ANALYSIS OF TRIACYLGLYCEROLS BY SILVER-ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

Triacylglycerols of the seed oils rich in alpha- and/or gamma-linoleni c acid moieties were separated by silver-ion high-performance liquid c hromatography (HPLC) followed by on-line atmospheric pressure chemical ionization-mass spectrometric (APCI-MS) detection. Mass spectra of mo st triacylglycerols exhibited abundant [M + H](+) and [M - RCO(2)](+) ions, which defined the molecular weight and the molecular association of fatty acyl residues of a triacylglycerol, respectively. Silver ion s formed weaker complexes with triacylglycerols containing gamma-linol enic acid than with those containing alpha-linolenic acid, i.e., the e lution order of molecules was XYT(gamma) > XYT(alpha), XT(gamma)T(gamm a) > XT(gamma)T(alpha) > XT(alpha)T(alpha), and TgammaTgammaTgamma > T gamma T?(gammaTalpha) > T(gamma)T(a)lpha T alpha > TalphaTalphaTalpha, (<where; T-alpha = alpha-linolenic acid; T-gamma = gamma-linolenic ac id, and X, Y = fatty acids different from linolenic acid. Furthermore, silver-ion HPLC resulted in partial separation within equally unsatur ated triacylglycerols according to differences in the combined number of acyl carbons. Regioisomeric forms of triacylglycerols were not dete rmined from the seed oil samples, although differences were measured w ith reference compounds in the relative abundances of [M - RCO(2)](+) ions formed by a loss of a fatty acyl residue from the sn-2 position a nd the sn-1/3 positions. Silver-ion HPLC/APCI-MS provided valuable inf ormation for structure elucidation of seed oil triacylglycerols: 43 mo lecular species were identified from cloudberry seed oil, 39 from even ing primrose oil, 79 from borage oil, 44 from alpine currant, and 56 f rom black currant seed oils. The quantitation requires to be studied f urther, especially in those cases where several molecular weight speci es of triacylglycerols eluted in a single chromatographic peak.