USE OF 1-ANILINO-8-NAPTHALENESULPHONATE AS AN ION PROBE FOR THE POTENTIOMETRIC STUDY OF THE BINDING OF SULFONAMIDES TO BOVINE SERUM-ALBUMINAND PLASMA

The binding of sulphafurazole, sulphamethizole and sulphamethoxazole t o bovine serum albumin (BSA) and human plasma has been studied in-vitr o by potentiometry using an electrode selective for the ion probe 1-an ilino-8-napthalenesulphonate (ANS). The method requires two separate p otentiometric titrations of the binder solution with ANS in the absenc e and in the presence of sulphonamides. ANS displaced sulphonamides fr om the first-class of binding sites of both binders. The binding const ants for sulphonamide-BSA interactions were higher than those for sulp honamide-human plasma. The expansion of the least linear limit of the response curve of the electrode down to 10(-7) M in the presence of BS A was also demonstrated. The reverse reaction, i.e. the displacement o f the probe from the binding sites induced by the sulphonamides, was a lso explored. The proposed method is suitable for studying competitive binding interactions in biological specimens.