BINDING OF SULFAMETHOXAZOLE TO HUMAN SERUM-ALBUMIN STUDIED BY A COMBINED TECHNIQUE OF MICRODIALYSIS WITH LIQUID-CHROMATOGRAPHY

A new, simple and fast method for the determination of the interaction parameters of sulfamethoxazole (SMZ) to human serum albumin (HSA) has been developed by utilizing a microdialysis sampling technique combin ed with liquid chromatography (LC). The drug and protein were mixed in different molar ratios in 0.067 M potassium phosphate buffer, pH 7.4, and incubated at 37 degrees C in a water-bath. Then the microdialysis probe was put in the SMZ-HSA solution and sampled at a perfusion rate of 1 mu l/min. The concentration of SMZ in the microdialysates was de termined by reversed-phase liquid chromatography. The recovery (R) was also determined in vitro under similar conditions, R is about 11.8% w ith an RSD of about 2.3%. The association constant (K) and the number of the binding sites on one HSA molecule (n) are calculated by three e quations, the values of nK estimated by three methods are quite simila r. The values found for K and n are 3.24x10(3) M-1 and 3.04, respectiv ely.