Analysis of tocopherols in margarine by on‐line 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 an on‐line HPLC–HRGC coupling method, which allows us to simplify the preparation of the analytical sample. The sample of margarine is solubilized in hexane in an ultrasonic bath in the dark; the filtered solution is then injected into the liquid chromatograph using a normal phase microbore column eluted with hexane–isopropanol 99.8:0.2. The α‐tocopherol, which is eluted with some wax esters, is transferred on‐line to the gas chromatograph, using a loop‐type interface with the concurrent eluent evaporation and solvent vapor exit, thus it is separated from interfering compounds and determined using an Alltech RSL 300 column (22 m × 0.25 μm i.d., 0.2 μm film thickness). The β, γ, and δ–tocopherols are determined in the same LC run, using fluorimetric detection. The analysis was carried out in 50 min.