U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006-1246

Quality-Assurance Data for Routine Water Analyses by the

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

July 1999 through June 2001
Cover. Purple aster with fly, Warwick, New York ©2006 M. Peter deVries
Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York—

July 1999 through June 2001

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

Gregory B. Lawrence

Open-File Report 2006–1246

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:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

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 1999 through June 

2001: U.S. Geological Survey Open-File Report 2006-1246, 27 p., online only.
iii

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

Contents

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

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

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

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

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

Quality-Control Samples......................................................................................................................3

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 ...............................................................................4

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

Control-Chart Evaluation...............................................................................................................................5

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

Filter Blanks and Analytical Blanks ...................................................................................................5

Triplicate Environmental Samples......................................................................................................5

NWRI Ecosystem Interlaboratory QA Program ...............................................................................5

Blind Reference Samples....................................................................................................................5

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
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. Fluoride.....................................................................................................................................19

I. Magnesium ...............................................................................................................................20

 J. Nitrate (ion chromatography).................................................................................................20

K. Potassium .................................................................................................................................20

L. Silicon ........................................................................................................................................20

M. Sodium..................................................................................................................................... 20

N. Specific conductance.............................................................................................................20

O. 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. Ammonium ................................................................................................................................21

F. Calcium ......................................................................................................................................21

G. Carbon, dissolved organic .....................................................................................................21

H. Chloride .....................................................................................................................................22

I. Fluoride ......................................................................................................................................22

J. Magnesium............................................................................................................................... 22

K. Nitrate (ion chromatography) ............................................................................................... 22

L. pH ...............................................................................................................................................22

M. Potassium ................................................................................................................................22

N. Silicon .......................................................................................................................................22

0. Sodium........................................................................................................................................22

P. Specific conductance..............................................................................................................23

Q. Sulfate........................................................................................................................................23

4. NWRI Ecosystem Interlaboratory QA Program results: 

A1. Acid-neutralizing capacity (for samples not in the range of ± 20 μeq/L)......................24

A2. Acid-neutralizing capacity (for samples in the range of ± 20 μeq/L) ............................24

B. Aluminum, total ........................................................................................................................24

C. Ammonium ...............................................................................................................................24

D. Calcium .....................................................................................................................................24

E. Carbon, dissolved organic ..................................................................................................... 24

F. Chloride .....................................................................................................................................24

G. Magnesium ..............................................................................................................................24

H. Nitrate (ion chromatography) ...............................................................................................25

I. pH ................................................................................................................................................25

J. Potassium .................................................................................................................................25

K. Silicon .......................................................................................................................................25

L. Sodium .......................................................................................................................................25
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 1999 

through June 2001 ..........................................................................................................................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 1999 through June 2001.........................................................................................................6

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

Reference Sample (SRS) Project, Octobber 1999 through October 2000..............................9

M. Specific conductance........................................................................................................... 25

N. Sulfate .......................................................................................................................................25

5. Blind reference sample results: 

A. Calcium......................................................................................................................................26

B. Chloride .....................................................................................................................................26

C. fluoride ......................................................................................................................................26

D. Magnesium ..............................................................................................................................26

E. pH ...............................................................................................................................................26

F. Potassium .................................................................................................................................26

G. Sodium...................................................................................................................................... 26

H. Specific conductance............................................................................................................ 26

I. Sulfate .........................................................................................................................................27
vi

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
Quality-Assurance Data for Routine Water Analyses by 

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

July 1999 through June 2001

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

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 and quality-control data were 

stored in the laboratory’s LabMaster data-management system, 

which provides efficient review, compilation, and plotting 

of data. This report presents and discusses results of qualityassurance and quality-control samples analyzed from July 

1999 through June 2001.

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 or 

low-concentration samples but were within control limits; 

these procedures were: acid-neutralizing capacity, total 

monomeric aluminum, total aluminum, calcium, chloride and 

nitrate (ion chromatography and colormetric method) and 

sulfate. The total aluminum and dissolved organic carbon 

procedures were biased throughout the analysis period for the 

high-concentration sample, but were within control limits. 

The calcium and specific conductance procedures were biased 

throughout the analysis period for the low-concentration 

sample, but were within control limits. The magnesium 

procedure was biased for the high-concentration and low 

concentration samples, but was within control limits.

Results from the filter-blank and analytical-blank 

analyses indicate that the procedures for 14 of 15 analytes 

were within control limits, although the concentrations for 

blanks were occasionally outside the control limits. The dataquality objective was not met for dissolved organic carbon.

Sampling and analysis precision are evaluated herein 

in terms of the coefficient of variation obtained for triplicate 

samples in the procedures for 17 of the 18 analytes. At least 

90 percent of the samples met data-quality objectives for 

all analytes except ammonium (81 percent of samples met 

objectives), chloride (75 percent of samples met objectives), 

and sodium (86 percent of samples met objectives).

Results of the USGS interlaboratory Standard Reference 

Sample (SRS) Project indicated good data quality over 

the time period, with most ratings for each sample in the 

good to excellent range. The P-sample (low-ionic-strength 

constituents) analysis had one satisfactory rating for the 

specific conductance procedure in one study. The T-sample 

(trace constituents) analysis had one satisfactory rating for 

the aluminum procedure in one study and one unsatisfactory 

rating for the sodium procedure in another. The remainder of 

the samples had good or excellent ratings for each study.

Results of Environment Canada’s National Water 

Research Institute (NWRI) program indicated that at least 

89 percent of the samples met data-quality objectives for 

10 of the 14 analytes; the exceptions were ammonium, total 

aluminum, dissolved organic carbon, and sodium. Results 

indicate a positive bias for the ammonium procedure in all 

studies. Data-quality objectives were not met in 50 percent of 

samples analyzed for total aluminum, 38 percent of samples 

analyzed for dissolved organic carbon, and 27 percent of 

samples analyzed for sodium.

Results from blind reference-sample analyses 

indicated that data-quality objectives were met by at least 

91 percent of the samples analyzed for calcium, chloride, 

fluoride, magnesium, pH, potassium, and sulfate. Dataquality objectives were met by 75 percent of the samples 

analyzed for sodium and 58 percent of the samples 

analyzed for specific conductance.

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 
stream-water samples. The methods used in this laboratory 

are described in detail in Lawrence and others (1995). The 

entire historical database was moved from the laboratory’s 

SAS data-management system to a LabMaster laboratory 

information management system in January 2000. Qualityassurance and quality-control data were then collected, 

stored, and reviewed through the laboratory’s LabMaster 

information management system for the remainder of this 

report period (July 1999-June 2001).

The 18 analytes represented by this study were: 

acid-neutralizing 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 qualitycontrol 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: 176 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: 2,354 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: 610 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: 667 stream-water samples.

Project: Adirondack Effects Assessment Program

Cooperator: Rensselaer Polytechnic Institute

Analyses: 442 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: 735 stream-water samples.

Project: Hydrologic Geomorphology, Water Quality, and 

Biology of the Neversink River

Cooperator: Town of Thompson, New York

Analysis: 162 stream-water samples.

Project: Collaborative Environmental Monitoring and 

Research Initiative|

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

and U.S. Forest Service

Analyses: 32 stream-water samples.

Additional information on projects of the New York 

Water Science Center is given 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-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
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 

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 environmentalsample 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.

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

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 P-samples as the blind reference samples during the time 

period represented in this report.

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001

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 1999 through June 2001. 

[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 5,067 161 424 0 21 0 0

Aluminum, total monomeric 4,739 623 623 1 1 0 0

Aluminum, organic monomeric1 4,746 0 0 0 0 0 0

Aluminum, total 5,471 718 717 0 0 0 0

Ammonium 4,521 840 837 0 2 0 0

Calcium 5,227 655 655 0 0 0 0

Carbon, dissolved organic 5,068 804 805 6 7 6 6

Chloride 5,303 861 866 0 0 0 0

Fluoride 1,384 0 1742 0 0 0 0

Magnesium 5,226 656 655 0 0 0 0

Nitrate (ion chromatography) 5,212 878 882 0 1 0 0

Nitrate (colorimetric method) 620 285 285 2 0 0 0

pH 5,108 233 521 3 16 0 0

Potassium 5,223 741 741 2 6 0 1

Silicon 5,228 654 655 0 1 0 0

Sodium 5,224 658 658 6 5 4 3

Specific conductance 4,054 0 479 0 6 0 0

Sulfate 5,304 1006 1011 0 0 0 0

1

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

2

Mid-level QC samples are used for fluoride.
Control-Chart Evaluation

Control charts (figs. 1–5, p. 14–27) 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.

Quality-Control Samples

QC sample-analysis data are plotted on control charts 

(fig. 1) in which the central line is equal to 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).

Filter Blanks and Analytical Blanks

Results from the blank analyses are plotted on control 

charts 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 in order 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, total aluminum, and ammonium, 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 ± 20-μeq/L; 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 1999 through April 2001. 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.

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. 4I).

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.

CV S

X

CV = ( ) 100 S

X = ( ) 100

D A = − ( ) V MCV MCV  

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

D A = − ( ) V MPV MPV  

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

Control-Chart Evaluation   
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 1999 through June 2001.

[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 15 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 10 0.5

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) 10 1.5

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.

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. 21–23), (D) SRS samples 

(table 3), (E) NWRI samples (fig. 4, p. 24–25), and (F) 

blind samples (fig. 5, p. 26–27).

A. Quality-Control Samples

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

by 96 percent of the samples. The QC-high sample had 

a negative bias through July 2000. 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-low sample had a 

slight positive bias through 2000.

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
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 100 

percent of the samples. The QC-high sample had a 

positive bias during this period; the QC-low sample had a 

positive bias through May 2000.

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

the samples. No apparent trends or biases were evident 

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 2001; the QC-low sample had a negative bias during 

this period.

Carbon, Dissolved Organic (fig. 1F)—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.

Chloride (fig. 1G)—DQOs were met by 100 percent of the 

samples. The QC-high sample had a negative bias from 

November 1999 through November 2000; the remaining 

time it indicated a positive bias. No apparent trends or 

biases were evident for the QC-low sample. 

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. The QC-high sample had a positive bias and 

the QC-low sample had a negative bias during this period.

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

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

a negative bias from November 1999 through November 

2000; the remaining time it indicated a positive bias. 

No apparent trends or biases were evident for the 

QC-low sample.

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

by 99 percent of the samples. The QC-high and QC-low 

samples had a negative bias in 2000.

pH (fig. 1L)—DQOs were met by 97 percent of the 

samples. No apparent trends or biases were evident during 

this period.

Potassium (fig. 1M)—DQOs were met by 99 percent of the 

samples. No apparent trends or biases were evident during 

this period.

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 99 percent of the 

samples. No apparent trends or biases were evident during 

this period. 

Specific conductance (fig. 1P)—DQOs were met by 99 

percent of the samples. The QC-high concentration 

sample was not analyzed during period. The QC-low 

sample had a negative bias from May 2000 through 

April 2001.

Sulfate (fig. 1Q)—DQOs were met by 100 percent of the 

samples. The QC-high sample had a negative bias from 

November 1999 through November 2000; the remainder 

of the period it indicated a positive bias. No apparent 

trends or biases were evident for the QC-low sample.

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 99 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 92 

percent of the samples. No systematic trends were 

evident for this analysis.

Ammonium (fig. 2D)—The DQO was met by 91 percent 

of the samples. No systematic trends were evident for 

this analysis.

Calcium (fig. 2E)—The DQO was met by 98 percent 

of the samples. No systematic trends were evident 

for this analysis.

Carbon, Dissolved Organic (fig. 2F)—The DQO was not 

met for DOC. Blank data results are significantly higher 

in DOC concentrations since a new instrument was 

purchased in 1998. The current DQO is being evaluated. 

Chloride (fig. 2G)—The DQO was met by 82 percent of 

the samples. The chloride contamination problem has 

continued to improve.

Fluoride (fig. 2H)—The DQO was met by 100 percent 

of the samples. No systematic trends were evident 

for this analysis.

Magnesium (fig. 2I)—The DQO was met by 100 percent 

of the samples. No systematic trends were evident 

for this analysis.

Summary of Results 
Nitrate (ion chromatography) (fig. 2J)—The DQO was met 

by 92 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 during 

this period.

Potassium (fig. 2K)—The DQO was met by 92 percent 

of the samples. No systematic trends were evident for 

this analysis.

Silicon (fig. 2L)—The DQO was met by 100 percent of 

the samples. No systematic trends were evident for 

this analysis.

Sodium (fig. 2M)—The DQO was met by 94 percent 

of the samples. No systematic trends were evident 

for this analysis.

Specific conductance (fig. 2N)—The DQO was met by 80 

percent of the samples. No systematic trends were evident 

for this analysis.

Sulfate (fig. 2O)—The DQO was met by 98 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 96 percent of the triplicate samples.

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

by 96 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 90 

percent of the triplicate samples.

Ammonium (fig. 3E)—The DQO was met by 81 percent of 

the triplicate samples.

Calcium (fig. 3F)—The DQO was met by 100 percent of the 

triplicate samples.

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

by 92 percent of the triplicate samples.

Chloride (fig. 3H)—The DQO was met by 75 percent of the 

triplicate samples.

Fluoride (fig. 3I)—The DQO was met by 91 percent of the 

triplicate samples.

Magnesium (fig. 3J)—The DQO was met by 100 percent of 

the triplicate samples.

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

met by 95 percent of the triplicate samples.

Nitrate (colorimetric method)—Triplicate samples were 

not available for this constituent during this period.

pH (fig. 3L)—The DQO was met by 100 percent of the 

triplicate samples.

Potassium (fig. 3M)—The DQO was met by 95 percent of 

the triplicate samples.

Silicon (fig. 3N)—The DQO was met by 100 percent of the 

triplicate samples.

Sodium (fig. 3O)—The DQO was met by 86 percent of the 

triplicate samples.

Specific conductance (fig. 3P)—The DQO was met by 91 

percent of the triplicate samples.

Sulfate (fig. 3Q)—The DQO was met by 100 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-34 3.6 T-161 3.0 N-63 3.0

P-35 3.9 T-163 3.2 N-65 3.0

 N-67 4.0

Missing SRS results for the Troy Laboratory were due to 

instrument failure during the SRS study period. The laboratory 

did not submit results for the SRS samples distributed in 

April 2001. 

All analyses received a satisfactory or better rating for 

each constituent with one exception: 

Sodium—The cause of a zero rating for SRS T-161 is 

erroneous data entry.

 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Table 3. Results obtained by the Troy Laboratory for the U.S. Geological Survey Standard Reference Sample (SRS) Project, 

October 1999 through October 2000.

[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

N-63

10-99b

T-161

03-00c

N-65

03-00c

P-34

03-00c

T-163

10-00d

N-67

10-00d

P-35

10-00d

Aluminum MPV 

TV 

Rating

--

--

--

38.4

38.3

3

--

--

--

--

--

--

16.8

14.54

2

--

--

--

--

--

--

Ammoniume MPV 

TV 

Rating

0.150

0.165

3

--

--

--

0.124

0.142

3

--

--

--

--

--

--

0.433

0.4466

4

--

--

--

Calcium MPV 

TV 

Rating

--

--

--

7.17

7.10

4

--

--

--

1.63

1.58

3

6.30

6.45

4

--

--

--

0.541

0.522

4

Chloride MPV 

TV 

Rating

--

--

--

--

--

--

--

--

--

4.18

4.22

4

--

--

--

--

--

--

5.31

5.032

3

Magnesium MPV 

TV 

Rating

--

--

--

1.51

1.51

4

--

--

--

0.592

0.577

4

1.23

1.299

3

--

--

--

0.090

0.089

4

pH MPV 

TV 

Rating

--

--

--

--

--

--

--

--

--

4.32

4.32

4

--

--

--

--

--

--

4.89

4.96

4

Potassium MPV 

TV 

Rating

--

--

--

1.26

1.36

3

--

--

--

0.238

0.230

4

1.02

1.08

4

--

--

--

0.184

0.1786

4

Siliconf MPV 

TV 

Rating

--

--

--

14.8

14.8

4

--

--

--

--

--

--

4.56

4.759

3

--

--

--

--

--

--

Sodium

MPV 

TV 

Rating

--

--

--

43.0

3.8

0

--

--

--

0.439

0.450

4

--

--

--

--

--

--

3.00

2.995

4

Specific conductanceMPV 

TV 

Rating

--

--

--

--

--

--

--

--

--

41.8

39.4

2

--

--

--

--

--

--

27.0

26.05

4

Sulfate

MPV 

TV 

Rating

--

--

--

--

--

--

--

--

--

0.437

0.437

4

--

--

--

--

--

--

0.673

0.626

4

a

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

b

Sample described in Farrar (2000).

c

Sample described in Farrar and Copen (2000).

d

Sample described in Connor, Currier, and Woodworth (2001).

e

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

f

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).

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

was met by 90 percent of the NWRI samples. No trend or 

bias was evident. Data were not submitted for study 77 

due to instrument failure.

Aluminum, Total (fig. 4B)—The DQO was met by 50 

percent of the NWRI samples. The cause of the erratically 

high outliers is unknown.

Ammonium (fig. 4C)—The DQO was not met for the 

NWRI samples. The cause of the positive bias is currently 

being investigated. The reporting limit for ammonium is 

being reevaluated.

Calcium (fig. 4D)—The DQO was met by 98 percent of the 

NWRI samples. No trend or bias was evident.

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

by 62 percent of the NWRI samples. The data exhibited a 

positive bias for studies 75 and 78. The cause is unknown.

Chloride (fig. 4F)—The DQO was met by 90 percent of the 

NWRI samples. The data exhibited a negative bias during 

studies 76 and 78.

Magnesium (fig. 4G)—The DQO was met by 100 percent 

of the NWRI samples. The data exhibited a slight positive 

bias during studies 75 and 78 and a slight negative bias 

during studies 76 and 77. 

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

met by 89 percent of the NWRI samples. No trend or bias 

was evident.

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

NWRI samples. No trend or bias was evident. Data were 

not submitted for study 77 due to instrument failure.

Potassium (fig. 4J)—The DQO was met by 98 percent of 

the NWRI samples. The data exhibited a positive bias 

during studies 75, 76, and 77.

Silicon (fig. 4K)—The DQO was met by 100 percent of the 

NWRI samples. No trend or bias is evident.

Sodium (fig. 4L)—The DQO was met by 73 percent of the 

NWRI samples. The cause of the erratically high outliers 

is unknown.

Specific Conductance (fig. 4M)—The DQO was met by 97 

percent of the NWRI samples. The data exhibited a negative 

bias during study 76. Data were not submitted for study 77 

due to instrument failure.

Sulfate (fig. 4N)—The DQO was met by 98 percent of the 

NWRI samples. The data exhibited a slight negative bias for 

studies 76 and 77.

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 blind reference samples are not analyzed for acidneutralizing capacity, total monomeric aluminum, organic 

monomeric aluminum, total aluminum, ammonium, dissolved 

organic carbon, nitrate and silicon. 

Calcium (fig. 5A)—The DQO for calcium was met by 95 

percent of the blind reference samples. The data exhibited a 

negative bias for this period.

Chloride (fig. 5B)—The DQO was met by 100 percent of 

the blind reference samples. A negative bias was evident 

through 1999.

Fluoride (fig. 5C)—The DQO was met by 100 percent of the 

blind reference samples. The laboratories began fluoride 

analysis on blind reference samples in 2001.

Magnesium (fig. 5D)—The DQO was met by 94 percent 

of the blind reference samples. Most data indicated a 

negative bias.

pH (fig. 5E)—The DQO was met by 91 percent of the blind 

reference samples. A slight positive bias was evident during 

1999 and again in 2001.

Potassium (fig. 5F)—The DQO was met by 93 percent of the 

blind reference samples. No trend or bias was evident.

Sodium (fig. 5G).—The DQO was met by 75 percent of the 

blind reference samples. The cause of the negative bias 

is unknown.

Specific conductance (fig. 5H)—The DQO was met by 58 

percent of the blind reference samples. A negative bias 

is evident.

Sulfate (fig. 5I)—The DQO was met by 100 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 1999 through June 2001
Selected References

Connor, B.F., Currier, J.P., and Woodworth, M.T., 2001, 

Results of the U.S. Geological Survey’s analytical 

evaluation program for standard reference samples 

distributed in October 2000: U.S. Geological Survey 

Open-File Report 01–137, 116 p.

Farrar, J.W., 2000, Results of the U.S. Geological Survey’s 

analytical evaluation program for standard reference 

samples distributed in October 1999: U.S. Geological 

Survey Open-File Report 00–227, 107 p.

Farrar, J.W. and Copen, A.M., 2000, Results of the U.S. 

Geological Survey’s analytical evaluation program for 

standard reference samples distributed in March 2000: U.S. 

Geological Survey Open-File Report 00–398, 107 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.

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.

Selected References 11
12 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figures 1–5

Figures 13
Figure 1. High- and low-concentration quality-control sample results: A. Acid-neutralizing capacity. B. Aluminum, total 

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

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

ALUMINUM, TOTAL,

IN MICROMOLES PER LITER

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

1999 2000 2001

DATE OF ANALYSIS

AMMONIUM,

IN MICROMOLES PER LITER

AMMONIUM,

IN MICROMOLES PER LITER

8

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

4

5

6

7

8

9

10

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

12

14

16

18

20

22

24

26

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

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

1999 2000 2001

DATE OF ANALYSIS

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

B. ALUMINUM, TOTAL MONOMERIC

High Concentration Sample

C. ALUMINUM, TOTAL

High Concentration Sample

14

13

12

11

10

9

8

ALUMINUM, TOTAL,

IN MICROMOLES PER LITER

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

14  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figure 1. High- and low-concentration quality-control sample results: E. Calcium. F. Carbon, dissolved organic. G. Chloride. 

H. Fluoride.—Continued CARBON, DISSOLVED ORGANIC, IN MICROMOLES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

Low Concentration Sample

CHLORIDE,

IN MICROMOLES PER LITER

H. FLUORIDE

Control Sample

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

1999 2000 2001

DATE OF ANALYSIS

FLUORIDE,

IN MICROMOLES PER LITER

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

80

85

90

95

100

105

110

115

120

20

22

24

26

28

30

250

300

350

400

450

500

10

30

50

70

90

110

65

70

75

80

85

90

95

100

105

6

7

8

9

12

1

2

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

1999 2000 2001

Low Concentration Sample

F. CARBON, DISSOLVED ORGANIC

High Concentration Sample

CALCIUM,

IN MICROMOLES PER LITER

E. CALCIUM

High Concentration Sample

DATE OF ANALYSIS

CALCIUM,

IN MICROMOLES PER LITER

10

11

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

1999 2000 2001

DATE OF ANALYSIS

G. CHLORIDE

High Concentration Sample

CHLORIDE,

IN MICROMOLES PER LITER

1.2

1.4

1.6

1.8

Figures 15
Figure 1. High- and low-concentration quality-control sample results: I. Magnesium. J. Nitrate (ion chromatography). 

K. Nitrate (colorimetric method). L. pH.—Continued MAGNESIUM, IN MICROMOLES PER LITER

I. MAGNESIUM

High Concentration Sample

MAGNESIUM,

IN MICROMOLES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

NITRATE,

IN MICROMOLES PER LITER

J. NITRATE (ION CHROMATOGRAPHY)

High Concentration Sample

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

NITRATE,

IN MICROMOLES PER LITER

K. NITRATE (COLORIMETRIC METHOD)

High Concentration Sample

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

NITRATE,

IN MICROMOLES PER LITER

NITRATE,

IN MICROMOLES PER LITER

L. pH

High Concentration Sample

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

pH pH

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

40

42

44

46

48

50

52

54

56

58

60

3

3.5

4

4.5

5

5.5

6

80

85

90

95

100

105

110

115

120

25

30

35

40

45

50

55

6.6

6.8

7

7.2

4.3

4.35

4.4

4.45

4.5

4.55

4.6

30

32

34

36

38

40

42

44

46

48

50

8

9

10

11

12

13

14

16  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figure 1. High- and low-concentration quality-control sample results: M. Potassium. N. Silicon. O. Sodium. P. Specific 

conductance.—Continued POTASSIUM, IN MICROMOLES PER LITER

M. POTASSIUM

High Concentration Sample

POTASSIUM,

IN MICROMOLES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

SILICON,

IN MICROMOLES PER LITER

N. SILICON

High Concentration Sample

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

SILICON,

IN MICROMOLES PER LITER

O. SODIUM

High Concentration Sample

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

SODIUM,

IN MICROMOLES PER LITER

SODIUM,

IN MICROMOLES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

P. SPECIFIC CONDUCTANCE

20

21

22

23

24

25

26

27

28

29

30

4

4.5

5

5.5

6

6.5

7

7.5

8

80

90

100

110

120

130

140

25

30

35

40

45

50

35

37

39

41

43

45

47

49

51

53

55

8

9

10

11

12

13

14

15

10

12

14

16

18

20

22

24

26

7

Figures 17
Figure 1. High- and low-concentration quality-control sample results: Q. Sulfate.—Continued SULFATE, IN MICROMOLES PER LITER

Q. SULFATE

High Concentration Sample

SULFATE,

IN MICROMILES PER LITER

Low Concentration Sample

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

1999 2000 2001

DATE OF ANALYSIS

CONTROL SAMPLE TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

6

7

8

9

10

11

12

65

70

75

80

85

90

95

100

18  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
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. Fluoride.

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

1999 2000 2001

DATE OF COLLECTION

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

1999 2000 2001

DATE OF COLLECTION

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

FLUORIDE,

IN MICROMOLES PER LITER

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

A. ALUMINUM, TOTAL MONOMERIC

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.5

1

1.5

2

2.5

3

3.5

4

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

D. AMMONIUM

C. ALUMINUM, TOTAL

B. ALUMINUM, ORGANIC MONOMERIC

0

0.5

1

1.5

2

2.5

3

3.5

4

E. CALCIUM

0

10

20

30

40

50

60

70

80

F. CARBON, DISSOLVED ORGANIC

-4

1

6

11

16

21

26

G. CHLORIDE

0

0.5

1

1.5

2

2.5

3

3.5

4

H. FLUORIDE

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

Figures 19
Figure 2. Filter-blank and analytical-blank sample results: I. Magnesium. J. Nitrate (ion chromatography). K. Potassium. 

L. Silicon. M. Sodium. N. Specific conductance O. Sulfate.—Continued

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

1999 2000 2001

DATE OF COLLECTION

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

1999 2000 2001

DATE OF COLLECTION

MAGNESIUM,

IN MICROMOLES PER LITER

NITRATE,

IN MICROMOLES PER LITER

POTASSIUM,

IN MICROMOLES PER LITER

SILICON,

IN MICROMOLES PER LITER

SODIUM,

IN MICROMOLES PER LITER

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER CENTIMETER

SULFATE,

IN MICROMOLES PER LITER

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

0

0.5

1

1.5

2

2.5

3

3.5

4

I. MAGNESIUM

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.5

1

1.5

2

2.5

3

3.5

4

J. NITRATE (ION CHROMATOGRAPHY)

K. POTASSIUM

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.5

1

1.5

2

2.5

3

3.5

4

L. SILICON

M. SODIUM

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.5

1

1.5

2

2.5

3

3.5

4

N. SPECIFIC CONDUCTANCE

O. SULFATE

20 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
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. Ammonium. F. Calcium. G. Carbon, dissolved organic. 

Jul Oct Jan Jul

1999 2000 2001

DATE OF COLLECTION

COEFFICIENT OF VARIATION

COEFFICIENT OF VARIATION CONTROL LIMIT

Apr Oct Jan Apr Jul Oct Jan Jul

1999 2000 2001

DATE OF COLLECTION

Apr Oct Jan Apr

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

-30

-20

-10

0

10

20

30

40

0

5

10

15

20

25

30

35

40

45

50

A1. ACID-NEUTRALIZING CAPACITY

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

0

5

10

15

20

25

30

35

40

45

50

B. ALUMINUM, TOTAL MONOMERIC

0

5

10

15

20

25

30

35

40

45

50

C. ALUMINUM, ORGANIC MONOMERIC

0

10

20

30

40

50

60

0

5

10

15

20

25

30

35

40

45

50

D. ALUMINUM, TOTAL

0

5

10

15

20

25

30

35

40

45

50

F. CALCIUM

0

5

10

15

20

25

30

35

40

45

50

G. CARBON, DISSOLVED ORGANIC

A2. ACID-NEUTRALIZING CAPACITY E. AMMONIUM

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

Figures 21
Figure 3. Triplicate environmental sample results: H. Chloride. I. Fluoride. J. Magnesium. K. Nitrate (ion chromatography) . 

L. pH. M. Potassium. N. Silicon. O. Sodium—Continued 

Jul Oct Jan Jul

1999 2000 2001

DATE OF COLLECTION

COEFFICIENT OF VARIATION

COEFFICIENT OF VARIATION CONTROL LIMIT

Apr Oct Jan Apr Jul Oct Jan Jul

1999 2000 2001

DATE OF COLLECTION

Apr Oct Jan Apr

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

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

H. CHLORIDE

0

5

10

15

20

25

30

35

40

45

50

J. MAGNESIUM

0

5

10

15

20

25

30

35

40

45

50

K. NITRATE (ION CHROMATOGRAPHY)

0

5

10

15

20

25

30

35

40

45

50

L. pH

0

5

10

15

20

25

30

35

40

45

50

N. SILICON

0

5

10

15

20

25

30

35

40

45

50

O. SODIUM

I. FLUORIDE M. POTASSIUM

0

5

10

15

20

25

30

35

40

45

50

0

10

20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

30

35

40

45

50

22 Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figure 3. Triplicate environmental sample results: P. Specific conductance. Q. Sulfate.—Continued COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

P. SPECIFIC CONDUCTANCE

Q. SULFATE

Jul Oct Jan Jul

1999 2000 2001

DATE OF COLLECTION

COEFFICIENT OF VARIATION CONTROL LIMIT

Apr Oct Jan Apr

Figures 23
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. Aaluminum, total. C. Ammonium. D. Calcium. 

E. Carbon, dissolved organic. F. Chloride. G. Magnesium.

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. ALUMINUM, TOTAL

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

C. AMMONIUM

D. CALCIUM

E. CARBON, DISSOLVED ORGANIC

F. CHLORIDE

G. MAGNESIUM

NWRI STUDIES 75 THROUGH 78 NWRI STUDIES 75 THROUGH 78

STUDY 75 STUDY 76 STUDY 77 STUDY 78 STUDY 75 STUDY 76 STUDY 77 STUDY 78

PERCENT DIFFERENCE

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) -40

-30

-20

-10

0

10

20

30

40

-20

-15

-10

-5

0

5

10

15

20

DIFFERENCE

-50

-40

-30

-20

-10

0

10

20

30

40

50

-40

-30

-20

-10

0

10

20

30

40

-20

-10

0

10

20

30

40

50

60

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

340

132

101

24  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figure 4. NWRI Ecosystem Interlaboratory QA Program results: H. Nitrate (ion chromatography). I. pH. J. Potassium. K. Silicon. 

L. Sodium. M. Specific conductance. N. Sulfate.—Continued.

H. NITRATE (ION CHROMATOGRAPHY)

I. pH

J. POTASSIUM

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

K. SILICON

L. SODIUM

M. SPECIFIC CONDUCTANCE

N. SULFATE

NWRI STUDIES 75 THROUGH 78

NWRI STUDIES 75 THROUGH 78

STUDY 75 STUDY 76 STUDY 77 STUDY 78

STUDY 75 STUDY 76 STUDY 77 STUDY 78

PERCENT DIFFERENCE

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)

-40

-30

-20

-10

0

10

20

30

40

-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%)

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

-60

-40

-20

0

20

40

60

Figures 25
Figure 5. Blind reference sample results: A. Calcium. B. Chloride. C. Fluoride. D. Magnesium. E. pH. F. Potassium. G. Sodium. 

H. Specific conductance. 

-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

-40

-30

-20

-10

0

10

20

30

40

D. MAGNESIUM

F. POTASSIUM

H. SPECIFIC CONDUCTANCE

DATE OF COLLECTION DATE OF COLLECTION

PERCENT DIFFERENCE

A. CALCIUM

-40

-30

-20

-10

0

10

20

30

40

C. FLUORIDE

-40

-30

-20

-10

0

10

20

30

40

E. pH

G. SODIUM

1999 2000 2001 1999 2000 2001

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)

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

-40

-30

-20

-10

0

10

20

30

40

26  Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 1999 through June 2001
Figure 5. Blind reference sample results: I. Sulfate.—Continued

TARGET VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

DATE OF COLLECTION

PERCENT DIFFERENCE

I. SULFATE

1999 2000 2001

DIFFERENCE FROM MOST

PROBABLE VALUE (IN PERCENT) -40

-30

-20

-10

0

10

20

30

40

Figures 27
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For additional information write to: 

New York Water Science Center

U.S. Geological Survey

2045 Route 112, Bldg. 4

Coram, NY 11727

Information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov
Lincoln, Horan-Ross, McHale, and Lawrence— —Open-File Report 2006–1246

July 1999 through June 2001U.S. Geological Survey Laboratory in Troy, New York—Quality-Assurance Data for Routine Water Analyses by the