ANALYSIS OF TOCOPHEROLS IN MARGARINE BY ONLINE HPLC-HRGC COUPLING

Tocopherol analysis in margarine is usually carried out by HPLC after saponification of the sample and extraction of the vitamin compounds; these steps consume both time and solvents. In this paper we propose a n on-line HPLC-HRGC coupling method, which allows us to simplify the p reparation of the analytical sample. The sample of margarine is solubi lized in hexane in an ultrasonic bath in the dark; the filtered soluti on is then injected into the liquid chromatograph using a normal phase microbore column eluted with hexane-isopropanol 99.8:0.2. The alpha-t ocopherol, which is eluted with some wax esters, is transferred on-lin e to the gas chromatograph, using a loop-type interface with the concu rrent eluent evaporation and solvent vapor exit, thus it is separated from interfering compounds and determined using an Alltech RSL 300 col umn (22 m x 0.25 mum i.d., 0.2 mum film thickness). The beta, gamma, a nd delta-tocopherols are determined in the same LC run, using fluorime tric detection. The analysis was carried out in 50 min.