Electroanalytical study and square wave voltammetric techniques for the determination of β-blocker timolol at the mercury electrode (original) (raw)
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Journal of the Brazilian Chemical Society, 2014
Levobunolol HCl é um agente bloqueador ß-adrenoceptor potente e não seletivo usado no tratamento tópico de pressão intraocular aumentada em pacientes com glaucoma de ângulo aberto crônico ou hipertensão ocular. Um método voltamétrico de onda quadrada e redissolução catódico adsortivo (SW-AdCSV) preciso, rápido e sem extração foi descrito para quantificação de traços de levobunolol HCl puro, formulações comerciais (gotas oftalmológicas) e sérum humano. Os limites de quantificação (LOQ) de 1,0 × 10-10 mol L −1 (na forma pura) e 2,5 × 10-10 mol L −1 levobunolol HCl (em sérum humano adulterado) foram obtidos pelo método descrito. Foram obtidas interferências não significativas dos excipientes associados à formulação de levobunolol HCl e de alguns íons metálicos comuns, medicamentos co-administrados, alguns outros agentes ß-bloqueadores e seu metabolito diidrolevobunolol, que possivelmente estão presentes em fluidos biológicos. O método SW-AdCSV descrito é sensível o suficiente para determinar o medicamento em sérum humano, comparado à maioria dos métodos relatados. Levobunolol HCl is a potent non-selective ß-adrenoceptor blocking agent used for the topical treatment of increased intraocular pressure in patients with chronic open angle glaucoma or ocular hypertension. Precise, rapid and extraction-free square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for trace quantitation of levobunolol HCl in bulk form, commercial formulation (ophthalmologic drops) and human serum. Limits of quantification (LOQ) of 1.0 × 10-10 mol L −1 (in bulk form) and 2.5 × 10-10 mol L −1 levobunolol HCl (in spiked human serum) were achieved by the described method. Insignificant interferences from excipients associated with formulation of levobunolol HCl and from some common metal ions, co-administrated drugs, some other ß-blocker agents and its metabolite dihydrolevobunolol that are likely to be present in the biological fluids were obtained. The described SW-AdCSV method is sensitive enough to assay the drug in human serum compared to most of the reported methods.
Analytical applications of electrode sensitive to labetalol in pharmaceuticals
Central European Journal of Chemistry, 2003
The analytical properties of an ion-selective electrode sensitive to labetalol with a liquid membrane, based on ion-pair complexes with sodium tetraphenylborate (TPB-Na+) are described. The studied electrode can be used for the determination of labetalol hydrochloride as a protonated form of labetalol in pharmaceuticals. The calibration curve, e.g. EMF=f(pCLabHCl) is linear in the range from 10−5 to 10−2 mol L−1 with a correlation coefficient of 0.9992 and slope of 61.13 mV/decade, which is close to the Nernstian slope. The detection limit of the examined electrode is 7.20×10−6 mol L−1. The influence of pH of the tested solutions on the formulation of the electrode is not as considerable since the electrode works correctly in the pH range 3.0–8.0. The main attributes of the developed electrode are: stability, good reproducibility of EMF and short response time, close to 30 seconds depending on labetalol concentration in the solution. The electrode shows good selectivity for many ino...
Journal of the Iranian Chemical Society, 2017
treatment group of the International Olympic Committee and conditionally utilized by sports donors. All these mentioned above make it quite important to add beta-blockers to urine analysis routine and use it for the medical doping analysis. Many modern separation methods with excellent sensitivity and selectivity such as gas chromatography with mass spectrometry [2, 3], liquid chromatography [4-8], capillary electrophoresis [9] and spectrophotometry [10, 11] mostly dominate the determination of ACE in different matrices (e.g., urine, blood, serum, plasma, pharmaceuticals) in analytical and clinical laboratories. Although these methods are very effective, most of them have several disadvantages such as being expensive and time-consuming to prepare the complex samples involving different derivation types, extraction and purification processes before the analyses. The simplicity, responsiveness and higher sensitivity of electrochemical methods make the alternative analyses of electro active compounds available. However, according to the reviewed literature, there are four studies available for the determination of ACE using electrochemical method based on potentiometry [12, 13] and voltammetry [14-16]. The first of these voltammetric methods [14], electrochemical reduction of ACE, has been examined by square-wave adsorptive stripping voltammetry (SW-AdSV) at a hanging mercury drop electrode (HMDE). The second method has been based on the electrochemical behavior of ACE and indicates the practicality of a graphene film modified as glassy carbon electrode (GF-GC) for the electroanalysis of ACE utilization voltammetry techniques (CV and DPV) [15]. The last study has been based on the electroanalysis of ACE with various electrochemical techniques using carbon paste electrode (prepared by hand mixing of graphite powder) [16]. Through reviewing the literature, it has been found that there are no reports on pencil graphite (PG) electrodes for Abstract In this work, an electrochemical investigation of acebutolol (ACE), a beta-blocker drug, was carried out in alkaline medium using pencil graphite (PG) electrode. In cyclic voltammetry, the compound displayed a reversible and adsorption-controlled oxidation peak. By using squarewave anodic stripping voltammetry, the oxidation peak current observed at +0.78 V showed a linear relationship with concentration at 0.4-7 nM interval in Britton-Robinson buffer (pH 10.0) and a detection limit of 0.09 nM. The relative standard deviation of 4.72% for the concentration level of 2.0 nM (n = 11) was also calculated. The PG electrode that is used for the first time in this method was successfully applied to determine the ACE in pharmaceutical formulations and urine.
Voltammetric study of danazol and its determination in capsules and spiked biological fluids
Journal of Pharmaceutical and Biomedical Analysis, 2005
The voltammetric behaviour of danazol DZ (antigonadotropin) was studied using cyclic voltammetry, direct current, differential pulse polarography (DPP) and alternating current polarography. Danazol exhibited irreversible cathodic waves over the pH range of 1-5 in Britton Robinson buffers. At pH 1 (the analytical pH), a well-defined wave with E1/2 of −1.04 V versus Ag/AgCl reference electrode was obtained. The diffusion current constant (I d ) was 4.8 ± 0.14 A.L.m mole −1 and the current-concentration plot was rectilinear over the range from 5 × 10 −6 to 1 × 10 −4 M with correlation coefficient (n = 11) of 0.995. The calculated detection limit was 1 × 10 −6 M using the DPP mode. The wave was characterized as being irreversible, diffusion-controlled although adsorption phenomenon played a limited role in the electrode process. The proposed method was applied to commercial capsules and the average percentage recovery was in agreement with that obtained by the official USP method. The method was extended to the in vitro determination of DZ in spiked human urine and plasma samples, the percentage recoveries were 96 ± 4 and 97 ± 5, respectively. A proposal of the electrode reaction was postulated.
Chemistry Central Journal, 2012
A validated simple, rapid, sensitive and specific square-wave voltammetric technique is described for the determination of acebutolol (AC) following its accumulation onto a hanging mercury drop electrode in a Britton-Robinson universal buffer of pH 7.5. The optimal procedural conditions were: accumulation potential E acc =-0.8 V versus Ag/AgCl/KCl, accumulation duration t acc = 30 s, pulse-amplitude = 70 mV, scan rate = 100 mV/s, frequency = 30 Hz, surface area of the working electrode = 0.6 mm 2 and the convection rate = 2000 rpm. Under these optimized conditions, the adsorptive stripping voltammetry (AdSV) peak current was proportional over the concentration range 5 × 10-7-6 × 10-6 M (r = 0.999). Recoveries for acebutolol from human plasma and urine were in the range 97-103% and 96-104% respectively. The method proved to be precise (intra-day precision expressed as %RSD in human plasma ranged from 2.9-3.2% and inter-day precision expressed as %RSD ranged from 3.4-3.8%) and accurate (intra-day accuracies expressed as % error in human urine ranged from-3.3-2.8% and inter-day accuracies ranged from-3.3-1.7%). The limit of quantitation (LOQ) and limit of detection (LOD) for acebutolol were 1.7 × 10-7 and 5 × 10-7 M, respectively. Possible interferences by substances usually present in the pharmaceutical formulations were investigated with a mean recovery of 101.6 ± 0.64%. Results of the developed square-wave adsorptive stripping voltammetry (SW-AdSV) method were comparable with those obtained by reference analytical method.
Colorimetric determination of β-blockers in pharmaceutical formulations
Journal of Pharmaceutical and Biomedical Analysis, 2002
A simple, accurate, precise and sensitive colorimetric method for the determination of some b-blockers as atenolol (Ateno), metoprolol (Metop), sotalol (Sot) and nadolol (Nad) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD Á/Cl) in methanolic Á/aqueous (for Ateno and Metop) or acetone Á/aqueous (for Sot and Nad) medium [30% (v/v)]. The orange color products are measured at 485, 470, 465 and 462 nm for Ateno, Metop, Sot and Nad, respectively. The optimization of various experimental conditions is described. Beer's law is obeyed in the range 0.4 Á/60 mg ml (1 while that obtained applying Ringbom is 0.8 Á/56 mg ml (1 . The molar absorptivity, Sandell sensitivity, detection and quantification limits are calculated. The results obtained showed good recoveries of 99.59/1.1, 100.39/1.2, 100.59/1.0 and 99.39/1.1% with relative standard deviations of 0.74, 0.98, 1.15 and 0.87% for Ateno, Metop, Sot and Nad, respectively. Applications of the proposed method to representative pharmaceutical formulations are successfully presented. #
Talanta, 2010
The independent determination of two -blocker agents, namely propranolol (PROP) and atenolol (ATN), in pharmaceutical formulations using square-wave voltammetry and a cathodically pretreated borondoped diamond electrode is described. These electroanalytical determinations of propranolol or atenolol were carried out in 0.1 mol L −1 H 2 SO 4 or 0.5 mol L −1 NaNO 3 (pH 1.0, adjusted with concentrated HNO 3 ), respectively. Excellent linear calibration curves, ranging from 0.20 to 9.0 mol L −1 for PROP and from 2.0 to 41 mol L −1 for ATN, with detection limits of 0.18 and 0.93 mol L −1 , respectively, were obtained. The obtained recoveries range from 93.9% to 105.0%, for PROP, and from 92.5% to 106.0%, for ATN. The proposed method was successfully applied in the determination of both -blockers in several pharmaceutical formulations (tablets), with results in close agreement at a 95% confidence level with those obtained using official spectrophotometric methods.