Characterization of complex mixtures of polyglycerol fatty acid esters using temperature and solvent gradients in packed capillary LC

摘要

A highly complex sample of polyglycerol fatty acid esters has been characterized using both temperature gradient and solvent gradient reversed-phase packed capillary LC coupled to ELSO and ESI-TOF-MS. The techniques showed fairly similar performance in terms of selectivity and efficiency, providing a nice separation of not only the polyglycerol mono-, di-, tri- and tetra-fatty acid esters, but also the non-reacted polyglycerols. The different groups were identified by coupling the packed capillary LC system to a TOF-MS using an electrospray interface, although the identification of the latest eluting groups in the temperature gradient separation was hampered due to significant column bleeding at elevated column temperatures. By calculating the peak areas in the ELSD chromatograms, the PGE sample was estimated to contain 20.2 ± 0.4 and 22.6 ± 0.5% non-reacted polyglycerols, 44.4 ± 1.9 and 34.1 ± 1.4% mono-fatty acid esters, 26.2 ± 1.5 and 27.9 ± 1.7% di-fatty acid esters, 7.7 ± 0.7 and 12.6 ± 1.0% tri-fatty acid esters, and 1.4 ± 0.2 and 2.8 ± 0.3% tetra-fatty acid esters in temperature and solvent gradient mode (n = 3), respectively. The intra-day precision of the retention times was 0.5-1.4% (n = 3) in the temperature gradient mode, while it was 0.3-1.7% (n = 3) in the solvent gradient mode.