Flow-injection stopped-flow spectrofluorimetric kinetic determination of paracetamol based on its oxidation reaction by hexacyanoferrate(III)

A simple and economic system, easily adaptable to any spectrophotometer or spectrofluorimeter in order to carry out kinetic measurements by means of the FIA stopped-flow technique, is described. The system consists of a 12 bit analogical digital converter that receives analogue signals at −10 and +10 V and enables the electrical supply to the peristaltic pump to be interrupted. A stopped-flow method with fluorescence detection for the determination of paracetamol (N-acetyl-p-aminophenol). based on its oxidation with hexacyanoferrate(III), is described. A kinetic study of the reaction is developed measuring the initial rate of change of the fluorescence intensity of the oxidized product formed at 241 and 426 nm excitation and emission wavelengths, respectively. The calibration graph is linear in the range of concentrations 0.5–15.0 μg/ml. The relative standard deviation is 2.5%. The method was applied to authentic pharmaceutical preparations and was found to be satisfactory. The effect of same possible interferences has been studied.