Ion Selective Electrodes for Potentiometric Determination of Tizanidine in Its Pharmaceutical Dosage Form

The development and general performance of the PVC membrane sensors for tizanidine HCl (Tz) are evaluated. The method included two ion -pair complexes of tizanidine cation and tetraphenyl borate (TPB) or phosphotungstate (PT) as electroactive sensing materials. The characteristic performance of the two sensors was evaluated according to the IUPAC guidelines, which revealed that both sensors show fast, stable and near-Nernstian response over a relatively wide tizanidine concentration range with detection limits of 3 x 10-6 and 2 x 10-6 M for Tz-TPB (sensor 1), and Tz-PT (sensor 2), respectively over a wide pH range of 3.0 - 7.0. The sensors show good selectivity for tizanidine as compared with different ions. The direct determinations of Tz show an average recovery 97.5 and 98.0% and a mean relative standard deviation of 1 . 7 a n d 1 . 5% at 500.0 μg/ml for sensor 1 and sensor 2, respectively. The investigated sensors have been applied for direct determination of Tz in some pharmaceutical preparations. The proposed methods were applied for the determination of Tz in tablets, and the results are compared with those obtained by spectrophotometric method.