Abstract Two carbon paste electrodes for oxymetazoline hydrochloride were constructed based on ion pair complexes of this drug, with sodium tetraphenylborate (NaTPB) or ammonium reineckate, using dibutyl phthalate and dioctyl phthalate as solvent mediators, respectively. The developed electrodes displayed a fast, stable response over the concentration range from 3.98x10-5 to 1x10-2 M oxymetazoline hydrochloride, with a near-nernstian slope of 59.0, 58.2 mV of concentration decade-1 and a limit of detection (LOD) of 3.31x10-5 and 3.72x10-5 M, in the oxymetazoline-tetraphenylborate and oxymetazoline-reineckate cases, respectively. The developed electrodes have been successfully applied for oxymetazoline hydrochloride determination in the Afrin nasal drop pharmaceutical formulation.

ABSTRACT The electrochemical oxidation of hydroxyzine dihydrochloride at carbon paste electrode has been studied in 0.04 M Britton-Robinson buffer pH 6.2 using cyclic and differential pulse voltammetry. The oxidation process has been shown to irreversible and diffusion controlled with adsorption characterstics. Based on these studies, simple, rapid, and sensitive differential pulse anodic voltammetric method has been developed for the determination of the drug over the concentration range 0.45-5.36 μg/ml, with detection and quantification limits of 0.27 and 0.90 μg/ml hydroxyzine dihydrochloride, respectively. The proposed method was successfully used for quantification of hydroxyzine dihydrochloride in Atarax tablets and spiked human urine.

The electrochemical behavior of pramipexole dihydrochloride was studied at carbon paste electrodes in 0.04 M Britton-Robinson buffer of pH 6.08, using cyclic and differential pulse voltammetric techniques. The oxidation of pramipexole dihydrochloride is an irreversible diffusion-controlled process. A differential pulse anodic voltammetric procedure has been developed for determination of the drug over the concentration range of 1.20 - 8.23 μg/mL, with detection and quantification limits of 0.21 and 0.68 μg/mL, respectively. The proposed method was successfully applied for the determination of the drug in its commercial tablets.

A fabricação e as características de desempenho de três novos sensores potenciométricos para a determinação de citrato de oxeladina são descritas. Os sensores propostos incluem um sensor do tipo membrana em plástico PVC, um sensor de pasta de carbono e um sensor de fio de cobre revestido com compósito de nanotubos de carbono de parede múltiplas (MWCNT). Os sensores são baseados no íon associado oxeladina-fosfotungstato como material eletroativo e dibutilftalato como mediador solvente. Os sensores desenvolvidos exibiram coeficientes quase nernstianos de 58,00 ± 0,22, 55,00 ± 0,69 e 57,80 ± 0,13 mV concentração década-1 a 25 ºC, nos intervalos de concentração de citrato de oxeladina de 5,96 × 10-6 - 1,00 × 10-2, 1,96 × 10-5 - 1,00 × 10-2 e 3,98 × 10-6 - 1,00 × 10-2 mol L-1 com limites de detecção de 4,14 × 10-6, 8,58 × 10-6 e 2,51 × 10-6 mol L-1 de citrato de oxeladina para os sensores de membrana plástica, de pasta de carbono e de fio de cobre revestido com compósito de MWCNT, respectivamente. Os sensores propostos exibiram boa seletividade para oxeladina com relação a um grande número de cátions inorgânicos, açúcares, aminoácidos e vitaminas. Os sensores desenvolvidos foram aplicados com êxito na determinação potenciométrica de citrato de oxeladina em preparação farmacêutica (cápsulas de Paxeladine®) sob condições de injeção em fluxo e batelada. Os sensores também foram aplicados na determinação de citrato de oxeladina em amostras de urina humana utilizando o método de adição padrão.

The fabrication and performance characteristics of three novel potentiometric sensors for the determination of oxeladin citrate are described. The proposed sensors include a PVC plastic membrane sensor, a carbon paste sensor and a multiwalled carbon nanotube (MWCNT) composite coated copper wire sensor. The sensors are based on the oxeladin-phosphotungstate ion associate as electroactive material and dibutyl phthalate as solvent mediator. The developed sensors exhibited near nernstian slopes of 58.00 ± 0.22, 55.00 ± 0.69 and 57.8 ± 0.13 mV concentration decade-1 at 25 ºC, in the concentration ranges 5.96 × 10-6 - 1.00 × 10-2, 1.96 × 10-5 - 1.00 × 10-2 and 3.98 × 10-6 - 1.00 × 10-2 mol L-1 oxeladin citrate with limits of detection of 4.14 × 10-6, 8.58 × 10-6 and 2.51 × 10-6 mol L-1 oxeladin citrate for plastic membrane, carbon paste and MWCNT composite coated copper wire sensors, respectively. The proposed sensors exhibit good selectivity for oxeladin with respect to a large number of inorganic cations, sugars, amino acids and vitamins. The developed sensors were successfully applied for the potentiometric determination of oxeladin citrate in the pharmaceutical preparation (Paxeladine® capsules) in batch and flow injection conditions. The sensors were also applied for the determination of oxeladin citrate in human urine samples by using the standard addition method.