Cathodic stripping voltammetric determination of ceftazidime with reactive accumulation at a poly-l-lysine modified hanging mercury drop electrode Original Research Article

Ceftazidime is hydrolysed only slowly at pH 10 at room temperature. This is indicated by a small cathodic stripping voltammetric peak obtained at pH 10 at a hanging mercury drop electrode at about −0.6 V which corresponds to the reduction of the hydrolysis product. This peak is enhanced more than tenfold by the addition of poly-l-lysine (PLL) to the electrolyte solution. The optimum accumulation potential is between 0 and −0.1 V: the size of the peak decreases steadily, however, as the accumulation potential is moved to more negative potentials and is about one-sixth the size for accumulation at −0.4 V. Existing knowledge of the organic chemistry of cephalosporins indicates that the accumulation must involve an aminolysis reaction of the unprotonated PLL with the β-lactam ring of the ceftazidime. The limit of detection (3σ) in standard solutions was calculated to be 1 × 10−10 mol l−1. The detection limit in buffer solution containing 1% of urine was calculated to be 5 × 10−9 mol l−1, i.e. 5 × 10−6 mol l−1 in the urine.