Flow injection on-line photochemical reaction coupled to spectrofluorimetry for the determination of thiamine in pharmaceuticals and serum

Abstract

The photochemical reaction of thiamine was studied with a photochemical reactor made by coiling a knotted PTFE reactor around a low-pressure mercury lamp. Acetone, which was previously reported to be a sensitizer for the photochemical reaction that took place in situ in a flow-through cell, severely depressed the fluorescence signal of the photochemical reaction that took place on-line in the knotted PTFE reactor when sodium sulfite was involved in the photochemical reaction. Experiments revealed that the effect of acetone on the photochemical reaction was dependent on the intensity of the irradiation that was used to induce the photochemical reaction, and that acetone might impair the photochemically induced fluorescence if strong UV irradiation was applied to induce the photochemical reaction and sodium sulfite was used to enhance the fluorescence signal. Based on these observations, a flow injection on-line photochemical–spectrofluorimetric method for the determination of thiamine was developed without using acetone. With the proposed method, a detection limit of 0.11 µg l^–1 thiamine, a relative standard deviation of 0.36% for 11 determinations of 1 mg l^–1 thiamine and a sampling frequency of 100 h^–1 were achieved. The developed method was successfully applied to the determination of the thiamine content in various pharmaceutical preparations and serum.