engleski

Optimising the conditions for S-phenylmercapturic acid analysis in urine using gas chromatography-mass spectrometry

Benzene is an aromatic compound with cancerogenic properties to which people, except in professional settings where various exposures may be present, are exposed by cigarette smoke or motor vehicle exhaust. S-phenylmercapturic acid (S-PMA) is considered a specific marker of benzene exposure in the general and occupationally exposed population. For occupational exposure, the European Chemical Agency (ECHA) recommended an S‐PMA biological limit value of 2 μg/g creatinine. The aims of this study were to optimise the conditions of S-PMA extraction from urine and to develop and validate a sensitive and specific an analytical method for determining the mass concentration of S-PMA in urine using gas chromatography-mass spectrometry (GC-MS). Factors that affect the extraction efficiency (sample volume, pH value and volume of ethyl acetate) and the derivatisation of S-PMA (type and amount of derivatisation agent, temperature and time of reaction) were examined. Optimised conditions included extraction of 1 mL urine with 4 mL ethyl acetate at pH 2 and derivatisation with 1 mL of 1.25 M hydrochloric acid in methanol at 50 °C for 15 minutes. The proposed GC-MS method showed good linearity (R2>0.9996) in the examined concentration range (0.5–100 μg/L), good precision (RSD<7%), accuracy (>95%) and sensitivity (limit of detection: 0.03 μg/L and limit of quantification: 0.09 μg/L). The method was applied to determine the mass concentration of S-PMA in the urine of 20 subjects who were not occupationally exposed to benzene. Smokers (N = 10, mean: 0.8 μg/g creatinine ; range: 0.3–5.8 μg/g creatinine) had a significantly higher (p=0.014) concentration of S-PMA in urine compared to non-smokers (N = 10, mean: 0.2 μg/g creatinine ; range: 0.1–2.3 μg/g creatinine). The described method permits sensitive, fast and reliable determination of low μg/L S-PMA levels in urine.

benzene ; biomarker ; GC-MS ; method development

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