Report of the U.S. Geological Survey's evaluation program for standard reference samples distributed in April 1993; T-123 (trace constituents), T-125 (trace constituents), M-126 (major constituents, N-38 (nutrients), N-39 (nutrients), P-20 (low ionic strength, and Hg-16 (mercury)

Abstract

This report presents the results of the U.S. Geological Survey's analytical evaluation program for 7 standard reference samples I-131 (trace constituents), T-133 (trace constituents), M-132 (major constituents), N-43 (nutrients), N-44 (nutrients), P-23 (low ionic strength), and Hg-19 (mercury).the samples were distributed in October 1994 to 131 laboratories registered in the U.S. Geological Survey sponsored interlaboratory testing program. Analytical data that were received from 121 of the laboratories were evaluated with respect to: overall laboratory performance and relative laboratory performance for each analyte in the seven reference samples. Results of these evaluations are presented in tabular form. Also presented are tables and graphs summarizing the analytical data provided by each laboratory for each analyte in the seven standard reference samples. The most probable value for each analyte was determined using nonparametric statistics. One hundred eighty-five USGS and non-USGS laboratories are registered in the program, which can currently provide eight standard reference sample types: 1. Trace constituents. 2. Major constituents. 3. Nutrients. 4. Low ionic strength. 5. Mercury. 6. Whole water (water with suspended sediment). 7. Acid mine drainage. 8. Sediment (bed material) for major and trace constituents. When sufficient data are available, a most probable value is statistically determined for each analyte in the SRS. Though this is not a laboratory certification program, participation in this continuing quality assurance program is mandatory for all laboratories providing water-analyses data for USGS data storage or use (publications). Federal, State, municipal, and university laboratories can participate even though they do not provide data to the USGS. Analyses of these SRS provides the means to alert participating laboratories of possible deficiencies in their analytical operations, and also provides reference materials for in-house quality control programs. Participating laboratories are identifed only by a confidential code number. A library of SRS, from previous evaluations, are available on request. Participating laboratories can request previous SRS for further testing, continuing quality assurance, and quality control programs by contacting: