The electrochemical response characteristics of poly(vinyl)chloride (PVC) based membrane sensors for determination of tetramisole hydrochloride (TmCl) is described. The membranes of these electrodes consist of tetramisoletetraphenyl borate (Tm-TPB), chlorophenyl borate (Tm-ClPB), and phosphotungstate (Tm3-PT) ion associations dispersed in a PVC matrix with dibutylpthalate as a plasticizer. The electrodes were fully characterized in terms of composition, life span, usable pH range, and working concentration range and ionic strength. The electrodes showed Nernstian response over the concentration ranges of 7.4 x 10-7 to 1.0x10-2 M, 1.7 x 10-6 to 1.0x10-2 M, and 5.6 x 10-6 to 1.0x10-2 M TmCl, respectively, and were applied to the potentiometric determination of tetramisole ion in pure solutions and pharmaceutical preparations. The potentiometric determination was also used in the determination of tetramisole in pharmaceutical preparations in four batches of different expiration dates. The electrodes exhibited good selectivity for TmCl with respect to a large number of excipients such as inorganic cations, organic cations, amino acids, and sugars. The solubility product of the ion-pair and the formation constant of the precipitation reaction leading to the ion-pair formation were determined conductometrically. The new potentiometric method offers the advantages of high-throughput determination, simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions.
Keywords: Ion-selective electrode, potentiometry, pharmaceutical analysis, ion-pairing, tetramisole hydrochloride, statistical analysis, conductometry, solubility product
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