Effect of sample freezing on the SPME performance in the analysis of chiral volatile compounds in foods

The sensitivity of SPME/GC/MS for the analysis of chiral volatile compounds in food matrices was intended to be improved. To that end, a new approach based on the freezing/defrosting of the sample prior to the extraction is described. The defrosting time was carefully optimised, obtaining different optimal values according to the matrix studied. Relative standard deviations from three replicates of the overall procedure were lower than 12% in all cases. By applying the method proposed, peak areas for the compounds of interest up to nine times higher were obtained in some cases. This improvement in the sensitivity allowed to increase the reliability in the identification of volatile components as well as to detect certain chiral minor compounds in foods. The results shown in the present work suggest the usefulness of sample freezing in food quality studies by increasing the sensitivity achievable in SPME analysis.