Determination of beta-lactam antibiotics in water by fluorescence quenching of mercurochrome, and application for simple investigation of potency.

The fluorescence quenching reaction between fluorescein mercury or halogeno-fluorescein mercury compounds (fl. Hg, 2,7- or 2,4-dichloro-fl.Hg, 3',4',5',6'-tetrachloro-fl.Hg, mercurochrome) and beta-lactam antibiotics (ampicillin (AB-PC) and cephalexin (CEX] was investigated, and mercurochrome was selected for the detection of beta-lactam antibiotics; the detection limit was about 0.8 micrograms/ml. A fluorimetric assay of beta-lactam antibiotics was established by measuring the fluorescence of mercurochrome and mercurochrome-beta-lactam antibiotics solutions in weakly basic media to determine the degree of fluorescence quenching. The maximum emission wavelength of mercurochrome solution was at 544 nm with excitation at 470 nm. The calibration graphs were linear over the ranges of about 0-6 micrograms/ml beta-lactam antibiotics penicillins (AB-PC, penicillin G, sulbenicillin, amoxicillin, cyclacillin, oxacillin, hetacillin and piperacillin) and cepham antibiotics (CEX, cefazolin, cephaloglycin, cephaloridine and cefpyramide), and the relative standard deviation was 2.7% for 1.4 micrograms/ml of AB-PC (n = 5). This fluorescence quenching reaction between mercurochrome and beta-lactam antibiotics was applied in a survey of decomposition and remaining potency of beta-lactam antibiotics.