Development of a novel solid-phase extraction, LC-MS/MS method for the analysis of ethyl carbamate in alcoholic beverages: application to South African wine and spirits

Abstract

Ethyl carbamate (EC) is a known genotoxic carcinogen that is frequently present in alcoholic beverages and is therefore a public health concern. As a consequence, maximum concentration levels for EC in these commodities are legislated in several countries. Quantitative analytical methods are therefore essential to monitor EC levels in beverages. Most published analytical methods for the determination of EC in alcoholic beverages utilise elaborate sample pre-treatment procedures to obtain injectable samples, or yield low sensitivity, for example where direct injection is used. In addition, these procedures often require large volumes of toxic solvents and are not generally applicable to diverse alcoholic beverages. This paper describes a novel procedure for the determination of EC in wines, fortified wines and spirits. The procedure is based on reversed-phase solid-phase extraction (SPE) sample clean-up combined with normal-phase liquid chromatography-atmospheric pressure chemical ionisation tandem mass spectrometric (NP-LC-APCI-MS/MS) analysis. This method provides a rapid, robust and simple analytical procedure suitable for the analysis of a diverse range of alcoholic beverages. The accuracy of the method (expressed as average recovery from diverse matrices) is 94.5%, with limits of detection (LODs) ranging between 0.25 and 0.63 µg l⁻¹ for different matrices. Benefits such as simplified sample preparation, low detection limits, low solvent consumption and good selectivity render the methodology ideally suited to study the occurrence of EC in diverse commodities. The method was applied to study the occurrence of EC in South African wines, fortified wines and spirits. South African wines, aged 1–9 years, contained 1.8–31 µg l⁻¹ EC (RSD = 69%, n = 106), fortified wines aged 2–34 years contained 2.8–79 µg l⁻¹ EC (RSD = 89%, n = 21), and brandies aged 3–20 years contained 4.4–95 µg l⁻¹ EC (RSD = 105%, n = 26). Factors affecting the formation of EC in these commodities were investigated and storage temperature, alcohol content and pH were found to affect the rate of EC formation. Of these variables storage temperature has by far the greatest effect.

Keywords:

• liquid chromatography/mass spectrometry
• clean-up
• survey
• ethyl carbamate
• beverages
• wine