A multicommuted flow analysis method for the spectrophotometric determination of amoxicillin in pharmaceutical formulations is reported. The proposed method is based on the reaction of diazotised o-nitroaniline with amoxicillin in an alkaline medium, producing a yellow compound that was monitored at 435 nm. The main features of the method were: a linear relationship with amoxicillin concentration ranging from 25 to 400 mg L-1; a detection limit of 5.1 mg L-1; an analytical throughput of 50 determinations per hour; and a relative standard deviation lower than 3.9% for a typical amoxicillin sample with concentration of 100 mg L-1 (n = 10). To verify the accuracy of the method, samples were also analyzed employing an independent method, and applying the paired t-test to the results no significant difference at the 95% confidence level was observed.
amoxicillin; multicommuted flow analysis; photometry; diazo coupling reaction; o-nitroaniline
