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| Publications—Open-File Report |
By Tricia A. Lincoln, Debra A. Horan-Ross, Michael R. McHale, and Gregory B. Lawrence
U.S. Geological Survey Open-File Report 2006-1245
AVAILABLE ONLINE ONLY
The body of the report is available in PDF Format ( 2,764 KB)
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/quality-control data for the time period addressed in this report were stored in the laboratory’s SAS 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 1997 through June 1999.
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 and (or) low-concentration samples but were within control limits; these procedures were: acid-neutralizing capacity, total monomeric aluminum, total aluminum, ammonium, calcium, chloride, specific conductance, and sulfate. The data from the potassium and sodium analytical procedures are insufficient for evaluation. Results from the filter-blank and analytical-blank analyses indicate that the procedures for 11 of 13 analytes were within control limits, although the concentrations for blanks were occasionally outside the control limits. Blank analysis results for chloride showed that 22 percent of blanks did not meet data-quality objectives and results for dissolved organic carbon showed that 31 percent of the blanks did not meet data-quality objectives.
Sampling and analysis precision are evaluated herein in terms of the coefficient of variation obtained for triplicate samples in the procedures for 14 of the 18 analytes. At least 90 percent of the samples met data-quality objectives for all analytes except total aluminum (70 percent of samples met objectives) and potassium (83 percent of samples met objectives).
Results of the USGS interlaboratory Standard Reference Sample (SRS) Project indicated good data quality for most constituents over the time period. The P-sample (low-ionic-strength constituents) analysis had good ratings in two of these studies and a satisfactory rating in the third. The results of the T-sample (trace constituents) analysis indicated high data quality with good ratings in all three studies. The N-sample (nutrient constituents) studies had one each of excellent, good, and satisfactory ratings.
Results of Environment Canada’s National Water Research Institute (NWRI) program indicated that at least 80 percent of the samples met data-quality objectives for 9 of the 13 analytes; the exceptions were dissolved organic carbon, ammonium, chloride, and specific conductance. Data-quality objectives were not met for dissolved organic carbon in two NWRI studies, but all of the samples were within control limits for the last study. Data-quality objectives were not met in 41 percent of samples analyzed for ammonium, 25 percent of samples analyzed for chloride, and 30 percent of samples analyzed for specific conductance.
Results from blind reference-sample analyses indicated that data-quality objectives were met by at least 84 percent of the samples analyzed for calcium, chloride, magnesium, pH, and potassium. Data-quality objectives were met by 73 percent of those analyzed for sulfate. The data-quality objective was not met for sodium. The data are insufficient for evaluation of the specific conductance results.
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
6 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
1–5 Graphs showing—
1. High- and low-concentration quality-control sample results:
A. Acid-neutralizing capacity
B. Aluminum, total monomeric
C. Aluminum, total
D. Ammonium
E. Calcium
F. Carbon, dissolved organic
G. Chloride
H. Fluoride
I. Magnesium
J. Nitrate (ion chromatography)
K. Nitrate (colorimetric method)
L. pH 16 M. Potassium
N. Silicon
O. Sodium
P. Specific conductance
Q. Sulfate
2. Filter-blank and analytical-blank sample results:
A. Aluminum, total monomeric
B. Aluminum, organic monomeric
C. Aluminum, total
D. Ammonium
E. Calcium
F. Carbon, dissolved organic
G. Chloride
H. Magnesium
I. Nitrate (ion chromatography)
J. Potassium
K. Silicon
L. Sodium
M. Sulfate
3. Triplicate environmental samples:
A1. Acid-neutralizing capacity (for triplicate means not in ±20 µeq/L range)
A2. Acid-neutralizing capacity (for triplicate means in ± 20 µeq/L range)
B. Aluminum, total monomeric
C. Aluminum, organic monomeric
D. Aluminum, total
E. Calcium
F. Carbon, dissolved organic
G. Chloride
H. Magnesium
I. Nitrate (ion chromatography)
J. pH
K. Potassium
L. Silicon
M. Sodium
N. Sulfate
4. NWRI Ecosystem Interlaboratory QA Program results:
A1. Acid-neutralizing capacity (for samples not in the range of ± 20 µeq/L)
A2. Acid-neutralizing capacity (for samples in the range of ± 20 µeq/L)
B. Ammonium
C. Calcium
D. Carbon, dissolved organic
E. Chloride
F. Magnesium
G. Nitrate (ion chromatography)
H. pH
I. Potassium
J. Silicon
K. Sodium
L. Specific conductance
M. Sulfate
5. Blind reference sample results:
A. Calcium
B. Chloride
C. Magnesium
D. pH
E. Potassium
F. Sodium
G. Specific conductance
H. Sulfate
1. Number of environmental and quality-control (QC) samples analyzed by the Troy Laboratory, and summary of quality-control data for each constituent, July 1997 through June 1999
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 1997 through June 1999
3. Results obtained by the Troy Laboratory for the U.S. Geological Survey Standard Reference Sample (SRS) Project, September 1997 through March 1999
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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
(518) 285-5600
or visit our Web site at: http://ny.water.usgs.gov
U.S. Department of the Interior | U.S. Geological Survey
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