectrometry (ICP–

OES) and inductively coupled plasma–mass 

spectrometry (ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

Figure 14a. Scattergrams and regression 

analyses showing boron whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former direct current 

plasma–atomic emission spectrometric (DCP–

AES) method. Concentrations are in 

micrograms per liter (g/L). 

-50

0

50

100

150

200

250

300

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300

DCP-AES, in μg/L

Scattergram

-17.79 -50.30 14.71

2.01 1.27 2.74

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. DCP-AES, in μg/L

-50

0

50

100

150

200

250

300

ICP-OES, in μg/L

-50 0 50 100 150 200 250 300

DCP-AES, in μg/L

Scattergram

3.92 -9.12 16.96

0.67 0.38 0.97

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. DCP-AES, in μg/L

-2

0

2

4

6

8

10

12

14

ICP-MS, in μg/L

-2 0 2 4 6 8 10 12 14

ICP-OES, in μg/L

Scattergram

0.18 -0.37 0.72

1.04 0.93 1.14

Coefficient 95% Low er 95% Upper

Intercept

ICP-OES, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. ICP-OES, in μg/L

-2

0

2

4

6

8

10

12

14

ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

-0.30 4 -2.16 0.0974

Mean Diff. DF t-Value P-Value

ICP-OES, in μg/L, ICP-MS, ...

Paired t-test

Hypothesized Difference = 0
APPENDIX 69

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 14b. Box plots and Kruskal-Wallis Test 

results showing boron data from the former 

direct current plasma–atomic emission 

spectrometric (DCP–AES) method (group 3), 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 14c. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing boron data from the former 

direct current plasma–atomic emission 

spectrometric (DCP–AES) method and 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES) for whole-water 

digests. Concentrations are in micrograms per 

liter (g/L).

-50

0

50

100

150

200

250

300

DCP-AES, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

2

12.37

0.0021

12.37

0.0021

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

28 855.00 30.54

28 1495.00 53.39

28 1220.00 43.57

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method

-200

0

200

400

600

800

1000

ICP-OES, in μg/L

-200 0 200 400 600 800 1000

DCP-AES, in μg/L

Scattergram

-200

0

200

400

600

800

1000

DCP-AES, in μg/L ICP-OES, in μg/L

Box Plot

-8.41 -14.60 -2.21

1.00 0.97 1.03

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. DCP-AES, in μg/L

25

11

0

0.0288

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 70

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 14d. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing boron data from the former 

direct current plasma–atomic emission 

spectrometric (DCP–AES) method and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 15. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing cadmium data from the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method and inductively coupled 

plasma–mass spectrometry (ICP–MS) for wholewater digests. Concentrations are in 

micrograms per liter (g/L). 

-50

0

50

100

150

200

250

300

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300

DCP-AES, in μg/L

Scattergram

-17.79 -50.30 14.71

2.01 1.27 2.74

Coefficient 95% Low er 95% Upper

Intercept

DCP-AES, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. DCP-AES, in μg/L

-50

0

50

100

150

200

250

300

DCP-AES, in μg/L ICP-MS, in μg/L

Box Plot

5

23

0

0.0009

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-1

0

1

2

3

4

5

6

7

ICP-MS, in μg/L

-1 0 1 2 3 4 5 6 7

GF-AAS, in μg/L

Scattergram

0.03 -2.02E-3 0.06

1.00 0.98 1.02

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-1

0

1

2

3

4

5

6

7

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

8

19

0

0.0522

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 71

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 16. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing calcium data from the former flame–

atomic absorption spectrophotometric (F–AAS) 

method and inductively coupled plasma–optical 

emission spectrometry (ICP–OES) for wholewater digests. Concentrations are in milligrams 

per liter (mg/L). 

Figure 17a. Scattergrams and regression 

analyses showing chromium whole-water 

digest data from inductively coupled plasma–

optical emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method. Concentrations are in 

micrograms per liter (g/L). 

-20

0

20

40

60

80

100

120

140

160

180

ICP-OES, in μg/L

-20 0 20 40 60 80 100 120 140 160 180

GF-AAS, in μg/L

Scattergram

3.86E-3 -2.54 2.55

0.52 0.47 0.58

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. GF-AAS, in μg/L

-20

0

20

40

60

80

100

120

140

160

180

ICP-MS, in μg/L

-20 0 20 40 60 80 100 120 140 160 180

GF-AAS, in μg/L

Scattergram

3.76 1.01 6.51

1.04 0.98 1.09

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

0

10

20

30

40

50

60

70

ICP-OES, in mg/L

0 10 20 30 40 50 60 70

F-AAS, in mg/L

Scattergram

0.48 -0.42 1.38

1.03 1.00 1.06

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in mg/L

Confidence Intervals

ICP-OES, in mg/L vs. F-AAS, in mg/L

0

10

20

30

40

50

60

70

F-AAS, in mg/L ICP-OES, in mg/L

Box Plot

3

29

0

<0.0001

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 72

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 17b. Box plots and Kruskal-Wallis Test 

results showing chromium data from the former 

graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method (group 3), 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and inductively 

coupled plasma–mass spectrometry (ICP–MS, 

group 2) for whole-water digests. Concentrations 

are in micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 17c. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing chromium data from the 

former graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method and 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES) for whole-water 

digests. Concentrations are in micrograms per 

liter (g/L). 

2

3

0

9.71

0.0078

9.71

0.0078

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

15 225.00 15.00

15 447.00 29.80

15 363.00 24.20

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method

-20

0

20

40

60

80

100

120

140

160

180

GF-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

-20

0

20

40

60

80

100

120

140

160

ICP-OES, in μg/L

-20 0 20 40 60 80 100 120 140 160

GF-AAS, in μg/L

Scattergram

3.86E-3 -2.54 2.55

0.52 0.47 0.58

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. GF-AAS, in μg/L

-20

0

20

40

60

80

100

120

140

160

GF-AAS, in μg/L ICP-OES, in μg/L

Box Plot

15

0

0

<0.0001

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 73

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 17d. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing chromium data from the 

former graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

Figure 18a. Scattergrams and regression 

analyses showing cobalt whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method. Concentrations are in 

micrograms per liter (g/L). 

-20

0

20

40

60

80

100

120

140

160

180

ICP-MS, in μg/L

-20 0 20 40 60 80 100 120 140 160 180

GF-AAS, in μg/L

Scattergram

3.24 1.53 4.94

1.04 1.00 1.09

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-20

0

20

40

60

80

100

120

140

160

180

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

3

23

0

<0.0001

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-50

0

50

100

150

200

250

300

350

400

ICP-OES, in μg/L

-50 0 50 100 150 200 250 300 350 400

GF-AAS, in μg/L

Scattergram

193.26 -175.66 562.18

-0.61 -6.40 5.18

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. GF-AAS, in μg/L

10

20

30

40

50

60

70

80

90

100

ICP-MS, in μg/L

10 20 30 40 50 60 70 80 90 100

GF-AAS, in μg/L

Scattergram

1.10 -15.19 17.40

0.85 0.60 1.11

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L
APPENDIX 74

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 18b. Box plots and Kruskal-Wallis Test 

results showing cobalt data from the former 

graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method (group 

3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 18c. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing cobalt data from the former 

graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

-50

0

50

100

150

200

250

300

350

400

GF-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

0

5.24

0.0728

5.24

0.0728

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

6 81.00 13.50

6 41.00 6.83

6 49.00 8.17

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method

-20

0

20

40

60

80

100

ICP-MS, in μg/L

-20 0 20 40 60 80 100

GF-AAS, in μg/L

Scattergram

0.16 -0.85 1.16

0.87 0.83 0.90

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-20

0

20

40

60

80

100

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

24

7

0

0.0033

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 75

Figure 19a. Scattergrams and regression 

analyses showing copper whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method. Concentrations are in 

micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 19b. Box plots and Kruskal-Wallis Test 

results showing copper data from the former 

graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method (group 

3), inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

-50

0

50

100

150

200

250

300

350

400

ICP-OES, in μg/L

-50 0 50 100 150 200 250 300 350 400

GF-AAS, in μg/L

Scattergram

-1.30 -13.71 11.11

0.93 0.79 1.07

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. GF-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300 350 400

GF-AAS, in μg/L

Scattergram

-2.81 -13.36 7.74

1.04 0.92 1.16

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

GF-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

0

1.28

0.5285

1.28

0.5285

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

28 1071.00 38.25

28 1248.00 44.57

28 1251.00 44.68

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method
APPENDIX 76

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 19c. Scattergram, box plots, Onesample Sign Test results, and regression 

coefficients showing copper data from the 

former graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 20. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing iron data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method 

and inductively coupled plasma–optical emission 

spectrometry (ICP–OES) for whole-water 

digests. Concentrations are in micrograms per 

liter (g/L). 

-50

0

50

100

150

200

250

300

350

400

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300 350 400

GF-AAS, in μg/L

Scattergram

-1.61 -8.17 4.95

1.03 0.94 1.12

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

19

23

0

0.6440

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

ICP-OES, in μg/L

-2000 2000 6000 10000 14000

F-AAS, in μg/L

Scattergram

56.02 -111.77 223.81

0.87 0.84 0.90

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

F-AAS, in μg/L ICP-OES, in μg/L

Box Plot

30

7

1

0.0002

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 77

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 21. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing lead data from the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method and inductively coupled 

plasma–mass spectrometry (ICP–MS) for wholewater digests. Concentrations are in 

micrograms per liter (g/L). 

Figure 22a. Scattergrams and regression 

analyses showing lithium whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method. 

Concentrations are in micrograms per liter 

(g/L). 

-10

0

10

20

30

40

50

60

70

80

ICP-MS, in μg/L

-10 0 10 20 30 40 50 60 70 80

GF-AAS, in μg/L

Scattergram

0.12 -1.19 1.43

0.98 0.92 1.04

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-10

0

10

20

30

40

50

60

70

80

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

12

19

0

0.2810

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-20

0

20

40

60

80

100

120

ICP-OES, in μg/L

-20 0 20 40 60 80 100 120

F-AAS, in μg/L

Scattergram

1.93 -2.10 5.96

0.90 0.81 1.00

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-20

0

20

40

60

80

100

120

ICP-MS, in μg/L

-20 0 20 40 60 80 100 120

F-AAS, in μg/L

Scattergram

-2.49 -7.48 2.50

1.14 1.03 1.26

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L
APPENDIX 78

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 22b. Box plots and Kruskal-Wallis Test 

results showing lithium data from the former 

flame–atomic absorption spectrophotometric (F–

AAS) method (group 3), inductively coupled 

plasma–optical emission spectrometry (ICP–

OES, group 1), and inductively coupled plasma–

mass spectrometry (ICP–MS, group 2) for 

whole-water digests. Concentrations are in 

micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 23. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing magnesium data from the former 

flame–atomic absorption spectrophotometric (F–

AAS) method and inductively coupled plasma–

optical emission spectrometry (ICP–OES) for 

whole-water digests. Concentrations are in 

milligrams per liter (mg/L). 

-20

0

20

40

60

80

100

120

F-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

7

0.17

0.9191

0.17

0.9191

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

27 1066.00 39.48

27 1128.00 41.78

27 1127.00 41.74

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method

-10

0

10

20

30

40

50

60

ICP-OES, in mg/L

-10 0 10 20 30 40 50 60

F-AAS, in mg/L

Scattergram

0.78 0.07 1.49

0.93 0.90 0.96

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in mg/L

Confidence Intervals

ICP-OES, in mg/L vs. F-AAS, in mg/L

19

23

0

0.6440

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-10

0

10

20

30

40

50

60

F-AAS, in mg/L ICP-OES, in mg/L

Box Plot
APPENDIX 79

Figure 24a. Scattergrams and regression 

analyses showing manganese whole-water 

digest data from inductively coupled plasma–

optical emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 24b. Box plots and Kruskal-Wallis Test 

results showing manganese data from the 

former flame–atomic absorption 

spectrophotometric (F–AAS) method (group 3), 

inductively coupled plasma–optical emission 

spectrometry (ICP–OES, group 1), and 

inductively coupled plasma–mass spectrometry 

(ICP–MS, group 2) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

-200

0

200

400

600

800

1000

ICP-OES, in μg/L

-200 0 200 400 600 800 1000

F-AAS, in μg/L

Scattergram

-3.91 -15.84 8.02

0.99 0.95 1.04

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-200

0

200

400

600

800

1000

ICP-MS, in μg/L

-200 0 200 400 600 800 1000

F-AAS, in μg/L

Scattergram

-6.24 -20.07 7.59

0.94 0.89 0.98

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L

-200

0

200

400

600

800

1000

F-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

3

0.29

0.8669

0.29

0.8669

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

36 1960.00 54.44

36 1892.00 52.56

36 2034.00 56.50

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method
APPENDIX 80

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 25. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing molybdenum data from the former 

graphite furnace–atomic absorption 

spectrophotometric (GF–AAS) method and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 26. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing nickel data from the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method and inductively coupled 

plasma–mass spectrometry (ICP–MS) for wholewater digests. Concentrations are in 

micrograms per liter (g/L). 

-2

0

2

4

6

8

10

12

14

16

18

20

ICP-MS, in μg/L

-2 0 2 4 6 8 10 12 14 16 18 20

GF-AAS, in μg/L

Scattergram

-0.03 -0.66 0.60

1.05 0.90 1.20

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-2

0

2

4

6

8

10

12

14

16

18

20

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

16

12

0

0.5716

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0

-20

0

20

40

60

80

100

ICP-MS, in μg/L

-20 0 20 40 60 80 100

GF-AAS, in μg/L

Scattergram

0.17 -0.35 0.70

0.87 0.85 0.89

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-20

0

20

40

60

80

100

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

24

10

0

0.0243

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 81

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 27. Scattergram, box plots, Paired t-Test 

results, and regression coefficients showing 

selenium data from the former graphite 

furnace–atomic absorption spectrophotometric 

(GF–AAS) method and inductively coupled 

plasma–mass spectrometry (ICP–MS) for wholewater digests. Concentrations are in 

micrograms per liter (g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 28. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing sodium data from the former flame–

atomic absorption spectrophotometric (F–AAS) 

method and inductively coupled plasma–optical 

emission spectrometry (ICP–OES) for wholewater digests. Concentrations are in milligrams 

per liter (mg/L). 

-2

0

2

4

6

8

ICP-MS, in μg/L

-2 0 2 4 6 8

GF-AAS, in μg/L

Scattergram

1.95 -4.05 7.95

0.66 -0.86 2.18

Coefficient 95% Low er 95% Upper

Intercept

GF-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. GF-AAS, in μg/L

-2

0

2

4

6

8

GF-AAS, in μg/L ICP-MS, in μg/L

Box Plot

-0.90 3 -1.06 0.3670

Mean Diff. DF t-Value P-Value

GF-AAS, in μg/L, ICP-MS, ...

Paired t-test

Hypothesized Difference = 0

-5

0

5

10

15

20

25

30

35

40

45

ICP-OES, in mg/L

-5 0 5 10 15 20 25 30 35 40 45

F-AAS, in mg/L

Scattergram

-0.10 -0.43 0.23

1.08 1.06 1.10

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in mg/L

Confidence Intervals

ICP-OES, in mg/L vs. F-AAS, in mg/L

-5

0

5

10

15

20

25

30

35

40

45

F-AAS, in mg/L ICP-OES, in mg/L

Box Plot

8

25

0

0.0046

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
APPENDIX 82

Figure 29a. Scattergrams and regression 

analyses showing strontium whole-water digest 

data from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 29b. Box plots and Kruskal-Wallis Test 

results showing strontium data from the former 

flame–atomic absorption spectrophotometric (F–

AAS) method (group 3), inductively coupled 

plasma–optical emission spectrometry (ICP–

OES, group 1), and inductively coupled plasma–

mass spectrometry (ICP–MS, group 2) for 

whole-water digests. Concentrations are in 

micrograms per liter (g/L). 

-200

0

200

400

600

800

1000

1200

ICP-OES, in μg/L

-200 0 200 400 600 800 1000 1200

F-AAS, in μg/L

Scattergram

-7.40 -16.59 1.80

1.06 1.04 1.09

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-200

0

200

400

600

800

1000

1200

ICP-MS, in μg/L

-200 0 200 400 600 800 1000 1200

F-AAS, in μg/L

Scattergram

-0.71 -8.44 7.03

0.98 0.96 1.00

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L

-200

0

200

400

600

800

1000

1200

F-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

2

0.13

0.9369

0.13

0.9369

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

37 2022.00 54.65

37 2122.00 57.35

37 2072.00 56.00

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method
APPENDIX 83

Figure 30a. Scattergrams and regression 

analyses showing zinc whole-water digest data 

from inductively coupled plasma–optical 

emission spectrometry (ICP–OES) and 

inductively coupled plasma–mass spectrometry 

(ICP–MS) in relation to the former flame–atomic 

absorption spectrophotometric (F–AAS) method. 

Concentrations are in micrograms per liter 

(g/L). 

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

DF – Degrees of Freedom 

H – Null hypothesis test statistic 

P-Value – Level of significance 

Figure 30b. Box plots and Kruskal-Wallis Test 

results showing zinc data from the former 

flame–atomic absorption spectrophotometric (F–

AAS) method (group 3), inductively coupled 

plasma–optical emission spectrometry (ICP–

OES, group 1), and inductively coupled plasma–

mass spectrometry (ICP–MS, group 2) for 

whole-water digests. Concentrations are in 

micrograms per liter (g/L). 

-50

0

50

100

150

200

250

300

350

400

450

500

ICP-OES, in μg/L

-50 0 50 100 150 200 250 300 350 400 450 500

F-AAS, in μg/L

Scattergram

4.55 -12.55 21.65

0.96 0.86 1.06

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-OES, in μg/L vs. F-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

450

500

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300 350 400 450 500

F-AAS, in μg/L

Scattergram

2.67 -5.46 10.80

0.90 0.85 0.95

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

450

500

F-AAS, in μg/L ICP-OES, in μg/L ICP-MS, in μg/L

Box Plot

2

3

2

0.42

0.8097

0.42

0.8097

DF

# Groups

# Ties

H

P-Value

H corrected for ties

Tied P-Value

Kruskal-Wallis Test for Data

Grouping Variable: Method

17 473.00 27.82

17 418.00 24.59

17 435.00 25.59

Count Sum Ranks Mean Rank

1

2

3

Kruskal-Wallis Rank Info for Data

Grouping Variable: Method
APPENDIX 84

EXPLANATION 

Box plot – horizontal lines, from bottom, 

represent the 10th, 25th, 50th, 75th, and 90th 

percentiles; data below the 10th and above 

90th are plotted as circles. 

Figure 30c. Scattergram, box plots, One-sample 

Sign Test results, and regression coefficients 

showing zinc data from the former flame–atomic 

absorption spectrophotometric (F–AAS) method 

and inductively coupled plasma–mass 

spectrometry (ICP–MS) for whole-water digests. 

Concentrations are in micrograms per liter (g/L).

-50

0

50

100

150

200

250

300

350

400

450

500

ICP-MS, in μg/L

-50 0 50 100 150 200 250 300 350 400 450 500

F-AAS, in μg/L

Scattergram

2.24 -2.08 6.55

0.90 0.87 0.93

Coefficient 95% Low er 95% Upper

Intercept

F-AAS, in μg/L

Confidence Intervals

ICP-MS, in μg/L vs. F-AAS, in μg/L

-50

0

50

100

150

200

250

300

350

400

450

500

F-AAS, in μg/L ICP-MS, in μg/L

Box Plot

13

11

2

0.8388

# Obs. > Hyp. Value

# Obs. < Hyp. Value

# Obs. = Hyp. Value

P-Value

One-Sample Sign Test for Difference

Hypothesized Value: 0
Table 8. Statistical analysis of short-term ICP–OES results for U.S. Geological Survey’s

Standard Reference Water Sample T107

[ICP–OES, inductively coupled plasma–optical emission spectrometry; element results are in micrograms per liter except for calcium, magnesium, silicon, and sodium, which are in milligrams per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon 

Signed Rank Test; p-value, level of significance; ld, less than the method detection limit (see table 1); 

<, less than] 

ICP–OES 

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 1 220 45 204 7 T -7.0 <0.0001

Barium 192 11 192.6 0.5 T 3.6 0.0058 

Beryllium 11.0 1.1 11.7 0.2 T 9.6 <0.0001

Boron 130 21 135 3 T 4.5 0.0015 

Cadmium 14.3 2.1 13 2 T -2.0 0.073 

Calcium 1 11.7 0.7 11.32 0.02 T -47 <0.0001

Chromium 13.0 2.1 13 3 T 0.47 0.65 

Cobalt 11.0 1.4 12 2 T 1.6 0.14 

Copper 30.0 2.3 29 1 W 5.0 0.025 

Iron 52 7 50 2 T -2.8 0.020 

Lead 26 4 ld ld ld ld

Lithium 193 14 191 2 T -3.8 0.0042 

Magnesium 1 2.10 0.13 2.02 0.01 W 0 0.006 

Manganese 45 6 45.4 0.4 T 3.2 0.011 

Molybdenum 15.0 1.9 ld ld ld ld

Nickel 28.1 3.9 ld ld ld ld

Silicon as SiO2 7.7 0.5 7.42 0.02 T -33 <0.0001

Silver 12.3 2.2 11 6 T 8.8 <0.0001

Sodium 1 20.7 1.1 20.6 0.2 W 19 0.42 

Strontium 61 4 60.5 0.2 T -6.8 0.0001 

Vanadium 14.0 2.8 12 1 T -4.1 0.0029 

Zinc 75.8 9.9 74 4 T -0.94 0.37 

1

Used emission wavelength that was most suitable. 

APPENDIX 85
Table 9. Statistical analysis of short-term ICP–OES results for U.S. Geological Survey’s 

Standard Reference Water Sample T119

[ICP–OES, inductively coupled plasma–optical emission spectrometry; element results are in micrograms per liter except for calcium, magnesium, silicon, and sodium, which are in milligrams per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of 

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon 

Signed Rank Test; p-value, level of significance; ld, less than the method detection limit (see table 1); 

<, less than] 

ICP–OES 

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

1 Aluminum 170 30 162 7 T -4.0 0.0026 

Barium 44 3 44.8 0.7 T 3.6 0.0056 

Beryllium 13.6 1.7 13.5 0.4 T -1.1 0.31 

Boron 28 9 28 4 T -0.17 0.87 

Cadmium 2.8 0.4 ld ld ld

Calcium 1 11.0 0.8 12.0 0.2 T 15 <0.0001 

Chromium 19 2 18 1 T -0.46 0.65 

Cobalt 5.1 1.0 5 2 T -0.58 0.58 

Copper 2.0 1.0 ld ld ld ld

Iron 46 7 43 2 T -5.1 0.0007 

Lead 6.7 1.2 ld ld ld ld

Lithium 60 4 59 1 T -4.l 0.0028 

Magnesium 1 3.1 0.2 3.08 0.05 T -1.1 0.31 

Manganese 35 3 34.9 0.6 T -0.67 0.52 

Molybdenum 11.9 2.4 ld ld ld ld

Nickel 21.8 2.2 ld ld ld ld

Silicon as SiO2 9.0 0.5 8.8 0.2 T -4.0 0.0033 

Silver 4.0 1.3 ld ld ld ld

Sodium 1 20.3 1.0 21.0 0.3 T 7.1 <0.0001 

Strontium 73 5 73 1 T 0.56 0.59 

Vanadium 3.8 0.9 5 1 T 2.4 0.042 

Zinc 24.8 4.7 26 6 W 40 0.22 

ld

1

Used emission wavelength that was most suitable.

APPENDIX 86
Table 10. Statistical analysis of short-term ICP–OES results for U.S. Geological Survey’s 

Standard Reference Water Sample T133

[ICP–OES, inductively coupled plasma–optical emission spectrometry; element results are in micrograms per liter except for calcium, magnesium, silicon, and sodium, which are in milligrams per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; p-value, level of significance; T, indicates the Student’s t-Test; 

W, indicates the Wilcoxon Signed Rank Test; ld, less than the method detection limit (see table 1); 

<, less than] 

ICP–OES 

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 1 52.1 8.1 48 6 T -2.2 0.052

Barium 148 9 143.8 0.6 T -24 <0.0001

Beryllium 35.0 2.2 36.2 0.3 T 12 <0.0001

Boron 297 16 292 5 T -3.3 0.0091

Cadmium 23.0 2.1 25 2 T 2.1 0.077

Calcium 1 7.0 0.3 6.85 0.02 W 0 0.006

Chromium 38.0 3.2 40 3 T 2.0 0.087

Cobalt 20.0 1.5 20 6 T 0.03 0.97

Copper 85.3 4.5 85 2 T -1.2 0.24

Iron 31.4 6.7 31 2 T -0.35 0.73

Lead 27.8 2.7 ld ld ld ld

Lithium 51.0 3.5 47.9 0.7 T -15 <0.0001

Magnesium 1 5.8 0.2 5.56 0.02 W 0 0.006

Manganese 121 7 114.9 0.6 T -32 <0.0001

Molybdenum 46.0 4.2 46 12 T -0.10 0.92

Nickel 27.2 3.1 ld ld ld ld

Silicon as SiO2 10.1 0.7 9.78 0.06 W 0 0.006

Silver 7.4 0.9 6.4 0.7 T -4.7 0.0011

Sodium 1 29.4 1.2 28.8 0.1 T -17 <0.0001

Strontium 123 6 119.9 0.3 T -31 <0.0001

Vanadium 13.0 1.7 10 1 T -9.4 <0.0001

Zinc 53.0 4.4 44 6 T -4.4 0.0017 1

Used emission wavelength that was most suitable.

APPENDIX 87
Table 11. Statistical analysis of short-term ICP–OES results for U.S. Geological Survey’s 

Standard Reference Water Sample T135

[ICP–OES, inductively coupled plasma–optical emission spectrometry; element results are in micrograms per liter except for calcium, magnesium, silicon, and sodium, which are in milligrams per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon Signed 

Rank Test; p-value, level of significance; ld, less than the method detection limit (see table 1); <, less than] 

ICP–OES 

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 1 10.5 6.8 ld ld ld ld 

Barium 67.8 4.3 64.7 0.2 W 0 0.006 

Beryllium 59.0 2.6 58.4 0.3 T -7.4 <0.0001

Boron 13.1 11.1 ld ld ld ld

Cadmium 50.5 3.2 49 2 T -1.9 0.092

Calcium 1 10.4 0.6 10.27 0.03 T -14 <0.0001

Chromium 79.0 5.5 76 1 T -5.7 0.0003 

Cobalt 40.0 2.6 38 2 T -1.8 0.097

Copper 62.0 4.2 60 1 T -7.3 <0.0001

Iron 228 11 219 4 T -6.3 0.0001 

Lead 103 7 107 16 T 0.80 0.45

Lithium 73.7 5.2 69.4 0.8 T -17 <0.0001 

Magnesium 1 2.00 0.09 1.97 0.01 W 0 0.006

Manganese 423 20 397 1 T -61 <0.0001

Molybdenum 63.0 5.1 62 11 W 13 0.15

Nickel 65.6 5.0 59 11 T -2.1 0.068

Silicon as SiO2 4.28 0.31 4.09 0.03 W 0 0.006 

Silver 9.8 1.0 11.5 0.8 T 7.1 <0.0001

Sodium 1 30.8 1.2 30.2 0.2 T -11 <0.0001

Strontium 46.0 2.3 45.5 0.3 T -5.2 0.0005

Vanadium 52.8 3.6 52 1 T -1.1 0.30

Zinc 48.2 4.7 44 4 T -3.1 0.012 1

Used emission wavelength that was most suitable.

APPENDIX 88
Table 12. Statistical analysis of long-term ICP–MS results for U.S. Geological Survey’s Standard 

Reference Water Sample T107

[ICP–MS, inductively coupled plasma–mass spectrometry; element results are in micrograms per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon Signed 

Rank Test; p-value, level of significance; <, less than] 

ICP–MS

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 220 45 237 8 T 6.4 0.0001

Antimony 10.1 2.5 9.8 0.3 T -3.1 0.013

Barium 192 11 197 6 W 50 0.025

Beryllium 11.0 1.1 13.2 1.4 T 5.0 0.0007

Boron 130 21 158 14 T 6.0 0.0002

Cadmium 14.3 2.1 14.2 0.3 T -0.67 0.52

Chromium 13.0 2.1 16 2 W 55 0.006

Cobalt 11.0 1.4 11.8 0.4 W 55 0.006

Copper 30.0 2.3 30.0 1.8 T 0.07 0.94

Lead 26 4 27.9 0.4 T 14 <0.0001

Lithium 193 14 220 20 T 4.2 0.0025

Manganese 45 6 48.8 0.6 T 21 <0.0001

Molybdenum 15.0 1.9 15.5 0.5 T 3.4 0.0075

Nickel 28.1 3.9 28.0 1.4 T -0.23 0.82

Selenium 11.0 1.9 11.4 1.3 T 0.99 0.35

Silver 12.3 2.2 11.1 0.3 T -11 <0.0001

Strontium 61 4 61.1 1.7 T 0.18 0.86

Zinc 75.8 9.9 82 4 T 4.3 0.0020

APPENDIX 89
Table 13. Statistical analysis of long-term ICP–MS results for U.S. Geological Survey’s 

Standard Reference Water Sample T119

[ICP–MS, inductively coupled plasma–mass spectrometry; element results are in micrograms per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon Signed 

Rank Test; p-value, level of significance]

ICP–MS

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 170 30 174 4 T 2.0 0.076

Antimony 8.6 1.5 8.7 0.2 T 1.0 0.34

Barium 44 3 43.2 1.1 T -2.4 0.040

Beryllium 13.6 1.7 14.7 1.0 T 3.4 0.0074

Boron 28 9 34 10 T 5.1 0.0006

Cadmium 2.8 0.4 2.8 0.1 W 46 0.067

Chromium 19 2 19 2 W 24 0.76

Cobalt 5.1 1.0 5.2 0.1 T 1.5 0.17

Copper 2.0 1.0 2.2 0.1 T 5.6 0.0003

Lead 6.7 1.2 7.2 0.1 T 13 <0.0001

Lithium 60 4 63 4 T 2.18 0.057

Manganese 35 3 34.9 0.4 T -0.61 0.55

Molybdenum 11.9 2.4 12.2 0.3 T 2.6 0.029

Nickel 21.8 2.2 21.3 0.7 T -2.1 0.066

Selenium 9.8 1.3 9.8 1.3 T -0.07 0.95

Silver 4.0 1.3 2.6 1.0 T -4.5 0.0015

Strontium 73 5 71 2 T -2.8 0.021

Zinc 24.8 4.7 24.4 0.8 T -1.6 0.14

APPENDIX 90
Table 14. Statistical analysis of long-term ICP–MS results for U.S. Geological Survey’s Standard 

Reference Water Sample T133

[ICP–MS, inductively coupled plasma–mass spectrometry; element results are in micrograms per liter; 

MPV, the published most probable value; , the plus or minus symbol precedes the F-pseudosigma in 

the MPV column and the standard deviation at 1 in the experimental column; n, equals the number of

replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon Signed 

Rank Test; p-value, level of significance]

ICP–MS

Element MPV Experimental

mean, n=10 

Test Test

statistic 

p-value

Aluminum 52.1 8.1 51.6 1.8 T -0.79 0.45

Antimony 14.4 2.4 14.5 0.5 T 0.39 0.71

Barium 148 9 151 4 T 2.2 0.051

Beryllium 35.0 2.2 36.4 1.1 T 4.1 0.0027

Boron 297 16 309 11 T 3.5 0.0067

Cadmium 23.0 2.1 22.5 0.5 T -3.0 0.016

Chromium 38.0 3.2 37.0 0.9 T -3.4 0.0076

Cobalt 20.0 1.5 20.2 0.6 T 1.4 0.21

Copper 85.3 4.5 84 3 W 18 0.36

Lead 27.8 2.7 28.7 0.6 T 4.3 0.0021

Lithium 51.0 3.5 51.6 1.8 T 1.01 0.34

Manganese 121 7 120 4 W 28 1.0

Molybdenum 46.0 4.2 47.0 1.2 T 2.7 0.026

Nickel 27.2 3.1 26.7 0.7 T -2.1 0.064

Selenium 21.4 3.7 20.8 1.4 T -1.5 0.16

Silver 7.4 0.9 7.5 0.2 T 1.8 0.10

Strontium 123 6 124 3 T 0.99 0.35

Zinc 53.0 4.4 52 2 T -1.2 0.26

APPENDIX 91
Table 15. Statistical analysis of long-term ICP–OES and ICP–MS results for U.S. Geological Survey’s Standard Reference 

[ICP–OES, inductively coupled plasma–optical emission spectrometry; ICP–MS, inductively coupled plasma–mass spectrometry; elem

micrograms per liter except for calcium, magnesium, silicon, and sodium, which are in milligrams per liter; MPV, the published most prplus or minus symbol precedes the F-pseudosigma in the MPV column and the standard deviation at 1in the experimental columns; n, replicates used to calculate the mean; T, indicates the Student’s t-Test; W, indicates the Wilcoxon Signed Rank Test; nd, element was nspecific analytical method; ld, less than the method detection limit (see table 1); p-value, level of significance; gl, greater than upper cal

analytical method; <, less than] 

ICP–OES ICP–

Element MPV Experimental

mean, n=20 

Test Test

statistic 

p-value Experimental

mean, n=20 

Test 

Aluminum 1 7,080  5,700 8,500  200 W 210 <0.0001 gl gl Antimony 3.6  2.5 nd nd nd nd 2.6  0.2 T 

Barium 156  34 161  3 T 8.0 <0.0001 168  4 T 

Beryllium 9.0  0.9 8.2  0.2 T -8.8 <0.0001 8.9  0.9 T 

Boron 31  38 16  2 T -11 <0.0001 18  3 T Cadmium 6.1  1.1 4.6  0.6 T -3.3 0.0037 6.1  0.2 T 

Calcium 1 17.9  1.3 17.9  0.2 T 0.29 0.78 nd nd 

Chromium 22  5 19.9  0.4 T -4.5 0.0003 26  6 T 

Cobalt 2 13.5  2.7 ld ld ld ld 13.3  0.6 T 

Copper 28  6 24  1 T -7.9 <0.0001 26.8  0.9 T 

Iron 14,000  4,000 13,280  170 T -19 <0.0001 nd nd 

Lead 25.8  5.1 ld ld ld ld 25.0  0.4 T 

Lithium 19.0  4.4 15.6  0.2 W 0 <0.0001 18  2 W 

Magnesium 1 7  1 7.1  0.1 T 2.2 0.040 nd nd 

Manganese 595  54 593  9 T -1.2 0.26 560  40 W 
Table 15. Statistical analysis of long-term ICP–OES and ICP–MS results for U.S. Geological Survey’s Standard Refere

Sample WW-1—Continued

ICP–OES ICP–M

Element MPV Experimental

mean, n=20 

Test Test

statistic 

p-value Experimental

mean, n=20 

Test 

Molybdenum 4.9  1.8 ld ld ld ld 3.3  0.1 T Nickel 24.0  7.9 ld ld ld ld 22.6  0.7 T 

Selenium 5.5  2.1 nd nd nd nd 6.3  0.8 T 

Silicon as SiO2 31  15 40.3  1.2 W 210 <0.0001 nd nd 

Silver 2.3  1.8 ld ld ld ld 1.60  0.06 T 

Sodium 1 19.7  1.7 19.9  0.3 T 4.5 0.0002 nd nd 

Strontium 84  7 85  1 T 4.8 0.0001 85.8  1.7 T Vanadium 24  9 20.7  0.5 W 0 <0.0001 nd nd Zinc 80  20 74  4 W 120 0.72 65  5 T 

1The most suitable emission wavelength was used for ICP–OES.2Cobalt result is not reported because iron concentration exceeds correction limit for ICP–OES 
Table 16. Analytical variability of ICP–OES and ICP–MS results for Standard Reference 

Water Sample WW-1

[ICP–OES, inductively coupled plasma–optical emission spectrometry; ICP–MS, inductively

coupled plasma–mass spectrometry; based on three sequential determinations of an aliquot of

Standard Reference Water Sample (SRWS) WW-1 in-bottle digest; g/L, microgram per liter; 

%RSD, percent relative standard deviation; nd, not determined; ld, less than method detection

limit (see table 1); mg/L, milligram per liter] 

Element Concentration,

in g/L 

%RSD

ICP–OES 

%RSD

ICP–MS

Aluminum 1 220 4 0.4

Antimony 3.6 nd 3

Barium 156 0.1 1

Beryllium 9.0 0.07 2

Boron 31 10 4

Cadmium 6.1 50 2

Calcium, mg/L 18 0.1 nd

Chromium 22 5 2

Cobalt 1 11 20 2

Copper 28 9 4

Iron 14,000 0.2 nd

Lead 2 160 20 0.1

Lithium 19 2 2

Magnesium, mg/L 7.0 0.04 nd

Manganese 595 0.05 3

Molybdenum 2 65 6 2

Nickel 24 ld 0.2

Selenium 5.5 nd 20

Silicon, mg/L as SiO2 31 0.2 nd

Silver 1 12 10 3

Sodium, mg/L 20 0.5 nd

Strontium 84 0.05 1

Thallium 3 0.18 nd 6

Uranium 3 1.0 nd 3

Vanadium 24 2 nd

Zinc 80 8 4 1

Results are for SRWS T107 digest. 2

Estimated concentration for spiked SRWS T117 digest. 3

Unpublished mean concentration for WW-1 digest based on numerous determinations.

APPENDIX 94
Table 17. Analytical variability of ICP–OES and ICP–MS over an extended concentration range

[ICP–OES, inductively coupled plasma–optical emission spectrometry; ICP–MS, inductively

coupled plasma–mass spectrometry; based on three sequential determinations of an aliquot of

standard prepared in calibration blank solution; g/L, microgram per liter; mg/L, milligram per 

liter; RSD, relative standard deviation; <MDL, less than method detection limit; na, not applicable; 

nd, not determined] 

Concentration

Percent

RSD 

Percent

RSD 

Percent

RSD 

Percent

RSD 

(g/L) ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

Aluminum Antimony Barium Beryllium

5 <MDL 2 na 2 0.8 5 4 2

12.5 <MDL 0.8 na 0.9 1 1 2 1

25 20 0.5 na 2 0.8 2 1 1

50 8 0.6 na 0.4 0.08 1 1 0.9

100 3 0.2 na 1 0.5 0.8 0.7 1

250 5 0.5 na 0.5 0.4 0.9 0.5 0.7

500 2 0.9 na 0.4 0.2 0.9 0.3 0.6

1,000 2 0.3 na nd 0.2 2 0.2 nd

2,500 0.5 nd na nd 0.6 nd 0.4 nd

Boron Cadmium Chromium Cobalt

5 <MDL 16 <MDL 10 <MDL 3 50 1

12.5 <MDL 4 20 4 10 3 20 1

25 20 2 6 1 10 8 10 2

50 6 2 5 0.6 10 3 3 1

100 8 2 6 1 0.7 1 4 0.7

250 3 0.8 0.8 0.6 2 0.3 2 0.2

500 2 1 1 0.9 1 2 0.8 0.6

1,000 2 nd 0.5 nd 0.6 nd 0.7 nd

2,500 0.6 nd 0.4 nd 0.2 nd 0.6 nd

Copper Lead Lithium Manganese

5 <MDL 20 <MDL 1 <MDL 5 10 3

12.5 30 4 <MDL 0.4 10 2 1 2

25 1 2 <MDL 0.7 3 1 0.8 1

50 1 2 <MDL 0.7 1 2 0.7 1

100 1 2 60 0.3 2 1 1 1

250 2 2 20 2 0.7 0.6 0.2 0.7

500 0.6 0.8 7 0.4 0.2 2 0.4 2

1,000 0.5 nd 7 nd 0.1 nd 0.1 1

2,500 0.5 nd 2 nd 0.6 nd 0.5 nd

Molybdenum Nickel Selenium Silver

5 <MDL 3 <MDL 4 na 70 30 1

12.5 <MDL 2 <MDL 4 na 20 10 2

25 <MDL 3 <MDL 3 na 20 7 1

50 20 2 3 1 na 6 4 nd

100 8 1 30 2 na 2 2 nd

250 3 0.7 8 2 na 4 0.6 nd

500 3 0.7 2 1 na 1 0.4 nd

1,000 2 nd 3 nd na nd 0.7 nd

2,500 0.9 nd 2 nd na nd nd nd

APPENDIX 95
Table 17. Analytical variability of ICP–OES and ICP–MS over an extended concentration 

range—Continued

Concentration

Percent

RSD 

Percent

RSD 

Percent

RSD 

Percent

RSD 

(g/L) ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

ICP–

OES 

ICP–

MS

Strontium Thallium Uranium Vanadium

5 0.7 1 na 1 na 0.3 <MDL na

12.5 3 0.4 na 2 na 0.4 6 na

25 0.7 2 na 0.5 na 1 10 na

50 0.4 0.8 na 0.6 na 1 2 na

100 0.8 1 na 0.6 na 1 2 na

250 0.4 0.8 na 2 na 1 0.4 na

500 0.2 0.8 na 0.08 na 0.4 0.9 na

1,000 0.2 nd na nd na nd 0.4 na

2,500 0.6 nd na nd na nd 0.3 na

Zinc

5 <MDL 3

12.5 <MDL 0.4

25 4 2

50 10 4

100 20 0.8

250 10 1

500 2 0.9

1,000 3 0.4

2,500 0.3 nd

Concentration

(g/L) Calcium Iron Magnesium 

Silicon as

SiO2 

0.01 5 na 0.7 na 5 na <MDL na

0.05 0.8 na 4 na 0.8 na <MDL na

0.1 0.3 na 4 na 0.7 na 20 na

0.5 0.3 na 0.2 na 0.3 na 5 na

1 0.3 na 0.1 na 0.5 na 3 na

5 0.2 na 0.5 na 0.2 na 2 na

10 0.7 na 0.7 na 0.8 na 1 na

50 0.6 na 0.8 na 0.4 na 2 na

100 0.4 na 0.4 na 0.2 na 1 na

Sodium 

0.01 <MDL na

0.05 <MDL na

0.1 6 na

0.5 4 na

1 0.3 na

5 0.7 na

10 0.8 na

50 0.09 na

100 0.5 na

APPENDIX 96
Table 18. Spike recovery results for whole-water digests

[S/cm, microsiemens per centimeter at 25 C; g/L, microgram per liter; % rec, percent spike recovery; ICP–OES, inductively cou

spectrometry; ICP–MS, inductively coupled plasma–mass spectrometry; nd, not determined] 

Specific 

conductance, 

S/cm 1

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

Aluminum Antimony 

103 340 98 340 99 nd nd 10 98 50 230 710 95 720 96 nd nd 10 100 61 519 1,520 94 1,520 99 nd nd 10 100 40 683 610 97 660 105 nd nd 10 100 61 

1,600 130 110 17 82 nd nd 10 102 180 1,900 130 84 30 92 nd nd 10 98 81 

Average  % rec 

96 96 nd 100 

Beryllium Boron 

103 15 92 0.4 120 81 92 102 96 50 230 15 92 0.4 120 120 98 140 103 50 519 15 92 4.0 120 101 98 50 109 50 683 15 92 0.4 120 101 104 92 120 50 

1,600 15 91 0.4 93 101 95 102 87 50 1,900 15 88 0.4 104 250 103 280 96 50 

Average % rec 

91 113 98 102 

Chromium Cobalt 

103 50 110 5.0 80 71 95 1.3 98 50 230 50 97 9.6 74 71 99 1.3 93 50 519 50 99 7.8 99 160 99 150 98 50 683 50 104 15 97 71 102 1.0 105 50 

1,600 50 105 82 80 71 94 1.1 79 50 1,900 50 101 12 91 71 98 0.6 92 50 

Average % rec 

103 87 98 94 
Table 18. Spike recovery results for whole-water digests—Continued 

Specific 

conductance, 

S/cm 1

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

Iron Lead 

103 1,010 101 nd nd 505 106 1.3 101 71 230 182 97 nd nd 505 105 3.2 99 71 519 4,848 101 nd nd 505 98 5.4 97 71 683 859 102 nd nd 505 107 1.3 97 71 

1,600 1,616 104 nd nd 505 98 0.9 102 71 1,900 303 105 nd nd 505 97 1.0 99 71 

Average % rec 

102 nd 102 99 

Manganese Molybdenum 

103 320 101 300 93 303 96 5.0 99 303 230 202 100 200 89 303 101 5.0 89 303 519 4,850 99 nd nd 303 101 5.0 99 303 683 71 101 70 92 303 99 6.0 102 30 

1,600 20 98 13 74 303 105 6.0 87 303 1,900 404 103 340 87 303 100 5.0 89 303 

Average % rec 

100 87 100 94 

Selenium Silver 

103 nd nd 20 94 26 108 10 87 120 230 nd nd 20 90 26 102 10 91 120 519 nd nd 20 95 26 106 10 89 130 683 nd nd 17 100 26 107 10 89 1,620 

1,600 nd nd 20 93 26 102 10 86 1,210 1,900 nd nd 20 78 26 106 10 82 660 

Average % rec 

nd 92 105 87 
Table 18. Spike recovery results for whole-water digests—Continued

Specific 

conductance, 

S/cm 1

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

% rec 

ICP– 

OES 

Spike, 

g/L 

% rec 

ICP– 

MS 

Spike, 

g/L 

Thallium Uranium 

103 nd nd 2.0 94 nd nd 4.0 90 40 230 nd nd 2.0 91 nd nd 4.0 102 40 519 nd nd 2.0 89 nd nd 4.0 96 40 683 nd nd 2.0 93 nd nd 3.0 102 40 

1,600 nd nd 2.0 98 nd nd 6.8 96 40 1,900 nd nd 2.0 95 nd nd 4.4 98 40 

Average % rec 

nd 93 nd 97 

Zinc 

103 202 105 10 97230 202 96 17 92519 760 102 720 102683 505 105 10 100

1,6001,900

202 100 7.2 64

202 112 6.2 92

Average % rec 

103 91

1Specific conductance of sample before acidification and in-bottle digestion.
Table 19. Chemical characteristics of natural whole-water samples

[< MDL, less than the method detection limit; ICP–OES, inductively coupled plasma–optical emission

spectrometry; ICP–MS, inductively coupled plasma–mass spectrometry; g/L, microgram per liter; mg/L, milligram

per liter; S/cm, microsiemens per centimeter at 25C; nd, not determined by method; no, no

former method is available; —, not applicable] 

Element or 

constituent mum 

25th

percentile 

Median 75th

percentile 

MaxiFraction 

of 

samples 

< MDL for 

the 

former

method 

Fraction 

of 

samples 

< MDL for 

the ICP–

OES 

method 

Fraction 

of 

samples 

< MDL for 

the ICP–

MS

method 

Aluminum, in g/L 60 320 850 20,400 1/43 1/43 0/43

Antimony, in g/L 0.8 1 5 6 31/43 nd 31/43

Barium, in g/L 110 140 180 660 23/43 0/43 0/43

Beryllium, in g/L 0.9 2 

7/43

nd

 37/43 

74

20 

0/43 

24 

 15/43 

2 12 43/43 28/43 21/43

Boron, in g/L 19 22 36 83 6/43 2/43

Cadmium, in g/L 0.2 0.4 0.7 6 14/43 42/43 4/43 

Calcium, in mg/L 9 27 47 67 10/43 0/43 

Chromium, in g/L 6 11 20 160 3/43 28/43 17/43

Cobalt, in g/L 0.8 3 7 84 12/43 0/43 

Copper, in g/L 2 6 17 360 1/43 15/43 0/43

Iron, in g/L 380 1,400 4,200 14,000 1/43 1/43 nd

Lead, in g/L 2 4 20 9/43 39/43 0/43

Lithium, in g/L 10 40 160 15/43 11/43 0/43 

Magnesium, in mg/L 3 11 22 50 0/43 nd

Manganese, in g/L 76 260 820 1/43 1/43 0/43 

Molybdenum, in g/L 1 2 4 14 43/43 11/43 

Nickel, in g/L 2 4 10 95 7/43 36/43 2/43

Selenium, in g/L Limited data set 40/43 nd 39/43 

Silicon, in mg SiO2/L 9 17 30 90 no 0/43 nd

Silver, in g/L Limited data set 42/43 43/43 42/43 

Sodium, in mg/L 3 10 18 40 0/43 0/43 nd

Strontium, in g/L 60 230 400 1,000 0/43 0/43 0/43 

Thallium, in g/L Limited data set no nd 41/43 

Uranium, in g/L 0.5 1 2 16 no nd 5/43

Vanadium, in g/L 8 9 20 60 no 23/43 nd

Zinc, in g/L 14 38 120 400 19/43 24/43 1/43 

Alkalinity, in mg/L 43 68 130 410 — — —

Chloride, in mg/L 6 12 36 9,500 — — —

Cond., in S/cm 1 170 300 620 25,400 — — —

Sulfate, in mg/L 5 28 60 1,600 — — —

1

Specific conductance (Cond.) in microsiemens per centimeter (S/cm) of the whole-water sample prior to

digestion.

APPENDIX 100 
Table 20. Statistical analysis summary of ICP–OES and ICP–MS results for natural wholewater digests

[ICP–OES, inductively coupled plasma–optical emission spectrometry; ICP–MS, inductively coupled

plasma–mass spectrometry; DCP–AES, direct current plasma–atomic emission spectrometry; GF–

AAS, stabilized temperature graphite furnace–atomic absorption spectrophotometry; F–AAS, flame–

atomic absorption spectrophotometry; n, number of sample results used in the statistical analysis; id, 

insufficient data; nd, not determined by an analytical method; —, no data; <, less than] 

Element

Former method 

to ICP–OES to

ICP–MS

Former method 

to ICP–OES 

Former method to 

ICP–MS

Former

method 

n 

KruskalWallis 

p-value

n 

Onesample 

Sign Test

p-value

n 

One-sample 

Sign Test 

p-value

Aluminum DCP–AES 25 0.9750 — Redundant — Redundant

Antimony 1 GF–AAS — Inappropriate — nd 9 0.3061

Barium F–AAS 20 0.3749 — Redundant — Redundant

Beryllium F–AAS — id — id — id

Boron DCP–AES 28 0.0021 36 0.0288 28 0.0009

Cadmium GF–AAS — id — id 27

F–AAS Inappropriate 42 nd

0.0033 

Iron

0.0522

Calcium — <0.0001 —

Chromium GF–AAS 15 0.0078 15 <0.0001 26 <0.0001

Cobalt GF–AAS 6 0.0728 — Redundant 31

Copper GF–AAS 28 0.5285 — Redundant 42 0.6440

F–AAS — Inappropriate 38 0.0002 — nd

Lead GF–AAS — id — id 31 0.2810

Lithium F–AAS 27 0.9191 — Redundant — Redundant

Magnesium F–AAS — Inappropriate 42 0.6440 — nd

Manganese F–AAS 36 0.8669 — Redundant — Redundant

Molybdenum GF–AAS — id — id 28 0.5716

Nickel GF–AAS — id — id 34 0.0243

Selenium 1 GF–AAS — Inappropriate — nd 4 0.3670

Silicon as SiO2 None — Inappropriate — id — nd

Silver GF–AAS — id — id — id

Sodium GF–AAS — Inappropriate 33 0.0046 — nd

Strontium GF–AAS 37 0.9369 — Redundant — Redundant

Thallium None — Inappropriate — nd — id

Uranium None — Inappropriate — nd — id

Vanadium None — Inappropriate — id — nd

Zinc F–AAS 17 0.8097 — Redundant 26 0.8388 1

The paired Student t-test was used on a limited data set. 

APPENDIX 101