Abstract
In neutral medium, rifamycin antibiotics such as rifapentin (RFPT), rifampicin (RFP), rifandin (RFD) and rifamycin SV (RFSV) can bind with human serum albumin (HSA) and bovine serum albumin (BSA) to form complexes, resulting in the quenching of the intrinsic fluorescence (Ξ»~ex~/Ξ»~em~ = 285/355 nm) of the BSA and HSA. The quenching intensity (Ξ__F__) is directly proportional to the concentration of the rifamycin antibiotics. Therefore, a new analytical method was established to determine trace rifamycin antibiotics. The method had fairly high sensitivity and the detecting limits (3__Ο__) for RFPT, RFP, RFD and RFSV were 0.85, 0.98, 1.83, 1.89 ng/mL, respectively, for the HSA system and 0.76, 0.89, 1.55, 1.77 ng/mL, respectively, for the BSA system. All relative standard deviations (RSDs) were <3.8%. In this work, the characteristics of the fluorescence spectra were studied and the optimum reaction conditions and influencing factors were investigated. The influence of coexisting substances was tested and the results showed that the method had good selectivity and could be applied to determine trace rifamycin antibiotics in medicine capsules and urine samples. Taking the RFSVβserum albumin system as an example, the reaction mechanisms, such as binding constants, binding sites, binding distance and the type of fluorescence quenching, were investigated. Copyright Β© 2007 John Wiley & Sons, Ltd.