A Quantitative Photochemical-Fluorimetric Method for Measurement of Nonfluorescent Vitamin K₁

Abstract

Vitamin K 1 (2-methyl-3-phytyl-1,4-naphthoquinone) is not naturally fluorescent, but yields a fluorescent photochemical product upon ultraviolet irradiation. Among several solvents, dioxane was found to be the most suitable for the determination of vitamin K 1 . A photochemical-fluorimetric method is proposed for measurement of original vitamin K 1 concentration using two different readout methods: (1) digital integration of the fluorescence increase due to the photoproduct at 431 nm; and (2) analog recording of photoproduct fluorescence as a function of irradiation time. The two methods gave limits of detection of 5 ppb, with a better precision for the digital procedure. Limits of detection and speed of analysis are shown to be more satisfactory for the determination of vitamin K 1 than in previously reported analytical methods. The specific data obtained depends greatly on the quality of the solvent and excitation-photolysis source used.