Reiko Sugihara

Quantitative determination of urinary hippuric acid and m- or p-methylhippuric acid as indices of toluene and m- or p-xylene exposure by high performance liquid chromatography.

SummaryA high performance liquid chromatographic method for the determination of hippuric and m-(p-)methylhippuric acids in urine, metabolites of toluene and m-(p-)xylene, is described. A stainless-steel column packed with octadecyl silanized silica gel was used and the mobile phase was a mixed solution of methanol/water/acetic acid (20/80/0.2). The method is simple and specific. Urine can be analyzed directly, without solvent extraction or pretreatment. The method has a lower detection limit of 0.2 μg on column. All the analysis and quantitative determination can be performed within about 30 min. for samples containing m-(p-)methylhippuric acid.

High performance liquid chromatographic procedure for quantitative determination of urinary phenyl-glyoxylic, mandelic, and hippuric acids as indices of styrene exposure

SummaryA method is described for the quantitative determination of phenyl-glyoxylic, mandelic, and hippuric acids in urine are all metabolites of styrene monomer. After o-methylhippuric acid was added to urine as an internal standard, these three acids and o-methylhippuric acid were extracted with a mixture of ethyl ether and methanol (9/1, by vol.).After 1.0 ml of extract was transferred to a test tube and dried, 0.25 ml of methanol was added. An aliquot of this solution was injected into a high performance liquid chromatography equipped with column packed with octadecylsilicate. Phenylglyoxylic acid was estimated from the peak height at wave length 254 nm. Mandelic, hippuric and o-methylhippuric acids were estimated from their peak height at 225 nm.For a micro-determination of urinary mandelic acid, phenacyl esterification of mandelic acid could be performed by combination with phenacyl bromide and thriethylamine. This was then analyzed at 254 nm using the column packed with silica gel.

Quantitation of urinary o-xylene metabolites of rats and human beings by high performance liquid chromatography

SummaryA high performance liquid chromatographic method for the determination of urinary o-xylene metabolites of rats, volunteers, and workers was described. In rat urine, the major metabolite, indicated by the glucuronic acid reaction, was separated with thin-layer liquid chromatography and identified as o-toluic acid glucuronide by high performance liquid chromatography. Another rather minor metabolite was demonstrated to be o-methyl hippuric acid. One of the major urinary metabolite in volunteers administered o-xylene orally was demonstrated to be o-methylhippuric acid and another minor metabolite was o-toluic acid glucuronide. In the urine of volunteers exposed to 138 ppm of o-xylene for 3 h in an artificial exposure chamber, o-methylhippuric acid was found to be the major metabolite and a minute amount of o-toluic acid glucuronide was found to be the minor metabolite. In the urine of shipbuilding workers, using a thinner containing toluene and xylenes (o-, m- and p-), hippuric acid and methylhippuric acids (o-, m- and p-) were recognized. Thus, urinary o-methylhippuric acid could be an index of o-xylene exposure of workers.

Quantitation of urinary m- and p-methylhippuric acids as indices of m- and p-xylene exposure

SummaryThe method described here enables the accurate indentification and subsequent analysis of urinary m- and p-methylhippuric acids. Urinary m- and p-methylhippuric acids were extracted with methyl ethyl ketone, and the extract was dehydrated with sodium sulfate anhydrate. Benzoxylation of these acids was performed by heating with phenacyl bromide and triethylamine in a methyl ethyl ketone solution. An aliquot of this solution was injected into a high performance liquid chromatography column packed with silica gel.Urinary m- and p-methy1hippuric acids could be determined individually, with a lower detection limit of about 0.02 μg. Urinary m- and p-methylhippuric acids derived from m- and p-xylene administered to rats could be measured by this method. Data indicated that excretion rates of m-methylhippuric acid from m-xylene and p-methylhippuric acid from p-xylene are identical.