Chemiluminescence determination of cefotaxime sodium with flow-injection analysis of cerium (IV)–rhodamine 6G system and its application to the binding study of cefotaxime sodium to protein with on-line microdialysis sampling

A simple, sensitive and rapid flow-injection chemiluminescence (CL) method has been developed for the determination of cefotaxime sodium based on the chemiluminescence reaction of cefotaxime sodium with ceric sulfate and rhodamine 6G in nitric acid solution. The concentration of cefotaxime sodium was proportional with the CL intensity in the range of 4 × 10−8 – 8 × 10−6 mol L−1. The detection limit (signal-to-noise ratio = 3) was 1 × 10−8 mol L−1. Coupled to the technique of on-line microdialysis sampling, this method was successfully applied to study cefotaxime sodium–protein interaction. The drug and protein were mixed in different molar ratios in Ringer's solution, pH 7.4, and incubated at 37 °C in a water bath. The microdialysis probe was utilized to sample the mixed solution at a perfusion rate of 5 μL min−1 and the recovery of cefotaxime sodium under experimental condition was 16.2%. The data obtained by the present Microdialysis-Flow Injection Analysis-CL method was analyzed with the Scatchard analysis and Klotz plot. The estimated association constant (K) and the number of the binding sites (n) on one of BSA molecule were 5.94 × 104 M−1 and 1.29 (Klotz equation), respectively.