Application of micellar electrokinetic capillary chromatography for monitoring of hippuric and methylhippuric acid in human urine.

The factors affecting micellar electrokinetic capillary chromatographic separation of hippuric and o-, m-, p-methylhippuric acid were investigated by changing the species of micelles, and adding urea to the micellar solution. The analysis of hippurates in human urine is demonstrated under optimum conditions using 20 mM phosphate buffer (pH 8.0) containing 100 mM dodecyltrimethylammonium bromide and 4 M urea at -22 kV applied voltage. This method proved suitable for the screening of hippurates in human urine following occupational exposure to toluene and xylene.