Quality-Assurance Data for Routine Water Analyses by the 

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

July 2001 through June 2003 

 

 

 

 

 

Open-File Report 2009–1232 

U.S. Department of the Interior

U.S. Geological Survey
 

 

 

 

 

 

 

 

Cover. Late October view showing ferns, beech, other hardwood-conifer, and snow along the Wittenberg-Cornell-Slide Trail to 

Wittenberg Mountain in Catskill State Park, New York City Watershed, Ulster County, New York ©2006 Amanda Bailey
Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York—

July 2001 Through June 2003

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

Open-File Report 2009–1232

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 2009

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 material contained within this report.

Suggested citation:

Lincoln, T.A., Horan-Ross, D.A., McHale, M.R., and Lawrence, G.B., 2009, Quality-assurance data for routine 

water analyses by the U.S. Geological Survey laboratory in Troy, New York—July 2001 through June 2003: 

U.S. Geological Survey Open-File Report 2009–1232, 32 p., available only at http://pubs.usgs.gov/of/2009/1232/.
iii

Contents

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

Introduction.................................................................................................................................................................... 2

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

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

Quality-Assurance/Quality-Control (QA/QC) Program................................................................................................... 3

Quality-Control Samples ............................................................................................................................................ 4

Filter Blanks and Analytical Blanks ............................................................................................................................ 4

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

U.S. Geological Survey’s Standard Reference Sample Project ................................................................................. 6

National Water Research Institute Ecosystem Interlaboratory QA Program .............................................................. 6

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

Control-Chart Evaluation ............................................................................................................................................... 7

Quality-Control Samples ............................................................................................................................................ 7

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

Triplicate Environmental Samples.............................................................................................................................. 7

National Water Research Institute Ecosystem Interlaboratory QA Program .............................................................. 9

Blind Reference Samples........................................................................................................................................... 9

Summary of Results ...................................................................................................................................................... 9

A. Quality-Control Samples........................................................................................................................................ 9

B. Filter Blanks and Analytical Blanks...................................................................................................................... 11

C. Triplicate Environmental Samples ....................................................................................................................... 12

D. U.S. Geological Survey’s Standard Reference Sample Project........................................................................... 12

E. National Water Research Institute Ecosystem Interlaboratory QA Program........................................................ 14

F. Blind Reference Samples .................................................................................................................................... 15

Selected References ................................................................................................................................................... 16

Figures

1. Plots showing high- and low-concentration quality control sample results...................................................... 18

2. Plots showing filter-blank and analytical-blank sample results........................................................................ 23

3. Plots showing triplicate environmental sample results.................................................................................... 26

4. Plots showing National Water Research Institute (NWRI) Ecosystem Interlaboratory Quality-Assurance 

Program results .............................................................................................................................................. 29

5. Plots showing blind reference sample results................................................................................................. 31

Tables

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

N.Y., and summary of quality-control data for each constituent, July 2001 through June 2003........................ 5

2. Reporting limits and data-quality objectives (DQOs) for accuracy, precision, and blanks for solution 

analyses performed by the USGS Laboratory in Troy, N.Y., July 2001 through June 2003.............................. 8

3. Results obtained by the USGS Laboratory in Troy, N.Y., for the U.S. Geological Survey Standard 

Reference Sample (SRS) Project, September 2001 through March 2003...................................................... 13
iv

Conversion Factors and Abbreviations

Multiply By To obtain

Length

 centimeter (cm) 0.3937 inch (in.)

Volume

 liter (L) 33.82 ounce, fluid (fl. oz)

Abbreviated Units of Measurement

mq/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

USGS U.S. Geological Survey
1

Quality-Assurance Data for Routine Water Analyses by the 

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

July 2001 Through June 2003

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 Lab Master data-management system, which provides efficient review, compilation, and 

plotting of data. This report presents and discusses results of quality-assurance and quality control 

samples analyzed from July 2001 through June 2003.

Results for the quality-control samples for 19 analytical procedures were evaluated for bias and 

precision. Control charts indicate that data for six 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, chloride, magnesium, nitrate (ion chromatography), 

potassium, and sodium. The calcium procedure was biased throughout the analysis period for the highconcentration sample, but was within control limits. The total monomeric aluminum and fluoride 

procedures were biased throughout the analysis period for the low-concentration sample, but were 

within control limits. The total aluminum, pH, specific conductance, and sulfate procedures were biased 

for the high-concentration and low-concentration samples, but were within control limits.

Results from the filter-blank and analytical-blank analyses indicate that the procedures for 16 of 

18 analytes were within control limits, although the concentrations for blanks were occasionally outside 

the control limits. The data-quality objective was not met for the dissolved organic carbon or specific 

conductance procedures.

Sampling and analysis precision are evaluated herein in terms of the coefficient of variation 

obtained for triplicate samples in the procedures for 18 of the 21 analytes. At least 90 percent of the 

samples met data-quality objectives for all procedures except total monomeric aluminum (83 percent of 

samples met objectives), total aluminum (76 percent of samples met objectives), ammonium (73 percent 

of samples met objectives), dissolved organic carbon (86 percent of samples met objectives), and nitrate 

(81 percent of samples met objectives). The data-quality objective was not met for the nitrite procedure.

Results of the USGS interlaboratory Standard Reference Sample (SRS) Project indicated 

satisfactory or above data quality over the time period, with most performance ratings for each sample 

in the good-to-excellent range. The N-sample (nutrient constituents) analysis had one unsatisfactory 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

2

rating for the ammonium procedure in one study. The T-sample (trace constituents) analysis had one 

unsatisfactory rating for the magnesium procedure and one marginal rating for the potassium procedure 

in one study and one unsatisfactory rating for the sodium procedure in another.

Results of Environment Canada’s National Water Research Institute (NWRI) program indicated 

that at least 90 percent of the samples met data-quality objectives for 10 of the 14 analytes; the 

exceptions were acid-neutralizing capacity, ammonium, dissolved organic carbon, and sodium. Dataquality objectives were not met in 37 percent of samples analyzed for acid-neutralizing capacity, 28 

percent of samples analyzed for dissolved organic carbon, and 30 percent of samples analyzed for 

sodium. Results indicate a positive bias for the ammonium procedure in one study and a negative bias in 

another.

Results from blind reference-sample analyses indicated that data-quality objectives were met by 

at least 90 percent of the samples analyzed for calcium, chloride, magnesium, pH, potassium, and 

sodium. Data-quality objectives were met by 78 percent of the samples analyzed for sulfate. Dataquality objectives were not met by samples analyzed for fluoride and 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 watershed-research 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). Quality-assurance and 

quality-control data were collected, stored, and reviewed through the laboratory’s Lab Master 

information management system during this report period.

The 21 analytes represented by this study were: acid-neutralizing capacity (ANC), total 

monomeric aluminum, organic monomeric aluminum, total aluminum, ammonium, boron, calcium, 

dissolved organic carbon (DOC), chloride, fluoride, magnesium, nitrate (ion chromatograph), nitrite, 

total dissolved nitrogen, pH, potassium, silicon, sodium, specific conductance, sulfate, and turbidity.

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 qualityassurance 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: 12 samples (stream water, shallow ground water, and snow).
Quality Assurance/Quality Control (QA/QC) Program

3

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: 1,682 samples (stream water, shallow groundwater, 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: 642 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: 258 stream-water samples.

Project: Adirondack Effects Assessment Program

Cooperator: Rensselaer Polytechnic Institute

Analyses: 702 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: 1,234 stream-water samples.

Project: Neversink River Natural Resources Study

Cooperator: The Nature Conservancy

Analysis: 98 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: 1,452 stream-water samples.

Project: Catskill Stream Restoration Study

Cooperator: New York City Department of Environmental Protection

Analyses: 98 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 dataquality 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 2001 through June 2003

4

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 respectively) are prepared for most analyses; exceptions are inorganic 

monomeric aluminum, for which column efficiency is used to determine the acceptability of the data;

fluoride, for which only one mid-level QC sample is prepared because the concentrations encountered 

by the laboratory are within a narrow range; and turbidity, for which a second set of calibration 

standards is checked against the daily calibration response factor of the instrument.

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 the 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 environmental-sample data preceding it are considered to be out-of-control, 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 the 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. Filterblank 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.
Quality Assurance/Quality Control (QA/QC) Program

5

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

N.Y., and summary of quality-control data for each constituent, July 2001 through June 2003.

[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 5,837 528 234 19 5 0 0

Aluminum, total monomeric 6,126 676 674 1 1 0 0

Aluminum, organic monomeric1 6,126 0 0 0 0 0 0

Aluminum, total 6,853 957 959 0 0 0 0

Ammonium 5,888 764 765 3 1 0 0

Boron 443 36 36 0 0 0 0

Calcium 6,063 851 846 0 0 0 0

Carbon, dissolved organic 5,899 879 881 2 5 0 0

Chloride 6,093 809 823 0 3 0 0

Fluoride 1,681 0 200 0 3 0 0

Magnesium 6,064 851 846 0 0 0 0

Nitrate (ion chromatography) 6,086 809 823 1 12 0 0

Nitrite 4,052 512 512 5 5 0 0

Nitrogen, total dissolved 4,053 517 517 4 7 1 3

pH 6,044 615 284 18 6 0 0

Potassium 5,988 809 807 0 0 0 0

Silicon 6,064 848 841 0 0 0 0

Sodium 5,976 737 735 0 0 0 0

Specific conductance 6,010 584 222 0 5 0 1

Sulfate 6,083 809 823 1 5 0 0

Turbidity2 97 0 0 0 0 0 0

1

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

2 Comparison of standards to calibration response factor is used to determine the acceptability of the data.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

6

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 sample-processing 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 days of 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 and nitrate. 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.

National Water Research Institute Ecosystem Interlaboratory QA Program

The Troy Laboratory participates in Environment Canada’s NWRI Ecosystem Interlaboratory 

QA program, in which a set of 10 samples is analyzed twice per year. 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 

MPVs 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.
Summary of Results

7

Control-Chart Evaluation

Control charts (figs. 1–5) 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 the CV is 15 percent. Each circle within the control charts represents the CV of a 

triplicate environmental sample.

(100) s CV

X

= (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.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

8

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

analyses performed by the USGS Laboratory in Troy, N.Y., July 2001 through June 2003.

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

control] 

Constituent or property

Reporting 

limit 

(μmol/L)

Accuracy Precision

Low-concentration QC 

sample

High-concentration QC 

sample Environmental 

triplicate 

samples 

DQO (CV)

Filter and 

analytical 

blanks DQO

(μmol/L)

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 15 1.49 10 11.2 15 1.0

Ammonium 2.0 15 7.14 10 17.9 15 1.5

Boron 1.0 10 3.70 10 18.5 10 1.0

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 20 1.58 none none 10 0.6

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

Nitrite 0.5 15 7.14 10 28.6 10 1.0

Nitrogen, total dissolved 0.5 15 21.4 10 100 10 2.0

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 15 (17.0) 15 (39.0) 10 1.5

Sulfate 2.0 10 8.33 10 83.3 10 0.3

Turbidity6 none 5 none none none none none

1

ANC: values in parentheses are in microequivalents per liter. For values within ±20 microequivalents per liter, an absolute DQO 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.

6

Comparison standards must be within 5 percent of the daily response factor of the instrument.
Summary of Results

9

National Water Research Institute 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:

100

MCV

AV MCV D × − = (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

100

MPV

AV MPV D × − = (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), (B) filter 

blanks and analytical blanks (fig. 2), (C) triplicate environmental samples (fig. 3), (D) SRS samples 

(table 3), (E) NWRI samples (fig. 4), and (F) blind samples (fig. 5).

A. Quality-Control Samples

Acid-Neutralizing Capacity (fig. 1A).— DQOs were met by 98 percent of the samples. The QC-high 

sample had a negative bias from September 2002 through June 2003. The QC-low sample had a 

positive bias in 2002.

Aluminum, Total Monomeric (fig. 1B).—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 had a positive bias 

during this period.

Aluminum, Total (fig. 1C).—DQOs were met by 100 percent of the samples. The QC-high sample and 

the QC-low sample had a positive bias during this period.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

10

Ammonium (fig. 1D).—DQOs were met by 99 percent of the samples. No apparent trends or biases 

were evident during this period.

Boron (fig. 1E).—DQOs were met by 100 percent of the samples. There are insufficient data to 

establish any apparent trends or biases during this period.

Calcium (fig. 1F).—DQOs were met by 100 percent of the samples. The QC-high sample had a slight 

positive bias during this period. No apparent trends or biases were evident for the QC-low 

sample.

Carbon, Dissolved Organic (fig. 1G).—DQOs were met by 99 percent of the samples. No apparent 

trends or biases were evident during this period.

Chloride (fig. 1H).—DQOs were met by 99 percent of the samples. The QC-high sample had a positive 

bias in 2001 and 2003; the remaining time it indicated a slight negative bias. No apparent trends 

or biases were evident for the QC-low sample.

Fluoride (fig. 1I).—DQOs were met by 98 percent of the samples. The QC sample had a positive bias 

during this period.

Magnesium (fig. 1J).—DQOs were met by 100 percent of the samples. The QC-high sample had a 

positive bias through 2001. The QC-low sample had a negative bias during this period.

Nitrate (ion chromatography) (fig. 1K).—DQOs were met by 99 percent of the samples. The QC-high 

sample had a positive bias in 2001 and 2003. No apparent trends or biases were evident for the 

QC-low sample.

Nitrite (fig. 1L).—DQOs were met by 99 percent of the samples. No apparent trends or biases were 

evident during this period.

Nitrogen, Total Dissolved (fig. 1M).—DQOs were met by 99 percent of the samples. No apparent 

trends or biases were evident during this period.

pH (fig. 1N).—DQOs were met by 97 percent of the samples. The QC-high sample had a negative bias 

through June 2002. The QC-low sample had a positive bias during this period.

Potassium (fig. 1O).—DQOs were met by 100 percent of the samples. The QC-high sample and the 

QC-low sample had a positive bias through August 2002.

Silicon (fig. 1P).—DQOs were met by 100 percent of the samples. No apparent trends or biases were 

evident during this period.

Sodium (fig. 1Q).—DQOs were met by 100 percent of the samples. The QC-high sample had a 

negative bias through February 2002 and in May 2003. The QC-low sample had a negative bias 

during this period.

Specific Conductance (fig. 1R).—DQOs were met by 99 percent of the samples. The QC-high sample 

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

Sulfate (fig. 1S).—DQOs were met by 99 percent of the samples. The QC-high sample had a positive 

bias during this period. The QC-low sample had a positive bias through 2002.
Summary of Results

11

B. Filter Blanks and Analytical Blanks

Aluminum, Total Monomeric (fig. 2A).—The DQO was met by 100 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 96 percent of the samples. No systematic trends 

were evident for this analysis.

Ammonium.—(fig. 2D).—The DQO was met by 84 percent of the samples. Blank data results show 

improvement in December 2002 through 2003 when 99 percent of the samples met the DQO.

Boron (fig. 2E).—The DQO was met by 100 percent of the samples. There are insufficient data for 

trend analysis.

Calcium (fig. 2F).—The DQO was met by 92 percent of the samples. No systematic trends were 

evident for this analysis.

Carbon, Dissolved Organic (fig. 2G).—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 and the instrument operating procedures are being evaluated.

Chloride (fig. 2H).—The DQO was met by 72 percent of the samples. Chloride contamination peaked 

in late 2002 when the laboratory was experiencing deionized water tank quality issues.

Fluoride (fig. 2I).—The DQO was met by 99 percent of the samples. Fluoride blank values increased in 

2002 and remained higher during 2003.

Magnesium (fig. 2J).—The DQO was met by 99 percent of the samples. No systematic trends were 

evident for this analysis.

Nitrate (ion chromatography) (fig. 2K).—The DQO was met by 99 percent of the samples. No 

systematic trends were evident for this analysis.

Nitrite (fig. 2L).—The DQO was met by 100 percent of the samples. No systematic trends were evident 

for this analysis.

Nitrogen, Total Dissolved (fig. 2M).— The DQO was met by 86 percent of the samples. No systematic 

trends were evident for this analysis.

Potassium (fig. 2N).—The DQO was met by 80 percent of the samples. Potassium blank values peaked 

in late 2002 when the laboratory was experiencing deionized water tank quality issues.

Silicon (fig. 2O).—The DQO was met by 82 percent of the samples. Silicon blank values peaked in late 

2002 when the laboratory was experiencing deionized water tank quality issues.

Sodium (fig. 2P).—The DQO was met by 80 percent of the samples. Sodium blank values peaked in 

late 2002 when the laboratory was experiencing deionized water tank quality issues.

Specific Conductance (fig. 2Q).—The DQO was not met for specific conductance. Specific 

conductance blank values peaked in late 2002 when the laboratory was experiencing deionized 

water tank quality issues. The DQO was met by 92 percent of the samples for the remainder of 

the period.

Sulfate (fig. 2R).—The DQO was met by 99 percent of the samples. No systematic trends were evident 

for this analysis.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

12

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 83 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 76 percent of the triplicate samples.

Ammonium (fig. 3E).—The DQO was met by 73 percent of the triplicate samples.

Boron.— There were insufficient boron triplicate data to create a control chart.

Calcium (fig. 3F).—The DQO was met by 96 percent of the triplicate samples.

Carbon, Dissolved Organic (fig. 3G).—The DQO was met by 86 percent of the triplicate samples.

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

Fluoride (fig. 3I).—The DQO was met by 97 percent of the triplicate samples.

Magnesium (fig. 3J).—The DQO was met by 97 percent of the triplicate samples.

Nitrate (ion chromatography) (fig. 3K).—The DQO was met by 81 percent of the triplicate samples.

Nitrite.— There were insufficient nitrite triplicate data to create a control chart.

Nitrogen, Total Dissolved (fig. 3L).—The DQO was met by 56 percent of the triplicate samples.

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

Potassium (fig. 3N).—The DQO was met by 90 percent of the triplicate samples.

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

Sodium (fig. 3P).—The DQO was met by 92 percent of the triplicate samples.

Specific Conductance (fig. 3Q).—The DQO was met by 93 percent of the triplicate samples.

Sulfate (fig. 3R).—The DQO was met by 93 percent of the triplicate samples.

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

The USGS 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

Missing SRS results for the Troy Laboratory were due to instrument downtime during the SRS 

study period.
Summary of Results

13

All analyses (table 3) received a satisfactory or better rating for each constituent with the 

following exceptions:

Ammonium.—The zero rating for SRS N–71 was for a result very close to the laboratory’s ammonium 

reporting limit.

Magnesium.—The zero rating for SRS T–169 was for a value which was 12 percent above the SRS 

most probable value.

Potassium.—The rating of 1 for SRS T–169 was for a value which was 8 percent above the SRS most 

probable value.

Sodium.—The cause of a zero rating for SRS T–173 was an erroneous dilution calculation. The 

laboratory was sent an additional sample for this study which received a rating of 4.

Table 3. Results obtained by the USGS Laboratory in Troy, N.Y., for the U.S. Geological Survey Standard 

Reference Sample (SRS) Project, September 2001 through March 2003.

[MPV, most probable value; TV, Troy Laboratory value. All values are in milligrams per liter except aluminum (micrograms per liter,

μg/L), pH (pH units), and specific conductance (microsiemens per centimeter, μS/cm). Dashes indicate no results reported]

Analyte

MPV, 

TV, and 

ratinga

SRS sample number and date of sample distribution

T–167 N–71 P–37 T–169 N–73 P–38 T–171 N–75 P–39 T–173 N–77 P–40

09–01b 09–01b 09–01b 03–02c 03–02c 03–02c 09–02d 09–02d 09–02d 03–03e 03–03e 03–03e

Aluminum MPV 21.5 — — 33.6 — — 19.4 — — 71 — —

TV 20.5 — — 34.1 — — 18.6 — — 71.7 — —

Rating 4 — — 4 — — 4 — — 4 — —

Ammoniumf MPV — 0.063 — — 0.127 — — 0.077 — — 0.073 —

TV — 0.041 — — 0.139 — — 0.09 — — 0.08 —

Rating — 0 — — 2 — — 2 — — 3 —

Calcium MPV 5.15 — 1.03 37.6 — 6.4 6.75 — 8.65 34.8 — 0.728

TV 5.09 — 1 36.6 — 6.4 6.82 — 8.46 34.9 — 0.756

Rating 4 — 4 3 — 4 4 — 4 4 — 3

Chloride MPV — — 3.1 — — 8.37 — — 2.07 — — 15.2

TV — — 3.26 — — 8.17 — — 1.98 — — 14.9

Rating — — 3 — — 4 — — 3 — — 4

Fluoride MPV — — — — — — — — — — — 0.127

TV — — — — — — — — — — — 0.124

Rating — — — — — — — — — — — 4

Magnesium MPV 4.8 — 0.506 4.3 — 1.15 2.78 — 0.812 9.38 — 1.62

TV 4.56 — 0.477 4.83 — 1.11 2.8 — 0.758 9.29 — 1.57

Rating 3 — 3 0 — 3 4 — 2 4 — 4

Nitrate MPV — 0.067 — — — — — 0.092 — — 0.067 —

TV — 0.061 — — — — — 0.09 — — 0.068 —

Rating — 2 — — — — — 4 — — 4 —

pH MPV — — 4.61 — — 6.01 — — 3.66 — — —

TV — — 4.61 — — 5.94 — — 3.68 — — —

Rating — — 4 — — 4 — — 4 — — —

Potassium MPV 4.76 — 0.5 2.59 — 0.83 — — — 3.85 — 0.384

TV 4.93 — 0.5 2.79 — 0.839 — — — 3.68 — 0.357

Rating 3 — 4 1 — 4 — — — 3 — 3

Silicong MPV 5.9 — — 6.04 — — 3.5 — — 11.1 — —

TV 5.76 — — 6.05 — — 3.49 — — 11 — —

Rating 4 — — 4 — — 4 — — 4 — —

Sodium MPV 7.34 — 0.8 10.6 — 1.8 — — — 36.5 — 5.42

TV 7.18 — 0.777 10.1 — 1.77 — — — 64.4 — 5.08

Rating 4 — 4 3 — 4 — — — 0 — 2

Specific 

conductance

MPV — — 28.3 — — 65 — — 193 — — 66.8

TV — — 27.7 — — 61.5 — — 183 — — 63.3

Rating — — 4 — — 2 — — 2 — — 2

Sulfate MPV — — 1.44 — — 2.99 — — 29.3 — — 0.89

TV — — 1.44 — — 3.01 — — 28.2 — — 0.865

Rating — — 4 — — 4 — — 3 — — 4

a

Laboratory rating system: 4 is highest score; 0 is lowest. bSample described in Woodworth and Connor (2001). c

Sample described in Woodworth and Connor (2002). dSample described in Woodworth and Connor (2003a). e

Sample described in Woodworth and Connor (2003b). fThe SRS Project reports data as “Ammonia as Nitrogen.” g

The SRS Project reports data as “Silica.”
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

14

E. National Water Resource Institute Ecosystem Interlaboratory QA Program

Environment Canada’s NWRI program does not audit the analysis of total monomeric 

aluminum, organic monomeric aluminum, boron, fluoride, nitrite, total dissolved nitrogen, and turbidity.

Acid-Neutralizing Capacity (figs. 4A1 and 4A2).—The DQO was met by 63 percent of the NWRI

samples. Data outliers exhibited a negative bias except for study 82 which had a positive bias.

Aluminum, Total (fig. 4B).—The DQO was met by 94 percent of the NWRI samples. The data 

exhibited a positive bias except for study 81.

Ammonium (fig. 4C).—The DQO was not met for the NWRI samples. 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 72 percent of the NWRI samples. The 

data outliers exhibited a positive bias.

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

exhibited a positive bias; the data exhibited a negative bias during studies 81 and 82.

Magnesium (fig. 4G).—The DQO was met by 100 percent of the NWRI samples. The data exhibited a 

slight negative bias.

Nitrate (ion chromatography) (fig. 4H).—The DQO was met by 100 percent of the NWRI samples. 

The data exhibited a positive bias except for study 81.

pH (fig. 4I).—The DQO was met by 100 percent of the NWRI samples. The data exhibited a negative 

bias.

Potassium (fig. 4J).—The DQO was met by 90 percent of the NWRI samples. Data outliers exhibited a 

positive bias except for study 82 which had a negative bias.

Silicon (fig. 4K).—The DQO was met by 100 percent of the NWRI samples. The data exhibited a 

negative bias.

Sodium (fig. 4L).—The DQO was met by 70 percent of the NWRI samples. The data exhibited a 

negative bias for studies 79 and 82 and a positive bias for studies 80 and 81.

Specific Conductance (fig. 4M).—The DQO was met by 90 percent of the NWRI samples. The data 

exhibited a negative bias.

Sulfate (fig. 4N).—The DQO was met by 95 percent of the NWRI samples. The data exhibited a slight 

negative bias for studies 80 through 82.
Summary of Results

15

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 acid-neutralizing capacity, total monomeric aluminum, organic monomeric 

aluminum, total aluminum, ammonium, boron, dissolved organic carbon, nitrate, nitrite, total dissolved 

nitrogen, silicon, and turbidity.

Calcium (fig. 5A).—The DQO for calcium was met by 98 percent of the blind reference samples. The 

data exhibited a negative bias for this period.

Chloride (fig. 5B).—The DQO was met by 90 percent of the blind reference samples. A positive bias 

was evident in 2003.

Fluoride (fig. 5C).—The DQO was not met. Since the laboratory has a history of good fluoride results, 

it is possible that the fluoride most probable value is unstable for the blind samples used during 

the latter part of the period.

Magnesium (fig. 5D).—The DQO was met by 90 percent of the blind reference samples. Data indicated 

a negative bias.

pH (fig. 5E).—The DQO was met by 91 percent of the blind reference samples. A positive bias was 

evident.

Potassium (fig. 5F).—The DQO was met by 92 percent of the blind reference samples. A negative bias 

was evident in 2003.

Sodium (fig. 5G).—The DQO was met by 91 percent of the blind reference samples. Data indicated a 

negative bias.

Specific Conductance (fig. 5H).—The DQO was not met. The blind sample used in 2001 is listed as an 

unstable value on the SRS project web site.

Sulfate (fig. 5I).—The DQO was met by 78 percent of the samples. Data indicated a negative bias.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

16

Selected References

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.

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.

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.

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.

Woodworth, M.T., and Connor, B.F., 2001, Results of the U.S. Geological Survey’s analytical 

evaluation program for standard reference samples distributed in September 2001: U.S. Geological 

Survey Open-File Report 02–8, 113 p.

Woodworth, M.T., and Connor, B.F., 2002, Results of the U.S. Geological Survey’s analytical 

evaluation program for standard reference samples distributed in March 2002: U.S. Geological Survey 

Open-File Report 02–243, 108 p.

Woodworth, M.T., and Connor, B.F., 2003a, Results of the U.S. Geological Survey’s analytical 

evaluation program for standard reference samples distributed in September 2002: U.S. Geological 

Survey Open-File Report 02–481, 108 p.

Woodworth, M.T., and Connor, B.F., 2003b, Results of the U.S. Geological Survey’s analytical 

evaluation program for standard reference samples distributed in March 2003: U.S. Geological Survey 

Open-File Report 03–261, 109 p.
Figures

17

Figures 1–5
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

19
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

21
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

25
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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Figures

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2001 through June 2003

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For more information concerning this report, contact

Director

U.S. Geological Survey

New York Water Science Center

425 Jordan Road

Troy, NY 12180-8349

dc_ny@usgs.gov

or visit our Web site at:

http://ny.water.usgs.gov
Lincoln and others—Quality-Assurance Data for Routine Water Analyses by the Laboratory in Troy, New York—July 2001 through June 2003—Open-File Report 2009–1232