Gaschromatographic determination of butoxyacetic acid after hydrolysis of conjugated metabolites in urine from workers exposed to 2-butoxyethanol

Abstract

For the gaschromatographic determination of total butoxyacetic acid (BAA), i.e., free plus conjugated BAA in urine, we studied the acid hydrolysis condition to cleave the conjugate. The optimum condition for hydrolysis was chosen to be 60 min boiling of the mixture of 1 ml twofold diluted urine and 1.2 ml hydrochloric acid. For the biological monitoring of workers exposed to 2-butoxyethanol (BE), we applied our acid hydrolysis method to the urine from 6 workers exposed to the solvent for 7 days and determined total BAA as well as free BAA and conjugated BAA, which was calculated as the difference between the concentrations of free and conjugated BAA. The percentages of conjugated BAA vs. total BAA varied from 44.4% to 92.2% (mean value 71.1%) among 6 individual workers over 7 days and decreased gradually over the consecutive work days. In the latter half of the work week, free BAA comparatively accounted for the larger portion of urinary BAA. Significant correlations were found between urinary BAA concentrations and BE levels in the breathing-zone air (TWA). The correlation coefficients of urinary concentrations of total or conjugated BAA vs. BE levels was higher than that of free BAA concentrations vs. BE levels. Hence, the determination of total BAA in urine is a suitable test for the biological monitoring of BE exposure, because of the simplicity in procedures and the good agreement with BE exposure levels.