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

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Abstract
Vitamin K1 (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 K1. A photochemical-fluorimetric method is proposed for measurement of original vitamin K1 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 K1 than in previously reported analytical methods. The specific data obtained depends greatly on the quality of the solvent and excitation-photolysis source used.