Rapid preparation of fluorescent 9-anthrylmethyl esters for fatty acid analysis of small amount of triacylglycerols

This paper proposes a one-step method for preparation of fluorescent 9-anthrylmethyl esters from triacylglycerols (TAG) ranging in amount from 0.1 to 5 mu g. It involves base-catalyzed transesterification using potassium 9-anthracenemethoxide, prepared by proton exchange between 9-anthracenemethanol and potassium tert-butoxide. Transesterification for 10 min at room temperature gave the fatty acid 9-anthrylmethyl esters in nearly maximal yields (82-85%). The products could be analyzed by reversed-phase HPLC without purification. Excellent linear relationships were observed for standard curves of 10-250 pmol of TAG standards (16:0, 19:0, 18:2 and 22:6), and differences in the slopes were less than 5% among the standards. Almost consistent compositions of the esters were observed for the products formed from 0.5 to 5 mu g or less of fish oils TAG, and they were similar to those obtained by HPLC of ordinary multi-step synthesis products and by GLC of methyl esters. The present method is a great improvement of derivatization time, and is powerful for fatty acid analysis of small amounts of natural TAG.