Voltammetric Behavior of Telmisartan and Cathodic Adsorptive Stripping Voltammetric Method for Its Assay in Pharmaceutical Dosage Forms and Biological Fluids

Recent advances in carbon nanomaterials-based electrochemical sensors for food azo dyes detection

Azo dyes as widely applied food colorants are popular for their stability and affordability. On the other hand, many of these dyes can have harmful impacts on living organs, which underscores the need to control the content of this group of dyes in food. Among the various analytical approaches for detecting the azo dyes, special attention has been paid to electro-analytical techniques for reasons such as admirable sensitivity, excellent selectivity, reproducibility, miniaturization, green nature, low cost, less time to prepare and detect of specimens and the ability to modify the electrode. Satisfactory results have been obtained so far for carbon-based nanomaterials in the fabrication of electrochemical sensing systems in detecting the levels of these materials in various specimens. The purpose of this review article is to investigate carbon nanomaterial-supported techniques for electrochemical sensing systems on the analysis of azo dyes in food samples in terms of carbon nanomaterials used, like carbon nanotubes (CNT) and grapheme (Gr).

Determination of D&C Red 33 and Patent Blue V Azo dyes using an impressive electrochemical sensor based on carbon paste electrode modified with ZIF-8/g-C3N4/Co and ionic liquid in mouthwash and toothpaste as real samples

Synthetic azo dyes are widely used in a variety of industries, but many of them pose a risk to human health, particularly when consumed in large quantities. As a result, their existence in products should be closely monitored. D&C red 33 and Patent Blue V are mostly used in cosmetics, especially in toothpaste and mouthwashes. A novel carbon paste electrode modified with ZIF-8/g-C3N4/Co nanocomposite and 1-methyl-3-butylimidazolium bromide as an ionic liquid was employed as a highly sensitive reproducible electrochemical sensor for the simultaneous determination of these common dyes. ZIF structure has unique properties such as high surface area, suitable conductivity, and excellent porosity. The electrochemical behavior of the suggested electrode was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). To characterize the synthesized nanocomposites, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were applied to investigate the structure of nanocomposites. Under the optimized conditions, the modified sensor offered a wide linear concentration range 0.08-10 μM (R2 = 0.9906) and 10-900 μM (R2 = 0.9932) with a low limit of detection of 0.034 μM. The value of diffusion coefficient (D), and the electron transfer coefficient (α) was calculated to be 310 × 10-5, and 0.9 respectively. This technique offered a successful performance for the determination of target analyte in the real samples with acceptable results between 96% and 107%.

Telmisartan

Telmisartan is an angiotensin-II receptor antagonist (ARB) used in the treatment of hypertension. Generally, angiotensin-II receptor blockers such as telmisartan bind to the angiotensin-II type 1 receptors with high affinity, causing inhibition of the action of angiotensin II on vascular smooth muscle, ultimately leading to a reduction in arterial blood pressure. The present study gives a comprehensive profile of telmisartan, including detailed nomenclature, formulae, elemental analysis, and appearance of the drug are mentioned. The uses and applications and the several methods described for its preparation of the drug are outlined. The profile contains the physicochemical properties including: pKa value, solubility, X-ray powder diffraction, melting point, and methods of analysis (including compendial, electrochemical, spectroscopic, and chromatographic methods of analysis). Developed validated stability-indicating (HPLC and biodiffusion assay methods under accelerated acidic, alkaline, and oxidative conditions, in addition to effect of different types of light, temperature, and pH. Detailed Pharmacology also presented (Pharmacological actions, Therapeutic uses and Dosing, Interactions, and adverse effects and precautions). More than 80 references were given as a proof of the above-mentioned studies.

A cooperative computational and experimental investigation on electrochemical behavior of metoprolol and its voltammetric determination

The electrochemical behavior of metoprolol (MTP) was studied via experimental and computational approaches. Theoretical calculations were performed at the B3LYP/6-31+G(d)//AM1 level whereas experimental studies were carried out on a hanging mercury drop electrode (HMDE) and glassy carbon electrode (GCE). According to the computational results, both HOMO and LUMO of MTP were located at the phenyl ring. Hence, oxidation and reduction are expected to take place at the phenyl ring. Experimental studies on HMDE were based on reversible reduction at approximately –1.4 V and studies on GCE were based on irreversible oxidation at approximately 0.9 V versus Ag/AgCl (3 mol L−1 KCl) in Britton−Robinson buffer. Voltammetric methods with and without adsorptive stripping modes were developed. Proposed methods were successfully applied to tablet solutions and spiked human serum samples. Results are satisfactory with recovery values between 94.5% and 102.5% and a relative standard deviation lower than 6%.

Adsorptive stripping voltammetric methods for determination of aripiprazole

Anodic behavior of aripiprazole (ARP) was studied using electrochemical methods. Charge transfer, diffusion and surface coverage coefficients of adsorbed molecules and the number of electrons transferred in electrode mechanisms were calculated for quasi-reversible and adsorption-controlled electrochemical oxidation of ARP at 1.15 V versus Ag/AgCl at pH 4.0 in Britton–Robinson buffer (BR) on glassy carbon electrode. Voltammetric methods for direct determination of ARP in pharmaceutical dosage forms and biological samples were developed. Linearity range is found as from 11.4 μM (5.11 mg/L) to 157 μM (70.41 mg/L) without stripping mode and it is found as from 0.221 μM (0.10 mg/L) to 13.6 μM (6.10 mg/L) with stripping mode. Limit of detection (LOD) was found to be 0.11 μM (0.05 mg/L) in stripping voltammetry. Methods were successfully applied to assay the drug in tablets, human serum and human urine with good recoveries between 95.0% and 104.6% with relative standard deviation less than 10%.

Electrochemical behavior of Moclobemide at mercury and glassy carbon electrodes and voltammetric methods for its determination

Electrochemical oxidation and reduction properties of Moclobemide (MCB) were investigated at glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). Diffusion-adsorption behavior and some extra electrochemical parameters such as diffusion coefficient, number of transferred electrons and proton participated to its electrode mechanisms on both electrode and surface coverage coefficient were calculated from the results of cyclic voltammetry and square-wave voltammetry. Reversible catalytic hydrogen wave mechanism was proposed at HMDE and single two-electron/two-proton irreversible oxidation mechanism controlled by adsorption with some diffusion contribution at GCE was proposed. Experimental parameters were optimized to develop new, accurate, rapid, selective and simple voltammetric methods for direct determination of MCB in pharmaceutical dosage forms and spiked human serum samples without time-consuming steps prior to drug assay. In these methods, the lowest limit of detection (LLOD) was found to be 0.0235 μM. Methods were successfully applied to determine the MCB content of commercial pharmaceutical preparations and spiked human urine. The methods were found to be highly accurate and precise.

Square-wave cathodic adsorptive stripping voltammetry of risperidone

Electrochemical properties and diffusion-adsorption behavior of risperidone (RPN), an antiphyscotic drug, on hanging mercury drop electrode (HMDE) were carried out in Britton–Robinson (BR) buffer. Some electrochemical parameters such as diffusion coefficient, number of transferred electrons and proton participated to its reduction mechanism and surface coverage coefficient were calculated from the results of cyclic voltammetry, square-wave voltammetry and constant potential electrolysis. RPN was found to be reduced with single two-electron/two-proton quasi-reversible mechanism controlled mainly by adsorption with some diffusion contribution at the potential about –1.58 V (vs Ag|AgCl electrode). Experimental parameters were optimized to develop a new, accurate, rapid, selective and simple square-wave cathodic adsorptive stripping voltammetric (SWCAdSV) method for direct determination of RPN in pharmaceutical dosage forms, spiked human urine and human serum samples without time-consuming steps prior to drug assay. This method was based on the relation between the peak current and the concentration of RPN and it was recognized that peak current of reduction wave linearly changes with the concentration of RPN in the concentration range of 1.5–150 nM, when optimum preconcentration potential –0.65 V and optimum preconcentration time 60 s were applied. In this method, limit of detection (LOD) was found as 5.18 nM (2.12 ppb). The method was successfully applied to determine the RPN content of commercial pharmaceutical preparations, spiked human serum and spiked human urine. The method was found to be highly accurate and precise, having a relative standard deviation of less than 4.80% for all applications.