Blood and Urine Bioindicators for Methanol Exposure: Effect of Chilled and Frozen Sample Storage

Abstract

Measurements of methanol concentrations in blood and urine may be used as bioindicators of methanol exposure that account for all exposure pathways. These measurements will be practical if the integrity of samples from the time of collection to the time of analysis can be maintained. This study was designed to test the stability of methanol in blood and urine samples stored at 4° and −20°C for various periods of time up to 7 months. Methanol recoveries of the stored blood samples were found to fit a first-order decay model, with the best estimates for the half-life of methanol in chilled and frozen blood of 114 ± 14 and 240 ± 58 days, respectively. A half-life of 562 ± 145 days is estimated for chilled and frozen urine. These long half-lives enhance the utility of methanol bioindicators. While freezing increased the recovery in blood, it also decreased the reproducibility of results. Thus, refrigeration of samples is recommended if the analysis will be completed within about a month of sample collection, and freezing of samples is suggested otherwise. For blood, sample preservation was not enhanced using an all-glass storage system, and a conventional sampling container yielded equivalent results. Batterman, S.A.; Xiao, H.; Franzblau, A.: Blood and Urine Bioindicators for Methanol Exposure: Effect of Chilled and Frozen Sample Storage. Appl. Occup. Environ. Hyg. 11(1):25–29; 1996.