Flow-injection analysis–electrochemical detection for the determination of drug–protein interactions with microdialysis sampling Original Research Article

Microdialysis sampling was combined with flow-injection analysis–electrochemical detection (FIA–ECD) to determine the interactions between streptomycini sulfas (STS) and bovine serum albumin (BSA). In the mobile phase of NaOH (pH=13), a Ni–Ti alloy electrode was used as working electrode. At this electrode good electrocatalytical oxidation of streptomycini sulfas occurs with a detection limit of 8.0×10−7 mol/l and a linear concentration range 1.0×10−6–1.0×10 3 mol/l at +500 mV (vs. Ag/AgCl). Microdialysis is an excellent complement to directly monitor chemical events in different organs in vivo. This method has been widely used for many fields. We applied microdialysis to determine the interactions of drug–protein. Streptomycini sulfas and BSA were mixed at different molar ratios and incubated at 37°C in a water-bath. The microdialysis probe was then used to sample the mixed STS–BSA solution at a perfusion rate of 1.0 μl/min. The concentration of unbound streptomycini sulfas in the microdialysate was determined by FIA–ECD. Relative recovery (R) of streptomycini sulfas, determined in vitro under similar conditions, was approximately 16.0% at 1.0 μl/min. The estimated association constant (K) and the number of the binding sites (n) on one molecule of BSA were 5.45×103 (mol/l)−1 and 1.21, respectively. The method provided a fast and simple technique for the study of drug–protein interactions.