POLYGLYCEROL FATTY ACID ESTERS
The analysis of polyglycerol fatty acid esters (or polyglyceryl esters) was tried in various ways using thin-layer chromatography ( Neissner R, Fette Seifen Anstrichm 1980, 82, 93), gas (Sahasrabudhe MR, JAOCS 1967, 44,376), or high-performance liquid (Garti N et al., J Liq Chromatogr 1981, 4, 1173). These techniques are only qualitative and provide poor resolution of the different esters.
De Meulenaer et al. (J Chromatogr A 2000, 896, 239) presented a convenient method for the complete analysis of the polyglycerol fatty acid esters up to the diesters of triglycerol.
The proposed method is based on a prefractionation of complex mixtures on a silicagel column followed by analysis of the eluted fractions by GLC.
The silicagel column enables the separation of three fractions, eluted with chloroform–acetone (96:4, v/v), containing the diesters of diglycerol, the cyclic esters of diglycerol, and the diesters of triglycerol. Monoesters of diglycerol are eluted with acetone, while methanol elution allowed a final elution of monoesters of tri- and tetraglycerol. The purity of the fractions may be verified by TLC on silicagel plates and chloroform–acetone (96:4, v/v) as eluent. A quantitative analysis of the species contained in each fraction after derivatization was obtained by GLC using a polar column. Confirmation of their identity was achieved by LC-MS analysis.
Thus, a simplified fractionation scheme was proposed in order to allow a reliable LC–GC combined analysis of polyglycerol fatty acid esters up to the diesters of triglycerol.