Direct potentiometry and potentiotitrimetry of warfarin and ibuprofen in pharmaceutical preparations using PVC ferroin-based membrane sensors

Sensitive and fast-responding potentiometric sensors are described for the determination of warfarin and ibuprofen. They consist of PVC matrix membranes containing the drug-ferroin ion-association complexes as electroactive materials and dioctylphthalate as a solvent mediator. Linear dynamic response range between 1 x 10(-2) and 2 x 10(-5) M with Nernstian slopes of 59-60 mV/decade concentration and a detection limit of 0.8-1.3 mu g/ml are obtained. A. wide range of organic anions and drug excipients do not interfere. Titration of the drugs with a standard ferroin solution using either a drug-ferroin or ferroin-TPB PVC sensor in conjunction with an Ag-AgCl reference electrode displays S-shaped titration curves with sharp potential breaks at stoichiometric 1:2 (ferroin:dreg) reaction, Differential titration curves with well-defined peaks at the equivalence points are obtained using drug-ferroin/ferroin-TPB PVC membrane sensors. Direct potentiometry and potentiotitrimetry of warfarin and ibuprofen in various pharmaceutical preparations are presented and compared. Several advantages over the pharmacopoeial methods and other techniques in current use are offered by the proposed technique.