7 

Quality-Assurance Data for Routine Water Analyses by the 

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

July 2003 through June 2005 

 

 

 

 

 

Open-File Report 2009–1233

U.S. Department of the Interior

U.S. Geological Survey
 

 

 

 

 

 

 

 

Cover. Fern along access road near Bog Lake, Robinwood Park Club, western Adirondack State Park, Town of Long Lake, 

Hamilton County, New York ©2006 Peter deVries
Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York—

July 2003 Through June 2005 

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

Open-File Report 2009–1233 

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 2003 through June 2005: U.S. Geological 

Survey Open-File Report 2009–1233, 34 p., available only at http://pubs.usgs.gov/of/2009/1233/.
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............................................................................13

E. National Water Research Institute Ecosystem Interlaboratory QA Program.........................................................13

F. Blind Reference Samples .....................................................................................................................................16

Selected References ....................................................................................................................................................17

Figures

1. Plots showing high- and low-concentration quality control sample results.......................................................20

2. Plots showing filter-blank and analytical-blank sample results ........................................................................25

3. Plots showing triplicate environmental sample results.....................................................................................28

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

Program results ...............................................................................................................................................31

5. Plots showing blind reference sample results..................................................................................................33

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 2003 through June 2005................................. 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 2003 through June 2005............................................. 8

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

Sample (SRS) Project, fall 2003 through spring 2005 .....................................................................................14
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
1

Quality-Assurance Data for Routine Water Analyses by the 

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

July 2003 Through June 2005 

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 2003 through June 2005. 

Results for the quality-control samples for 20 analytical procedures were evaluated for bias and 

precision. Control charts indicate that data for five 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, pH, silicon, and sodium. Seven 

of the analytical procedures were biased throughout the analysis period for the high-concentration 

sample, but were within control limits; these procedures were: dissolved organic carbon, chloride, 

nitrate (ion chromatograph), nitrite, silicon, sodium, and sulfate. The calcium and magnesium 

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

within control limits. The total aluminum and specific conductance procedures were biased for the highconcentration and low-concentration samples, but were within control limits. 

Results from the filter-blank and analytical-blank analyses indicate that the procedures for 17 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 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 18 of the 22 analytes. At least 85 percent of the 

samples met data-quality objectives for all analytes except total monomeric aluminum (82 percent of 

samples met objectives), total aluminum (77 percent of samples met objectives), chloride (80 percent of 

samples met objectives), fluoride (76 percent of samples met objectives), and nitrate (ion 

chromatograph) (79 percent of samples met objectives). The ammonium and total dissolved nitrogen did 

not meet the data-quality objectives. 

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

data quality over the time period, with ratings for each sample in the satisfactory, good, and excellent 

ranges or less than 10 percent error. The P-sample (low-ionic-strength constituents) analysis had one 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

2

marginal and two unsatisfactory ratings for the chloride procedure. The T-sample (trace constituents) 

analysis had two unsatisfactory ratings and one high range percent error for the aluminum procedure. 

The N-sample (nutrient constituents) analysis had one marginal rating for the nitrate procedure.

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

that at least 84 percent of the samples met data-quality objectives for 11 of the 14 analytes; the 

exceptions were ammonium, total aluminum, and acid-neutralizing capacity. The ammonium procedure 

did not meet data quality objectives in all studies. Data-quality objectives were not met in 23 percent of 

samples analyzed for total aluminum and 45 percent of samples analyzed acid-neutralizing capacity. 

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

at least 86 percent of the samples analyzed for calcium, chloride, fluoride, magnesium, pH, potassium, 

sodium, and sulfate. Data-quality objectives were not met by samples analyzed for fluoride. 

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 groundwater, and stream-water samples. The methods used 

in this laboratory are described in detail in Lawrence and others (1995). Quality-assurance (QA) and 

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

information management system during this report period. 

The 22 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), nitrate 

(colorimetric method), nitrite, total dissolved nitrogen, pH, potassium, silicon, sodium, specific 

conductance, sulfate, and turbidity. 

Purpose and Scope 

This report documents the QA practices and QC data of this laboratory and is intended for use 

by cooperating agencies. It (1) describes QC and QA procedures of the laboratory; (2) presents graphs 

showing the results from analyses of QC samples, filter blanks and analytical blanks, triplicate 

environmental samples, interlaboratory QA 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: 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: 2,988 samples (stream water, shallow groundwater, soil-water solution, soil-water by 

expulsion method, and snow). 
Quality-Assurance/Quality-Control (QA/QC) Program 

3

Project: Long-Term Monitoring of Five Streams in the Catskill Mountains 

Cooperator: U.S. Environmental Protection Agency 

Analyses: 697 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: 252 stream-water samples. 

Project: Adirondack Effects Assessment Program 

Cooperator: Rensselaer Polytechnic Institute 

Analyses: 484 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: 1,263 stream-water samples. 

Project: Neversink River Natural Resources Study 

Cooperator: The Nature Conservancy 

Analysis: 25 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: 1,451 stream-water samples. 

Project: Catskill Stream Restoration Study 

Cooperator: New York City Department of Environmental Protection 

Analyses: 71 stream-water samples. 

Project: Potential Recovery of Water Chemistry in Stream Biota from Reduced Levels of Acid 

Deposition at a Sensitive Watershed in the Catskill Mountains 

Cooperator: New York Energy Research and Development Authority 

Analyses: 31 stream-water samples. 

Additional information on projects of the New York Water Science Center is given in 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 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 2003 through June 2005 

4

Quality-Control Samples 

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. 

QC 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 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 QA 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 2003 through June 2005.

[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 5,918 954 131 13 3 0 0

Aluminum, total monomeric 6,073 829 828 0 1 0 0

Aluminum, organic monomeric1 6,072 0 0 0 0 0 0

Aluminum, total 6,919 814 835 5 2 0 0

Ammonium 6,574 759 755 2 5 0 1

Boron 143 44 44 0 0 0 0

Calcium 6,021 707 688 1 0 0 0

Carbon, dissolved organic 6,432 868 871 5 18 0 2

Chloride 6,092 1,057 1,054 4 10 1 4

Fluoride 1,530 0 240 0 6 0 0

Magnesium 6,021 683 664 0 0 0 0

Nitrate (ion chromatography) 6,096 1,045 1,064 6 5 1 0

Nitrate (colorimetric method) 650 21 22 4 1 0 0

Nitrite 3,983 453 465 2 0 0 0

Nitrogen, total dissolved 3,380 473 474 0 7 0 3

pH 5,968 991 194 23 6 2 4

Potassium 5,990 734 732 0 0 0 0

Silicon 6,021 707 688 1 1 0 0

Sodium 6,000 717 717 1 0 0 0

Specific conductance 5,967 1,011 192 0 0 0 0

Sulfate 6,098 1,051 1,057 4 2 1 1

Turbidity2 540 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 2003 through June 2005 

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 day’s analytical runs.

U.S. Geological Survey’s Standard Reference Sample (SRS) 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, 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. Beginning with the evaluation program in the spring of 2005, laboratory results are compared to the 

MPV and a percent difference is calculated for each constituent. The SRS project discontinued use of 

the laboratory rating system. 

National Water Research Institute 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 

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 
Control-Chart Evaluation

7

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.

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 it is 15 percent. Each circle within the control charts represents the CV of a 

triplicate environmental sample.

(100) sCV

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 2003 through June 2005 

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 2003 through June 2005. 

[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 monomeric21.5 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 organic341.0 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 0.5

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

Nitrite 0.5 15 7.14 10 28.6 10 1.0

Nitrogen, total dissolved 10 20 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

Turbidity6none 5 none none none none none

1ANC: 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. 

2Quality-control samples for organic monomeric aluminum are unavailable. 

3Concentrations 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. 

6Comparison 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) QC 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 99 percent of the samples. The QC-high 

sample had a negative bias through July 2004 and a positive bias from December 2004 through 

June 2005. The QC-low sample had a positive bias in 2005. 

Aluminum, Total Monomeric (fig. 1B).—DQOs were met by 99 percent of the samples. The QC 

samples had a positive bias from January 2004 through June 2005.

Aluminum, Organic Monomeric.—A QC sample has not been developed for this analysis. Separationcolumn efficiency is used to determine acceptability of the data. 

Aluminum, Total (fig. 1C).—DQOs were met by 99 percent of the samples. The QC samples had a 

positive bias during this period. 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005

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. No apparent trends or biases were 

evident during this period.

Calcium (fig. 1F).—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 negative bias during this period.

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

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

Fluoride (fig. 1I).—DQOs were met by 98 percent of the samples. No apparent trends or biases were 

evident during this period.

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

were evident for the QC-high sample; 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 during this period. No apparent trends or biases were evident for the 

QC-low sample.

Nitrate (colorimetric method) (fig. 1L).—DQOs were met by 88 percent of the samples. There are 

insufficient data to establish a trend for this period.

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

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

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

trends or biases were evident during this period.

pH (fig. 1O).—DQOs were met by 98 percent of the samples. No apparent trends or biases were evident 

for the QC-high sample; the QC-low sample had a positive bias in 2004 and 2005.

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

were evident during this period.

Silicon (fig. 1Q).—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 from October 2004 through June 

2005.

Sodium (fig. 1R).—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 in 2005.

Specific Conductance (fig. 1S).—DQOs were met by 100 percent of the samples. The QC samples had 

a negative bias during this period.

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

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

Turbidity.—Comparison standards are compared to the daily response factor of the instrument and 

used to determine acceptability of the data.
Summary of Results

11

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 99 percent of the samples. No 

systematic trends were evident for this analysis.

Aluminum, Total (fig. 2C).—The DQO was met for 84 percent of the samples. No systematic trends 

were evident for this analysis.

Ammonium (fig. 2D).—The DQO was met by 96 percent of the samples. No systematic trends were 

evident for this analysis.

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

establish a trend for this period.

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 is being evaluated and method modifications are being considered.

Chloride (fig. 2H).—The DQO was met by 94 percent of the samples. A long-term chloride 

contamination problem has continued to improve.

Fluoride (fig. 2I).—The DQO was met by 73 percent of the samples. No systematic trends were evident 

for this analysis.

Magnesium (fig. 2J).—The DQO was met by 97 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.

Nitrate (colorimetric method).—Blanks were not available for this constituent during this period.

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 84 percent of the samples. No systematic 

trends were evident for this analysis.

pH.—Blanks were not analyzed for this constituent during this period.

Potassium (fig. 2N).—The DQO was met by 99 percent of the samples. Potassium analysis began on an 

inductively coupled plasma spectrophotometer in 2005; improved blank data are apparent.

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

for this analysis.

Sodium (fig. 2P).—The DQO was met by 99 percent of the samples. Sodium analysis began on an 

inductively coupled plasma spectrophotometer in 2005; improved blank data are apparent.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005

12

Specific Conductance (fig. 2Q).—The DQO was met by 90 percent of the samples. No systematic 

trends were evident for this analysis.

Sulfate (fig. 2R).—The DQO was met by 98 percent of the samples. No systematic trends were evident 

for this analysis.

Turbidity.—Blanks were not analyzed for this constituent during this period.

C. Triplicate Environmental Samples

Acid-Neutralizing Capacity (figs. 3A1 and 3A2).—The DQO was met by 85 percent of the triplicate 

samples.

Aluminum, Total Monomeric (fig. 3B).—The DQO was met by 82 percent of the triplicate samples.

Aluminum, Organic Monomeric (fig. 3C).—The DQO was met by 91 percent of the triplicate 

samples.

Aluminum, Total (fig. 3D).—The DQO was met by 77 percent of the triplicate samples.

Ammonium (fig. 3E).—The DQO was not met for ammonium triplicate samples.

Boron.—Triplicate samples were not available for this constituent during this period.

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

Carbon, Dissolved Organic (fig. 3G).—The DQO was met by 89 percent of the triplicate samples.

Chloride (fig. 3H).—The DQO was met by 80 percent of the triplicate samples.

Fluoride (fig. 3I).—The DQO was met by 76 percent of the triplicate samples.

Magnesium (fig. 3J).—The DQO was met by 95 percent of the triplicate samples.

Nitrate (ion chromatography) (fig. 3K).—The DQO was met by 79 percent of the triplicate samples.

Nitrate (colorimetric method).—Triplicate samples were not available for this constituent during this 

period.

Nitrite.—Triplicate samples were not available for this constituent during this period.

Nitrogen, Total Dissolved (fig. 3L).—The DQO was not met for total dissolved nitrogen triplicate 

samples.

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

Potassium (fig. 3N).—The DQO was met by 94 percent of the triplicate samples.

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

Sodium (fig. 3P).—The DQO was met by 95 percent of the triplicate samples.

Specific Conductance (fig. 3Q).—The DQO was met by 99 percent of the triplicate samples.

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

Turbidity.—Triplicate samples were not available for this constituent during this period.
Summary of Results

13

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. 

Beginning with the spring 2005 study, the SRS project discontinued the use of laboratory ratings and 

instead reports a percent difference from the MPV for each analyte. The Troy laboratory DQO is ±10 

percent from the MPV.

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 (sample no., rating):

T–175 3.0 N–79 2.5 P–41 2.8

T–177 3.6 N–81 2.5 P–42 3.3

T–179 3.0 N–83 2.0 P–43 3.3

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

study period.

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

exceptions:

Aluminum.—The cause of a zero ratings for SRS T–175 and T–179 and the 28.8 percent high value for 

T–181 is unknown and being investigated.

Chloride.—The zero and marginal ratings for SRS P–41 and P–43 were for values which were within 

12 percent and 10 percent of the SRS MPVs, respectively. The cause of the zero rating for P–42 

is erroneous data entry.

Nitrate.—The marginal rating for SRS N–81 was for a value which was 10 percent above the SRS most 

probable value.

E. National Water Research Institute Ecosystem Interlaboratory QA Program

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

monomeric aluminum, organic monomeric aluminum, boron, fluoride, nitrate (colorimetric method), 

nitrite, total dissolved nitrogen, and turbidity.

Acid-Neutralizing Capacity (figs. 4A1 and 4A2).—The DQO was met by 55 percent of the NWRI

samples. The cause of the inconsistent results is unknown. Data were not submitted for study 84 

due to instrument downtime.

Aluminum, Total (fig. 4B).—The DQO was met by 77 percent of the NWRI samples. The cause of the 

high outliers is unknown.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005

14

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Summary of Results

15

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

16

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. Data were 

not submitted for studies 83 and 86 due to instrument downtime. 

Calcium (fig. 4D).—The DQO was met by 88 percent of the NWRI samples. The data exhibited a 

positive bias during this period. 

Carbon, Dissolved Organic (fig. 4E).—The DQO was met by 84 percent of the NWRI samples. The 

data exhibited a positive bias for this period. 

Chloride (fig. 4F).—The DQO was met by 88 percent of the NWRI samples. The data exhibited a 

negative bias during this period. 

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

negative bias during studies 84 and 86. 

Nitrate (ion chromatography) (fig. 4H).—The DQO was met by 94 percent of the NWRI samples. 

The data exhibited a negative bias during study 83. 

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 84 due to instrument downtime. 

Potassium (fig. 4J).—The DQO was met by 94 percent of the NWRI samples. The data exhibited a 

negative bias during this period. Data were not submitted for studies 84 and 85 due to instrument 

upgrades. 

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

negative bias during this period. 

Sodium (fig. 4L).—The DQO was met by 85 percent of the NWRI samples. The cause of the erratically 

low outliers is unknown. The data exhibited a positive bias during this period. Data was not 

submitted for studies 84 and 85 due to instrument upgrades. 

Specific Conductance (fig. 4M).—The DQO was met by 100 percent of the NWRI samples. The data 

exhibited a negative bias during this period. Data were not submitted for study 84 due to 

instrument downtime. 

Sulfate (fig. 4N).—The DQO was met by 100 percent of the NWRI samples. No trend or bias was 

evident. 

F. Blind Reference Samples 

Blind reference samples (SRS low-ionic-strength constituent P-samples) are analyzed for the 

Troy Laboratory procedures for which the SRS project reports an analyte MPV. The 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 100 percent of the blind reference samples. The 

data exhibited a negative bias for this period. 

Chloride (fig. 5B).—The DQO was met by 86 percent of the blind reference samples. A positive bias 

was evident through July 2004. 
Summary of Results 

17

Fluoride (fig. 5C).—The DQO was not met for the fluoride blind reference samples. The data are being 

investigated. 

Magnesium (fig. 5D).—The DQO was met by 86 percent of the blind reference samples. Most data 

indicated a negative bias. 

pH (fig. 5E).—The DQO was met by 99 percent of the blind reference samples. A positive bias was 

evident during this period. 

Potassium (fig. 5F).—The DQO was met by 96 percent of the blind reference samples. A negative bias 

was evident during this period. 

Sodium (fig. 5G).—The DQO was met by 99 percent of the blind reference samples. No trend or bias 

was evident. 

Specific Conductance (fig. 5H).—The DQO was met by 89 percent of the blind reference samples. A 

negative bias was evident during this period. 

Sulfate (fig. 5I).—The DQO was met by 89 percent of the samples. No trend or bias was evident.

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., 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.

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.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

18

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Figures 

19

Figures 1-5 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

20
Figures 

21
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

22
Figures 

23
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

24
Figures 

25
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

26
Figures 

27
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

28
Figures 

29
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

30
Figures 

31
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

32
Figures 

33
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2003 through June 2005 

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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 2003 through June 2005—Open-File Report 2009–1233