Modified method for determination of hippuric acid and methylhippuric acid in urine by gas chromatography

A modified method for the simultaneous determination of hippuric acid (HA) and o-, m- and p-methylhippuric acids (o-, m- and p-MHAs) in urine is described. These metabolites were extracted, derivatized into their methyl ester derivatives and analyzed using a gas chromatograph equipped with flame ionization detector and a DB-1 capillary column. The derivatives of HA, o-, m- and p-MHAs were well separated within 11 min. The accuracy and precision in the present method were sufficient for quantitative analysis, and the results obtained by the GC method were highly correlated with those by the HPLC method (NIOSH 8301).