Novel ibuprofen potentiometric membrane sensors based on tetraphenylporphyrinato indium(III)

Two novel potentiometric membrane sensors responsive to the ibuprofen drug have been developed. These incorporate poly(vinyl chloride) and polyurethane matrix membranes containing 5,10,15,20-tetraphenylporphrinato (TPP) indium(III) ionophore plasticized with dibutylsebacate. The sensors show a near-Nernstian response with anionic slopes of -53 and -55 mV decade(-1), over the concentration range of 4.2 x 10(-6) - 1.0 x 10(-2) and 3.3 x 10(-6) - 1.0 x 10(-2) M ibuprofen within pH ranges of 4 - 9 and 5 - 9 for PVC and PU matrix membranes, respectively. A sensor based on a polyurethane membrane displays a lower detection limit and a wider linear working range, and a sensor based on a PVC membrane exhibits a better overall selectivity, especially in the presence of lipophilic organic anions. Both sensors are used for the quantification and quality-control assessment of ibuprofen in pharmaceutical preparations. The average recoveries are 99.1+/-0.3\% and 99.3+/-0.3\% for TPP In(Ill)-PVC and TPP In(Ill)-PU based membrane sensors, respectively. High selectivities towards ibuprofen in the presence of many anions, drug excipients and diluents are offered by both sensors, which exhibit a non-Hofmeister selectivity pattern.