Direct microwave transesterification of fingertip prick blood samples for fatty acid determinations

Omega-3 polyunsaturated fatty acid (PUFA) dietary intakes and tissue levels are positively associated with various health benefits. The development of cost efficient, high throughput methodologies would enable research in large clinical and population studies, and clinical fatty acid profiling. Microwave heating for the transesterification of blood fatty acids was examined. Samples were collected by venous puncture and fingertip prick onto chromatography paper. Aliquots of serum, plasma, erythrocytes and whole blood were prepared from venous blood. Boron trifluoride in methanol was used for transesterification but sample preparation and heating varied. Fatty acid determinations and markers of omega-3 fatty acid status including the sum of eicosapentaenoic acid and docosahexaenoic acid, the ratio of total n-3 PUFA to n-6 PUFA, and the percentage of n-3 highly unsaturated fatty acids (HUFA, >= 20 carbons and >= 3 carbon-carbon double bonds) in total HUFA were compared. Quantitative determinations indicate that microwave transesterification results in significantly lower estimates of monounsaturates and polyunsaturates, possibly through incomplete transesterification of triacylglycerols. However, qualitative estimates of omega-3 fatty acid status were relatively similar. Fingertip prick blood collection combined with direct transesterification by microwave may be a very rapid method to estimate omega-3 fatty acid status for selected applications.