Report of the U.S. Geological Survey's analytical evaluation program; standard reference water samples M-82 (major constituents), T-83 (trace constituents), N-8 (nutrients), and P-2 (precipitation snowmelt)

The U.S. Geological Survey began an interlaboratory testing program of reference water samples in 1962. Principal purposes of the program are to provide a means for participating water laboratories to: (1) identify analytical problem areas; (2) ascertain the accuracy and precision of common water analyses and analytical methods and; (3) provide reference samples for continuing quality assurance testing. Participation in this continuing quality assurance program is mandatory for all domestic laboratories providing water analysis data for Survey use. Analytical data submitted by the participating laboratories that analyzed the respective reference samples distributed in October 1982 are presented. Relative performance ratings achieved by the laboratories for each determination and statistical evaluation of the data are given in 14 tables. (Author 's abstract)