Open-File Report 2009–1232
ABSTRACTThe 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 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 2001 through June 2003. Results for the quality-control samples for 19 analytical procedures were evaluated for bias and precision. Control charts indicate that data for six 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, chloride, magnesium, nitrate (ion chromatography), potassium, and sodium. The calcium procedure was biased throughout the analysis period for the high-concentration sample, but was within control limits. The total monomeric aluminum and fluoride procedures were biased throughout the analysis period for the low-concentration sample, but were within control limits. The total aluminum, pH, specific conductance, and sulfate procedures were biased for the high-concentration and low-concentration samples, but were within control limits. Results from the filter-blank and analytical-blank analyses indicate that the procedures for 16 of 18 analytes were within control limits, although the concentrations for blanks were occasionally outside the control limits. The data-quality objective was not met for the dissolved organic carbon or specific conductance procedures. Results of the USGS interlaboratory Standard Reference Sample (SRS) Project indicated satisfactory or above data quality over the time period, with most performance ratings for each sample in the good-to-excellent range. The N-sample (nutrient constituents) analysis had one unsatisfactory rating for the ammonium procedure in one study. The T-sample (trace constituents) analysis had one unsatisfactory rating for the magnesium procedure and one marginal rating for the potassium procedure in one study and one unsatisfactory rating for the sodium procedure in another. Results of Environment Canada’s National Water Research Institute (NWRI) program indicated that at least 90 percent of the samples met data-quality objectives for 10 of the 14 analytes; the exceptions were acid-neutralizing capacity, ammonium, dissolved organic carbon, and sodium. Data-quality objectives were not met in 37 percent of samples analyzed for acid-neutralizing capacity, 28 percent of samples analyzed for dissolved organic carbon, and 30 percent of samples analyzed for sodium. Results indicate a positive bias for the ammonium procedure in one study and a negative bias in another. |
First posted January 06, 2010 For additional information contact: Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge. |
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. available at https://pubs.usgs.gov/of/2009/1232/.
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
National Water Research Institute Ecosystem Interlaboratory QA Program
Blind Reference Samples
Control-Chart Evaluation
Quality-Control Samples
Filter Blanks and Analytical Blanks
Triplicate Environmental Samples
National Water Research Institute 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 Project
E. National Water Research Institute Ecosystem Interlaboratory QA Program
F. Blind Reference Samples
Selected References