Abstract
This work describes the construction and the evaluation of the general performance of new ampicilli-nate-selective electrodes based on manganese (III) tetraphenylporphyrin [Mn(III) TPP-Cl] as ionophore, incorporated in both PVC and sol-gel membranes and directly applied onto a conductive graphite/epoxy resin support. The units were constructed without inner reference solution adopting conventional configuration and in the case of PVC membrane the tubular configuration was also adopted. The good working characteristics of these electrodes, made possible its application to the determination of ampicillin in pharmaceuticals formulations, both in conventional batch analysis and in flow conditions, when the electrodes were coupled to a SIA system. In the last case the potentiometric sensors presented linear response towards ampicillin concentration between 5.0 × 10–4 and 5.0 × 10–2 mol?l–1 with slopes of –57.4 and –63.5 mV?dec–1 for the PVC and sol-gel membranes, respectively. The developed procedures enable mean relative standard deviations better than 3% for all the samples analysed. The obtained results do not statistically differ from those furnished by applying the HPLC reference method.
Highlights
This work describes the construction and the evaluation of the general performance of new ampicillinate-selective electrodes based on manganese (III) tetraphenylporphyrin [Mn(III) TPP-Cl] as ionophore, incorporated in both PVC and sol-gel membranes and directly applied onto a conductive graphite/epoxy resin support
Several PVC membranes based on metalloporphyrins have been used on the construction of selective electrodes for the potentiometric determination of organic species with pharmaceutical interest such us: salicylate [1], penicillin-G [2], valproate [3,4], ibuprofen [5], 2-hydroxybenzyhydroxamate [6] and diclofenac [7]
A valproate-selective electrode based on Mn (III)-tetraphenylporphyrin incorporated in a sol-gel matrix was previously reported [4]
Summary
Several PVC membranes based on metalloporphyrins have been used on the construction of selective electrodes for the potentiometric determination of organic species with pharmaceutical interest such us: salicylate [1], penicillin-G [2], valproate [3,4], ibuprofen [5], 2-hydroxybenzyhydroxamate [6] and diclofenac [7]. A valproate-selective electrode based on Mn (III)-tetraphenylporphyrin incorporated in a sol-gel matrix was previously reported [4] Some of these sol-gel sensor membranes were used as potentiometric detectors in FIA [11] and SIA [4] systems. In the case of the sol-gel membrane electrodes the 1.0 × 10–2 morpholinoethanesulfonic acid solution was used for the ionic strength and pH adjustment, as carrier solution and for filling up the outer chamber of the double junction reference electrode Both ISA/ carrier solutions contained 1.0 × 10–8 mol·l–1 sodium ampicillin for the rapid reestablishment of the potentiometric baseline. All solutions were prepared with distilled and deionized water with conductivity less than 0.1 μS·cm–1, and analytical grade reagents were used without any additional purification
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