[Analysis of positional distribution of fatty acids in triacylglycerols from lard by high performance liquid...

A high performance liquid chromatographic (HPLC) method for the determination of fatty acid positional distribution on triacylglycerols from lard has been established. The analysis was carried out with an sn-1, 3 specific lipase to deacylate the fatty acid residues esterified at sn-1 and sn-3 positions of triacylglycerols, forming sn-2 monoglycerides and free fatty acids. After lipase action, it was possible to determine the fatty acid esterified at the sn-2 position by the substraction of the results of the sn-1, 3 analysis from an overall composition analysis based on complete saponification of the original sample. The free fatty acid mixtures were converted to phenacyl esters via 2-bromoacetophenone and analyzed on an Agilent 1100 series high performance liquid chromatograph, equipped with a ZORBAX SB C18 column (4.6 mm i.d. x 250 mm, 5 microm) and a UV detector. Elution was performed at a flow rate of 1 mL/min, with a gradient of methanol-acetonitrile-water starting at 80: 10: 10 (v/v), increasing linearly to 86: 10: 4 (v/v) in 35 min, then returning'to the initial conditions in 5 min. Elution of phenacyl esters was monitored by absorbance at 254 nm. Pentadecanoic acid was used to be an internal standard. The results showed that palmitic and oleic acids were the major components in lard, accounting for 26.61% and 43.18% respectively. Among these, palmitic acid mainly locates at sn-2 position, while oleic acid at sn-1, 3 positions. These results were consistent with those obtained via gas chromatographic method. The new method is simpler and easier to use as it eliminates time-consuming thinner-layer chromatography used in standard regioselective analysis. It is possible to be an effective laboratory analytical method.