DETERMINATION OF DISSOCIATION CONSTANT (Ka) OF CAPTOPRIL AND NIMESULIDE - ANALYTICAL CHEMISTRY EXPERIMENTS FOR UNDERGRADUATE PHARMACY

DETERMINATION OF DISSOCIATION CONSTANT (K-a) OF CAPTOPRIL AND NIMESULIDE - ANALYTICAL CHEMISTRY EXPERIMENTS FOR UNDERGRADUATE PHARMACY. This paper presents the determination of the dissociation constant (K-a) of captopril and nimesulide as contextualized experiments to teach chemical concepts to students of Pharmacy. Captopril is an antihypertensive drug, which presents high water-solubility and weak acid properties. The pK(a) of carboxylic acid group of captopril is 3.7. Nimesulide is a non-steroidal anti-inflammatory drug sparingly soluble in water. It is weakly acidic (pK(a) approximate to 6.5) because of its methanesulfonamide functional group. The pKa of captopril was determined by potentiometric titration with NaOH 2.0 x 10(-2) moL L-1. The pK(a) of nimesulide was determined by using spectrophotometry and photometric titration. The experimental values of pK(a) of both drugs are in very good agreement with those from literature.