Flow-injection solvent extraction without phase separation: Fluorimetric determination of thiamine by the thiochrome method

Abstract

Two modes of liquid–liquid extraction in flow-injection systems were compared and applied to the fluorimetric determination of thiamine (Vitamin B 1). The first included phase segmentation, but fluorescence was measured without phase separation. In this mode, thiamine was detected at concentrations higher than 8 μg/l with a linear application range of 30–2000 μg/l, an R.S.D. of 1.9% (150 μg/l, n = 10) and a sampling frequency of 60/h. In the second mode, a single segment of organic solution was injected into the aqueous stream and fluorescence was also measured without phase separation. Using this mode, concentrations of thiamine higher than 1 μg/l were detected, with a linear application range between 5 and 280 μg/l, an R.S.D. of 2.4% (150 μg/l, n = 10) and a sampling frequency of 60/h. The two forms were applied to the analysis of thiamine in pharmaceuticals.