Analytical methods for

chemical analysis of

geologic and other

materials, U.S. Geological

Survey 

by Joseph E. Taggart, Jr. editor1 

Open-File Report 02-223 

2002 

This report is preliminary and has not been reviewed for conformity with 

U.S. Geological Survey editorial standards. Any use of trade, product or firm 

names is for descriptive purposes only and does not imply endorsement by 

the U.S. Government. 

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY 

1

Denver, Colorado 

i 
Table of Contents 

Page 

Introduction ...........................................................................................................................................................vi 

Safety Policy...........................................................................................................................................................vi 

Analytical Method Format..................................................................................................................................vii 

Method Validation ...............................................................................................................................................vii 

Definition of Terms .............................................................................................................................................viii 

Limit of Detection.........................................................................................................................................viii 

Lower Reporting Limit................................................................................................................................viii 

Limit of Quantitation ...................................................................................................................................viii 

Analytical Performance Summary...................................................................................................................... ix 

Reference Materials........................................................................................................................................ ix 

Duplicate Samples........................................................................................................................................... x 

Method Blank................................................................................................................................................... x 

Acknowledgments................................................................................................................................................. xi 

References Cited .................................................................................................................................................... xi 

ii 
 Analytical Methods 

Method codes 

CHAPTER A Sample Preparation 

A1 Rock sample preparation. 

Cliff D. Taylor and Peter M. Theodorakos........................................................................................... Q010 

A2 Stream-sediment sample preparation. 

Thomas R. Peacock, Cliff D. Taylor and Peter M. Theodorakos........................................................ Q020 

A3 Soil sample preparation. 

Thomas R. Peacock................................................................................................................................... Q030 

CHAPTER B 

Plant material preparation and determination of weight percent ash. 

Thomas R. Peacock and James G. Crock ..............................................................................................Q050,T17 

CHAPTER C 

Dry moist samples to constant weight under ambient conditions, calculate % moisture. 

Steve A. Wilson and Matt Herron...................................................................................................................T18 

CHAPTER D 

Conductivity measured using a self contained Myron L Digital DS Meter model DC4.

Peter M. Theodorakos........................................................................................................................................T28 

CHAPTER E 

Automated preset endpoint (4.5) total alkalinity titration using the Orion 960 Autochemistry 

system. 

Peter M. Theordorakos ......................................................................................................................................T04 

CHAPTER F 

The determination of twenty-seven elements in aqueous samples by inductively coupled plasmaatomic emission spectrometry.

Paul H. Briggs .................................................................................................................................... E080,T02,T03 

CHAPTER G 

The determination of forty elements in geological and botanical samples by inductively coupled

plasma-atomic emission spectrometry.

Paul H. Briggs ............................................................................................................................................E011,T01 

CHAPTER H 

The determination of forty-four elements in aqueous samples by inductively coupled plasma -

mass spectrometry.

Paul J. Lamothe, Allen L. Meier, and Stephen A. Wilson......................................................................T21,T23 

iii 
CHAPTER I 

The determination of forty-two elements in geological materials by inductively coupled plasma – 

mass spectrometry. 

Paul H. Briggs and Allen L. Meier...................................................................................................................T20 

CHAPTER J 

The determination of forty-two elements in geologic materials by inductively coupled plasma– 

mass spectrometry for NAWQA. 

Paul H. Briggs and Allen L. Meier...................................................................................................................T22 

CHAPTER K 

Rare earth elements by inductively coupled plasma–mass spectrometry.

Allen L. Meier and Tara Slowik............................................................................................................. M020,T19 

CHAPTER L 

Arsenic and selenium by flow injection or continuous flow–hydride generation–atomic 

absorption spectrophotometry. 

Philip L. Hageman, Zoe Ann Brown, and Eric Welsch................................................................ A011,T06,T24 

CHAPTER M 

Mercury in water, geologic, and plant materials by continuous flow–cold vapor–atomic 

absorption spectrometry.

Zoe Ann Brown, Richard M. O’Leary, Philip L. Hageman and James G. Crock.............................A091,T12 

CHAPTER N 

Mercury in water by flow injection-cold vapor-atomic fluorescence spectrometry. 

Philip L. Hageman..............................................................................................................................................T13 

CHAPTER O 

Mercury in plants and animal tissue by thermal decomposition-atomic spectrometry. 

Philip L. Hageman..............................................................................................................................................T30 

CHAPTER P 

Flame photometric determination of K2O

Terry L. Fries, Joe Christie, Sarah Pribble and David F. Siems ...........................................................E061,T29 

CHAPTER Q 

Total sulfur by combustion. 

Zoe Ann Brown and Kenneth Joe Curry...............................................................................................N021,T25 

CHAPTER R 

Total carbon by combustion. 

Zoe Ann Brown and Kenneth Joe Curry...............................................................................................N011,T10 

iv 
CHAPTER S 

Carbonate carbon by coulometric titration. 

Zoe Ann Brown, Clara Papp, Elaine Brandt and Phillip Aruscavage .............................................. C011,T08 

CHAPTER T 

Major element analysis by wavelength dispersive X-ray fluorescence spectrometry. 

Joseph E. Taggart, Jr. and David F. Siems............................................................................................. X051,T16 

CHAPTER U 

The determination of 30 elements in geological materils by energy dispersive X-ray fluorescence 

spectrometry. 

David F. Siems ................................................................................................................................OFR00-475,T27 

CHAPTER V 

Fluoride, chloride, nitrate and sulfate in aqueous solution utilizing autosuppression chemically 

suppressed ion chromatography. 

P.M. Theodorakos, W.M. d'Angelo and W.H. Ficklin............................................................................I011,T05 

CHAPTER W 

Ferrous iron (Fe

2+

) from 0 to 3.00 mg/L for water, wastewater, and seawater utilizing the HACH 

DR/2010 spectrophotometer method. 

Peter M. Theodorakos........................................................................................................................................T11 

CHAPTER X 

Instrumental neutron activation by long count. 

James R. Budahn and Gregory A. Wandless.......................................................................................... R030,T14 

CHAPTER Y 

Instrumental neuton activation by abbreviated count. 

James R. Budahn and Gregory A. Wandless......................................................................................... R021,T15 

CHAPTER Z 

Uranium and thorium by delayed neutron counting. 

Roy J. Knight and David M. McKown ...........................................................................................................R011 

APPENDICES 

Appendix A. Conversion Factors and Equivalents Tables 

Table A1. Element to oxide conversion factors 

Table A2. Weight to ppm to ppb equivalents 

Table A3. Grain size and sieve equivalents 

Appendix B. Glossary of Symbols and Terms 

v 
INTRODUCTION 

This manual presents validated analytical methods used by the Mineral Resources Team, 

Geologic Division. The manual updates the methods manual edited by Belinda Arbogast, OpenFile Report 96-525 published in 1996. This edition contains a few methods that have not 

changed signifcantly from the 1996 edition, a number of methods that are essentially the same 

but involve changes in instrumentation or minor changes in the procedure, and a number of new 

methods that were recently developed and approved. 

This manual is intended primarily for use by laboratory scientists; but can also assist laboratory 

users to evaluate the data they receive. The analytical methods are written in a step by step 

approach so that they may be used as a training tool and provide detailed documentation of the 

procedures for quality assurance. This manual is also available on the Internet at 

http://cpg.cr.usgs.gov/pub/publications.html

SAFETY POLICY1 

Because the laboratory work area inherently contains potential hazards, laboratory safety and 

health is a top priority. All federal, state, and local regulations concerning worker and 

community safety are to be strictly followed. Included in this policy is the propagation and 

distribution of Chemical Hygiene Plans (CHP) and Material Safety Data Sheets (MSDS) for every 

laboratory procedure that involves hazardous or toxic chemicals. These regulations affect Team 

management, personnel, facilities, and activities. If violated, some of these regulations carry 

financial and criminal penalties. 

1

 Sutley, 1994 

vi 
ANALYTICAL METHOD FORMAT 

The written analytical methods contained in this volume reflect the procedures actually being 

used in the laboratory. Routine methods are written in the following standard format: 

TITLE—contains the name(s) of the analyte and the measurement method 

PRINCIPLE—brief discussion of the scientific basis 

INTERFERENCE—physical or chemical conditions or processes which cause analytical error. 

SCOPE—the range of analyte concentration and applicable sample matrices for which the 

method is useful, and an estimate of time required for analysis 

APPARATUS—instruments and special equipment required 

REAGENTS—chemical name, chemical symbol, purity, method of preparation, and shelf life if 

stability is a problem 

SAFETY PRECAUTIONS—hazards peculiar to the method of analysis and handling procedures 

PROCEDURE—describes a strict time sequence and the critical steps in the analysis 

CALCULATION—equation(s) necessary to calculate the results of the analysis 

ASSIGNMENT OF UNCERTAINTY—statistical summary table of the historical analytical results 

for selected reference materials, duplicate samples, and method blank. For a detailed discussion 

please refer to the Analytical Performance Summary section. 

BIBLIOGRAPHY—references to the literature on which the method is based 

METHOD VALIDATION 

Before any method is approved to generate analytical data under the QA program, the method is 

assigned a unique code and must be validated. If a method is provisional, two dashes (--) are 

entered for the approval date. Method validation includes: 

1. A copy of the analytical method in standard written format 

2. Research report of analytical data from testing the proposed method 

using reference materials, duplicate samples, and method blanks 

3. Quality assurance review 

4. Research section review 

5. Operations section review 

vii 
DEFINITION OF TERMS 

Limit of Detection 

The limit of detection (LOD) must refer to the entire analytical measurement process and is 

usually regarded as the lowest concentration level of the analyte that can be determined to be 

statistically different from the analytical blank. 

According to the American Chemical Society (ACS, 1980) a confidence level of 3 sigma above the 

measured average blank is considered minimum since this implies the risk for 7 percent false 

positives (concluding the analyte is present when it is absent) and false negatives (the reverse). 

The 3 sigma value actually corresponds to a confidence level of about 90 percent as “a 99.6 

percent confidence level applies only for a strictly one-sided Gaussian distribution. At low 

concentrations, non-Gaussian distributions are more likely” (International Union of Pure and 

Applied Chemistry, 1978). 

Lower Reporting Limit 

The terms “lower reporting limit” , “lower limits of determination” and “lower limits of 

quantification” are confusing in the literature, and are described as either 5 sigma to 10 sigma. In 

this report the terms will be used for concentrations expected to be at or above five times the 

standard deviation determined from the method blank or low analyte concentration samples. 

Because of the different definitions given for these terms in the literature, the method 

descriptions will give the information in tables as 3s and 5s numbers. Given the varied matrices 

submitted to the laboratory and diverse data quality needs, these tables of method-blank and 

reference material results are included to assist in appropriate use of laboratory data. 

All submitted samples are initially run undiluted unless sample dilutions are required in order to 

reduce or eliminate known matrix/interference effects. When an analyte concentration exceeds 

the calibration or linear range, the sample is re-analyzed after appropriate dilution. The analyst 

will use the least dilution necessary to bring the analyte within range. In both cases, a loss of 

sensitivity is experienced. All sample dilutions result in an increase in the lower reporting limit 

by a factor equal to the dilution. 

Assuming independent normally distributed measurements, confidence limits may be assigned 

from the mean and standard deviation (based on a relatively large number of observations, or by 

use of a significance test). “In order to detect bias equal in magnitude to the standard deviation, 

one needs at least 12 degrees of freedom (13 replicates)” (Currie, 1988). 

Limit of Quantitation 

Ten sigma above the average blank is often suggested for the limit of quantitation or limit of 

determination. This is the lower limit for quantitative measurements (as opposed to qualitative 

measurements) and at this level the risk of false positives and negatives is decreased. 

viii 
ANALYTICAL PERFORMANCE SUMMARY 

A table is included under the Assignment of uncertainty section in each method write-up and 

provides an estimate of the analytical method performance. The results of the analytical 

measurement process are estimates of general performance only, given the sample matrix and 

analyte concentration. Outliers are not rejected unless reasons are known why the results are 

unacceptable. Calculated results (i.e. percent recovery) may not appear to match initial numbers 

due to rounding-off. 

The analytical performance summary table is arranged in three sections: (1) reference materials, 

(2) duplicates, and (3) method blank results. 

Reference Materials 

Reference material (RM) samples are materials having one or more well established or certified 

concentrations or physical properties to be used for instrument calibration, method accuracy, or 

testing. The RM is used for evaluation of the analytical method bias expressed as percent 

recovery (% R). An attempt is made to test methods (if appropriate reference material is 

available) at the lower, mid-point, and upper end of the operating range with a number of varied 

matrices. Solid phase samples are reported on an as received basis. No corrections are made for 

moisture content unless noted in the method. 

The first section of the table lists selected reference materials tested and associated results in 

rows. The table has column headings as follows: 

REFERENCE—sample name of the geochemical reference material 

DESCRIPTION—identification of the reference material 

n—number of observed measurements or samples in a subgroup 

Mean—arithmetic mean. Generally, the result is quoted with all digits which are certain, plus the 

first uncertain one. In order to compare some laboratory to proposed values and avoid the loss of 

information, whole numbers may not appear rounded-off. Less than symbol, “<“ is used for 

qualified data below the lower reporting limit 

s—standard deviation 

pv—proposed value taken from the published reference material compositions of Potts and 

others (1992). Where the proposed value has an accompanying upper case letter, the 

corresponding reference is in the headnote. According to Potts the tabulated data are 

distinguished by: 

bold typeface indicates precision better than 10 percent relative (two sigma), normally 

based on five or more results from two or more independent techniques 

certified value from the distributor of reference materials is designated “cv” 

plain typeface indicates other compiled data; distinguished by a {?} question mark if 

there is additional uncertainty (for example, fewer than 3 reported results, large disparity 

in reported results, and/or data derived from only one non-definitive technique) 

italic typeface indicates data abstracted from individual schemes of analysis fully 

described in the literature 

%RSD—percent relative standard deviation 

%R—percent recovery =(determined value/pv) x 100 

ix 
Duplicate Samples 

Duplicate samples are a second aliquot of a submitted sample (taken at the time of sample 

weighing) selected to evaluate laboratory variance (precision) expressed as percent relative 

standard deviation (% RSD). The aliquot is treated the same as the original sample through the 

analytical process. Duplicate samples take into account the analyte concentration and matrix of 

the sample of interest, i.e. samples submitted by ACSG customers. 

The second section of the table deals with duplicate samples. The column headings are as 

follows: 

k—number of subgroups under consideration 

n—2, number of samples in the subgroup 

Mean—arithmetic mean for duplicate measurements 

s—standard deviation for duplicate measurements 

%RSD—relative standard deviation 

Concentration Range—the minimum and maximum values reported of unqualified data (data 

that are greater than the lower reporting limit) 

No. of "<" (total)—the number of values less than the lower reporting limit 

No. of "<" (pairs)—the number of times the duplicates were both reported as less than values 

Method Blank 

A method blank contains deionized water or other solutions processed through the entire 

analytical method with submitted samples. It is used as an indicator of possible contamination 

due to reagents or apparatus and sensitivity of the analytical method. The variability (standard 

deviation) of the method blank can be used for estimating the lower limits of detection or 

determination. Pure solutions, however, assume no matrix effects and tend to be normally

distributed. In reality, matrix effects occur even in methods considered to be relatively free from 

interferences. 

The last section of the table lists the results for the method blank. The column headings are as 

follows: 

n—number of observed measurements on completely independently prepared blanks 

Mean—arithmetic mean

s—standard deviation 

3s—three times the standard deviation (limit of detection) 

5s—five times the standard deviation (lower reporting limit) 

If the chapter author thinks the reporting limits should not be the same as the 3s and 5s

determinations on blanks, then a separate table of reporting limits will be included in that

chapter. 

x 
ACKNOWLEDGMENTS 

This manual was prepared with the assistance of many U.S. Geological Survey scientists. The 

contribution of the following individuals in writing or reviewing the analytical methods are 

gratefully acknowledged: 

` 


Phil Aruscavage 


Elaine Brandt 


Paul Briggs 


Zoe Ann Brown 


James Budahn 


Joe Christie 


Jim Crock 


Kenneth Joe Curry 


Dave Detra 


Terry Fries 


Phil Hageman 


Roy Knight 


Reinhard Leinz 


Paul Lamothe 


Dave McKown 


Al Meier 


Rich O’Leary 


Clara Papp 


Thomas Peacock 


Sara Pribble 


Rick Sanzolone 


Dave Siems 


Tara Slowik 


Steve Sutley 


Cliff Taylor 


Pete Theodorakos 


Gregory Wandless 


Eric Welsch 


Steve Wilson 


A thank you is due Barbara Ramsey who performed the word processing of this report. 

REFERENCES CITED 

American Chemical Society's Committee on Environmental Improvement, 1980, 

Guidelines for data acquisition and data quality evaluation in environmental 

chemistry: Analytical Chemistry, v.52, no. 14, p. 245. 

Currie, L.A., ed., 1988, Detection in analytical chemistry- importance, theory, and 

practice: American Chemical Society Symposium Series 361, p. 23. 

International Union of Pure and Applied Chemistry, 1978, Nomenclature, symbols, 

units, and their usage in spectrochemical analysis-II: Spectrochimica Acta, v. 33, 

p. 245. 

Potts, P.J., Tindle, A.G., and Webb, P.C., 1992, Geochemical Reference Materials 

Compositions: CRC Press Inc., Boca Raton, Fla., 313 p. 

Sutley, S.J., January 1994, Branch of Geochemistry, Written communication to the 

editor: U.S. Geological Survey, Denver, Colo. 

xi 
Chapter V 

Fluoride, chloride, nitrate, and sulfate in aqueous

solution utilizing AutoSuppression chemically

suppressed ion chromatography 

By P.M. Theodorakos, W.M. d'Angelo and W.H. Ficklin

U.S. Geological Survey Open File Report 02-223-V 

Analytical methods for chemical analysis of geologic and other materials, U.S. 

Geological Survey 
Contents 

Principle V-1 

Interferences V-1 

Scope V-2 

Apparatus V-2 

PeakNet software V-2 

Reagents V-3 

Safety precautions V-3 

Running under PeakNet Control V-3 

Procedure V-3 

Calculations V-4 

Assignment of uncertainty V-5 

Bibliography V-6 

Tables 

1. DX 120 operating conditions for determination of selected anions 

by IC V-3 

2. Anion calibration standards (ppm) for DX-120 IC analysis V-4 

3. Analytical performance summary for selected anions (ppm) by IC V-5 
Fluoride, chloride, nitrate, and sulfate in aqueous solution

utilizing AutoSuppression chemically suppressed Ion

Chromatography 

By P.M. Theodorakos, W.M. d'Angelo and W.H. Ficklin

Codes: I011 Accepted: 4/21/94 

T05 Revised: 1/15/02 

Principle 

Four common anions: fluoride, chloride, nitrate, and sulfate are determined in aqueous solutions 

by ion chromatography (IC). The anions are separated based on their differential affinity for a low 

capacity, strongly basic anion exchange resin (Small and others, 1975). Each anion elutes from the 

AS-14 analytical column with a characteristic retention time in the order fluoride, chloride, nitrate, 

and sulfate when using the conditions described below. 

Chemically suppressed ion chromatography is achieved by employing AutoSuppression 

technology with the Anion Self-Regenerating Suppressor (ASRS-II) to enhance analyte 

conductivity while decreasing eluent conductivity. The AutoSuppression Recycle Mode uses the 

neutralized conductivity cell effluent as the source of water for the regenerant chamber water. This 

is the preferable method of operation for the ASRS-II. As the eluent passes through the ASRS-II, 

it is neutralized to form its weakly ionized form. After passing through the conductivity cell, the 

effluent is redirected to the regenerant inlet on the ASRS-II, thus supplying it with a source of 

water containing minute amounts of dilute analyte. This eliminates the need for chemical 

regenerants and regenerant cartridges (Dionex 1997b). 

Interferences 

The following discussion on interferences is taken directly from Pfaff and others (1991): 

“Interference can be caused by substances with retention times that are similar to and overlap 

those of the anion of interest. Large amounts of anion can interfere with the peak resolution of an 

adjacent anion. Sample dilution and/or fortification can be used to solve most interference 

problems.” 

The water dip or negative peak that elutes near the fluoride peak can cause interference. This can 

usually be eliminated by the addition of the equivalent of 1 μl of concentrated (100x) eluent to 5 

ml of each standard and sample or choosing the “void negative volume treatment for this peak” 

statement in the data events. 

Method interference may be caused by contamination in the reagent water, reagents, glassware, 

and other sample processing apparatus that leads to discrete artifacts or elevated baseline in the ion 

chromatograms. 

Samples that contain particles larger than 0.45 microns and reagent solutions that contain particles 

larger than 0.20 microns require filtration to prevent damage to instrument columns and flow 

systems. 

Any anion that is not retained by the column or only slightly retained will elute in the area of 

fluoride and interfere. Known co-elution is caused by carbonate and other small organic anions. 

Using the AS-14 analytical column with the advantages of improved retention and excellent 

resolution of fluoride this interference should not be significant. It is the responsibility of the user 

to generate precision and accuracy in the analysis in each sample matrix. 

V-1 
The acetate anion elutes early during the chromatographic run. The retention time of the anions 

also seem to differ when large amounts of acetate are present. Therefore, this method is not 

recommended for leachates of solid samples when acetate is used for pH adjustments. 

In addition to these problems described by Pfaff and others (1991), another problem may arise 

from analysis of a large number of samples of low pH containing Fe and SO4. The sulfate may 

accumulate by adsorption on Fe precipitates, to be released in subsequent elutions, resulting in 

elevated SO4 concentrations. This problem can be solved by adding 100 μl of concentrated (100x) 

eluent to 5ml of sample to raise the pH >4.5. The solution is covered and allowed to sit over 

night, decanted and filtered through a .45 μm filter prior to running. 

Interference can also be caused by metal contamination on the columns. This was experienced 

when running samples containing 500 ppm CuSO4. The problem was not recognized until check 

standards were run at the end of the job. Washing the columns with 500 ml of .01M oxalic acid 

solution followed by 500ml DI water removed the contamination. 

Scope 

This method is applicable to the analysis of natural waters and leachate solutions that do not 

contain acetate. It can be extended to include the analysis of water leachates of solid samples. 

Liquid samples should be refrigerated at 4o

C and stored no longer than 28 days when sulfate and 

nitrate are to be analyzed. For fluoride, chloride, and bromide no refrigeration is required. If nitrite 

and/or phosphate are to be analyzed, the samples must be refrigerated and analyzed within 48 

hours. In a given sample, the anion that requires the most preservation treatment and the shortest 

holding time will determine the preservation treatment (Pfaff and others, 1991). 

Using the DX-120 ion chromatograph, PeakNet workstation, and the AS40 automated sampler, an 

operator can analyze about 32 samples, including blank, calibration standards and reference 

sample solutions, in a normal 8 hour day. An additional 66 samples can be analyzed overnight. 

Fluoride is generally determined from .08 to 4 mg/L, chloride from 0.08 to 4 mg/L, nitrate from 

0.08 to 4 mg/L, and sulfate from 1.2 to 80 mg/L. Solutions with higher concentrations can be 

diluted to the appropriate calibration range. If the majority of samples in the job have consistently 

high chloride values (>20 ppm) they are analyzed using a method for determining higher 

concentrations of chloride and nitrate while fluoride and sulfate concentration ranges remain as 

stated above. If the higher Cl- concentration method is used, the lower level of determination for 

both chloride and nitrate is higher than in the procedure normally used. 

Apparatus 

Ion Chromatograph (Dionex Model DX-120)

Guard column (Dionex AG-14) 

Analytical column (Dionex AS-14) 

Anion Self-Regenerating Suppresser (Dionex ASRS-II) 

Conductivity Detector (Dionex DS4 Detection Stablizer) 

Automated sampler (AS40)

PeakNet Workstation (computer, printer, monitor, mouse, DX LAN card, AS40 serial port, and an

operating environment supported by MS-DOS and Windows 3.1 or newer and PeakNet software.)

PeakNet Software 

PeakNet software controls the instrumentation; automatically collects, processes, and reports data; 

and provides utilities that interpret analytical results. (Dionex, 1996). 

V-2 
Reagents 

Deionized water with a resistivity of 17.8 mega-ohms or greater 

Sodium carbonate, Na2CO3 ACS reagent grade 

Sodium bicarbonate, NaHCO3 ACS reagent grade 

Eluent: 3.5 mM Na2CO3, 1.0 mM NaHCO3 . 

Safety precautions 

Normal laboratory safety procedures should be followed. The operator should take care when 

analyzing samples of an unknown nature. Refer to the CHP and MSDS for specific precautions, 

effects of overexposures, and first-aid treatment for reagents used in this method. 

Running under PeakNet Control 

When the DX-120 is connected to a PeakNet workstation via the DX LAN interface, PeakNet 

software (Release 4.30 or later) can monitor DX-120 status and control the following functions. 

Select the position of the injection and column selection valves, turn on the pump flow, SRS 

power, eluent pressure on and off, perform an auto offset, select the pressure units displayed on 

the screen (Mpa or psi), control TTL1 and TTL2 output signals, and control the auxiliary AC 

outlet (Dionex, 1996). 

Procedure 

Refer to the Dionex manual (Dionex 1994, 1996) for the proper procedure for operating the 

instrument. Allow the system to equilibate for 15 to 20 minutes prior to any sample or standard 

injection. The background conductivity should be between 15 and 17 microsiemens (μs). 

Instrumental operating conditions are summarized in table 1. 

Table 1.---DX 120 Operating conditions for determination of selected anions

by IC 

Columns ........................ AG-14 (4x50mm) guard column

........................... ......... AS-14 (4x250mm) analytical column

Suppresser ...................... ASRS II Anion self-regenerating suppresser 

Eluent ............................ 3.5 mM Na2CO3 sodium carbonate 

..................................... 1.0 mM NaHCO3 sodium bicarbonate 

Flow Rate ....................... eluent: 1.2 ml/min 

Detector Cell .................... CDM-3 or DS4 Detection Stabilizer

Sample loop ..................... 25 μl 

Sampler .......................... AS40 Automated Sampler 

The samples are prepared in 5 ml PolyVials with filtercap and placed in sample cassettes. The 

AS40 can take a maximum of 11 cassettes of 6 samples each, which are placed in the input tray 

ahead of the spring-loaded pusher. 

V-3 
Calibration is accomplished by injection of multi-element anion standards containing the anions of 

interest. For multi-level calibrations, several calibration standards covering the expected 

concentration range must be injected. A calibration curve for each component is determined from 

the data acquired for each different calibration level. Correlation coefficients of “r” value 0.995 or 

better should be obtained before proceeding with sample analysis. When typing the schedule use 

the special sample name AUTOCAL x, where x is the calibration level (1-10), only if the sample 

is a calibration standard. AUTOCAL x causes the Run program to use the current peak areas to 

update the Method Component Table. After the first sample of deionized water is run as a system 

flush, autocals 1-5 are run to establish a calibration curve for each anion of interest, plotting peak 

area vs. concentration. This calibration sequence is followed by a WRD anion standard to check 

precision and accuracy. After the WRD standard is run, samples 1-20, a duplicate, and a second 

WRD standard are run. This calibration sequence is repeated every 20 samples to compensate for 

drift in the system. Peak area for each anion detected is plugged into the individual quantitation 

equations established from the calibration curve for that specific anion and used to determine their 

concentration. The calibration standards and their concentrations are listed in table 2. 

Table 2.-- Anion Calibration standards (ppm) for DX-120 IC Analysis 

Anion Autocal 1 Autocal 2 Autocal 3 Autocal 4 Autocal5 

F- 0.08 0.4 0.8 2.0 4.0 

Cl- 0.08 0.4 0.8 2.0 4.0 

- NO3 0.08 0.4 0.8 2.0 4.0 

SO4

2- 1.6 8.0 16 40 80 

Calculations 

A calibration curve for each component is determined from the data acquired from each 

calibration level (table 2), using either a linear, quadratic, cubic, or point to point interpolation. A 

linear fit is used most often in this method and is determined by a least-squares calculation to fit a 

line through the calibration points. When the analyte concentration, for a specific component 

approaches the end of the calibration range and the detector response is known to “flatten out” 

toward one extreme or the other, a quadratic fitting may be used. 

Linear Fit Calculation: 

AMTi = (K1 x Area) + Ko 

Where: 

Amti = the amount of the component I in the sample 

Areai = the area of component I in the sample 

K1 = the slope of the response line of component I 

Ko = the Y-axis intercept of the component I calibration curve 

V-4 
Assignment of Uncertainty

Table 3. -- Analytical performance summary for selected anions (ppm) by IC 

Reference materials are water samples with pv from Water Resources Division, (USGS OPF 95-395, 96-138, 97-

20, 00-227, 00-398, and 01-137). See page ix of the introduction to this Methods Manual for an explanation of the 

abbreviations used in the analytical performance summary tables. 

Reference Description n Mean s pv % RSD % R 

Fluoride, FP-25 major constituents 28 0.150 0.019 0.139 12.7 92.7 

M-134 major constituents 18 0.563 0.033 0.561 5.81 99.6 

M-140 major constituents 19 0.573 0.031 0.530 5.47 92.6 

M-130 major constituents 30 1.115 0.186 1.23 16.7 110 

Chloride, ClP-25 major constituents 28 1.235 0.035 1.30 2.84 106 

M-130 major constituents 30 22.083 0.750 21.4 3.40 96.9 

M-140 major constituents 19 25.735 0.830 25.8 3.22 100 

M-134 major constituents 18 66.502 0.673 65.0 1.01 97.7 

-

Nitrate, NO3


N-63 major constituents 28 0.366 0.029 0.37 8.00 101 


N-66 major constituents 28 4.135 0.076 4.12 1.85 99.6 


N-64 major constituents 28 6.556 0.082 5.58 1.25 85.1 


N-68 major constituents 28 7.484 0.100 7.44 1.33 99.4 
 +

Values for nitrate were calculated from the nitrogen proposed values by multiplying by a 4.42680 

gravimetric factor. 

2- Sulfate, SO4


P-25 major constituents 28 2.435 0.224 2.34 9.19 96.1 


M-130 major constituents 30 55.883 0.903 58.0 1.62 104 


M-134 major constituents 18 78.071 1.347 78.0 1.72 99.9 


M-140 major constituents 19 149.89 4.559 150.0 3.22 100 


Table 3.—Continued—Duplicate samples results 

Duplicate samples k n Mean s % RSD Concentration Range No. of <No. of < 

(totals) (pairs) 

Fluoride 30 2 0.58 0.03 5.867 0.08 to 4.0 0 0 

Chloride 30 2 6.46 0.161 0.05 0.08 to 60 0 0 

Nitrate 30 2 14.36 0.13 0.923 0.08 to 18 0 0 

Sulfate 30 2 127.67 1.40 1.097 1.6 to 80 0 0 

V-5 
Table 3.—Continued—Method blank results 3s values are considered the lower limit 

of detection (LOD), and 5s values are considered the lower limit of determination (LLD) 

Method blank n Mean s 3s 5s 

Chloride 30 0.03 0.01 0.04 0.05 

Nitrate 30 0.04 0.02 0.06 0.1 

Sulfate 30 0.04 0.01 0.02 0.05 

Fluoride* 30 0.007 0.002 0.007 0.01 

*Fluoride blank values determined using a low standard (0.005 ppm) 3s values are considered the lower 

limit of detection (LOD), and 5s values are considered the lower limits of determination (LLD) 

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