Kinetic fluorimetric determination of aminoglycoside antibiotics by use of OPA and N-acetylcysteine as reagents

Abstract

The use of N-acetylcysteine for the kinetic fluorimetric determination of aminoglycoside antibiotics by reaction with o-phthaldialdehyde (OPA) in a basic medium was studied. The results obtained show that this thiol is a satisfactory substitute for 2-mercaptoethanol as reagent for the formation of isoindole derivatives of compounds containing primary amines such as amikacin, kanamicin and tobramycin, while avoiding its unpleasant odour. Due to the fast formation of the fluorescent derivatives the stopped-flow mixing technique must be used in order to acquire analytical kinetic data. This allowed the development of a kinetic automatic method for the determination of amikacin applicable to routine analyses. The initial rate was measured within ca. 5 s and the calibration graph was linear over the range 0.05–30.0 μg mL⁻¹. The method was satisfactorily applied to the determination of amikacin in two pharmaceutical preparations with a mean recovery of 98.7%.