Determination of Toluene and Ethanol in Urine by Headspace and Cryotrapping Gas Chromatography–Mass Spectrometry

ABSTRACT

Toluene is the major volatile organic compound found in glue and is often used as a hallucinogenic for abusers. Use with alcohol increases the risk of adverse effects from toluene exposure. In this study, a headspace and cryotrapping gas chromatography–mass spectrometry method was developed and validated for the determination of toluene and ethanol in urine. Experimental and instrumental variables were investigated to optimize the method for sensitivity. Excess sodium sulfate was used as the salting-out reagent before the headspace protocol. Linear least squares regression with a 1/x weighting factor was used to construct calibration curves from 0.002 to 0.4 µg mL⁻¹ for toluene and 10 to 2000 µg mL⁻¹ for ethanol. The correlation coefficients exceeded 0.9993. The limits of detection were 0.0005 µg mL⁻¹ for toluene and 0.21 µg mL⁻¹ for ethanol. Intraday and interday precisions were within 5.4 and 11.5%, while intraday and interday accuracies were between −11.3 to −4.0% and −11.0 to 1.2%, respectively. The method validation results for selectivity and stability were satisfactory. The validation results were used to estimate the expanded uncertainty and the contribution of individual steps in the method for the quantification of toluene and ethanol. The relative expanded uncertainties were 14.1% for toluene and 4.6% for ethanol.

KEYWORDS:

• Cryotrapping
• gas chromatography–mass spectrometry
• headspace
• uncertainty
• volatile organic compound