Spectrofluorimetric Determination of Vitamin K3 by a Solid-phase Zinc Reactor Immobilized in a Flow Injection Assembly

Abstract

The spectrofluorimetric determination of vitamin K ₃ (menadione) using a flow injection (FI) assembly provided with a solid-phase reactor with immobilized zinc is described. The naphthohydroquinone was produced by means of two coupled steps in the FI system: hydrolysis of the sodium sulfite derivative of the menadione in a basic medium and reduction of the generated menadione in the zinc reactor in an acidic medium. The fluorescent product was monitored spectrofluorimetrically (λ _ex 325 nm; λ _em 425 nm). The calibration graph was linear over the range 0.1–18 µg ml ^{- 1} with a reproducibility of 1.6%; the limit of detection was 0.005 µg ml ^{- 1} and the sample throughput was 70 h ^{- 1} . The influence of foreign compounds was studied and the procedure was applied to the determination of vitamin K ₃ in three different pharmaceutical formulations.