Thin-layer chromatography of hippuric and m-methylhippuric acid in urine after mixed exposure to toluene and xylene.

The separation of hippuric and m-methylhippuric acid as toluene and m-xylene metabolites present in urine of people exposed simultaneously to toluene and xylene is described. Chloroform was used for hippuric and m-methylhippuric acid extraction. Satisfactory separation of these metabolites was obtained on TLC plates covered with silica gels and developed in chloroform acetic acid-water (4:1:1);p-dimethylaminobenzaldehyde in acetic acid anhydride was applied to develop the colour. The sensitivity of the method was 6 micrograms hippuric acid per 1 ml urine and recovery was 100% (+/- 1).