Use of a stopped-flow/T-format spectrofluorimeter for simultaneous kinetic analyses

The potential of the joint use of a T-format spectrofluorimeter and the stopped-flow mixing technique in simultaneous kinetic determinations was studied. For this purpose, the direct resolution of a mixture of two analytes (neomycin and promethazine), by use of a condensation and an oxidation reaction that yield reaction products with similar maximum excitation wavelengths but different emission wavelengths was chosen. The determination was readily accomplished in a few seconds by simultaneously measuring the respective initial rates in the corresponding emission channels. Mixtures of neomycin and promethazine in ratios between 8:1 and 1:9 were thus satisfactorily resolved. The relative standard deviation was 1.0–1.8%. The proposed method was applied to the analysis of a commercially available pharmaceutical preparation, with a recovery of 99.3–102.0% for neomycin and 88.8–93.0% for promethazine.