A simple procedure to perform for the determination of amoxicillin is presented, based on reaction with 1-[(quinolin-6-ylcarbamoyl)oxy]pyrrolidine-2,5-dione (AccQ-Fluor) in borate buffer medium at pH of 7.4. The resulting amoxicillin+AccQ-Fluor derivative was determined by reversed-phase chromatography with combined fluorescence (λex=245 nm/λem=368 nm) and UV detection (λ=245 nm) for control. The calibration graph was linear (r=0.9992 ) over the range 5.0-30 μg/mL. The method was applied to the determination of amoxicillin in pharmaceutical formulations with acceptable precision and accuracy.
A simple and sensitive procedure for the determination of gentamicin is presented, based on reaction with o-phthaldialdehyde (OPA) in combination with N-acetylcysteine (NAC) in a basic medium. The use of N-acetylcysteine instead of liquid mercaptans for the formation of isoindole derivatives is a good solution for avoiding the unpleasant odour of thiol compounds. Determination of the resulting fluorescent derivatives was carried out by reversed-phase chromatography at λex=328 nm and λem=423. Stability of OPA/NAC/gentamicin-conjugate was improved by the addition of hydroxypropyl-β-cyclodextrin. The calibration graph was linear (r = 0.9997) over the range 0.4-12.8 μg mL-1. The precision (RSD%) of the method varied from 1.5 to 8.5. The method was satisfactorily applied to the determination of gentamicin in pharmaceutical preparations with a mean recovery of 100.02% for injections and 88.94% for drops.