Response enhancement for the evaporative light scattering detection for the analysis of lipid classes and molecular species

The response of an evaporative light scattering detector for the analysis o f lipids is enhanced by the addition of triethylamine and an equimolar amou nt of formic acid to the mobile phase. The generality of this phenomenon wa s demonstrated for different chromatographic techniques and various classes of lipids: for non-aqueous liquid chromatography with a porous graphitic c arbon packing for wax esters, fatty acid methyl esters and ceramides; for n ormal phase liquid chromatography with a PVA-Sil((R)) stationary phase for cerebrosides, digalactosyl-diacylglycerols and phospholipids; and for subcr itical chromatography with an octadecyl grafted silica column for ceramides . The response enhancement was quantified with cholesterol in non-aqueous l iquid chromatography with a porous graphitic carbon packing. This response modifier enhances the detection response of lipids and does not significant ly alter retention excepts in case of zwitterionic phospholipids.