Automated determination of alpha-tocopherol in food and feed. Part 2. Continuous flow technique.

The proposed determination of alpha-tocopherol is a continuous flow method with fluorometric detection. The only cleanup necessary is the usual saponification. A solution of the unsaponifiable matter in isooctane is automatically assayed. Isooctane is the carrier solvent and extractions are inserted between steps. These steps are selective reactions which render the method very specific. The natural homologs of alpha-tocopherol (alpha-T) do not interfere in the determination. A procedure for blank assays allows selective inhibition of alpha-T conversions and measurement of interfering fluorescence. The method is highly sensitive, which allows the determination of alpha-T in very dilute solutions. This in turn suppresses matrix effects and renders the results reliable. The time interval between 2 peaks is 6 min, washing included, and it is possible to carry out 50 determinations per day (sample preparation not included). The system is robust and maintenance is easy. Parallel determinations of foods and feeds have been carried out with a conventional thin layer chromatographic method.