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

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

U.S. Geological Survey Open-File Report 2006-1246

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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 quality-assurance samples and quality-control procedures that were developed to ensure proper sample collection, processing, and analysis. The quality-assurance and quality-control data were stored in the laboratory’s LabMaster data-management system, which provides efficient review, compilation, and plotting of data. This report presents and discusses results of quality-assurance and quality-control samples analyzed from July 1999 through June 2001.

Results for the quality-control samples for 18 analytical procedures were evaluated for bias and precision. Control charts indicate that data for eight of the analytical procedures were occasionally biased for either high-concentration or low-concentration samples but were within control limits; these procedures were: acid-neutralizing capacity, total monomeric aluminum, total aluminum, calcium, chloride and nitrate (ion chromatography and colormetric method) and sulfate. The total aluminum and dissolved organic carbon procedures were biased throughout the analysis period for the high-concentration sample, but were within control limits. The calcium and specific conductance procedures were biased throughout the analysis period for the low-concentration sample, but were within control limits. The magnesium procedure was biased for the high-concentration and low concentration samples, but was within control limits.

Results from the filter-blank and analytical-blank analyses indicate that the procedures for 14 of 15 analytes were within control limits, although the concentrations for blanks were occasionally outside the control limits. The 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 17 of the 18 analytes. At least 90 percent of the samples met data-quality objectives for all analytes except ammonium (81 percent of samples met objectives), chloride (75 percent of samples met objectives), and sodium (86 percent of samples met objectives).

Results of the USGS interlaboratory Standard Reference Sample (SRS) Project indicated good data quality over the time period, with most ratings for each sample in the good to excellent range. The P-sample (low-ionic-strength constituents) analysis had one satisfactory rating for the specific conductance procedure in one study. The T-sample (trace constituents) analysis had one satisfactory rating for the aluminum procedure in one study and one unsatisfactory rating for the sodium procedure in another. The remainder of the samples had good or excellent ratings for each study.

Results of Environment Canada’s National Water Research Institute (NWRI) program indicated that at least 89 percent of the samples met data-quality objectives for 10 of the 14 analytes; the exceptions were ammonium, total aluminum, dissolved organic carbon, and sodium. Results indicate a positive bias for the ammonium procedure in all studies. Data-quality objectives were not met in 50 percent of samples analyzed for total aluminum, 38 percent of samples analyzed for dissolved organic carbon, and 27 percent of samples analyzed for sodium.

Results from blind reference-sample analyses indicated that data-quality objectives were met by at least 91 percent of the samples analyzed for calcium, chloride, fluoride, magnesium, pH, potassium, and sulfate. Data-quality objectives were met by 75 percent of the samples analyzed for sodium and 58 percent of the samples analyzed for specific conductance.

Table of Contents

Abstract

Introduction

Purpose and Scope

Participating Projects

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

Quality-Control Samples

Filter Blanks and Analytical Blanks

Triplicate Environmental Samples

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

NWRI Ecosystem Interlaboratory QA Program

Blind Reference Samples

Control-Chart Evaluation

Quality-Control Samples

Filter Blanks and Analytical Blanks

Triplicate Environmental Samples

NWRI Ecosystem Interlaboratory QA Program

Blind Reference Samples

Summary of Results

A. Quality-Control Samples

B. Filter Blanks and Analytical Blanks

C. Triplicate Environmental Samples

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

E. NWRI Ecosystem Interlaboratory QA Program

F. Blind Reference Samples

Selected References

Figures

1–5 Graphs showing—

1. High- and low-concentration quality-control sample results:

A. Acid-neutralizing capacity 14
B. Aluminum, total monomeric 14
C. Aluminum, total 14
D. Ammonium. 14
E. Calcium 15
F. Carbon, dissolved organic 15
G. Chloride 15
H. Fluoride 15
I. Magnesium 16
J. Nitrate (ion chromatography) 16
K. Nitrate (colorimetric method) 16
L. pH 16
M. Potassium 17
N. Silicon 17
O. Sodium 17
P. Specific conductance 17
Q. Sulfate 18

2. Filter-blank and analytical-blank sample results:

A. Aluminum, total monomeric 19
B. Aluminum, organic monomeric 19
C. Aluminum, total 19
D. Ammonium 19
E. Calcium 19
F. Carbon, dissolved organic 19
G. Chloride 19
H. Fluoride. 19
I. Magnesium 20
J. Nitrate (ion chromatography) 20
K. Potassium 20
L. Silicon 20
M. Sodium 20
N. Specific conductance 20
O. Sulfate 20

3. Triplicate environmental samples:

A1. Acid-neutralizing capacity (for triplicate means not in ±20 µeq/L range) 21
A2. Acid-neutralizing capacity (for triplicate means in ±20 µeq/L range) 21
B. Aluminum, total monomeric 21
C. Aluminum, organic monomeric 21
D. Aluminum, total 21
E. Ammonium 21
F. Calcium 21
G. Carbon, dissolved organic 21
H. Chloride 22
I. Fluoride 22
J. Magnesium 22
K. Nitrate (ion chromatography) 22
L. pH 22
M. Potassium 22
N. Silicon 22
0. Sodium 22
P. Specific conductance 23
Q. Sulfate 23

4. NWRI Ecosystem Interlaboratory QA Program results:

A1. Acid-neutralizing capacity (for samples not in the range of ± 20 µeq/L) 24
A2. Acid-neutralizing capacity (for samples in the range of ± 20 µeq/L) 24
B. Aluminum, total 24
C. Ammonium 24
D. Calcium 24
E. Carbon, dissolved organic 24
F. Chloride 24
G. Magnesium 24
H. Nitrate (ion chromatography) 25
I. pH 25
J. Potassium 25
K. Silicon 25
L. Sodium 25
M. Specific conductance 25
N. Sulfate 25

5. Blind reference sample results:

A. Calcium 26
B. Chloride 26
C. fluoride 26
D. Magnesium 26
E. pH 26
F. Potassium 26
G. Sodium 26
H. Specific conductance 26
I. Sulfate 27

Tables

1. Number of environmental and quality-control (QC) samples analyzed by the Troy Laboratory, and summary of quality-control data for each constituent, July 1999 through June 2001

2. Reporting limits and data-quality objectives for accuracy, precision, and blanks for solution analyses performed by the U.S. Geological Survey Laboratory in Troy, N.Y., July 1999 through June 2001

3. Results obtained by the Troy Laboratory for the U.S. Geological Survey Standard Reference Sample (SRS) Project, Octobber 1999 through October 2000


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For further information, contact:

Rafael W. Rodriquez, Director
U.S. Geological Survey
New York Water Science Center
425 Jordan Road
Troy, NY 12080

dc_ny@usgs.gov

(518) 285-5600

or visit our Web site at: http://ny.water.usgs.gov



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