FIOH external quality assurance scheme for organic solvent metabolites.

The scheme consists of analyses for phenol,2,5-hexanedione, and mandelic, trichloroacetic and methylhippuric acids in urine. The present participants are 31 laboratories from 14 countries. Samples are prepared by pooling urine obtained from occupationally exposed workers or by spiking with appropriate pure metabolites. Four sets of samples at two concentration levels for each analyte are distributed annually. The report includes information on the arithmetic means, standard deviations and CVs for overall results and separately for different methods. During the last three years, the CVs have varied rather non systematically, being 21-31% for mandelic acid, 24-26% for trichloroacetic acid, 24-35% for phenol, 55-110% for 2,5-hexanedione and 44-50% for methylhippuric acid.