Quality-Assurance Data for Routine Water Analyses 

by the U.S. Geological Survey Laboratory 

in Troy, New York

May 1991 through June 1993

EyTricia A. Lincoln, Debra A. Horan-Ross, Mark. L. Olson, and Gregory B. Lawrence

U.S. GEOLOGICAL SURVEY 

Open-File Report 96-167

Troy, New York 

1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

425 Jordan Road Box 25286

Troy, N.Y., 12180 Denver, CO 80225-0286
CONTENTS

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

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

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

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

Quality-Assurance/Quality-Control Program Description ....................................... 2

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

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

Duplicate and Triplicate Environmental Samples ........................................ 4

U.S. Geological Survey's Standard Reference Sample Program ............................. 4

Environment Canada's LRTAP Interlaboratory Study ..................................... 4

Control-Chart Development and Evaluation ................................................. 4

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

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

Duplicate and Triplicate Environmental Samples ........................................ 7

Environment Canada's LRTAP Interlaboratory Study ..................................... 7

Summary of Results..................................................................... 7

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

Filter Blanks and Analytical Blanks ................................................... 9

Duplicate and Triplicate Environmental Samples ........................................ 10

U.S. Geological Survey's Standard Reference Sample Program ............................. 10

Environment Canada's LRTAP Interlaboratory Study ..................................... 10

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

FIGURES

1-4. Graphs showing results of quality-control data for water-sample analyses from May 1991 through June 1993.

1. High- and low-concentration quality-control samples 

A. Acid-neutralizing capacity ........................................................... 12

B. Aluminum, total monomeric. ......................................................... 12

C. Aluminum, total ................................................................... 12

D. Ammonium....................................................................... 12

E. Calcium.......................................................................... 13

F. Carbon, dissolved inorganic .......................................................... 13

G. Carbon, dissolved organic ........................................................... 13

H. Chloride ......................................................................... 13

I. Fluoride.......................................................................... 14

J. Magnesium....................................................................... 14

K. Nitrate (ion chromatography)......................................................... 14

L. Nitrate (colorimetric method)......................................................... 14

M. pH.............................................................................. 15

N. Potassium ........................................................................ 15

O. Silicon........................................................................... 15

P. Sodium .......................................................................... 15

Q. Sulfate........................................................................... 16
FIGURES (continued)

2. Filter blank and analytical blank samples

A. Aluminum, total monomeric ......................................................... 17

B. Aluminum, organic monomeric. ...................................................... 17

C. Aluminum, total................................................................... 17

D. Ammonium ...................................................................... 17

E. Calcium ......................................................................... 17

F. Carbon, dissolved organic ........................................................... 17

G. Chloride......................................................................... 17

H. Fluoride ......................................................................... 17

I. Magnesium ...................................................................... 18

J. Nitrate (ion chromatography) ........................................................ 18

K. Potassium........................................................................ 18

L. Silicon .......................................................................... 18

M. Sodium.......................................................................... 18

N. Sulfate .......................................................................... 18

3. Duplicate and triplicate environmental samples

A1 .Acid-neutralizing capacity (for triplicate means not in the range of ±20(^eq/L).................. 19

A2.Acid-neutralizing capacity (for triplicate means in the range of ±20(^eq/L). .................... 19

B. Aluminum, total monomeric ......................................................... 19

C. Aluminum, organic monomeric. ...................................................... 19

D. Aluminum, total................................................................... 19

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

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

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

H. Magnesium ...................................................................... 20

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

J. pH ............................................................................. 20

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

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

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

N. Sulfate .......................................................................... 20

4. Environment Canada's LRTAP Interlaboratory Study

Al .Acid-neutralizing capacity (for triplicate means not in the range of ±20(^eq/L).................. 21

A2.Acid-neutralizing capacity (for triplicate means in the range of ±20(^eq/L). .................... 21

B. Ammonium ...................................................................... 21

C. Calcium ......................................................................... 21

D. Carbon, dissolved organic ........................................................... 21

E. Chloride......................................................................... 21

F. Magnesium ...................................................................... 21

G. Nitrate (ion chromatography) ........................................................ 21

H. pH ............................................................................. 22

I. Potassium........................................................................ 22

J. Silicon .......................................................................... 22

K. Sodium. ......................................................................... 22

L. Sulfate .......................................................................... 22

IV
TABLES

1.

2.

3.

Number of environmental samples and quality-control samples analyzed by USGS New 

York District Laboratory and summary of quality control (QC) data for each constituent 

from May 1991 through June 1993. ..........................................

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

analyses performed by the U.S. Geological Survey New York District Laboratory in Troy, N.Y., 

May 1991 through June 1993 ......................................................

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

Sample (SRS) Program, May 1991 through June 1993 ..............................

ABBREVIATED UNITS OF MEASUREMENT

mg/L 

|Ueq/L 

jimol/L

milligrams per liter 

microequivalents per liter 

micromoles per liter

Other Abbreviations

ANC

cv

DI

DQO

LRTAP

MCV

MPV

QA

QC

QC-high

QC-low

SRS

USGS

acid-neutralizing capacity

coefficient of variation

deionized water

data-quality objective

Long-Range Transport of Atmospheric Pollutants

median concentration value

most probable value

quality assurance

quality control

high-concentration quality-control sample

low-concentration quality-control sample

Standard Reference Sample

U.S. Geological Survey

Quality-Assurance Data for Routine Water Analyses by the 

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

May 1991 through June 1993

ByTricia A. Lincoln, Debra A. Horan-Ross, Mark. L. Olson, and Gregory B. Lawrence

Abstract

A laboratory for analysis of low-ionic-strength 

water has been developed at the New York District 

office of the U.S. Geological Survey (USGS) in 

Troy, N.Y., to analyze samples collected by USGS 

projects in the Northeast. The laboratory's qualityassurance program is based on both internal and 

interlaboratory quality-assurance samples and 

quality-control procedures developed to ensure 

proper sample collection, processing, and analysis. 

The quality-assurance/quality-control data are 

stored in the laboratory's SAS data-management 

system, which provides efficient review, compilation, and plotting of quality-assurance/qualitycontrol data. This report presents and discusses data 

analyzed from May 1991 through June 1993.

Quality-control results for 18 analytical procedures were evaluated for bias and precision. Control 

charts show that four of the procedures have biases 

but were within control limits; they are: total aluminum (high in March and May 1993); calcium (low 

in 1991); chloride (low from January through June 

1993); and nitrate (colorimetric method low from 

June 1992 through June 1993). No quality-control 

sample has been developed for the organic 

monomeric aluminum procedure. Results from the 

filter-blank and analytical blank analyses indicate 

that, in 4 of the 14 procedures in which blanks were 

run, measurements approached or exceeded control 

limits. Organic and total monomeric aluminum 

concentrations showed upward trends in analyticalblanks in June 1992, but most of these values were 

within control limits. Total aluminum, calcium, and 

chloride concentrations periodically exceeded 

control limits. Blanks were not analyzed for pH,

1- Use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by 

the U.S. Government.

acid-neutralizing capacity, dissolved inorganic 

carbon, or nitrate (colorimetric method).

Sampling and analysis precision are evaluated in 

terms of the coefficient of variation obtained for 

duplicate and triplicate samples in 14 of the 18 

procedures. Data-quality objectives were met for at 

least 95 percent of duplicate and triplicate samples. 

Data quality objectives were not met in 32 percent 

of the total aluminum samples; 20 percent of the 

total monomeric aluminum samples; and 23 percent 

of the dissolved organic carbon samples. Duplicate 

and triplicate samples were not analyzed for 

ammonium, fluoride, dissolved inorganic carbon, or 

nitrate (colorimetric method).

Results of interlaboratory quality-assurance 

programs are presented. Laboratory ratings for the 

U.S. Geological Survey's Standard Reference 

Sample Program show satisfactory results overall. 

Environment Canada's LRTAP interlaboratory 

study results are plotted on control charts. Data 

quality objectives were met in 7 of the 12 procedures, for more than 80 percent of the LRTAP 

samples. Data quality objectives were not met for 

25 percent of the ammonium and calcium samples; 

35 percent of the dissolved organic carbon and 

silicon samples; and 45 percent of the sodium 

samples.

INTRODUCTION

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

laboratory at its Troy, N.Y. office to analyze lowionic-strength water for USGS watershed-research 

projects that require major-ion analyses of precipitation, soil-water, shallow ground-water, streamwater, and lake-water samples. The methods used in 

this laboratory are described in detail in Lawrence 

and others (1995).

Abstract
Analyses done during the 2-year period (May 

1991-June 1993) represented by this report were: 

acid-neutralizing capacity (ANC), total monomeric 

aluminum, organic monomeric aluminum, total 

aluminum, ammonium, calcium, chloride, fluoride, 

dissolved inorganic carbon (DIG), magnesium, 

nitrate (ion chromatograph and colorimetric 

method), dissolved organic carbon (DOC), pH, 

potassium, silicon, sodium, and sulfate.

Participating Projects

The numbers and types of samples analyzed by 

the laboratory during the 2-year period are summarized below, by project for which they are associated; numbers in parentheses are USGS project 

numbers .

Project: Neversink Watershed Study (NY91-200) 

Cooperator: New York City Department of 

Environmental Protection

Analyses: 3,095 stream, shallow ground water, and 

snow samples.

Project: Biogeochemical Processes that Control 

Nitrogen Cycling and Associated Hydrogen and 

Aluminum Leaching in an Undeveloped Headwater 

Basin (NY91-204)

Cooperator: New York City Department of 

Environmental Protection

Analyses: 1,147 stream, shallow ground-water, soilsolution, soil-extraction, and snow samples.

Project: Long-Term Monitoring of Five Streams in 

the Catskill Mountains (NY85-152) 

Cooperator: U.S. Environmental Protection Agency 

Analyses: 726 stream samples.

Project: Forest-Floor Aluminum and Calcium 

Chemistry Relations with Acid Deposition, Root 

Vitality, Stand Dynamics, and Red Spruce (NY91- 

208)

Cooperator: U.S. Forest Service 

Analyses: 868 stream, soil-solution, and soilextraction samples.

Project: Variable Source-Area Control of Episodic 

Stream Chemistry (NY91-209) 

Cooperator: U.S. Forest Service 

Analyses: 229 stream samples.

Project: Hydrologic Budget and Changes in Aquatic

Chemistry of Woods Lake Outlet After Watershed

Liming (NY 88-173)

Cooperator: Cornell University Department of

Natural Resources

Analyses: 56 stream samples.

Project: Relations Among Geochemical Processes 

that Control Pond-Water Chemistry in Hodge Pond 

Watershed in the Catskill Mountains (NY90-193) 

Cooperator: Town of Rockland, N.Y. 

Analyses: 245 stream and shallow ground-water 

samples.

Additional information on projects of the New York 

District is given in Marshall (1992) and Lee (1996).

Purpose and Scope

This report is the first in a planned series to 

document the quality-assurance practices of this 

laboratory and is intended for use by current and 

prospective cooperating agencies. It (1) describes 

quality-control and quality-assurance procedures of 

the laboratory, (2) presents graphs showing the 

results from analyses of quality-control samples, 

filter blanks and analytical blanks, and duplicate 

and triplicate environmental samples, and (3) 

explains analytical biases and outliers and the 

corrective actions taken.

QUALITY-ASSURANCE/QUALITY-CONTROL 

(QA/QC) PROGRAM DESCRIPTION

The quality of the data produced at this laboratory is maintained by adherence to the standard 

operating procedures described in Lawrence and 

others (1995) and by participation in externally 

administered quality-assurance (QA) programs. 

Results of QA data are evaluated by the laboratory 

supervisor and primary analysts, and appropriate 

corrective action is taken when needed.

Quality-Control Samples

Quality-control (QC) samples are used to determine the accuracy of an instrument's calibration and 

to detect variations in instrument response within an 

analytical run. Source material for all QC samples is

2 Quality-Assurance data from Routine Water Analyses by USGS Laboratory, Troy, N.Y., May 1991-June 1993
obtained from a manufacturer other than the producer 

of the source material used to make calibration 

standards, or is obtained from a different lot.

The concentrations of QC samples are chosen to 

bracket the expected range of the environmentalsample concentrations. A high-concentration QC 

sample and a low-concentration QC sample (referred 

to herein as QC-high and QC-low) are prepared for 

most constituents; exceptions are inorganic 

monomeric aluminum, for which column efficiency 

is used to determine the acceptability of the data, and 

fluoride, for which only one QC sample is prepared 

because of the narrow range of environmental 

concentrations measured by the laboratory.

Quality-control samples are analyzed immediately after calibration, after every 10 analyses of 

environmental samples, and at the end of each run. 

Exceptions to the frequency of QC sample analyses 

are ANC (QC sample after every 17 environmental 

samples), and pH (QC sample after every 10 to 13

environmental samples). The allowable differences both greater than and less than the theoretical value of each QC sample set the control limits 

for acceptance or rejection of environmentalsample data. QC samples that do not meet dataquality objectives (DQO's) 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 

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 accept or 

reject these data. The number of samples analyzed, 

and a summary of the quality-assurance data, are 

given in table 1.

Table 1 . Number of environmental and quality -control samples analyzed by USGS New York District Laboratory and summary 

of quality- control (QC) data for each constituent, May 1991 through June 1993

Summary of QC data

Number of samples analyzed

Constituent Environmenta 

samples

Acid-neutralizing capacity

Aluminum, total monomeric

Aluminum, organic monomeric

Aluminum, total

Ammonium

Calcium

Carbon, dissolved inorganic

Carbon, dissolved organic

Chloride

Fluoride

Magnesium

Nitrate

pH

Potassium

Silicon

Sodium

Sulfate

5318

5665

5665

3250

5544

5148

411

5705

5795

381

5144

6279

5691

5759

5605

5746

5803

il QC samples

QC-high

220

587

0

343

546

371

31

417

449

43

361

472

208

357

368

347

449

QC-low

240

587

0

343

546

371

31

415

436

0

361

473

345

357

368

347

449

Number of QC 

samples exceeding 

control limits

QC-high

5

1

0

9

3

0

1

9

8

0

2

2

4

8

19

1

4

QC-low

20

0

0

3

4

4

0

52

13

0

0

15

19

7

11

2

10

Number of QC samples 

exceeding control limits 

by more than 5 percent

QC-high

0

0

0

7

1

0

1

0

1

0

0

2

2

0

5

0

3

QC-low

2

0

0

1

0

1

0

19

2

0

0

2

4

0

5

0

1

Quality-Assurance/Quality-Control (QA/QC) Program 3
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 those constituents that require filtration. 

Filter-blank analysis indicates whether contamination has occurred during bottle-washing procedures, 

sample processing, 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 

bottle washing, sample preservation, or laboratory 

analysis, but not to filtration.

Duplicate and Triplicate Environmental 

Samples

One set of field duplicate or triplicate environmental samples is included in each group of 50 

samples. The purpose of environmental duplicate or 

triplicate samples is to determine long-term analytical precision. Precision can be affected by bottle 

washing and by sample-collection and processing 

procedures. Environmental samples are selected for 

triplicate analysis on a rotating basis to ensure a 

wide range of sample concentrations.

Duplicate and triplicate environmental samples 

were collected until November 1991, after which all 

samples used to estimate precision were collected in 

triplicate.

U.S. Geological Survey's Standard 

Reference Sample Program

The USGS Standard Reference Sample Program 

(SRS) conducts a national interlaboratory analytical 

evaluation program semiannually. The Troy, N.Y. 

laboratory participates in the low-ionic-strength 

component of this program. Reference samples are 

prefixed by a P and are analyzed for calcium, 

chloride, magnesium, pH, potassium, sodium, and 

sulfate. Typically, the low-ionic-strength sample 

consists of snow that is collected, melted, filtered, 

and possibly diluted or concentrated, to meet the 

goals of the SRS program. 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. The most probable value (MPV) for each 

constituent is determined through nonparametric 

statistics. Individual laboratory performances are 

rated numerically; the highest score is 4.0, and the 

lowest is 0.0.

Environment Canada's LRTAP Interlaboratory 

Study

The Troy laboratory participates in the LRTAP 

interlaboratory quality-assurance program, in 

which a set of 10 samples is analyzed three times 

per year. The samples are obtained from predominantly low-ionic-strength waters from various 

sources, such as precipitation, snow, lakes, and 

streams throughout North America and western 

Europe. The concentrations of the constituents in 

the LRTAP samples are similar to those of the 

environmental samples analyzed at the Troy laboratory. Laboratory results are compared with a 

median concentration value (MCV) determined 

from results from all participants in the LRTAP 

program. Laboratory personnel are aware of the 

presence of LRTAP samples at the time of analysis 

but do not know the MCV of the constituents until 

Environment Canada publishes a report after each 

study.

CONTROL-CHART DEVELOPMENT AND 

EVALUATION

Control charts (figs. 1-4) are plots of QC data in 

relation to time; in this report, they are used to (1) 

confirm that laboratory DQO's are met for individual QC samples, (2) detect long-term biases within 

the control limits, and (3) provide comparisons with 

results from other laboratories. All control charts, 

except those for the blanks, are edited by deleting 

each point that has a value below the laboratory's 

established reporting limits (table 2).

Quality-Control Samples

Results of QC sample analyses are plotted on 

control charts in which the central line is equal to the 

theoretical value of the control sample. Each analyte

4 Quality-Assurance data from Routine Water Analyses by USGS Laboratory, Troy, N.Y., May 1991-June 1993
Table 2. Reporting limits and data-quality objectives for accuracy, precision, and blanks for solution analyses 

performed by the U.S. Geological Survey New York District Laboratory in Troy, N.Y., May 1991 through 

June 1993.

[DQO, data-quality objective. umol/L, micromoles per liter. CV, coefficient of variation. ANC, acid-neutralizing capacity. Numbers in 

"dividing value" column are concentrations that divide high range from low range of precision DQO's. pH and ANC values (in parentheses) 

are in pH units and microequivalents per liter, respectively.]

Accuracy

Low-concentration 

quality-control sample

Constituent or property

Acid-neutralizing capacity

Aluminum, total monomeric

Aluminum, organic monomeric 2

Aluminum, total

Ammonium

Calcium

Chloride

Carbon, dissolved inorganic3

Carbon, dissolved organic3

Fluoride 4

Magnesium

Nitrate (ion chromatography)

Nitrate (colorimetric method)

PH 5

Potassium

Silicon

Sodium

Sulfate

Reporting 

limit 

(umol/L)

none

1.5

1.5

1.0

2.0

2.0

2.0

41.0

41.0

0.5

1.0

2.0

5.0

none

1.0

6.0

1.0

2.0

DQO 

(percent 

error)

10

10

none

15

15

10

10

15

15

15

10

10

12

10

10

15

10

10

Concentration 

(umol/L)

(-39.9)

7.4

none

1.8

7.1

25

8.5

83

83

1.6

8.2

5

42.9

(4.41)

5.1

35.6

8.7

8.3

Precision

High-concentration 

quality-control sample

DQO 

(percent 

error)

10

10

none

10

10

10

10

10

10

none

10

10

10

20

10

10

10

10

Concentration 

(umol/L)

(125)

18.5

none

28

17.5

100

85'

415

415

none

33

50

100

(6.88)

20

107

35

83

DQO (CV)

10

10

10

10

10

10

10

10

10

10

10

10

10

20

10

10

10

10

Filter and 

analytical 

blanks 

DQO

(umol/L)

none

0.75

0.75

0.5

1.0

1.0

0.5

18

18

none

0.5

0.3

none

none

0.5

3

1.0

0.3

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

data-quality objective of ±6 microequivalents per liter is used for precision. Blanks are not run for ANC. 

Quality-control samples for organic monomeric aluminum are unavailable.

 Concentrations are expressed as (Jmol C/L (carbon per liter).

4 Fluoride: No data are yet available for precision. Blanks are not run for fluoride.

5 pH: Percent error and coefficient of variation determined from [H4"]. Blanks are not run for pH.

Control-Chart Development and Evaluation 5
has prescribed control limits that have been established to meet project DQO's (table 2). The limits 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. All data are reported in micromoles per liter (jamol/L) except pH (pH units) and 

ANC (microequivalents per liter, (leq/L).

During the period represented by this report, 

several theoretical values for quality-control 

samples were changed to reflect more accurately 

than before environmental-sample concentrations 

(for example, fig. IB). Control limits were also 

changed in response to the improvement and refinement of certain analyses (for example, figure 1C). 

The dates on which the changes were made are 

identified on the graphs.

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

Standard Reference Sample (SRS) Program, May 1991 through June 1993

(MPV, most probable value; TV, Troy laboratory value; mg/L, milligrams per liter; 

dash indicates no results reported)

SRS sample number

Analyte

Calcium

Chloride

Potassium

Magnesium

Sodium

pH

Sulfate

MPV, TV, 

and rating3

MPV, mg/L

TV, mg/L

Rating

MPV, mg/L

TV, mg/L

Rating

MPV, mg/L

TV, mg/L

Rating

MPV, mg/L

TV, mg/L

Rating

MPV, mg/L

TV, mg/L

Rating

MPV

TV

Rating

MPV, mg/L

TV, mg/L

Rating

P-17 

6/91 b

0.30

0.37

0

0.416

0.372

4

0.057

0.080

I

0.045

0.080

0

0.283

0.270

4

5.55

5.55

4

0.500

0.55

4

P-18 

10/91°

0.94

0.85

3

6.60

6.74

4

1.60

1.59

4

P-19 

12/92d

0.24

0.224

3

1. 14

1.03

3

0.17

0.11

1

0.045

0.05

4

0.06

0.018

4

4.72

4.83

3

0.45

0.335

4

P-20 

6/93e

0.160

0.160

4

0.140

0.275

4

0.100

0.080

3

0.020

0.020

4

0.168

0.130

0

5.53

5.40

3

0.831

0.809

4

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

b Date submitted

c Date analyzed

d Sample described in Long and Ferrar (1993a)

e Sample described in Long and Ferrar (1993b)

6 Quality-Assurance data from Routine Water Analyses by USGS Laboratory, Troy, N.Y., May 1991-June 1993
Filter Blanks and Analytical Blanks

Results from blank analyses (fig. 2) are plotted 

on control charts, by constituent. The control limit 

was established to meet project DQO's (table 2) and 

is represented by a horizontal line on the control 

charts. Data are plotted as concentration in relation 

to date of collection. The control charts are evaluated to identify possible contamination or positive 

interferences. All negative numbers, except ANC 

values, for samples analyzed before May 8, 1992, 

were entered as zero in the data base; this explains 

the lack of scatter on several of the control charts 

for blanks analyzed before this date.

Duplicate and Triplicate Environmental 

Samples

The coefficient of variation (CV) for each triplicate sample 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. For this report, the DQO for all 

constituents is a CV of less than 10 percent. Each 

circle within the control charts represents the CV of 

a duplicate or triplicate environmental sample. CV 

values that plotted off the scale are represented by a 

circle accompanied by a number that gives the CV 

for that group of samples:

CV = z(100) 

x

where: 5 = standard deviation, and

x = arithmetic mean of triplicate samples

ANC duplicate and triplicate sample means were 

plotted on two graphs. The first graph shows the CV 

for duplicate and triplicate sample means outside 

the range of-20 to +20 |ieq/L (fig. 3A1); the second 

graph shows values that fall between -20 and +20 

(Oeq/L (fig. 3A2). Each symbol on the graph represents the difference between the duplicate or triplicate sample mean and the individual values of that 

duplicate or triplicate sample.

Environment Canada's LRTAP Interlaboratory 

Study

Interlaboratory comparison graphs (fig. 4) are 

based on results from LRTAP samples and represent LRTAP studies from August 1991 through

May 1993. Samples with MCV's less than the 

reporting limits were excluded from the graphs. The 

MCV and the control limits of ±10 percent are 

represented by lines on the graphs; the percent 

difference (D) is calculated as:

D = [(AV- MCV)/MCV] x 100

where: AV = analyzed value, and

MCV = mean concentration value

A separate graph is shown for ANC values in the 

+20 to -20 |ieq/L range; results for these samples are 

plotted as the difference between the laboratory 

value and the MCV (fig. 4A2). The LRTAP pH 

results consist of two sets of data pH values less 

than 6.00, and pH values equal to or greater than 

6.00. The two sets of data have different DQO's, 

which are represented by a solid line and a dashed 

line on the pH graph (fig. 4H).

SUMMARY OF RESULTS

The following sections summarize the results for 

(A) quality-control samples (fig. 1, p. 12-16), (B) 

filter blanks and analytical blanks (fig 2, p. 17-18), 

(C) duplicate and triplicate environmental samples 

(fig. 3, p. 19-20), (D) SRS samples (table 3, p. 6), 

and (E) LRTAP samples (fig. 4, p.21-22).

A. Quality-Control Samples

Acid-Neutralizing Capacity (fig. 1 A). DQO's 

were met for more than 95 percent of the 

samples. No apparent trends or biases were 

evident among the QC-high and QC-low 

samples.

Aluminum, Total Monomeric (fig. IB). DQO's 

were met for 100 percent of the samples. No 

apparent trends or biases were evident among 

the QC-high and QC-low samples. The total 

monomeric aluminum QC-high concentration 

was decreased from 27.8 to 18.5 |imol/L in April 

1992 to reflect environmental-sample concentrations from the projects more accuratley than 

before.

Aluminum, Organic Monomeric. A QC sample 

has not been developed for this analysis.

Interpretation of Control Charts, by Constituent
Aluminum, Total (fig. 1C). DQO's were met for 

more than 95 percent of the samples. The control 

limit for the QC-low was decreased from 37 

percent to 20 percent in March 1993 as a result 

of refinements of the analytical procedure. No 

apparent trends or biases were evident, except 

for the QC-high in March and May 1993. The 

bias did not appear in June 1993.

Ammonium (fig. 1D). DQO's were met for more 

than 95 percent of the samples. No apparent 

trends or biases were evident. The ammonium 

QC-high concentration was changed from 21.4 

to 17.8 nmol/L in April 1992; the QC-low 

concentration was changed from 10.7 to 7.1 

fimol/L in March 1992. These lower concentrations reflect environmental-sample concentrations from the projects more accuratley than 

before.

Calcium (fig. IE). DQO's were met for more than 

95 percent of the samples. A slight low bias was 

observed for analyses performed in 1991.

Carbon, Dissolved Inorganic (fig. IF). DQO's 

were met for more than 95 percent of the 

samples. No apparent trends or biases were 

evident for the QC-high and QC-low samples.

Carbon, Dissolved Organic (fig. 1G). DQO's 

were met for more than 90 percent of the 

samples. Dissolved organic carbon analysis was 

performed by the New York City Department of 

Environmental Protection Laboratory in 

Grahamsville, N.Y., from May 1991 until 

January 1992, after which analyses were 

performed in the Troy laboratory. A high bias 

was observed for the QC-low sample from May 

1991 through December 1991.

Chloride (fig. 1H). DQO's were met for more than 

95 percent of the samples. The QC-high graph 

illustrates a low bias after January 1993; this was 

due to an error in preparation of QC stock 

solution and has been corrected. No bias or trend 

was evident for the QC-low sample.

Fluoride (fig. II). DQO's were met for more than 

95 percent of the samples. No trends or biases 

were evident for the quality-control sample.

Magnesium (fig. 1J). DQO's were met for more 

than 95 percent of the samples. No trends or 

biases were evident for the QC-high and QC-low 

samples.

Nitrate (ion chromatography) (fig. IK). DQO's 

were met for more than 95 percent of the 

samples. No trends or biases were evident for the 

QC-high and QC-low samples.

Nitrate (colorimetric method) (fig. 1L). DQO's 

were met for more than 95 percent of the 

samples. The QC-high and QC-low samples 

appear to be biased low; this is attributed to 

incomplete conversion of nitrate to nitrite by the 

cadmium-reduction column. The column was 

operating at 90-percent efficiency during this 

period. Multiplying the environmental- and QCsample concentrations by 1.1 would correct the 

bias. The project chief determines whether to 

apply this correction factor.

pH (fig. 1M). DQO's were met for more than 95 

percent of the samples. No apparent trends or 

biases were evident for the QC-high and QC-low 

samples.

Potassium (fig. IN). DQO's were met for more 

than 95 percent of the samples. No trends or 

biases were evident for the QC-high and QC-low 

samples. The potassium QC-high concentration 

was increased from 12.8 to 25.6 |Limol/L in 1993 

to reflect environmental-sample concentrations 

from the projects more accuratley than before..

Silicon (fig. 1O). DQO's were met for more than 

90 percent of the samples. No trends or biases 

were evident or the QC-high and QC-low 

samples. In December 1991, the QC-high 

concentration was increased from 35.6 to 106.8 

|Limol/L and the QC-low concentration from 18.3 

to 35.6 (umol/L to reflect environmental-sample 

concentrations of the projects more accuratley 

than before. In May 1992, the silicon method 

was changed from segmented-flow analysis to 

flow-injection analysis.

Sodium (fig. IP). DQO's were met for more than 

95 percent of the samples. No trends or biases 

were evident for the QC-high and QC-low 

samples. The sodium QC-high concentration 

was increased from a theoretical value of 34.8 to

8 Quality-Assurance data from Routine Water Analyses by USGS Laboratory, Troy, N.Y., May 1991-June 1993
43.5 |Limol/L in 1993 to reflect environmentalsample concentrations of the projects more 

accuratley than before.

Sulfate (fig. 1Q). DQO's were met for more than 

95 percent of the samples. The slight high bias 

for the QC-low was corrected by upgrading 

components of the ion chromatograph in January 

1993. A slight low bias was evident for the QChigh sample.

B. Filter Blanks and Analytical Blanks

Aluminum, Total Monomeric (fig.1 2A). The DQO

was met for more than 85 percent of the samples. 

An upward trend in analytical blanks begain in 

June 1992. The software, which calculates 

sample-analysis results, was upgraded, and an 

incorrect default setting was discovered that 

subtracted the absorbance of the leading baseline 

from the sample peak absorbance. This has been 

corrected; the software now calculates an average 

absorbance from the leading and trailing 

baselines and subtracts this value from the 

sample peak.

Aluminum, Organic Monomeric (fig. 2B). The 

DQO was met for more than 95 percent of the 

samples. An upward trend in analytical blanks 

began in June 1992. The software, which calculates sample-analysis results, was upgraded, and 

an incorrect default setting was discovered that 

subtracted the absorbance of the leading baseline 

from the sample peak absorbance. This has been 

corrected; the software now calculates an average 

absorbance from the leading and trailing 

baselines and subtracts this value from the 

sample peak.

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

for more than 75 percent of the samples. 

Periodic blank contamination was attributed to 

inconsistent bottle-washing procedures; this 

conclusion was based on a study of washing 

procedures used for total aluminum aliquot 

bottles. As a result, a new aliquot containerpreparation procedure was implemented in 

March 1993 and is being tested.

Ammonium (fig. 2D). The DQO was met for more 

than 90 percent of the samples. No systematic 

trends were evident for this analysis.

Calcium (fig. 2E). The DQO was met for more than 

70 percent of the samples. The large number of 

samples that did not meet the DQO in 1992 was 

corrected through installation of a new hollowcathode lamp.

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

was met for more than 75 percent of the samples. 

The DQO is being reevaluated to determine 

whether it should be increased .

Chloride (fig. 2G). The DQO was met for more 

than 80 percent of the samples. A higher 

frequency of blank contamination in 1993 than 

for previous results was caused by the use of a 

dilute hydrochloric acid solution to wash sample 

bottles. Chloride aliquot bottles are now washed 

with deionized water only.

Fluoride (fig. 2H). The DQO was met for all of the 

samples. No systematic trends were evident for 

this analysis.

Magnesium (fig. 21). The DQO was met for more 

than 95 percent of the samples. No systematic 

trends were evident for this analysis.

Nitrate (ion chromatography) (fig. 2J). The DQO 

was met for more than 95 percent of the samples. 

No systematic trends were evident for this analysis.

Potassium (fig. 2K). The DQO was met for more 

than 90 percent of the samples. No systematic 

trends were evident for this analysis.

Silicon (fig. 2L). The DQO was met for more than 

95 percent of the samples. No systematic trends 

were evident for this analysis. In March 1992, 

the silicon analysis was upgraded from a 

segmented-flow instrument with a strip-chart 

recorder to a flow-injection analyzer with a 

computer for data capture. The greater resolution of electronic data capture than was possible 

with the strip chart recorder was indicated by 

the greater variability of measurements after 

March 1992.

Interpretation of Control Charts, by Constituent 9
Sodium (fig. 2M). The DQO was met for more than 

80 percent of the samples. The atomic absorption 

spectrophotometer was upgraded in the fall of 

1992. The graph of blank data shows the effect of 

improved software.

Sulfate (fig. 2N). The DQO was met for all of the 

samples. No systematic trends were evident for 

this analysis.

C. Duplicate and Triplicate Environmental 

Samples

Acid-neutralizing Capacity (figs. 3A1 and 3A2). 

More than 95 percent of the duplicate and triplicate samples met the DQO.

Aluminum, Total Monomeric (fig. 3B). Twenty 

percent of the duplicate and triplicate sample CV 

values were above the DQO of 10 percent. Nine 

percent of the duplicate and triplicate CV values 

were above DQO of 15 percent.

Aluminum, Organic Monomeric (fig. 3C). The 

DQO was met for more than 95 percent of the 

duplicate and triplicate samples.

Aluminum, Total (fig. 3D). Thirty-two percent of 

the samples exceeded the established precision 

DQO. The change in aliquot bottle-washing 

procedures discussed above is expected to 

significantly reduce this number.

Ammonium. All duplicate and triplicate sample 

data fell below the reporting limits for this 

constituent.

Calcium (fig. 3E).-More than 95 percent of the 

duplicate and triplicate samples met the DQO.

Carbon, dissolved organic (fig. 3F).-Thirty-five 

percent of samples exceeded the established 

DQO. This was attributed to a reporting limit 

that was too low (18 |imol/L). The reporting 

limit has since been increased to 41 (imol/L.

Chloride (fig. 3G).-More than 95 percent of the 

duplicate and triplicate samples met the DQO.

Magnesium (fig. 3H).-More than 95 percent of the 

duplicate and triplicate samples met the DQO.

Nitrate (ion chromatography) (fig. 31).-More than 

95 percent of the duplicate and triplicate samples 

met the DQO.

pH (fig. 3J). All duplicate and triplicate samples 

met the DQO.

Potassium (fig. 3K).-More than 95 percent of the 

duplicate and triplicate samples met the DQO.

Silicon (fig. 3L).-More than 95 percent of the duplicate and triplicate samples met the DQO.

Sodium (fig. 3M).-More than 95 percent of the 

duplicate and triplicate samples met the DQO.

Sulfate (fig. 3N).-More than 95 percent of the duplicate and triplicate samples met the DQO.

D. U.S. Geological Survey's Standard 

Reference Sample (SRS) Program

Overall laboratory results for all SRS samples 

were satisfactory. Average ratings for each SRS 

sample were:

P-17 2.4

P-18 3.7

P-19 3.1

P-20 3.1

Chloride, pH, and sulfate were rated 3 or 4 for 

each SRS sample. Calcium and magnesium were 

rated zero for sample P-17, but were satisfactory in 

samples P-19 and P-20. Potassium rated 1 for 

samples P-17 and P-19, and improved to a rating of 

3 by sample P-20. Sodium was rated zero for 

sample P-20. This was corrected thhrough installation of a new hollow cathode lamp.

10 Quality-Assurance data from Routine Water Analyses by USGS Laboratory, Troy, N.Y., May 1991-June 1993
E. Environment Canada's LRTAP 

Interlaboratory Study

Acid-neutralizing capacity (figs. 4A1 and 

4A2). The DQO was met for more than 95 percent 

of the LRTAP samples. No trend or bias was 

evident.

Ammonium (fig. 4B). The DQO was met for 

75 percent of the LRTAP samples. A low bias for 

ammonium which was corrected by use of a new 

standard stock.

Calcium (fig. 4C). The DQO was met for 75 

percent of the LRTAP samples. A high bias for 

calcium in studies 31 and 32 was corrected by use 

of a new hollow cathode lamp.

Carbon, dissolved organic (fig. 4D). The 

DQO was met for 65 percent of the LRTAP 

samples. A low bias for studies 28 through 30 was 

corrected by use of a new standard stock.

Chloride (fig. 4E). The DQO was met for 80 

percent of the LRTAP samples. No trend or bias 

was evident.

Magnesium (fig. 4F). The DQO was met for 

more than 90 percent of the LRTAP samples. No 

trend or bias was evident.

Nitrate (ion chromatography). The DQO was 

met for more than 85 percent of the LRTAP 

samples. The outliers were most often biased low.

pH (fig. 4H). The DQO was met for more than 

95 percent of the LRTAP samples with a pH less 

than 6.00. In study 27, the pH values above 6.00 

were biased low. This was corrected by use of a new 

pH probe. The DQO was met for more than 80 

percent of the LRTAP samples with a pH greater 

than 6.00 for studies 28 through 32.

Potassium (fig. 41). The DQO was met for 

more than 85 percent of the LRTAP samples. The 

outliers were most often biased low.

Silicon (fig. 4J). The DQO was met for 65 

percent of the LRTAP samples. A high bias for 

silicon was solved by use of a different type of 

standard stock.

Sodium (fig. 4K). The DQO was met for 55 

percent of the LRTAP samples. A low bias in 

studies 31 and 32 was corrcted through the installation of a new hollow-cathode lamp.

Sulfate (fig. 4L). The DQO was met for more 

than 95 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 

WaterAnalysis Laboratory: U.S. Geological Survey 

Open-File Report 95-416, 78 p.

Lee, M.P., 1996, U.S. Geological Survey Water-Resources 

Programs in the New York District-fiscal years 1993- 

94: U.S. Geological Survey Open-File Report 96-113,

48 p.

Long, H: K., and Ferrar, J. W., 1993a, Report on the U.S. 

Geological Survey's evaluation program for Standard 

Reference Samples distributed in October 1992 T-121 

(trace constituents), M-124 (major constituents), N-36 

(nutrients), P-19 (low ionic strength), and Hg-15 

(mercury): U.S Geological Survey Open-File Report 

93-32, 114 p.

___1993b, Report on the U.S. Geological Survey's 

evaluation program for Standard Reference Samples 

distributed in April 1993 T-123 (trace constituents), T125 (trace constituents), M-126 (major constituents), N38 (nutrients), P-20 (low ionic strength), and Hg-16 

(mercury): U.S Geological Survey Open-File Report 

93-436, 149 p.

Maloney, T. J, Ludtke, A. S., and Krizman, T.L., 1994, 

Quality-assurance Results for the routine water analysis 

in U.S. Geological Survey Laboratories, water year 

1991: U.S. Geological Survey Open-File Report 

94-4046, 144 p.

Marshall, M.P., 1992, Water Resources Programs in the 

New York District fiscal years 1990-1992: U.S. 

Geological Survey Open-File Report 92-473, 67 p.

11
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1992

DATE OF ANALYSIS

D. AMMONIUM

A. Acid-neutralizing capacity. B. Aluminum, total monomeric.

12 Quality-Assurance Data from Routine Water Analyses by the USGS Laboratory in Troy, N.Y., May 1991 - June 1993
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Figure 1. High- and low-concentration quality-control samples (continued): E. Calcium. F. Carbon, disssolved inorganic. G. 

Carbon, disssolved organic. H. Chloride.

Results of quality-control data for water-sample analyses 13
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Figure 1. High- and low-concentration quality-control samples (continued): I. Fluoride. J. Magnesium K. Nitrate 

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14 Quality-Assurance Data from Routine Water Analyses by the USGS Laboratory in Troy, N.Y., May 1991 - June 1993
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Results of quality-control data for water-sample analyses 15
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16 Quality-Assurance Data from Routine Water Analyses by the USGS Laboratory in Troy, N.Y., May 1991 - June 1993
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18 Quality-Assurance Data from Routine Water Analyses by the USGS Laboratory in Troy, N.Y., May 1991 - June 1993
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Figure 4. Environment Canaca, LRTAP laboratory study: A1. Acid-neutralizing capacity (for sample means not in the range 

of ± 20u_eq/L). A2. Acid-neutralizing capacity (for sample means in the range of ± 20-u.eq/L). B. Ammonium. C. Calcium. 

D. Carbon, dissolved organic. E. Chloride. F. Magnesium. G. Nitrate (ion chromatography.)

Results of quality-control data for water-sample analyses 21
3

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Figure 4. Environment Canada, LRTAP laboratory study (continued): H. pH. I. Potassium. J. Silicon. K. Sodium. 

L. Sulfate.

22 Quality-Assurance Data from Routine Water Analyses by the USGS Laboratory in Troy, N.Y., May 1991 - June 1993