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Eco-friendly solid-contact ion selective electrode was fabricated and optimized for the determination of flavoxate hydrochloride in presence of its main metabolite. The process is based on carbon screen printed electrode and polyvinyl chloride polymeric sensing membrane. The first optimization step involved the ionophore selection through screening various ionophores, where calix[4]arene showed the highest affinity towards flavoxate. The second step, a graphene nanocomposite interlayer was employed as the ion-to-electron transducer between the carbon electrode and the polymeric ion sensing membrane. The graphene layer decreased the potential drift down to < 500 μV/h and improved the electrode stability.

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Two sensitive and reproducible methods were developed and validated for the determination of ziprasidone (ZIP) in the presence of its degradation products in pure form and in pharmaceutical formulations. The fi rst method was based on reversed-phase high-performance liquid chromatography (HPLC), on a Lichrosorb RP C(18) column using water:acetonitrile:phosphoric acid (76:24:0.5 v/v/v) as the mobile phase at a fl ow rate of 1.5 mL min(-1) at ambient temperature. Quantification was achieved with UV detection at 229 nm over a concentration range of 10-500 micro g mL(-1) with mean percentage recovery of 99.71 +/- 0.55. The method retained its accuracy in presence of up to 90% of ZIP degradation products. The second method was based on TLC separation of ZIP from its degradation products followed by densitometric measurement of the intact drug spot at 247 nm. The separation was carried out on aluminium sheet of silica gel 60 F(254) using choloroform:methanol:glacial acetic acid (75:5:4.5 v/v/v) as the mobile phase, over a concentration range of 1-10 micro g per spot and mean percentage recovery of 99.26 +/- 0.39. Both methods were applied successfully to laboratory prepared mixtures and pharmaceutical capsules.

A new, simple and specific spectrophotometric method was developed and validated in accordance with ICH guidelines for the simultaneous estimation of Amlodipine (AML), Valsartan (VAL), and Hydrochlorothiazide (HCT) in their ternary mixture. In this method three techniques were used, namely, direct spectrophotometry, ratio subtraction, and isoabsorptive point. Amlodipine (AML) was first determined by direct spectrophotometry and then ratio subtraction was applied to remove the AML spectrum from the mixture spectrum. Hydrochlorothiazide (HCT) could then be determined directly without interference from Valsartan (VAL) which could be determined using the isoabsorptive point theory. The calibration curve is linear over the concentration ranges of 4–32, 4–44 and 6–20 μg/mL for AML, VAL, and HCT, respectively. This method was tested by analyzing synthetic mixtures of the above drugs and was successfully applied to commercial pharmaceutical preparation of the drugs, where the standard deviation is <2 in the assay of raw materials and tablets. The method was validated according to the ICH guidelines and accuracy, precision, repeatability, and robustness were found to be within the acceptable limits.