Direct sampling of orujo oil for determining residual hexane by using a ChemSensor

Hexane is used to extract edible oils from oleaginous seeds. The detection of hexane in orujo oil is mandatory, as its presence in the final product may negatively affect human health. Headspace-GC is the technique of choice for determining residual solvent in foods. In the present work, a new instrument based on the headspace principle and mass spectrometric detection without chromatographic separation, ChemSensor, is proposed for the direct screening of orujo oil to determine residual hexane. This instrument provided an overall response, corresponding to the volatiles profile, including that of hexane, which could not be directly discriminated. By selecting the m/z values corresponding to n-hexane (major component of commercial hexane), the selectivity of the method was good enough to determine residual hexane in the range of 2.0-65 mug mL(-1) (corresponding to 2.3-75.6 mg of hexane per kg of oil) with high precision. The detection limit achieved (0.7 mg per kg of oil) was lower than the maximum residual limit established by the European Union (5 mg per kg of oil). Two multivariate techniques, partial least squares and principal components regression (PCR), were compared with univariate regression; PCR provided the best results.