Alkaline saponification results in decomposition of tocopherols in milk and ovine blood plasma

Alkaline saponification of entire sample matrixes for quantification of α-, γ-, δ-tocopherols (α-T, γ-T, δ-T) and α-tocopherol acetate (α-TAc) was examined. High-performance liquid chromatography was used to measure α-T, γ-T, δ-T and α-TAc in tocopherol standard solutions, milk and ovine blood plasma. Saponification in the presence of vitamin C decreases the concentration of tocopherols, especially α-T and γ-T. The poor recovery of tocopherols is due to the decomposition of tocopherols in saponified standard solutions, milk or plasma. Saponification of samples in the presence of 2,[6]-ditertbutyl-p-cresol or flushed only with a stream of Ar resulted in a major decrease in the concentrations of α-T, γ-T, δ-T and α-TAc in comparison with saponification in the presence of vitamin C.