U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006-1245

Quality-Assurance Data for Routine Water Analyses by the

U.S. Geological Survey Laboratory in Troy, New York—

July 1997 through June 1999
Cover. Whitewater rafting on the Indian River near Indian Lake, New York.

Courtesy Middle Earth Expeditions ©2006 Melody Thomas Photography
Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York—

July 1997 through June 1999

By Tricia A. Lincoln, Debra A. Horan-Ross, Michael R. McHale, and 

Gregory B. Lawrence

Open-File Report 2006–1245

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment:

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Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Lincoln, T.A., Horan-Ross, D.A., McHale, M.R., and Lawrence, G.B., 2006, Quality-Assurance Data for Routine 

Water Analyses by the U.S. Geological Survey Laboratory in Troy, New York—July 1997 through June 

1999: U.S. Geological Survey Open-File Report 2006–1245, 25 p., online only.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Participating Projects ..........................................................................................................................2

Quality-Assurance/Quality-Control (QA/QC) Program.............................................................................2

Quality-Control Samples......................................................................................................................2

Filter Blanks and Analytical Blanks ...................................................................................................3

Triplicate Environmental Samples......................................................................................................3

U.S. Geological Survey’s Standard Reference Sample Project....................................................3

NWRI Ecosystem Interlaboratory QA Program ...............................................................................3

Blind Reference Samples....................................................................................................................4

Control-Chart Evaluation...............................................................................................................................4

Quality-Control Samples......................................................................................................................5

Filter Blanks and Analytical Blanks ...................................................................................................6

Triplicate Environmental Samples......................................................................................................6

NWRI Ecosystem Interlaboratory QA Program ...............................................................................6

Blind Reference Samples....................................................................................................................6

Summary of Results.......................................................................................................................................6

A. Quality-Control Samples .................................................................................................................6

B. Filter Blanks and Analytical Blanks ..............................................................................................7

C. Triplicate Environmental Samples .................................................................................................8

D. U.S. Geological Survey’s Standard Reference Sample (SRS) Project ....................................8

E. NWRI Ecosystem Interlaboratory QA Program.........................................................................10

F. Blind Reference Samples ..............................................................................................................10

Selected References...................................................................................................................................11

Figures

1–5 Graphs showing—

1. High- and low-concentration quality-control sample results: 

A. Acid-neutralizing capacity.................................................................................................14

B. Aluminum, total monomeric...............................................................................................14

C. Aluminum, total ....................................................................................................................14

D. Ammonium............................................................................................................................14

E. Calcium..................................................................................................................................15

F. Carbon, dissolved organic..................................................................................................15

G. Chloride.................................................................................................................................15

H. Fluoride .................................................................................................................................15

I. Magnesium ............................................................................................................................16

J. Nitrate (ion chromatography)............................................................................................16

K. Nitrate (colorimetric method)............................................................................................16

L. pH............................................................................................................................................16

M. Potassium ............................................................................................................................17

N. Silicon ...................................................................................................................................17
iv

O. Sodium ..................................................................................................................................17

P. Specific conductance.........................................................................................................17

Q. Sulfate ...................................................................................................................................18

2. Filter-blank and analytical-blank sample results: 

A. Aluminum, total monomeric...............................................................................................19

B. Aluminum, organic monomeric.........................................................................................19

C. Aluminum, total ....................................................................................................................19

D. Ammonium............................................................................................................................19

E. Calcium..................................................................................................................................19

F. Carbon, dissolved organic..................................................................................................19

G. Chloride.................................................................................................................................19

H. Magnesium...........................................................................................................................19

I. Nitrate (ion chromatography).............................................................................................20

J. Potassium..............................................................................................................................20

K. Silicon....................................................................................................................................20

L. Sodium ...................................................................................................................................20

M. Sulfate ..................................................................................................................................20

3. Triplicate environmental sample results: 

A1. Acid-neutralizing capacity (for triplicate means not in ±20 μeq/L range) ...............21

A2. Acid-neutralizing capacity (for triplicate means in ± 20 μeq/L range).....................21

B. Aluminum, total monomeric...............................................................................................21

C. Aluminum, organic monomeric .........................................................................................21

D. Aluminum, total....................................................................................................................21

E. Calcium..................................................................................................................................21

F. Carbon, dissolved organic..................................................................................................21

G. Chloride.................................................................................................................................21

H. Magnesium...........................................................................................................................22

I. Nitrate (ion chromatography).............................................................................................22

J. pH ...........................................................................................................................................22

 K. Potassium ............................................................................................................................22

L. Silicon ..................................................................................................................................22

M. Sodium .................................................................................................................................22

N. Sulfate...................................................................................................................................22

4. NWRI Ecosystem Interlaboratory QA Program results: 

A1. Acid-neutralizing capacity (for samples not in the range of ± 20 μeq/L).................23

A2. Acid-neutralizing capacity (for samples in the range of ± 20 μeq/L)........................23

B. Ammonium............................................................................................................................23

C. Calcium..................................................................................................................................23

D. Carbon, dissolved organic ................................................................................................23

E. Chloride .................................................................................................................................23

F. Magnesium ...........................................................................................................................23

G. Nitrate (ion chromatography)............................................................................................23

H. pH...........................................................................................................................................24

I. Potassium..............................................................................................................................24

J. Silicon ....................................................................................................................................24

K. Sodium...................................................................................................................................24

L. Specific conductance .........................................................................................................24

M. Sulfate ..................................................................................................................................24
Tables

1. Number of environmental and quality-control (QC) samples analyzed by the 

Troy Laboratory, and summary of quality-control data for each constituent, 

July 1997 through June 1999.......................................................................................................4

2. Reporting limits and data-quality objectives for accuracy, precision, and blanks 

for solution analyses performed by the U.S. Geological Survey Laboratory in 

Troy, N.Y., July 1997 through June 1999.....................................................................................5

3. Results obtained by the Troy Laboratory for the U.S. Geological Survey’s Standard 

Reference Sample (SRS) Project, September 1997 through March 1999 ...........................9

5. Blind reference sample results: 

A. Calcium .................................................................................................................................25 

B. Chloride.................................................................................................................................25

C. Magnesium...........................................................................................................................25

D. pH...........................................................................................................................................25

E. Potassium..............................................................................................................................25

F. Sodium ...................................................................................................................................25

G. Specific conductance ........................................................................................................25

H. Sulfate ...................................................................................................................................25

ABBREVIATED UNITS OF MEASUREMENT

mg/L milligrams per liter

μeq/L microequivalents per liter

μmol/L micromoles per liter

μS/cm microsiemens per centimeter

μg/L micrograms per liter

Other Abbreviations

ANC Acid-neutralizing capacity

AV Analyzed value

CV Coefficient of variation

D Percent difference

DI Deionized water

DOC Dissolved organic carbon

DQO Data-quality objective

MCV Mean concentration value

MPV Most probable value

NWRI National Water Research Institute

QA Quality assurance

QC Quality control

QC-high High-concentration quality-control sample

QC-low Low-concentration quality-control sample

SRS Standard Reference Sample

TV Troy Laboratory value

USGS U.S. Geological Survey
This page has been left blank intentionally. 
Quality-Assurance Data for Routine Water Analyses by 

the U.S. Geological Survey Laboratory in Troy, New York— 

July 1997 through June 1999

By Tricia A. Lincoln, Debra A. Horan-Ross, Michael R. McHale, and Gregory B. Lawrence 

Results of the USGS interlaboratory Standard Reference 

Sample (SRS) Project indicated good data quality for most 

constituents over the time period. The P-sample (low-ionicstrength constituents) analysis had good ratings in two of these 

studies and a satisfactory rating in the third. The results of 

the T-sample (trace constituents) analysis indicated high data 

quality with good ratings in all three studies. The N-sample 

(nutrient constituents) studies had one each of excellent, good, 

and satisfactory ratings.

Results of Environment Canada’s National Water 

Research Institute (NWRI) program indicated that at least 80 

percent of the samples met data-quality objectives for 9 of the 

13 analytes; the exceptions were dissolved organic carbon, 

ammonium, chloride, and specific conductance. Data-quality 

objectives were not met for dissolved organic carbon in two 

NWRI studies, but all of the samples were within control 

limits for the last study. Data-quality objectives were not met 

in 41 percent of samples analyzed for ammonium, 25 percent 

of samples analyzed for chloride, and 30 percent of samples 

analyzed for specific conductance.

Results from blind reference-sample analyses indicated 

that data-quality objectives were met by at least 84 percent of 

the samples analyzed for calcium, chloride, magnesium, pH, 

and potassium. Data-quality objectives were met by 73 percent 

of those analyzed for sulfate. The data-quality objective was 

not met for sodium. The data are insufficient for evaluation of 

the specific conductance results.

Introduction

The U.S. Geological Survey (USGS) maintains a 

laboratory at its Water Science Center in Troy, N.Y., to 

analyze low-ionic-strength water for USGS watershedresearch projects that require major-ion analyses of 

precipitation, soil-water, shallow ground-water, and streamwater samples. The methods used in this laboratory are 

described in detail in Lawrence and others (1995). Qualityassurance and quality-control data for the period of this report 

Abstract

The laboratory for analysis of low-ionic-strength water 

at the U.S. Geological Survey (USGS) Water Science Center 

in Troy, N.Y., analyzes samples collected by USGS projects 

throughout the Northeast. The laboratory’s quality-assurance 

program is based on internal and interlaboratory qualityassurance samples and quality-control procedures that were 

developed to ensure proper sample collection, processing, 

and analysis. The quality-assurance/quality-control data for 

the time period addressed in this report were stored in the 

laboratory’s SAS data-management system, which provides 

efficient review, compilation, and plotting of data. This report 

presents and discusses results of quality-assurance and qualitycontrol samples analyzed from July 1997 through June 1999.

Results for the quality-control samples for 18 analytical 

procedures were evaluated for bias and precision. Control 

charts indicate that data for eight of the analytical procedures 

were occasionally biased for either high-concentration and 

(or) low-concentration samples but were within control limits; 

these procedures were: acid-neutralizing capacity, total 

monomeric aluminum, total aluminum, ammonium, calcium, 

chloride, specific conductance, and sulfate. The data from the 

potassium and sodium analytical procedures are insufficient 

for evaluation.

Results from the filter-blank and analytical-blank 

analyses indicate that the procedures for 11 of 13 analytes 

were within control limits, although the concentrations for 

blanks were occasionally outside the control limits. Blank 

analysis results for chloride showed that 22 percent of blanks 

did not meet data-quality objectives and results for dissolved 

organic carbon showed that 31 percent of the blanks did not 

meet data-quality objectives.

Sampling and analysis precision are evaluated herein 

in terms of the coefficient of variation obtained for triplicate 

samples in the procedures for 14 of the 18 analytes. At least 

90 percent of the samples met data-quality objectives for 

all analytes except total aluminum (70 percent of samples 

met objectives) and potassium (83 percent of samples 

met objectives).
(July 1997–June 1999) were collected, stored, and reviewed 

through the laboratory’s SAS data-management system.

The 18 analytes represented by this study were: acidneutralizing capacity (ANC), total monomeric aluminum, 

organic monomeric aluminum, total aluminum, ammonium, 

calcium, dissolved organic carbon (DOC), chloride, fluoride, 

magnesium, nitrate (ion chromatograph and colorimetric 

method), pH, potassium, silicon, sodium, specific 

conductance, and sulfate.

Purpose and Scope

This report documents the quality-assurance practices and 

quality-control data of this laboratory and is intended for use 

by cooperating agencies. It (1) describes quality-control and 

quality-assurance procedures of the laboratory; (2) presents 

graphs showing the results from analyses of quality-control 

samples, filter blanks and analytical blanks, triplicate 

environmental samples, interlaboratory quality-assurance 

samples, and blind reference samples; and (3) describes 

analytical biases and outliers and the corrective actions taken.

Participating Projects

The numbers and types of samples analyzed by the 

laboratory during the 2-year period are summarized below, by 

the project for which they are associated.

Project: Neversink Watershed Study

Cooperator: New York City Department of 

Environmental Protection

Analyses: 251 samples (stream water, shallow ground water, 

and snow).

Project: Biogeochemical Processes that Control Nitrogen 

Cycling and Associated Hydrogen and Aluminum Leaching in 

an Undeveloped Headwater Basin

Cooperator: New York City Department of 

Environmental Protection

Analyses: 4,803 samples (stream water, shallow ground 

water, soil-water solution, soil-water by expulsion method, 

and snow).

Project: Long-Term Monitoring of Five Streams in the 

Catskill Mountains 

Cooperator: U.S. Environmental Protection Agency 

Analyses: 657 stream-water samples.

Project: The Effects of the Clean Air Act on Water Quality of 

Medium-Scale Rivers in the Northeastern United States

Cooperator: U.S. Geological Survey, Office of Water Quality

Analysis: 495 stream-water samples.

Project: Adirondack Effects Assessment Program

Cooperator: Rensselaer Polytechnic Institute

Analyses: 246 stream-water samples.

Project: Upper and Lower Node Water-Quality Operation 

and Maintenance in the Catskill Mountains, New York

Cooperator: New York City Department of 

Environmental Protection

Analyses: 361 stream-water samples.

Project: Hydrologic Geomorphology, Water Quality, and 

Biology of the Neversink River

Cooperator: Town of Thompson, New York

Analysis: 26 stream-water samples.

Additional information on projects of the New York 

Water Science Center is given in Lee (1996), and at 

http://ny.water.usgs.gov.

Quality-Assurance/Quality-Control 

(QA/QC) Program

The quality of the data produced at this laboratory is 

maintained by adherence to the standard operating procedures 

described in Lawrence and others (1995) and by participation 

in externally administered quality-assurance (QA) programs. 

Results of QA data are evaluated by the laboratory supervisor 

and primary analysts, and appropriate corrective action is 

taken when needed. The data-quality objectives (DQOs) 

are based on (1) the precision and accuracy levels generally 

required by projects that use the Troy Laboratory, and (2) the 

analytical limits of the methods used.

Quality-Control Samples

Quality-control (QC) samples are used to measure 

the accuracy of an instrument’s calibration and to detect 

variations in instrument response within an analytical 

run. Source material for all QC samples either is obtained 

from a manufacturer other than the producer of the source 

material used to make calibration standards, or is obtained 

from a lot other than the source material used to make 

calibration standards.

The concentrations of QC samples are chosen to 

bracket the expected range of the environmental sample 

concentrations. A high-concentration QC sample and a 

low-concentration QC sample (referred to herein as QC-high 

and QC-low) are prepared for most analyses; exceptions are 

organic monomeric aluminum, for which column efficiency 

is used to determine the acceptability of the data, and 

fluoride, for which only one mid-level QC sample is prepared 

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
because the concentrations encountered by the laboratory 

are within a narrow range. QC-high and QC-low samples 

are analyzed within a run for most constituents; exceptions 

are ANC, pH, and specific conductance. Either the QC-high 

sample or QC-low sample is analyzed within an ANC, pH, 

and specific conductance run, depending upon the expected 

concentration range of the environmental samples.

Quality-control samples are analyzed immediately 

after instrument calibration, after every 10 analyses of 

environmental samples, and at the end of each run. QC 

samples that do not meet DQOs for accuracy are rerun, 

and if the value is acceptable, the run is continued. If the 

rerun QC sample value is unacceptable, the environmentalsample data preceding it are considered to be out-ofcontrol, the data are rejected, and the instrument is 

recalibrated. Only accepted QC-sample and environmental 

sample data are entered into the database. An exception to 

this practice occurs when the volume of an environmental 

sample is insufficient for a rerun; in this case, the 

environmental sample and QC data are entered into the 

database and flagged, and the project chief then decides 

whether to use or exclude these data from their reports. 

The analytical results of QC samples in this report indicate 

(1) the frequency of out-of-control data that are not rerun, 

and (2) biases and trends of control data. The numbers of 

samples analyzed and a summary of the quality-assurance 

data are given in table 1.

Filter Blanks and Analytical Blanks

A filter blank and an analytical blank are included in each 

group of 50 environmental samples. 

Filter blanks are aliquots of deionized (DI) water that are 

processed and analyzed in the same manner as environmental 

samples. Filter blanks are analyzed only for constituents that 

require filtration. Filter-blank analysis indicates whether 

contamination has occurred during any step in sample 

handling, including bottle-washing procedures, filtration, 

sample preservation, or laboratory analysis.

Analytical blanks are aliquots of DI water that are 

processed and analyzed as environmental samples, except that 

the filtration step is omitted. Contamination found in analytical 

blanks may be attributed to any step in sample handling, but 

not to filtration.

Triplicate Environmental Samples

One set of triplicate environmental samples is included 

in each group of 50 samples. An environmental triplicate set 

consists of three consecutive samples collected at one field 

site. The purpose of environmental triplicate samples is to 

determine long-term analytical precision. Precision can be 

affected by bottle washing, sample-collection or sampleprocessing procedures, and analysis. Environmental samples 

are selected for triplicate analysis on a random basis to ensure 

a wide range of sample concentrations from several field sites. 

The laboratory alternates between analyzing a triplicate set 

consecutively and separating the triplicate set over a day or 

multiple day’s analytical runs.

U.S. Geological Survey’s Standard Reference 

Sample Project

The USGS Standard Reference Sample (SRS) Project 

conducts a national interlaboratory analytical evaluation 

program semiannually. The Troy Laboratory participates 

in the low-ionic-strength, nutrient, and trace components 

of this program. Typically, the reference samples consist 

of snow, rain, surface water, or deionized water that is 

collected, filtered, and possibly spiked with reagent-grade 

chemicals to meet the goals of the program. Reference 

samples for low-ionic-strength constituents are prefixed 

by a P and are analyzed for calcium, chloride, fluoride, 

magnesium, pH, potassium, sodium, specific conductance, 

and sulfate. Reference samples for nutrient constituents 

are prefixed by an N and are analyzed for ammonium. 

Reference samples for trace constituents are prefixed by 

a T and are analyzed for aluminum, calcium, magnesium, 

potassium, silicon, and sodium. Laboratory personnel are 

aware of the presence of the SRS sample at the time of 

analysis but do not know the constituent concentrations 

until a published report is received from the USGS after the 

conclusion of each study. The most probable value (MPV) 

for each constituent is equal to the median value calculated 

from the results submitted by participating laboratories. 

Laboratory performance is rated numerically by comparing 

analysis results to the MPVs for each constituent; the 

highest score is 4.0, and the lowest is 0.0.

NWRI Ecosystem Interlaboratory QA Program

The Troy Laboratory participates in Environment 

Canada’s National Water Research Institute (NWRI) 

Ecosystem Interlaboratory QA program, in which a set 

of 10 samples is analyzed twice yearly. The samples are 

obtained from predominantly low-ionic-strength waters 

from several sources such as precipitation, snow, lakes, and 

streams throughout North America. The concentrations of 

the constituents in the NWRI samples are similar to those of 

the environmental samples analyzed at the Troy Laboratory. 

Laboratory results are compared with a median concentration 

value (MCV) calculated from results from all participants in 

the NWRI program. Laboratory personnel are aware of the 

presence of NWRI samples at the time of analysis but do not 

know the MCV of the constituents until Environment Canada 

publishes a report at the conclusion of each study. 

Quality-Assurance/Quality-Control (QA/QC) Program 
Blind Reference Samples

The Troy Laboratory disguises USGS SRS samples 

from previous studies as routine environmental samples. 

These blind reference samples are processed and analyzed as 

environmental samples and therefore appear to the analyst to 

be project samples. The blind reference samples have most 

probable values that were reported by the USGS SRS project. 

The SRS samples are rotated as supplies are exhausted, and 

periodically the identity of the blind reference sample is 

changed. One blind reference sample is included in each set of 

50 environmental samples. The Troy Laboratory used SRS Psamples as the blind reference samples during the time period 

represented in this report.

Control-Chart Evaluation

Control charts (figs. 1–5, p. 14–25) are plots of 

QC data through time. This report uses control charts to 

(1) indicate whether the laboratory DQOs are met for 

individual QC samples; (2) reveal long-term biases within 

and outside the control limits; and (3) provide comparisons 

with results from other laboratories. 

Each analyte has prescribed control limits that have been 

established to meet project DQOs (table 2). A constituent 

analysis is considered biased if 70 percent or more of the 

points on a chart are above or below the target value.

Table 1. Number of environmental and quality-control (QC) samples analyzed by the Troy Laboratory, and summary of quality-control 

data for each constituent, July 1997 through June 1999. 

[QC-high, high concentration quality-control sample; QC-low, low concentration quality-control sample]

Constituent

Number of samples analyzed Number of QC samples 

exceeding control limits 

where environmental 

sample data are 

not rejected

Number of QC samples 

exceeding control limits 

by more than 5 percent 

where environmental 

sample data are 

not rejected

Environmental

samples

QC-high 

samples

QC-low 

samples

QC-high QC-low QC-high QC-low

Acid-neutralizing capacity 4,995 96 422 0 6 0 0

Aluminum, total monomeric 5,091 691 690 3 0 0 0

Aluminum, organic monomeric1 5,102 0 0 0 0 0 0

Aluminum, total 4,955 658 659 8 1 1 0

Ammonium 4,413 591 593 1 4 0 0

Calcium 5,219 544 546 0 0 0 0

Carbon, dissolved organic 5,286 692 693 1 8 0 0

Chloride 5,430 835 835 0 2 0 0

Fluoride 1,991 0 2372 0 0 0 0

Magnesium 5,200 545 547 0 0 0 0

Nitrate (ion chromatography) 5,861 949 948 0 3 0 1

Nitrate (colorimetric method) 620 169 169 0 0 0 0

pH 5,191 195 634 0 1 0 0

Potassium 5,093 77 77 0 0 0 0

Silicon 5,120 637 635 0 2 0 0

Sodium 4,597 69 69 0 0 0 0

Specific conductance 1,577 0 174 0 0 0 0

Sulfate 5,401 816 816 0 4 0 1

1

Column efficiency is used to determine the acceptability of the data.

2

Mid-level QC samples are used for fluoride.

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
Quality-Control Samples

QC sample-analysis data are plotted on control charts 

(fig. 1) in which the central line denotes the target value of 

the control sample. The control limits for the samples are 

represented by the upper and lower control-limit lines on each 

chart. QC-high and QC-low samples are plotted on separate 

graphs by constituent and date of analysis, and the control 

charts are evaluated for trends and (or) bias and precision. All 

data are reported in micromoles per liter (μmol/L) except for 

pH (pH units), ANC (microequivalents per liter, μeq/L), and 

specific conductance (microsiemens per centimeter, μS/cm).

During this period, the concentration of total aluminum 

in the QC-low sample (fig. 1C) was changed to more closely 

represent typical environmental-sample concentrations. The 

concentration change is discussed in the summary of results. 

Results of the QC-sample analyses for sodium and 

potassium were misplaced during a database upgrade in late 

1999, and neither electronic nor paper copies of the data have 

been located. The QC samples were run as usual, but the 

laboratory was unable to produce complete control charts for 

this period.

Table 2. Reporting limits and data-quality objectives for accuracy, precision, and blanks for solution analyses

performed by the U.S. Geological Survey Laboratory in Troy, N.Y., July 1997 through June 1999.

[DQO, data-quality objective; μmol/L, micromoles per liter; CV, coefficient of variation; ANC, acid-neutralizing capacity]

Constituent or property

Reporting 

limit 

(μmol/L)

Accuracy Precision

Filter and 

analytical 

blanks DQO

(μmol/L)

Low-concentration 

quality-control sample

High-concentration 

quality-control sample Environmental 

triplicate 

samples 

DQO (CV)

DQO 

(percent 

error)

Concentration

(μmol/L)

DQO 

(percent 

error)

Concentration

(μmol/L)

Acid-neutralizing capacity1 none 10 (-39.9) 10 (125) 15 none

Aluminum, total monomeric 1.5 15 7.41 10 18.5 15 1.0

Aluminum, organic monomeric2 1.5 none none none none 15 1.0

Aluminum, total 1.0 20 1.49 10 11.2 15 1.0

Ammonium 2.0 15 7.14 10 17.9 none 1.5

Calcium 2.0 10 25.0 10 99.8 10 1.0

Carbon, dissolved organic3 41.0 15 83.3 10 416 10 18

Chloride 3.0 10 8.47 10 84.7 10 2.0

Fluoride 0.5 15 1.58 none none none none

Magnesium 1.0 10 10.3 10 41.1 10 0.5

Nitrate (ion chromatography) 2.0 10 4.84 10 48.4 10 0.3

Nitrate (colorimetric method) 5.0 15 42.9 10 100 none none

pH4 none 10 (4.44) 20 (6.88) 10 none

Potassium 1.0 10 6.40 10 25.6 10 0.5

Silicon 6.0 10 35.6 10 107 10 3.0

Sodium 1.0 10 10.9 10 43.5 10 1.0

Specific conductance5 none 10 (17.0) 10 (39.0) none none

Sulfate 2.0 10 8.33 10 83.3 10 0.3

1

ANC: values in parentheses are in microequivalents per liter. For values within ±20 microequivalents per liter, an absolute data-quality objective of ±6 microequivalents per liter is used for precision. 

2

Quality-control samples for organic monomeric aluminum are unavailable.

3

Concentrations are expressed as micromoles carbon per liter.

4

pH: percent error and coefficient of variation are calculated from [H+]. Values in parentheses are in pH units.

5

Specific conductance: values in parentheses are in microsiemens per centimeter.

Control-Chart Evaluation   
Filter Blanks and Analytical Blanks

Results from the blank analyses are plotted by constituent 

in figure 2. The control limits are represented by horizontal 

lines on the control charts. Data are plotted as concentration 

in relation to date of collection. Negative blank concentrations 

are encountered frequently. During analysis, the instrument 

calibration curve is extrapolated beyond the lowest standard 

to evaluate blank samples, and negative concentrations reflect 

the practical limitations of the extrapolation. An outlier on the 

control chart indicates possible contamination.

Triplicate Environmental Samples

The coefficient of variation (CV) for each triplicate 

sample concentration is plotted by constituent and date of 

collection in figure 3. Data with mean concentrations less 

than the defined reporting limit (table 2) are excluded. The 

DQO for all constituents is a CV of less than 10 percent, with 

the exception of ANC, total monomeric aluminum, organic 

monomeric aluminum, and total aluminum, for which it is 15 

percent. Each circle within the control charts represents the 

CV of a triplicate environmental sample. 

 , (1)

where

S = standard deviation, 

and

X = arithmetic mean of triplicate samples.

The ANC data are plotted on two graphs. The first 

(fig. 3A1) shows the CV for triplicate sample means outside

the range of ±20-μeq/L; the absolute value of the mean is 

used to calculate the CV. The second (fig. 3A2) shows values 

within the±20-μeq/L range; each symbol on the second graph 

represents the difference between the triplicate sample mean 

and the individual values of that triplicate sample.

NWRI Ecosystem Interlaboratory QA Program

Interlaboratory-comparison graphs (fig. 4) are based 

on results from NWRI samples and represent NWRI studies 

from September 1997 through March 1999. Sample data with 

MCVs less than the Troy Laboratory reporting limits were 

excluded. The MCV and the control limits are represented by 

lines on the graphs; the percent difference (D) is calculated as:

 , (2)

where

AV = analyzed value, 

and

MCV = mean concentration value.

CV S

X

CV = ( ) 100 S

X = ( ) 100

D A = − ( ) V MCV MCV  

 D A = − ( ) V MCV MCV x100   x100

A separate graph is shown for ANC values within the 

±20-μeq/L range (fig. 4A2); these results are plotted as the 

difference between the laboratory value and the MCV. The pH 

results consist of two sets of data—values less than 6.00, and 

values equal to or greater than 6.00. The two sets of data have 

different DQOs, which are represented by a short dashed line 

and a long dashed line on the pH graph (fig. 4H).

Blind Reference Samples

Results from blind reference sample analyses are plotted 

in figure 5 by constituent and date of analysis. Sample data 

with MPVs less than the reporting limits were excluded. The 

MPV and the control limits of ±10 percent are represented by 

lines on the graphs; the percent difference (D) is calculated as:

 , (3)

where

AV = analyzed value, 

and

MPV = most probable value.

Summary of Results

The following sections summarize the results for (A) 

quality-control samples (fig. 1, p. 14–18), (B) filter blanks 

and analytical blanks (fig. 2, p. 19–20), (C) triplicate 

environmental samples (fig. 3, p. 21–22), (D) SRS samples 

(table 3), (E) NWRI samples (fig. 4, p. 23–24), and 

(F) blind samples (fig. 5, p. 25).

A. Quality-Control Samples

Acid-Neutralizing Capacity (fig. 1A)— DQOs were met 

by 99 percent of the samples. The QC-high sample had 

a negative bias during this period. No apparent trends or 

biases were evident for the QC-low sample.

Aluminum, Total Monomeric (fig. 1B)—DQOs were 

met by 99 percent of the samples. The QC-high sample 

and QC-low samples had a slight positive bias through 

mid-1998.

Aluminum, Organic Monomeric—A QC sample has not 

been developed for this analysis. Separation-column 

efficiency is used to determine acceptability of the data.

Aluminum, Total (fig. 1C)—DQOs were met by 99 percent 

of the samples. The QC-high sample had a positive bias 

from May through August 1998. The QC-low sample had 

a negative bias in April 1998. The QC-low concentration 

D A = − ( ) V MPV MPV  

 D A = − ( ) V MPV MPV ×100  ×100

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
was increased from 1.00 to 1.49 μmol/L in April 1998 to 

reflect environmental sample concentrations.

Ammonium (fig. 1D)—DQOs were met by 99 percent of 

the samples. No apparent trends or biases were evident 

among the QC-low samples. The QC-high sample had a 

slight positive bias during this period.

Calcium (fig. 1E)—DQOs were met by 100 percent of the 

samples. The QC-high sample had a slight positive bias 

in 1997; the QC-low sample had a slight positive bias in 

1997 and a slight negative bias in 1998.

Carbon, Dissolved Organic (fig. 1F)—DQOs were met by 

99 percent of the samples. No apparent trends or biases 

were evident during this period.

Chloride (fig. 1G)—DQOs were met by 99 percent of the 

samples. No apparent trends or biases were evident for the 

QC-high sample. The QC-low sample shows a positive 

bias until November 1998.

Fluoride (fig. 1H)—DQOs were met by 100 percent of the 

samples. No apparent trends or biases were evident during 

this period.

Magnesium (fig. 1I)—DQOs were met by 100 percent of 

the samples. No apparent trends or biases were evident 

during this period.

Nitrate (ion chromatography) (fig. 1J)—DQOs were met 

by 99 percent of the samples. No apparent trends or biases 

were evident during this period.

Nitrate (colorimetric method) (fig. 1K)—DQOs were 

met by 100 percent of the samples. No apparent trends or 

biases were evident during this period.

pH (fig. 1L)—DQOs were met by 99 percent of the 

samples. No apparent trends or biases were evident during 

this period.

Potassium (fig. 1M)—DQOs were met by 100 percent 

of the samples. The data are insufficient for trend 

analysis. Potassium analysis by inductively coupled 

plasma spectrophotometer in 1998 was unsuccessful. 

The Troy Laboratory reverted to atomic absorption 

spectrophotometer analysis in mid-1999.

Silicon (fig. 1N)—DQOs were met by 99 percent of the 

samples. No apparent trends or biases were evident during 

this period.

Sodium (fig. 1O)—DQOs were met by 100 percent 

of the samples. The data are insufficient for trend 

analysis. Sodium analysis by an inductively coupled 

plasma spectrophotometer in 1998 was unsuccessful. 

The Troy Laboratory reverted to atomic absorption 

spectrophotometer analysis in mid-1999. 

Specific conductance (fig. 1P)—DQOs were met by 100 

percent of the samples. The QC-high concentration 

sample was not analyzed during this period. The QC-low 

sample had a negative bias in 1997 and a positive bias in 

mid-1998.

Sulfate (fig. 1Q)—DQOs were met by 99 percent of the 

samples. The QC-high concentration sample had a 

positive bias from March through September of 1998. The 

QC-low concentration sample had a positive bias from 

May through November of 1998.

B. Filter Blanks and Analytical Blanks

Acid-Neutralizing Capacity—Blanks were not analyzed for 

this constituent during this period.

Aluminum, Total Monomeric (fig. 2A)—The DQO was met 

by 96 percent of the samples. No systematic trends were 

evident for this analysis.

Aluminum, Organic Monomeric (fig. 2B)—The DQO was 

met by 100 percent of the samples. No systematic trends 

were evident for this analysis.

Aluminum, Total (fig. 2C)—The DQO was met for 90 

percent of the samples. No systematic trends were 

evident for this analysis.

Ammonium (fig. 2D)—The DQO was met by 87 percent 

of the samples. No systematic trends were evident for this 

analysis. The DQO is being evaluated.

Calcium (fig. 2E)—The DQO was met by 96 percent 

of the samples. No systematic trends were evident for 

this analysis.

Carbon, Dissolved Organic (fig. 2F)—The DQO was met 

by 61 percent of the samples. The shift in blank data 

results in 1998 coincided with the purchase of a new 

carbon analyzer. The current DQO is being evaluated.

Chloride (fig. 2G)—The DQO was met by 78 percent of the 

samples. The chloride contamination problem has shown 

improvement with time.

Fluoride—Blanks were not analyzed for this constituent 

during this period.

Magnesium (fig. 2H)—The DQO was met by 99 percent 

of the samples. No systematic trends were evident 

for this analysis.

Nitrate (ion chromatography) (fig. 2I)—The DQO was met 

by 99 percent of the samples. No systematic trends were 

evident for this analysis.

Nitrate (colorimetric method)—Blanks were not available 

for this constituent during this period.

pH—Blanks were not analyzed for this constituent.

Summary of Results   
Potassium (fig. 2J)—The DQO was met by 87 percent 

of the samples. No systematic trends were evident for 

this analysis.

Silicon (fig. 2K)—The DQO was met by 85 percent of the 

samples. Blank samples which were prepared mid-1998 

and 1999 were analyzed by inductively coupled plasma 

spectrophotometry. Improved results are evident.

Sodium (fig. 2L)—The DQO was met by 99 percent 

of the samples. No systematic trends were evident 

for this analysis.

Specific conductance—Blanks were not analyzed for this 

constituent during this period.

Sulfate (fig. 2M)—The DQO was met by 99 percent of 

the samples. No systematic trends were evident for 

this analysis.

C. Triplicate Environmental Samples

Acid-Neutralizing Capacity (figs. 3A1 and 3A2)—The 

DQO was met by 90 percent of the triplicate samples.

Aluminum, Total Monomeric (fig. 3B)—The DQO was met 

by 91 percent of the triplicate samples.

Aluminum, Organic Monomeric (fig. 3C)—The DQO was 

met by 100 percent of the triplicate samples.

Aluminum, Total (fig. 3D)—The DQO was met by 70 

percent of the triplicate samples.

Ammonium—Triplicate samples were not analyzed for this 

constituent during this period.

Calcium (fig. 3E)—The DQO was met by 99 percent of the 

triplicate samples.

Carbon, Dissolved Organic (fig. 3F)—The DQO was met 

by 94 percent of the triplicate samples.

Chloride (fig. 3G)—The DQO was met by 91 percent of the 

triplicate samples.

Fluoride—Triplicate samples were not analyzed for this 

constituent during this period.

Magnesium (fig. 3H)—The DQO was met by 96 percent of 

the triplicate samples.

Nitrate (ion chromatography) (fig. 3I)—The DQO was 

met by 98 percent of the triplicate samples.

Nitrate (colorimetric method)—Triplicate samples were 

not available for this constituent during this period.

pH (fig. 3J)—The DQO was met by 99 percent of the 

triplicate samples.

Potassium (fig. 3K)—The DQO was met by 83 percent of 

the triplicate samples.

Silicon (fig. 3L)—The DQO was met by 96 percent of the 

triplicate samples.

Sodium (fig. 3M)—The DQO was met by 96 percent of the 

triplicate samples.

Specific conductance—Triplicate samples were not 

analyzed for this constituent during this period.

Sulfate (fig. 3N)—The DQO was met by 99 percent of the 

triplicate samples.

D. U.S. Geological Survey’s Standard Reference 

Sample (SRS) Project

The U.S. Geological Survey’s SRS Project rates 

laboratory performance for each analyte on a scale of 4 to 0:

Rating Performance

4.0 Excellent

3.0–3.99 Good

2.0–2.99 Satisfactory

1.0–1.99 Marginal

0.0–0.99 Unsatisfactory

Overall laboratory mean ratings for each SRS 

sample were:

P-29 3.9 T-151 3.5 N-55 3.0

P-30 3.8 T-153 3.0 N-61 4.0

P-31 2.0 T-155 3.5 N-62 2.5

Missing SRS results for the Troy Laboratory were due to 

instrument failure during the SRS study period. All analyses 

received a satisfactory or better rating for each constituent 

with five exceptions: 

Ammonium—The cause of the marginal rating for SRS N-62 

is unexplained.

Fluoride—The fluoride data for SRS P-31 were erroneously 

entered before unit conversion. Upon conversion, the data 

would have a good rating.

Potassium—The cause of a zero rating for SRS P-31 

is unexplained.

Silicon—The erroneous silicon data were due to a matrix 

interference. All T samples are acidified. An acidified 

sample was not compatible with the silicon method used 

during this period. SRS silicon analysis was discontinued 

until it was reinitiated on an inductively coupled plasma 

spectrophotometer.

Sodium—The cause of a zero rating for SRS P-31 

is unexplained.

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
Table 3. Results obtained by the Troy Laboratory for the U.S. Geological Survey’s Standard Reference Sample (SRS) Project, 

September 1997 through March 1999.

[MPV, most probable value; TV, Troy Laboratory value. All values are in milligrams per liter except aluminum (μg/L), pH (pH units) and specific conductance 

(microsiemens per centimeter); -- , dashes indicate no results reported] 

Analyte MPV, TV, 

and ratinga

SRS sample number and date of sample distribution

P-29

09-97b

T-151

09-97b

N-55

09-97b

T-153

4-98c

P-30

4-98c

T-155

09-98d

P-31

9-98d

N-61

03-99e

N-62

03-99e

Aluminum MPV 

TV 

Rating

--

--

--

--

--

--

 --

 --

 --

35.0

32.8

4

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

Ammoniumf MPV 

TV 

Rating

--

--

--

--

--

--

0.240

0.223

3

--

 --

 --

--

--

--

--

--

--

--

--

--

0.040

0.042

4

1.01

1.11

1

Calcium MPV 

TV 

Rating

1.84

1.93

3

37.9

38.2

4

 --

 --

 --

27.5

27.0

4

0.13

0.14

4

42.0

40.5

3

7.81

7.40

3

 --

--

--

--

--

--

Chloride MPV 

TV 

Rating

0.20

0.21

4

--

--

--

 --

 --

 --

 --

 --

 --

0.23

0.22

4

--

--

--

1.38

1.33

3

 --

 --

 --

--

--

--

Fluoride MPV 

TV 

Rating

0.056

0.050

4

--

--

--

 --

 --

 --

 --

 --

 --

--

--

--

--

--

--

0.33

16.52

0

--

--

--

--

--

--

Magnesium MPV 

TV 

Rating

0.57

0.58

4

17.5

17.2

3

 --

 --

 --

 8.72

 8.60

 4

0.27

0.040

3

11.1

11.3

4

1.00

0.95

2

--

--

--

--

--

--

Nitrate MPV 

TV 

Rating

--

--

--

--

--

--

 --

 --

 --

 --

 --

 --

--

--

--

--

--

--

--

--

--

0.036

0.035

4

0.917

0.940

4

pH MPV 

TV 

Rating

6.85

6.85

4

--

--

--

 --

 --

 --

 --

 --

 --

5.35

5.40

4

 --

 --

 --

7.44

7.04

4

--

--

--

--

--

--

Potassium MPV 

TV 

Rating

0.37

0.37

4

1.95

1.82

3

 --

 --

 --

 --

 --

 --

--

--

--

5.64

5.82

3

0.908

0.450

0

--

--

--

--

--

--

Silicong MPV 

TV 

Rating

--

--

--

--

--

--

 --

 --

 --

 5.79

 7.71

 0

--

--

--

--

--

--

--

--

--

--

--

--

--

--

--

Sodium

MPV 

TV 

Rating

0.66

0.66

4

55.0

55.7

 4

 --

 --

 --

 --

 --

 --

--

--

--

28.4

28.8

4

2.18

1.90

0

--

--

--

--

--

--

Specific 

condutance

MPV 

TV 

Rating

--

--

--

--

--

--

 --

 --

 --

 --

 --

 --

6.0

6.0

4

 --

 --

 --

59.9

57.2

2

--

--

--

--

--

--

Sulfate

MPV 

TV 

Rating

1.10

1.12

4

--

--

--

 --

 --

 --

 --

 --

 --

0.400

0.409

4

--

--

--

3.53

3.44

4

--

--

--

--

--

--

a

Laboratory rating system: 4 is highest score; 0 is lowest.

b

Sample described in Farrar (1998a).

c

Sample described in Farrar (1998b).

d

Sample described in Farrar (1999).

e

Sample described in Farrar and Chleboun (1999).

f

The SRS Project reports data as “Ammonia as Nitrogen.”

g

The SRS Project reports data as “Silica.”

Summary of Results   
E. NWRI Ecosystem Interlaboratory QA Program

Environment Canada’s NWRI program does not audit the 

analysis of total monomeric aluminum, organic monomeric 

aluminum, fluoride, and nitrate (colorimetric method). The 

laboratory did not submit results for total aluminum analyses 

during this period.

Acid-Neutralizing Capacity (figs. 4A1 and 4A2)—The 

DQO was met by 90 percent of the NWRI samples. The 

data indicate a negative bias for this period. The autotitrator was malfunctioning during study 73 and was 

repaired during 74.

Ammonium (fig. 4B)—The DQO was met by 59 percent 

of the NWRI samples. The cause of the positive bias is 

currently being investigated.

Calcium (fig. 4C)—The DQO was met by 80 percent of 

the NWRI samples. The high bias during study 71 was 

corrected with the purchase of an inductively coupled 

plasma spectrophotometer during study 72. Improved 

results are evident by studies 73 and 74. The cause of the 

erratically high sample in study 73 is unknown.

Carbon, Dissolved Organic (fig. 4D)—The DQO was met 

by 58 percent of the NWRI samples. The data indicated a 

positive bias for studies 71 and 72. A new carbon analyzer 

was purchased during study 73. Improved results are 

evident in study 74.

Chloride (fig. 4E)—The DQO was met by 75 percent of the 

NWRI samples. All outliers had a positive bias.

Magnesium (fig. 4F)—The DQO was met by 93 percent 

of the NWRI samples. No trend or bias was evident. 

NWRI samples were not analyzed for magnesium 

for study 72, when a new inductively coupled plasma 

spectrophotometer was being installed. 

Nitrate (ion chromatography) (fig. 4G)—The DQO was 

met by 100 percent of the NWRI samples. No trend or 

bias was evident.

pH (fig. 4H)—The DQO was met by 100 percent of the 

NWRI samples. No trend or bias was evident.

Potassium (fig. 4I)—The DQO was met by 100 percent of 

the NWRI samples. No trend or bias was evident. NWRI 

samples were not run for potassium during studies 72, 73, 

or 74. Potassium analysis was unsuccessfully attempted 

on the inductively coupled plasma spectrophotometer 

during this period.

Silicon (fig. 4J)—The DQO was met by 89 percent of the 

NWRI samples. Silicon was analyzed by colormetric 

method through study 72. Silicon was analyzed by 

inductively coupled plasma spectrophotometry in study 73 

and 74, and gave improved results.

Sodium (fig. 4K)—The DQO was met by 83 percent of the 

NWRI samples. The data indicated a negative bias during 

this period. Sodium analysis was unsuccessfully attempted 

on the inductively coupled plasma spectrophotometer 

during studies 72, 73, and 74.

Specific Conductance (fig. 4L)—The DQO was met by 

70 percent of the NWRI samples. The data indicated a 

negative bias.

Sulfate (fig. 4M)—The DQO was met by 95 percent of the 

NWRI samples. No trend or bias was evident.

F. Blind Reference Samples

Blind reference samples (SRS low-ionic-strength 

constituent P-samples) are analyzed for the Troy Laboratory 

procedures for which the SRS project reports an analyte MPV; 

the exceptions are acid-neutralizing capacity, total monomeric 

aluminum, organic monomeric aluminum, total aluminum, 

ammonium, dissolved organic carbon, nitrate, and silicon. 

Blind reference samples were not analyzed for fluoride during 

this period.

Calcium (fig. 5A)—The DQO for calcium was met by 96 

percent of the blind reference samples. A negative bias was 

evident for the entire time period.

Chloride (fig. 5B)—The DQO was met by 99 percent of the 

blind reference samples. A negative bias was evident from 

late 1998 through 1999.

Magnesium (fig. 5C)—The DQO was met by 84 percent 

of the blind reference samples. Most data indicated a 

negative bias.

pH (fig. 5D)—The DQO was met by 100 percent of the 

blind reference samples. A slight positive bias was evident 

during 1999.

Potassium (fig. 5E)—The DQO was met by 88 percent of the 

blind reference samples. No trend or bias was evident.

Sodium (fig. 5F)—The DQO was not met for the blind 

reference samples; the cause is unknown.

Specific conductance (fig. 5G)—Data are insufficient for 

DQO evaluation. The analytical procedure appears to have 

a negative bias which may be indicated on subsequent 

control charts.

Sulfate (fig. 5H)—The DQO was met by 73 percent of the 

samples. No trend or bias was evident.

10 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
Selected References

Farrar, J.W., 1998a, Report on the U.S. Geological Survey’s 

analytical evaluation program for standard reference 

samples: T-151 (trace constituents), M-144 (major 

constituents), N-55 (nutrient constituents), N-56 (nutrient 

constituents), P-29 (low ionic strength constituents), GWT-2 

(ground-water trace constituents), GWM-2 (ground-water 

major constituents), AMW-4 (acid mine water constituents), 

and Hg-25 (mercury) distributed in September 1997: U.S. 

Geological Survey Open-File Report 98–52, 191 p.

Farrar, J.W., 1998b, Report on the U.S. Geological Survey’s 

analytical evaluation program for standard reference 

samples: T-153 (trace constituents), M-146 (major 

constituents), N-57 (nutrient constituents), N-58 (nutrient 

constituents), P-30 (low ionic strength constituents), 

GWT-3 (ground-water trace constituents), GWM-3 (groundwater major constituents), and Hg-26 (mercury) distributed 

in April 1998: U.S Geological Survey Open-File Report 

98–391, 160 p.

Farrar, J.W., 1999, Report on the U.S. Geological Survey’s 

analytical evaluation program for standard reference 

samples: T-155 (trace constituents), M-148 (major 

constituents), N-59 (nutrient constituents), N-60 (nutrient 

constituents), P-31 (low ionic strength constituents), GWT-4 

(ground-water trace constituents), and Hg-27 (mercury) 

distributed in September 1998: U.S. Geological Survey 

Open-File Report 99–72, 143 p. 

Farrar, J.W. and Chleboun, K.M., 1999, Results of the U.S. 

Geological Survey’s analytical evaluation program for 

standard reference samples distributed in March 1999: U.S. 

Geological Survey Open-File Report 99–259, 166 p.

Lawrence, G.B., Lincoln, T.A., Horan-Ross, D.A., Olson, 

M.L., and Waldron, L.A., 1995, Analytical methods of the 

U.S. Geological Survey’s New York District Water Analysis 

Laboratory: U.S. Geological Survey Open-File Report 

95–416, 78 p.

Lee, M.P., 1996, U.S. Geological Survey water-resources 

programs in the New York District—fiscal years 1993–94: 

U.S. Geological Survey Open-File Report 96–113, 48 p.

Lincoln, T.A., Horan-Ross, D.A., Olson, M.L., and Lawrence, 

G.B., 1996, Quality-assurance data for routine water 

analyses by the U.S. Geological Survey Laboratory in Troy, 

New York: May 1991 through June 1993: U.S. Geological 

Survey Open-File Report 96–167, 22 p.

Lincoln, T.A., Horan-Ross, D.A., McHale, M.R., and 

Lawrence, G.B., 2001, Quality-assurance data for routine 

water analyses by the U.S. Geological Survey Laboratory 

in Troy, New York: July 1993 through June 1995: U.S. 

Geological Survey Open-File Report 01–171, 25 p.

Lincoln, T.A., Horan-Ross, D.A., McHale, M.R., and 

Lawrence, G.B., 2004, Quality-assurance data for routine 

water analyses by the U.S. Geological Survey Laboratory 

in Troy, New York: July 1995 through June 1997: U.S. 

Geological Survey Open-File Report 2004–1327, 25 p.

Selected References 11
12  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
Figures 1–5

Figures 13
ACID-NEUTRALIZING CAPACITY,

IN MICROEQUIVALENTS PER LITER

A. ACID-NEUTRALIZING CAPACITY

High Concentration Sample

160

150

140

130

120

110

100

ACID-NEUTRALIZING CAPACITY,

IN MICROEQUIVALENTS PER LITER

Low Concentration Sample

-30

-35

-40

-45

-50

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

B. ALUMINUM, TOTAL MONOMERIC

High Concentration Sample

23

21

19

17

15

Low Concentration Sample

10

9

8

7

6

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

C. ALUMINUM, TOTAL

High Concentration Sample

14

13

12

11

10

9

8

Low Concentration Sample

2

1.6

1.2

0.8

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

ALUMINUM, TOTAL,

IN MICROMOLES PER LITER

ALUMINUM, TOTAL,

IN MICROMOLES PER LITER1.8

1.4

1

0.6

D. AMMONIUM

High Concentration Sample

22

20

18

16

14

Low Concentration Sample

10

6

4

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

AMMONIUM,

IN MICROMOLES PER LITER

AMMONIUM,

IN MICROMOLES PER LITER

8

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

25

Figure 1. High- and low-concentration quality-control sample results: A. Acid-neutralizing capacity. B. Aluminum, total 

monomeric. C. Aluminum, total. D. Ammonium.

14  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
CALCIUM,

IN MICROMOLES PER LITER

E. CALCIUM

High Concentration Sample

115

105

95

80

Low Concentration Sample

30

26

24

22

20

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

CALCIUM,

IN MICROMOLES PER LITER

FLUORIDE,

IN MICROMOLES PER LITER

H. FLUORIDE

Control Sample

2

1.8

1.6

1.3

1.1

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

120

110

100

90

85

28

CHLORIDE,

IN MICROMOLES PER LITER

G. CHLORIDE

High Concentration Sample

95

75

Low Concentration Sample

11

10

7

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

CHLORIDE,

IN MICROMOLES PER LITER

105

85

9

8

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

F. CARBON, DISSOLVED ORGANIC

High Concentration Sample

Low Concentration Sample

110

90

70

60

120

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

490

470

430

370

450

410

350

390

100

80

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

65

1.9

1.7

1.5

1.2

1

1.4

Figure 1. High- and low-concentration quality-control sample results: E. Calcium. F. Carbon, dissolved organic. G. Chloride. 

H. Fluoride.—Continued

Figures 15
CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

I. MAGNESIUM

High Concentration Sample

44

38

34

30

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

MAGNESIUM,

IN MICROMOLES PER LITER

48

46

42

36

32

50

40

pH

L. pH

High Concentration Sample

7.2

6.9

6.6

Low Concentration Sample

4.6

4.5

4.4

4.3

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

pH

7.1

6.7

J. NITRATE (ION CHROMATOGRAPHY)

High Concentration Sample

60

58

50

46

40

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

54

48

44

42

6

5.5

4.5

3

5

4

3.5

NITRATE,

IN MICROMOLES PER LITER

K. NITRATE (COLORIMETRIC METHOD)

High Concentration Sample

120

100

90

80

Low Concentration Sample

55

35

25

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

NITRATE,

IN MICROMOLES PER LITER

110

45

Low Concentration Sample

14

13

11

10

9

8

12

MAGNESIUM,

IN MICROMOLES PER LITER

56

52

NITRATE,

IN MICROMOLES PER LITER

NITRATE,

IN MICROMOLES PER LITER

4.55

4.45

4.35

6.8

7

Figure 1. High- and low-concentration quality-control sample results: I. Magnesium. J. Nitrate (ion chromatography). K. Nitrate 

(colorimetric method). L. pH.—Continued

16  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
SODIUM,

IN MICROMOLES PER LITER

O. SODIUM

High Concentration Sample

55

53

45

37

35

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

SODIUM,

IN MICROMOLES PER LITER

49

41

15

14

10

8

7

12

9

SILICON,

IN MICROMOLES PER LITER

N. SILICON

High Concentration Sample

140

130

110

90

80

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

SILICON,

IN MICROMOLES PER LITER

120

100

45

25

30

40

35

POTASSIUM,

IN MICROMOLES PER LITER

M. POTASSIUM

High Concentration Sample

30

28

24

21

20

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

POTASSIUM,

IN MICROMOLES PER LITER

26

22

7.5

5.5

4.5

4

6.5

5

8

7

6

29

27

23

25

13

11

51

47

39

43

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

P. SPECIFIC CONDUCTANCE

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

SPECIFIC CONDUCTANCE,

IN MICROSEIMENS PER CENTIMETER

24

22

16

12

18

14

20

Figure 1. High- and low-concentration quality-control sample results: M. Potassium. N. Silicon. O. Sodium. P. Specific 

conductance.—Continued

Figures 17
CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

SULFATE,

IN MICROMOLES PER LITER

Q. SULFATE

High Concentration Sample

100

80

65

Low Concentration Sample

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

1997 1998 1999

DATE OF ANALYSIS

SULFATE,

IN MICROMOLES PER LITER

90

70

11

10

8

6

9

7

95

75

85

12

Figure 1. High- and low-concentration quality-control sample results: Q. Sulfate.—Continued

18  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
-1

0

1

2

3

4

5

6

7

8

A. ALUMINUM, TOTAL MONOMERIC

-1

0

1

2

3

4

5

6

7

8

-1

0

1

2

3

4

5

6

7

8

-1

0

1

2

3

4

5

6

7

8

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

D. AMMONIUM

C. ALUMINUM, TOTAL

B. ALUMINUM, ORGANIC MONOMERIC

-1

0

1

2

3

4

5

6

7

8

E. CALCIUM

-20

20

40

60

80

100

F. CARBON, DISSOLVED ORGANIC

0

1

2

3

4

5

6

7

8

G. CHLORIDE

-0.5

0.5

1.5

2.5

3.5

4.5

5.5

6.5

7.5

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

DATE OF COLLECTION DATE OF COLLECTION

H. MAGNESIUM

0

1997 1998 1999 1997 1998 1999

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

ALUMINUM, ORGANIC MONOMERIC,

IN MICROMOLES PER LITER

ALUMINUM, TOTAL,

IN MICROMOLES PER LITER

ALUMINUM, ,

IN MICROMOLES PER LITER

CALCIUM,

IN MICROMOLES PER LITER

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

CHLORIDE,

IN MICROMOLES PER LITER

MAGNESIUM,

IN MICROMOLES PER LITER

Figure 2. Filter-blank and analytical-blank sample results: A. Aluminum, total monomeric. B. Aluminum, organic monomeric. 

C. Aluminum, total. D. Ammonium. E. Calcium. F. Carbon, dissolved organic. G. Chloride. H. Magnesium.

Figures 19
0

1

2

3

4

5

6

7

8

I. NITRATE (ION CHROMATOGRAPHY)

-2

-1

0

1

2

3

4

5

6

7

8

-2

-1

0

1

2

3

4

5

6

7

8

J. POTASSIUM

K. SILICON

-2

-1

0

1

2

3

4

5

6

7

8

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

DATE OF COLLECTION

DATE OF COLLECTION

0

1

2

3

4

5

6

7

8

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

L. SODIUM

M. SULFATE

1997 1998 1999

1997 1998 1999

NITRATE,

IN MICROMOLES PER LITER

POTASSIUM,

IN MICROMOLES PER LITER

SILICON,

IN MICROMOLES PER LITER

SODIUM,

IN MICROMOLES PER LITER

SULFATE,

IN MICROMOLES PER LITER

Figure 2. Filter-blank and analytical-blank sample results: I. Nitrate (ion chromatography). J. Potassium. K. Silicon. L. Sodium. 

M. Sulfate.—Continued

20 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
0

5

10

15

20

25

30

35

40

45

50

-5

5

15

25

35

45

0

5

10

15

20

25

30

35

40

45

50

Jul Oct Jan Apr Jul Oct Jan Apr

COEFFICIENT OF VARIATION CONTROL LIMIT

0

10

20

30

40

50

60

0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

Jul Oct Jan Apr Jul Oct Jan Apr

DATE OF COLLECTION DATE OF COLLECTION

-30

-20

-10

0

10

20

30

40

A1. ACID-NEUTRALIZING CAPACITY

(for triplicate means not in ± 20 μeq/L range)

A2. ACID-NEUTRALIZING CAPACITY

B. ALUMINUM, TOTAL MONOMERIC

C. ALUMINUM, ORGANIC MONOMERIC

D. ALUMINUM, TOTAL

E. CALCIUM

F. CARBON, DISSOLVED ORGANIC

G. CHLORIDE

(for triplicate means in ± 20 μeq/L range)

1997 1998 1999 1997 1998 1999

COEFFICIENT OF VARIATION

DIFFERENCE FROM TRIPLICATE MEAN,

IN MICROEQUIVALENTS PER LITER

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

Figure 3. Triplicate environmental sample results: A1. Acid-neutralizing capacity (for triplicate means not in ±20 μeq/L range). 

A2. Acid-neutralizing capacity (for triplicate means in ±20 μeq/L range). B. Aluminum, total monomeric. C. Aluminum, organic 

monomeric. D. Aluminum, total. E. Calcium. F. Carbon, dissolved organic. G. Chloride. 

Figures  21
0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

0

10

20

30

40

50

60

Jul Oct Jan Apr Jul Oct Jan Apr

COEFFICIENT OF VARIATION CONTROL LIMIT

0

10

20

30

40

50

60

70

0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

Jul Oct Jan Apr Jul Oct Jan Apr

DATE OF COLLECTION

DATE OF COLLECTION

0

5

10

15

20

25

30

35

40

45

50

H. MAGNESIUM

I. NITRATE (ION CHROMATOGRAPHY)

J. pH

K. POTASSIUM

L. SILICON

M. SODIUM

N. SULFATE

1997 1998 1999

1997 1998 1999

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

Figure 3. Triplicate environmental sample results: H. Magnesium. I. Nitrate (ion chromatography). J. pH. K. Potassium. L. Silicon. 

M. Sodium. N. Sulfate.—Continued 

22  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
-50

-40

-30

-20

-10

0

10

20

30

40

50

-20

-15

-10

-5

0

5

10

15

20

DIFFERENCE

A1. ACID-NEUTRALIZING CAPACITY

(for samples not in the range of ± 20 μeq/L)

A2. ACID-NEUTRALIZING CAPACITY

(for samples in the range of ± 20 μeq/L)

-50

-40

-30

-20

-10

0

10

20

30

40

50

B. AMMONIUM

-50

-40

-30

-20

-10

0

10

20

30

40

50

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

C. CALCIUM

-50

-30

-10

10

30

50

70

90 D. CARBON, DISSOLVED ORGANIC

-50

-40

-30

-20

-10

0

10

20

30

40

50

E. CHLORIDE

-50

-40

-30

-20

-10

0

10

20

30

40

50

F. MAGNESIUM

-50

-40

-30

-20

-10

0

10

20

30

40

50

G. NITRATE (ION CHROMATOGRAPHY)

NWRI STUDIES 71 THROUGH 74 NWRI STUDIES 71 THROUGH 74

STUDY 71 STUDY 72 STUDY 73 STUDY 74 STUDY 71 STUDY 72 STUDY 73 STUDY 74

PERCENT DIFFERENCE

212

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN μeq/L)

Figure 4. NWRI Ecosystem Interlaboratory QA Program results: A1. Acid-neutralizing capacity (for samples not in the range of 

± 20 μeq/L). A2. Acid-neutralizing capacity (for samples in the range of ± 20 μeq/L). B. Ammonium. C. Calcium. D. Carbon, dissolved 

organic. E. Chloride. F. Magnesium. G. Nitrate (ion chromatography).

Figures  23
-30

-20

-10

0

10

20

30

40

50

60

70

PERCENT DIFFERENCE. pH<6.00 (Control 10%)

PERCENT DIFFERENCE. pH>6.00 (Control 20%)

H. pH

-50

-40

-30

-20

-10

0

10

20

30

40

50

I. POTASSIUM

-50

-40

-30

-20

-10

0

10

20

30

40

50

J. SILICON

-50

-40

-30

-20

-10

0

10

20

30

40

50

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

K. SODIUM

-50

-40

-30

-20

-10

0

10

20

30

40

50

NWRI STUDIES 71 THROUGH 74

STUDY 71 STUDY 72 STUDY 73 STUDY 74

-50

-40

-30

-20

-10

0

10

20

30

40

50

M. SULFATE

L. SPECIFIC CONDUCTANCE

PERCENT DIFFERENCE

NWRI STUDIES 71 THROUGH 74

STUDY 71 STUDY 72 STUDY 73 STUDY 74

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

DIFFERNCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

Figure 4. NWRI Ecosystem Interlaboratory QA Program results: H. pH. I. Potassium. J. Silicon. K. Sodium. L. Specific 

conductance. M. Sulfate.—Continued

24  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1997 through June 1999
-40

-30

-20

-10

0

10

20

30

40

B. CHLORIDE

-40

-30

-20

-10

0

10

20

30

40

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

-40

-30

-20

-10

0

10

20

30

40

D. pH

-40

-20

0

20

40

60

F. SODIUM

H. SULFATE

DATE OF COLLECTION DATE OF COLLECTION

-40

-30

-20

-10

0

10

20

30

40

50

PERCENT DIFFERENCE

A. CALCIUM

-40

-30

-20

-10

0

10

20

30

40

C. MAGNESIUM

-40

-30

-20

-10

0

10

20

30

40

E. POTASSIUM

G. SPECIFIC CONDUCTANCE

1997 1998 1999 1997 1998 1999

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT)

Figure 5. Blind reference sample results: A. Calcium. B. Chloride. C. Magnesium. D. pH. E. Potassium. F. Sodium. G. Specific 

conductance. H. Sulfate.

Figures  25
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U.S. Geological Survey

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Information requests:

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or visit our Web site at:

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Lincoln, Horan-Ross, McHale, and Lawrence— —Open-File Report 2006–1245

July 1997 through June 1999U.S. Geological Survey Laboratory in Troy, New York—Quality-Assurance Data for Routine Water Analyses by the