Direct, rapid, and efficient transesterification of total lipids in human serum by microwave irradiation

Microwave irradiation as the energy source for direct transesterification with acetyl chloride as catalyst was examined in human serum fatty acids determination. One‐hour convectional heating at 100°C was compared to microwave irradiation heating in either Manual Single Mode (DISCOVERY) or Multimode Microwave synthesis system (MARS). Fatty acid concentrations of human serum determined by microwave accelerated assays were close to those by the conventional Lepage & Roy assay (control method) when the microwave conditions were optimal, 100°C × 1 min with initial power at 300 W in the Single mode system, or 125°C × 5 min with initial power at 400 W in the Multimode system. Recoveries of 103 and 100% were observed for the total amount of fatty acids, 94% or greater for all identified fatty acids except about 80% for the usually very minor fatty acids 20:0, 22:0, 24:0 and 24:1n‐9. Furthermore, the proportion of n‐6 in total HUFA, its counterpart n‐3% and the ratio of n‐6 to n‐3 HUFA in a total of 11 tested conditions were consistent with the control group at ranges of 71–72%, 26–28% and 2.6–2.7, respectively. Thus, the microwave irradiation, accelerated transmethylation with acetyl chloride as catalyst methodology may be applied in both the absolute quantification (μg/mL serum) and relative quantification (weight%) of human serum fatty acids. This project was funded by the DICBR, NIAAA, NIH