DETERMINATION OF VITAMIN-E IN HUMAN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The use of selective protein precipitation to enhance the recovery of vitamin E from plasma, by minimising binding with very-low-density lip oproteins, is reported. The procedure employed treatment of plasma wit h magnesium chloride and tungstate, followed by methanol protein preci pitation. Separation of vitamin E was performed using reversed-phase h igh-performance liquid chromatography of the methanol extracts with su bsequent UV detection of the compound. Using this technique the proced ure was observed to be specific for vitamin E and linear over the rang e 1.0 to 40.0 mu g/ml. The within-run imprecision (C.V.) at three diff erent supplemented plasma vitamin E concentrations of 5.0, 10.0 and 20 .0 mu g/ml was 4.51, 3.33 and 2.58%, respectively, and the between-run imprecision (C.V.) estimated to be 5.19, 3.69 and 3.67%, respectively . With the same supplemented plasma vitamin E concentrations, the over all accuracy (bias) of the procedure, using an albumin matrix for cali bration, was estimated to be 6.0, -5.0 and -3.5%, respectively, and th e recovery of vitamin E from six different spiked plasma samples estim ated to be 98.2 +/- 2.6%.