Comparison of Three Methods for Extraction of Volatile Lipid Oxidation Products from Food Matrices for GC-MS Analysis

GC based methods are often used for determination of volatile oxidation products such as pentanal and hexanal. Different extraction methods for extracting volatiles before GC analysis can be used, e.g static headspace, dynamic headspace and solid phase microextraction (SPME). Traditionally, dynamic headspace extraction has been performed manually. Recently, automated dynamic headspace methods have become available. This presentation will summarize the principles of the different extraction methods. Moreover, results from fish oil, oil-in-water emulsion and milk obtained with SPME, manual dynamic headspace or automated dynamic headspace (TDU/DHS) extraction followed by GC-MS analysis will be compared. In all cases, concentrations of volatiles were quantified by calibration curves by addition of selected standards to oil, emulsion or milk. The results show that the linearity of calibration curves differs between the different extraction methods. Furthermore, in some cases the concentrations of volatiles obtained in the samples with the different methods were similar whereas in other cases very different concentrations were obtained. Finally, the findings indicated that when samples contained high concentration of volatiles the use of SPME can be problematic due to the fact that volatiles are competing for space on the SPME fiber. Thereby, the concentration of some volatiles may be under estimated.