ABSTRACT
High performance liquid chromatography (HPLC) with detection by both atmospheri c pressure chemical ionization (APCI) mass spectrometry (MS) and electrospray ionization (ESI) MS has been applied to both triacylglycerols (TAG) and phospholipids (PL). HPLC/APCI-MS for analysis of a mixture of TAG was first demonstrated by Byrdwell and Emken (1) in 1995. In this report, the authors showed several key features of APCI-MS spectra of TAG. First, the primary fragments that were produced were the diacylglycerol (DAG) fragment ions formed by loss of one fatty acyl chain. Second, the ratio of the protonated parent molecule to the DAG fragment ion depended on the number of sites of unsaturation in the TAG molecules. Later that year, Neff and Byrdwell (2) reported the HPLC/APCI-MS of soybean oil. Tabulated results showed that TAG having more than four sites of unsaturation had the protonated molecule as the base peak, and TAG with two or fewer sites of unsaturation had a DAG fragment ion as the base peak. TAG with either three or four sites of unsaturation could have either the protonated molecule or a DAG fragment ion as the base peak, depending on how the unsaturation was distributed. Byrdwell et al. (3-5) later reported how these fragmentation characteristics affected the quantitative analysis of TAG and demonstrated how response factors could be calculated. The tendency of TAG to yield simple mass spectra with structurally diagnostic fragment ions led APCI-MS to be recognized for its utility in TAG analysis. The number of publications describing HPLC/APCI-MS for TAG analysis is growing rapidly. Many of these applications have been described elsewhere in our reviews on APCI-MS for lipid analysis (6,7). The reports cited in this volume demonstrate that HPLC/APCI-MS is a valuable tool for TAG analysis.
