Published: Journal of Analytical Toxicology, Volume 20, Number 5, September 1996, pp. 309-312.
Gas Chromatographic Determination of Urinary o-Cresol
for the Monitoring of Toluene Exposure
G. Truchon, R. Tardif and J. Brodeur
A sensitive and reproducible gas chromatographic procedure for the quantitative determination of urinary o-cresol is described. The first step involves acid hydrolysis (2N HCl, 100°C, 10 min), which yields unconjugated o-cresol. After extraction (methylene chloride, pH 2), the organic layer is concentrated by evaporation and samples are analyzed by gas chromatography–flame ionization detection with a DB-5 column (30 m ¥ 0.25 mm, 0.25 µm). Initial oven temperature is set at 30°C for 12 min and then increased 2°C/min to 93°C. 3,4-Dimethylphenol is used as the internal standard. The detection limit of the method is 0.36 µmol/L (1-µL injection). Additional validation data were obtained by analysis of urine samples collected from volunteers exposed to various concentrations of toluene: 10, 20, 30, 50, and 100 ppm over 7 h. Urinary o-cresol concentrations (0–3, 3–7, 7–24, and 0–24 h) were highly correlated with toluene exposure.
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