Characteristics of new composite- and classical potentiometric sensors for the determination of pioglitazone in some pharmaceutical formulations

The construction and electrochemical response characteristics of poly(vinyl chloride) membrane sensors for pioglitazone HCl (PG) are described. The sensing membranes incorporate ion association complexes of pioglitazone cation and sodium tetraphenylborate (NaTPB) (sensor 1) or phosphomolybdic acid (PMA) (sensor 2) or phosphotungstic acid (PTA) (sensor 3) as electroactive materials. The sensors display a fast, stable and near-Nernstian response over a relative wide pioglitazone concentration range (1 × 10−2 to 10−6 M), with cationic slopes of 55.0 ± 0.5, 58.0 ± 0.5 and 53.0 ± 0.5 mV per concentration decade over a pH range of 1.0–5.0. The sensors show good discrimination of pioglitazone from several inorganic and organic compounds. The direct determination of 2.5–3900.0 μg/ml of pioglitazone show an average recovery of 98.5, 99.0 and 98.4% and a mean relative standard deviation of 1.6, 1.5 and 1.7% at 100.0 μg/ml for sensors 1, 2 and 3, respectively. The proposed sensors have been applied for direct determination of pioglitazone in some pharmaceutical preparations. The results obtained by determination of pioglitazone in tablets using the proposed sensors are comparable favorably with those obtained using the HPLC method. The sensors have been used as indicator electrodes for potentiometric titration of pioglitazone.