| Abstract: | A headspace–mass spectrometry with alternative chromatographic separation using a column switching system was developed for the screening and confirmation of BTEX and styrene in comestible oils. According to the position of the switching valve, the chromatographic column can be bypassed and the volatile sample constituents are transferred directly from the headspace sampler to the mass spectrometer providing a global, non resolved, signal in less than 1 min after injection. In this way, a set of samples can be rapidly processed in order to determine if they are (or not) contaminated with BTEX and styrene. Subsequently, only the samples with positive response in the previous screening can be processed by gas chromatography–mass spectrometry in the same analytical system by switching the position of the valve, thus confirming the presence of the analytes in the sample. The method presents good analytical features and it is applicable to the analysis of real samples. Detection limits were lower than 0.1 ng mL?1, and recoveries were between 97 and 105% with relative standard deviations lower than 4%. Analysis of real comestible oils showed the presence of toluene, benzene, and styrene in some samples packed in plastic bottles. |
