Kinetic fluorescence as an analytical technique to quantify non-fluorescent species is described, and the technique is applied to the determination of thiamine (vitamin B1) in solution. Fluorescence intensity is monitored as thiamine converts to fluorescent thiochrome, and a relationship is established between the rate of increase of intensity and the concentration of thiamine. The technique is shown to have good sensitivity and selectivity.
Luminescent substances are quantified readily by sensitive fluorescence and phosphorescence techniques. Kinetic fluorescent methods extend the sensitivity advantage of fluorescence analysis to non-fluorescing samples that can be converted chemically to fluorescent species. For example, the technique can be used in the analysis of pharmaceutical preparations to quantify non-fluorescing thiamine (vitamin B1), which oxidizes to fluorescent thiochrome.
Kinetic fluorescence is borrowed from the methodology of scientists who study reaction rates of chemical, biochemical, or physical transformations. In these studies, the increase or decrease in fluorescence intensity (corresponding to formation or degradation of a fluorescent species) is monitored during a reaction in order to understand the reaction mechanism. As an analytical method, kinetic fluorescence establishes a relationship between the change in fluorescence intensity during a reaction and the concentration of the non-fluorescing reactant. The precision and specificity offered by kinetic fluorescence make it possible to quantify individual components in a multicomponent solution without resorting to complicated separation procedures.
To illustrate the applicability of kinetic fluorescence for analytical work, we describe herein a reaction-rate method for the determination of thiamine, an experiment in commercial multiple-vita