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A highly selective and sensitive poly(vinyl chloride) membrane electrode, using 4-4 0 -Methylenediantipyrine as an ionophore, has been prepared and examined as a Ba 2þ -selective electrode. The influence of the anion excluder (sodium tetraphenyl borate, NaTPB) and the effect of the plasticizers dibutyl phthalate (DBP), nitrobenzene (NB), and benzyl acetate (BA) were studied. The best performance was obtained with the sensor having a membrane composition (w=w) of (MAP, 2.0%), (PVC, 30%), (NB, 66%), (NaTPB, 2.0%) with a wide working concentration range of 1.0 Â 10 À6 to 1.0 Â 10 À2 M between the pH values of 3.4 and 10.6. Furthermore, a Nernstian slope of 29.7 AE 0.3 mV= decade of activity was demonstrated with a response time of 15 s. The sensor could be used over a period of 2 months with no potential divergence, revealing a good selectivity for a broad variety of cations including alkali, alkaline earth, heavy and transition metals. Regarding the practical applicability of this sensing device, it was successfully applied for the Ba 2þ ions detection in a lithophone pigment and as an indicator electrode in the potentiometric titration of the under study cations.

A high sensitive electroanalytical-based sensor for determination of isoprenaline was fabricated by modification of carbon paste electrode (CPE) by NiO-Pt-Pd/CNTs composite as conductive mediator and n-hexyl-3-methylimidazolium hexafluoro phosphate (NHIHP) as conductive binder. The NHIHP/NiO-Pt-Pd/CNTs/CPE was improved the oxidation signal of isoprenaline ⁓3.47 times and reduced oxidation overpotential of drug ⁓180 mV. The pH investigation confirmed that redox behavior of isoprenaline is depended of pH solution with equal value of electron and proton in redox mechanism. The NHIHP/NiO-Pt-Pd/CNTs/CPE was successfully used for determination of isoprenaline in the concertation range 0.003-300 µM with detection limit 0.9 nM by square wave voltammetric method. The standard addition results showed powerful ability of NHIHP/NiO-Pt-Pd/CNTs/CPE as an electroanalytical tool for determination of isoprenaline in the pharmaceutical and clinical samples with recovery data 98.76-105.06%. KEYWORDSIsoprenaline; NiO-based composite; nanostructure sensor; modified carbon paste electrode; drug sensor.

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