Preparation and characterization of in situ carbon paste and screen-printed potentiometric sensors for determination of econazole nitrate: surface analysis using SEM and EDX

The construction and performance characteristics of new sensitive and selective in situ carbon paste (ICPE) and screen-printed (ISPE) potentiometric sensors modified with ion-pairing agents such as phosphotungstic acid, sodium tetraphenylborate, phosphomolybdic acid and ammonium reineckate for determination of econazole nitrate (ECN) have been developed. The reaction mechanism between ECN and ion-pairing agents at the electrode surface was studied through scanning electron microscope and energy-dispersive X-ray analysis. The electrodes under investigation showed potentiometric response for ECN in the concentration range from 1.0 x 10(-6) to 5.0 x 10(-3) mol L-1 and from 1.0 x 10(-6) to 1.0 x 10(-2) mol L-1 for ISPE (electrode I) and ICPE (electrode II) potentiometric sensors, respectively, at 25 A degrees C. The electrode response was pH independent in the range 2.5-7.5 and 2.5-6.5 for electrodes I and II, respectively. These sensors have Nernstian slope values of 59.4 +/- 0.2 and 59.10 +/- 0.2 mV decade(-1) with detection limit of 1.0 x 10(-6) mol L-1 for electrodes I and II, respectively. The electrodes showed fast response time of 4 and 9 s for electrodes I and II, respectively. The ISPE (electrode I) showed lifetime of 28 days, and this was considered as advantage over ICPE (electrode II). Selectivity for ECN with respect to a number of interfering materials was also investigated. The proposed electrodes were applied for determination of ECN in pure and pharmaceutical formulation using calibration, potentiometric titration and standard addition methods. The results showed good agreement with those obtained using official method. The t and F values indicated no significant difference between the suggested and reported methods. Method validation parameters were optimized according to ICH recommendations.