Spectrofluorimetric determination of vitamin K3

Abstract

A spectrofluorimetric method for determining vitamin K₃ (menadione) is described. Because this compound is not naturally fluorescent, a prior reduction of vitamin K₃ was effected by using SnCl₂ stabilized in glycerol to obtain the reduced fluorescent product (naphthohydroquinone). The fluorescence response (λ_ex = 334 nm; λ_em = 427 nm) was linear up to 180 µg l^–1 of vitamin K₃ with a detection limit of 0.62 µg l^–1 and a determination limit of 2.06 µg l^–1. The method was applied to commercial preparations with good results. The recoveries achieved in all cases varied between 104.4 and 98.92%. Vitamins such as folic acid, pyridoxamine and ascorbic acid did not interfere.