High resolution separation of non-polar lipid classes by HPLC-ELSD using alumina as stationary phase

This study describes the performance and capacity of alumina as stationary phase in an HPLC-ELSD (evaporative light-scattering detecetion) method opti mized for the separation of the non-polar lipid classes hydrocarbons, wax e sters, sterol esters, triacylglycerols, and sterols, including quantitative determination of these lipid classes in natural samples. By using gradient elution and constant equilibration times between injections, highly reprod ucible separations of triacontane, stearyl oleate, and cholesterol oleate w ere accomplished with a binary mobile phase system. Phase A contained 0.5% tetrahydrofuran in hexane and phase B 20% isopropanol and 20% tetrahydrofur an in hexane, The same system was also used to determine the non-polar lipi d classes in a zooplankton sample, the major lipid class being wax esters, followed by triacylglycerols, sterol esters, sterols, and hydrocarbons. Sub stantial amounts of an unknown compound, possibly acylated glyceryl ethers, were also found. The equilibration time of alumina was relatively slow com pared to a polyvinyl alcohol stationary phase used earlier by the authors a nd calibration curves for different lipid classes were more uniform and lin ear with alumina.