Sensitive chemiluminescence determination of thirteen cephalosporin antibiotics with luminol-copper(II) reaction.

A new chemiluminescence reaction, the luminol-Cu(2+) reaction, was investigated for the determination of thirteen (13) cephalosporin antibiotics, namely cefalexin, cefadroxil, cefradine, cefazolin sodium, cefaclor, cefuroxime axetil, cefotaxime sodium, cefoperazone sodium, ceftriaxone sodium, ceftazidime, cefetamet pivoxil hydrochloride, cefixime, and cefpodoxime. It was found that, without adding any special oxidant, strong chemiluminescent (CL) signal could be produced from the reaction of the alkaline luminol with the above-mentioned antibiotics in the presence of Cu(2+). The experimental conditions for the reaction were carefully optimized with flow-injection mode. The detection limits are 0.3 ng/mL cefalexin, 3 ng/mL cefadroxil, 0.3 ng/mL cefradine, 0.02 μg/mL cefazolin sodium, 0.8 ng/mL cefaclor, 0.02 μg/mL cefuroxime axetil, 5 ng/mL cefotaxime sodium, 0.02 μg/mL cefoperazone sodium, 0.8 ng/mL ceftriaxone sodium, 1 ng/mL ceftazidime, 0.08 ng/mL cefetamet pivoxil hydrochloride, 0.8 ng/mL cefixime, and 2 ng/mL cefpodoxime. The proposed method was validated by direct application to commercial formulations and spiked milk samples containing cefradine. A possible reaction mechanism is also discussed.