Penicillin-enhanced chemiluminescence of the luminol-H2O2-Co2+ system

The luminol-H2O2-Co2+ system has been widely used in chemical and biological analysis. We report here an investigation of the observation that penicillins have the ability to prolong and enhance the intensity of chemiluminescence from luminol. The basis of this phenomenon appears, as revealed by difference spectroscopy, to be the formation of a complex between the beta-lactam and the superoxide ion. The latter is the oxidizing species responsible for the oxidation of luminol in alkaline solution and has a mean lifetime, in solution, of milliseconds. The stabilization of the superoxide ion by penicillin complexation extends the effective lifetime of the superoxide ion by a few orders of magnitude and thereby allows for more efficient oxidation of the beta-lactam. Several penicillins were determined by their enhancement of luminol chemiluminescence. A detection limit of 100 ng mL was obtained for penicillin G with a less-than-ideal detection system.