FLOW INJECTION METHODS FOR THE DETERMINATION OF Α-TOCOPHEROL WITH SPECTROPHOTOMETRIC DETECTION

Abstract

The present paper describes flow injection procedures for α-tocopherol determination in pharmaceuticals and infant milk powder based on spectrophotometric detection. These two procedures are based on the reduction of iron(III) to iron(II) and of Mo(VI) to Mo(V) by α-­tocopherol and subsequent formation of iron(II)-o-phenanthroline, and phosphomolybdenum complexes which were monitored at 510 and 695 nm respectively. Calibration graphs were linear over the concentration range of 0.21–43 µg/mL for iron(III) and 0.25–10 µg/mL for Mo(VI) reduction methods respectively. The limits of detection (3s) of 0.05 and 0.1 µg/mL with sample throughput of 30 and 50/h respectively were obtained. The relative standard deviations of 1.2– 3.8% (n = 4) was achieved in the concentration range studied. The developed methods were applied to pharmaceuticals and infant milk powders and the results obtained were compared with official method and no significant difference between these methods was observed at 95% confidence level.