Determination of gentamicin sulfate by batch-injection amperometry after solid-phase extraction using a kanamycin-template imprinted polymer

Batch-injection analysis (BIA) with amperometric detection, using a boron-doped diamond (BDD) electrode, was developed for the determination of gentamicin sulfate (total components). System was operated at + 2000 mV with acetate buffer (1.0 x 10(-2) mol L-1; pH 4.40) as supporting electrolyte. Oxidation of analyte occurred right after the analyte solution plug (60 mu L) reaches the surface of the electrode. Solid-phase extraction, using a cartridge packed with a kanamycin-imprinted polymer, was used to improve selectivity in determinations. The instrumental precision was < 3% and the instrumental limit of quantification was 2.7 x 10(-6) mol L-1 (1.5 mu g mL(-1)). The analytical frequency was 90 measurements h(-1) and no memory effect was observed between sequential measurements. The performance of the proposed method was compared with that obtained by using HPLC with molecular absorption spectrophotometric detection (after chemical derivatization of the analyte with o-phthalaldehyde). The method was applied in injectable pharmaceutical formulations with recoveries close to 100%.