Improved method to measure urinary alkoxyacetic acids

Objectives-To simplify the current preparation of samples, and to improve t he specificity and reliability of the conventional analytical methods to me asure urinary alkoxyacetic acids. Methods-Samples containing alkoxyacetic acids including methoxy, ethoxy, an d butoxyacetic acids (MAA, EAA, and BAA) were acidified with HCl and extrac ted with a mixed solvent of methylene chloride and isopropyl alcohol, then analysed by gas chromatography/mass spectrometry(GC/MS). Results-Optimal results were obtained when pH was 1.05-1.45, the ratio of m ethylene chloride and isopropyl alcohol was 2:1, and when extraction time w as 10 minutes. Over the concentration range 0.3-200 mu g/ml, MAA, EAA, and BAA could be determined with a pooled coefficient of variation (nine concen trations, six replicate samples) of 5.55%, 6.37%, and 6.41%, respectively. Urine samples were stable for at least 5 months and 3 freeze-thaw cycles at -20 degrees C. The limits of detection of MAA, EAA, and BAA were 0.055, 0. 183, and 0.009 mu g/ml, respectively. The matrix effect of urine samples wa s negligible for MAA and EAA, but were marginally significant for BAA. The average recoveries of alkoxyacetic acids were 99%-101%. In urine samples MA A from 15 exposed workers showed a strong Linear correlation (r=0.999, slop e=1.01) between the new GC/MS method and Sakai's GC method. Conclusions-The simplified non-derivatisation pretreatment of samples coupl ed with GC/MS can provide a specific, sensitive, simple, safe, and reliable method for the biological monitoring of occupational exposure of ethylene glycol ethers.