7 

Quality-Assurance Data for Routine Water Analyses by the 

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

July 2005 through June 2007 

 

 

 

 

 

 

Open-File Report 2009–1234 

U.S. Department of the Interior

U.S. Geological Survey
 

 

 

 

 

 

 

Cover. Vibrant fall colors along Baxter Park Rd., entrance to Baxter State Park, northwest of Millinocket, Piscataquis County, 

Maine ©2009 Peter deVries
Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York— 

July 2005 Through June 2007 

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

Open-File Report 2009–1234

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 2005 through June 2007: U.S. Geological 

Survey Open-File Report 2009–1234, 33 p., available only at http://pubs.usgs.gov/of/2009/1234/.
iii

Contents

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

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

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

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

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

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

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

Triplicate Environmental Samples.............................................................................................................................. 4

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 ............................................................................................................................................... 6

Quality-Control Samples ............................................................................................................................................ 8

Filter Blanks and Analytical Blanks ............................................................................................................................ 8

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

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 2005 through June 2007 ................................. 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 2005 through June 2007............................................. 7

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

Sample (SRS) Project, fall 2005 through spring 2007 .....................................................................................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
 

Quality-Assurance Data for Routine Water Analyses by 

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

July 2005 through June 2007

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 2005 through June 2007. 

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

precision. Control charts indicate that data for eight of the analytical procedures were occasionally 

biased for either high-concentration or low-concentration samples but were within control limits; these 

procedures were: total aluminum, calcium, magnesium, nitrate (colorimetric method), potassium, 

silicon, sodium, and sulfate. Eight of the analytical procedures were biased throughout the analysis 

period for the high-concentration sample, but were within control limits; these procedures were: total 

aluminum, calcium, dissolved organic carbon, chloride, nitrate (ion chromatograph), potassium, 

silicon, and sulfate. The magnesium and pH procedures were biased throughout the analysis period for 

the low-concentration sample, but were within control limits. The acid-neutralizing capacity, total 

monomeric aluminum, nitrite, 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 indicated that the procedures for 16 

of 17 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 21 analytes. At least 93 percent of the 

samples met data-quality objectives for all analytes except acid-neutralizing capacity (85 percent of 

samples met objectives), total monomeric aluminum (83 percent of samples met objectives), total 

aluminum (85 percent of samples met objectives), and chloride (85 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 met the Troy 

Laboratory data-quality objectives for 87 percent of the samples analyzed. The P-sample (low-ionicstrength constituents) analysis had two outliers each in two studies. The T-sample (trace constituents) 

analysis and the N-sample (nutrient constituents) analysis had one outlier each in two studies. 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

2 

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

indicated that at least 85 percent of the samples met data-quality objectives for 11 of the 14 analytes; 

the exceptions were acid-neutralizing capacity, total aluminum and ammonium. Data-quality 

objectives were not met in 41 percent of samples analyzed for acid-neutralizing capacity, 50 percent of 

samples analyzed for total aluminum, and 44 percent of samples analyzed for ammonium. 

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

by at least 86 percent of the samples analyzed for calcium, magnesium, pH, potassium, and sodium. 

Data-quality objectives were met by 76 percent of the samples analyzed for chloride, 80 percent of the 

samples analyzed for specific conductance, and 77 percent of the samples analyzed for sulfate.

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). Qualityassurance (QA) and quality-control (QC) data were collected, stored, and reviewed through the 

laboratory’s LabMaster 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, 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: 4,710 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: 640 stream-water samples.
Quality-Assurance/Quality-Control (QA/QC) Program

3 

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: 350 stream-water samples.

Project: Adirondack Effects Assessment Program

Cooperator: Rensselaer Polytechnic Institute

Analyses: 430 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: 1,258 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: 218 stream-water samples.

Project: Upper Delaware Water Quality

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

Analyses: 609 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 QA programs. Results of QA data are evaluated by the laboratory supervisor and primary 

analysts, and appropriate corrective action is taken when needed. The data-quality objectives (DQOs) 

are based on (1) the precision and accuracy levels generally required by projects that use the Troy 

Laboratory, and (2) the analytical limits of the methods used. 

Quality-Control Samples

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, 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 QC-low sample is analyzed within 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

4 

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. 

Filter-blank analysis indicates whether contamination has occurred during any step in sample 

handling, including bottle-washing procedures, filtration, sample preservation, or laboratory 

analysis.

Analytical blanks are aliquots of DI water that are processed and analyzed as environmental samples, 

except that the filtration step is omitted. Contamination found in analytical blanks may be 

attributed to any step in sample-handling, but not to filtration. 

Triplicate Environmental Samples

One set of triplicate environmental samples is included in each group of 50 samples. An 

environmental triplicate set consists of three consecutive samples collected at one field site. The 

purpose of environmental triplicate samples is to determine long-term analytical precision. Precision 

can be affected by bottle washing, sample-collection or 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.
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 2005 through June 2007.

[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 5,280 851 27 19 6 1 2

Aluminum, total monomeric 5,418 892 888 0 0 0 0

Aluminum, organic monomeric1 5,418 0 0 0 0 0 0

Aluminum, total 6,005 1,019 1,020 0 2 0 0 

Ammonium 7,122 850 858 8 8 0 0

Boron 616 57 57 0 0 0 0

Calcium 5,283 862 863 0 0 0 0

Carbon, dissolved organic 5,126 921 921 0 14 0 5 

Chloride 5,177 939 971 6 5 0 1

Magnesium 5,283 860 860 0 0 0 0 

Nitrate (ion chromatography) 5,207 969 935 4 0 1 0

Nitrate (colorimetric method) 1,883 209 200 1 1 0 0

Nitrite 4,815 539 538 0 0 0 0

Nitrogen, total dissolved 2,932 643 642 1 7 0 2 

pH 5,280 815 38 7 1 1 0

Potassium 5,283 763 757 0 8 0 0

Silicon 5,283 859 860 0 0 0 0 

Sodium 5,283 882 881 1 0 0 0

Specific conductance 5,272 824 30 2 0 0 0

Sulfate 5,207 972 938 12 3 0 0

Turbidity2 849 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 2005 through June 2007

 6

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-ionicstrength, 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 results are posted on the SRS project Web site 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 results are 

compared with the MPV for each constituent and a percent difference is calculated.

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 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 

most probable values that were reported by the USGS SRS project. The SRS samples are rotated as 

supplies are exhausted, and periodically the identity of the blind reference sample is changed. One 

blind reference sample is included in each set of 50 environmental samples. The Troy Laboratory used 

SRS P-samples as the blind reference samples during the time period represented in this report. 

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.
Control-Chart Evaluation

7

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 2005 through June 2007. 

[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

Aluminum, organic monomeric2 1.5 none none none none 15 1

Aluminum, total 1 15 1.49 10 11.2 15 1

Ammonium 2 15 7.14 10 17.9 15 1.5

Boron 0.5 10 1.85 10 7.4 10 1

Calcium 2 10 25 10 99.8 10 1

Carbon, dissolved organic3 41 15 83.3 10 416 10 18

Chloride 3 10 8.47 10 84.7 10 2 

Magnesium 1 10 10.3 10 41.1 10 0.5

Nitrate (ion chromatography) 2 15 4.84 15 48.4 10 0.3

Nitrate (colorimetric method) 5 15 42.9 10 100 none none

Nitrite 0.5 15 7.14 15 28.6 10 1

Nitrogen, total dissolved 0.5 20 21.4 15 100 10 2

pH4 none 10 -4.44 20 -6.88 10 none

Potassium 1 10 6.4 10 25.6 10 0.5

Silicon 6 10 35.6 10 107 10 3

Sodium 1 10 10.9 10 43.5 10 1 

Specific conductance5 none 10 -17 10 -39 10 1.5

Sulfate 2 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

QC 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.
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

8

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) 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 microequivalents per liter (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.
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 97 percent of the samples. The QC 

samples had a positive bias during this period. 

Aluminum, Total Monomeric (fig. 1B).—DQOs were met by 100 percent of the samples. The QC 

samples had a positive bias during this period. 

Aluminum, Organic Monomeric.—A QC sample has not been developed for this analysis. 

Separation-column efficiency is used to determine acceptability of the data.

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

a negative bias during this period; the QC-low sample had a negative bias in 2006. 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

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

positive bias during this period; the QC-low sample had a positive bias in 2006.

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.

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

negative bias in 2005 and a positive bias in 2006. The QC-low sample had a negative bias 

during this period. 

Nitrate (ion chromatography) (fig. 1J).—DQOs were met by 99 percent of the samples. The QChigh sample had a positive bias during this period. No apparent trends or biases were evident 

for the QC-low sample.

Nitrate (colorimetric method) (fig. 1K).—DQOs were met by 99 percent of the samples. The QChigh sample had a negative bias in 2005 and 2006. The QC-low sample had a negative bias in 

2006. 

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

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

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

positive bias in 2006. No apparent trends or biases were evident for the QC-low sample.

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

bias during this period. The QC-low sample had a positive bias in 2006. 

Sodium (fig. 1Q).—DQOs were met by 99 percent of the samples. The QC samples had a negative 

bias in 2007. 

Specific Conductance (fig. 1R).—DQOs were met by 99 percent of the samples. The QC samples 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 from June 2006 through 

December 2006.

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 100 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 89 percent of the samples. No systematic trends were 

evident for this analysis. 

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

for this analysis.

Calcium (fig. 2F).—The DQO was met by 81 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 

DQO was evaluated and method modifications were made. 

Chloride (fig. 2H).—The DQO was met by 95 percent of the samples. No systematic trends were 

evident for this analysis. 

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

evident for this analysis. 

Nitrate (ion chromatography) (fig. 2J).—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. 2K).—The DQO was met by 100 percent of the samples. No systematic trends were 

evident for this analysis. 

Nitrogen, Total Dissolved (fig. 2L).—The DQO was met by 69 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. 2M).—The DQO was met by 96 percent of the samples. No systematic trends were 

evident for this analysis. 

Silicon (fig. 2N).—The DQO was met by 92 percent of the samples. The Troy Laboratory experienced 

a problem with the water filtering system from April through June 2006, which is evident in the 

silicon and specific conductance control charts.

Sodium (fig. 2O).—The DQO was met by 97 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 2005 through June 2007

12

Specific Conductance (fig. 2P).—The DQO was met by 80 percent of the samples. The Troy 

Laboratory experienced a problem with the water filtering system from April through June 

2006, which is evident in the silicon and specific conductance control charts. 

Sulfate (fig. 2Q).—The DQO was met by 99 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 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 85 percent of the triplicate samples.

Ammonium (fig. 3E).—The DQO was met by 56 percent of the triplicate samples.

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

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

Carbon, Dissolved Organic (fig. 3H).—The DQO was met by 94 percent of the triplicate samples.

Chloride (fig. 3I).—The DQO was met by 85 percent of the triplicate samples.

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

Nitrate (ion chromatography) (fig. 3K).—The DQO was met by 95 percent of the triplicate samples.

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

period. 

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

Nitrogen, Total Dissolved (fig. 3L).—The DQO was met by 65 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 93 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 97 percent of the triplicate samples.

Specific Conductance (fig. 3Q).—The DQO was met by 100 percent of the triplicate samples.

Sulfate (fig. 3R).—The DQO was met by 100 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 reports laboratory performance using a percent difference between the 

reported value and the MPV for each analyte (table 3). The Troy Laboratory DQO is ±10 percent from 

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

SRS study period. 

The Troy Laboratory met the established DQO’s for all of the samples submitted, with these 

exceptions:

Aluminum.—SRS T–187 (15.83 percent) and SRS T–189 (85.03 percent). 

Ammonium.—SRS N–89 (10.95 percent) and SRS N–91 (46.58 percent). 

Calcium.—SRS P–45 (11.94 percent). 

Magnesium.—SRS P–46 (-20.00 percent). 

Potassium.—SRS P–45 (-14.63 percent). 

Specific Conductance.—SRS P–46 (-11.32 percent). 

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, nitrate (colorimetric method), nitrite, 

total dissolved nitrogen and turbidity. 

Acid-Neutralizing Capacity (figs. 4A1 and 4A2).—The DQO was met by 59 percent of the NWRI 

samples. The data exhibited a negative bias during this period. 

Aluminum, Total (fig. 4B).—The DQO was met by 50 percent of the NWRI samples. The data 

exhibited a positive bias during this period. 

Ammonium (fig. 4C).—The DQO was met 56 percent of the NWRI samples. The cause of the 

positive bias is being investigated. The reporting limit for ammonium is being reevaluated.

Calcium (fig. 4D).—The DQO was met by 85 percent of the NWRI samples. The data exhibited a 

positive bias during this period. 

Carbon, Dissolved Organic (fig. 4E).—The DQO was met by 92 percent of the NWRI samples. No 

trend or bias was evident. 

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

evident. 

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

negative bias during studies 87, 88 and 89. 

Nitrate (ion chromatography) (fig. 4H).—The DQO was met by 97 percent of the NWRI samples. 

The data exhibited a positive bias during this period. 

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

Potassium (fig. 4J).—The DQO was met by 91 percent of the NWRI samples. The data exhibited a 

negative bias during study 89. 
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

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Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

16

Silicon (fig. 4K).—The DQO was met by 92 percent of the NWRI samples. The data exhibited a 

negative bias during this period. 

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

positive bias during study 87 and a negative bias during studies 88 and 89. 

Specific Conductance (fig. 4M).—The DQO was met by 98 percent of the NWRI samples. The data 

exhibited a negative bias during this period. 

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

positive bias during this period. 

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 86 percent of the blind reference samples. The 

data exhibited a positive bias for this period. 

Chloride (fig. 5B).—The DQO was met by 76 percent of the blind reference samples. The data 

exhibited a positive bias for this period. 

Magnesium (fig. 5C).—The DQO was met by 97 percent of the blind reference samples. The data 

exhibited a negative bias for this period. 

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

positive bias for this period. 

Potassium (fig. 5E).—The DQO was met by 99 percent of the blind reference samples. The data 

exhibited a negative bias for this period. 

Sodium (fig. 5F).—The DQO was met by 99 percent of the blind reference samples. The data 

exhibited a negative bias for this period. 

Specific Conductance (fig. 5G).—The DQO was met by 80 percent of the blind reference samples. 

The data exhibited a negative bias for this period. Troy Laboratory data were consistently lower 

than the SRS MPV for the SRS precipitation sample used as the blind reference sample 

beginning in November 2006. 

Sulfate (fig. 5H).—The DQO was met by 77 percent of the samples. Troy Laboratory data were 

consistently lower than the SRS MPV for the SRS precipitation sample used as the blind 

reference sample beginning in November 2006.
Selected References

17

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., 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, 33 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 2005 through June 2007

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 2005 through June 2007

20
Figures

21
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

22
Figures

23
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

24
Figures

25
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

26
Figures

27
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

28
Figures

29
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

30
Figures

31
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

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Figures

33
Quality-Assurance Data for Routine Water Analyses by the USGS Laboratory in Troy, New York, July 2005 through June 2007

 This page has been left blank intentionally. 
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 2005 through June 2007—Open-File Report 2009–1234