Abstract
The Proficiency Analytical Testing (PAT) program is operated by the American Industrial Hygiene Association in cooperation with the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, under a Cooperative Research and Development Agreement. Currently more than 300 laboratories in the program report annually over 15,000 analyses for organic solvents on charcoal sorbent tubes. The evaluation of organic solvent determinations reported here covers almost 20 years of the PAT program (1974–92). Estimates are obtained for total variability, intraanalyst variability, and interanalyst variability. Each of these components is shown to have improved since the early rounds of the PAT program. For the most recent data, four analytes (chloroform, 1,2-dichloroethane, o-xylene, and trichloroethylene) have total relative standard deviations less than 0.10 relative standard deviation (RSD). Analytes collected at the lowest loadings (benzene and carbon tetrachloride) and toluene have somewhat higher RSDs. Of the eight analytes studied, all show an improvement in total variability, four of which are statistically significant (p<0.01). Averaging over the analytes indicates a reduction of more than 55% in total RSD between the periods 1974–80 and 1981 to the present (p<0.003).