Simultaneous Square‐Wave Voltammetric Determination of Paracetamol,Caffeine and Orphenadrine in Pharmaceutical Formulations Using a Cathodically Pretreated Boron‐Doped Diamond Electrode

An electroanalytical method for the simultaneous determination of paracetamol (PAR), caffeine (CAF), and orphenadrine (ORPH) using the square‐wave voltammetry (SWV) and a cathodically pretreated boron‐doped diamond electrode was developed. The method exhibits linear responses to PAR, CAF, and ORPH in the concentration ranges 5.4×10^?7–6.1×10^?5 M, 7.8×10^?7–3.5×10^?5 M, and 7.8×10^?7–3.5×10^?5 M, respectively, with detection limits of 2.3×10^?7 M, 9.6×10^?8 M, and 8.4×10^?8 M, respectively. The proposed method was successfully applied in the simultaneous determination of these analytes in pharmaceutical formulations.     

A Selective and Sensitive Method for Simultaneous Determination of Traces of Paracetamol and p‐Aminophenol in Pharmaceuticals Using Carbon Ionic Liquid Electrode

A reliable and simple electrochemical method has been proposed for the simultaneous determination of paracetamol (PAR) and p‐aminophenol (PAP) in pharmaceutical formulations. The oxidation and reduction peak potentials in cyclic voltammetry (CV) for PAR on carbon ionic liquid electrode (CILE) were occurred at 370 and 225 mV vs. Ag/AgCl, respectively at pH 7.0, while those for PAP on CILE appeared at 128 mV and 68 mV, respectively at the scan rate of 0.05 V s^?1. In comparison to the conventional carbon paste electrode, the apparent reversibility and kinetics of the electrochemical reactions of PAR and PAP were significantly improved on CILE. In differential pulse voltammetric technique, the peak potentials for PAR and PAP appeared at 345 and 130 mV, respectively, with the peak separation of 215 mV, sufficient for their simultaneous determination in samples containing these two species. The proposed method was used for simultaneous determination of PAR and PAP in tablets. PAR and PAP can be determined in the ranges of 2.0×10^?6–2.2×10^?3 M and 3.0×10^?7–1.0×10^?3 M, with the detection limits of 5.0×10^?7 and 1.0×10^?7 M (calculated by 3σ), respectively. The relative standard deviations for the determination of PAR and PAP were less than 2%.     

Colorimetric Determination of Ampicillin and 6-Aminopenicillanic Acid Using Acenaphthenequinone as a Chromophoric Reagent

Abstract

A colorimetric method for the determination of ampicillin (Amp.) and 6-aminopenicillanic acid (6-APA) are described, based on the reaction of these drugs with acenaphthenequinone in basic media to give a highly intense red coloured product. The latter exhibits an absorption maximum at 610 nm with apparent molar absorptivities of 2.83 and 1.45 × 10⁴ l. mol^?1 cm^?1 and Sandell sensitivities of 0.013 and 0.015 μg cm^?2 for Amp. and 6-APA, respectively. The optimum concentration ranges are 0.4-10 and 0.4-14 μg ml^?1 for Amp. and 6-APA, respectively. For more accurate results, Ringbom optimum concentration ranges are 1–8.5 and 1–12 μg ml^?1 for Amp. and 6-APA, respectively. Statistical analysis indicated that there was no significant difference between the results obtained by the described method and those of the official methods. The mean recoveries percentage were found to be 99.5 × 1.1% for pharmaceutical formulations and 99.1 × 1.6% for serum and urine samples. The method is selective for the determination of Amp. or 6-APA in the presence of their degradation products, additives and excipiences that are normally encountered in dosage forms. The proposed method was applied successfully to the determination of Amp. in pharmaceutical formulations. Also, applicability of the proposed method to human serum and urine is presented and the validity assessed by applying the standard addition technique.     

Flow Injection and Batch Spectrophotometric Determination of Ibuprofen Based on its Competitive Complexation Reaction with Phenolphthalein‐β‐Cyclodextrin Inclusion Complex

Abstract

Rapid, simple, and accurate spectrophotometric method is presented for the determination of ibuprofen by batch and flow injection analysis methods. The method is based on ibuprofen competitive complexation reaction with phenolphthalein‐β‐cyclodextrin (PHP‐β‐CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of ibuprofen was measured. Ibuprofen can be determined in the range 8.0×10^?6 ?3.2×10^?4 and 2.0×10^?5?5.0×10^?3 mol l^?1 by batch and flow methods, respectively. The limit of detection and limit of quantification were 6.19×10^?6 and 2.06×10^?5 mol l^?1 for batch and 1.77×10^?5 and 5.92×10^?5 mol l^?1 for flow method, respectively. The sampling rate in flow injection analysis method was 120±5 samples h^?1. The method was applied to the determination of pharmaceutical formulations.     

Kinetic Spectrophotometric Determination of Thiols and Ascorbic Acid

Abstract

This paper describes a kinetic spectrophotometric method for the determination of L‐ascorbic acid (AA) and thiols (RSH). Absorbance of Fe(II)‐phen complex formed during the reaction of AA or RSH with Fe(III)‐phen was continuously measured at 510 nm by double‐beam spectrophotometer with flow cell. For determination some thiols, the catalytic effect of Cu²⁺ ions was used. AA and RSH can be determined in concentration ranges from 4.0×10^?6 to 4.0×10^?5 M and from 8.0×10^?6 to 8.0×10^?5 M, respectively. The applicability of the proposed method was demonstrated by determination of chosen compounds in pharmaceutical dosage forms.     

Photometric Flow Injection Determination of Psychotropic Drugs: Brotizolam and Midazolam

Abstract

Brotizolam and Midazolam, psychotropic drugs belonging to thienotriazolodiazepine and imidazobenzodiazepine families, have been determined by flow injection analysis with photometric detection. At pH 7, signals showed to be rectilinear from 1.27 × 10^?6M to 1.07 × 10^?4 M for brotizolam and from 1.53 × 10^?6 M to 1.07 × 10^?4M for midazolam. Methods developed were applied to the determination of both drugs in their formulations (Lendormin and Dormicum).     

Extraction-spectrophotometric determination of mefenamic acid in pharmaceutical preparations

The optimal conditions of the formation and extraction of mefenamic acid ion associates with the astrafloxin polymethine dye are studied. The extraction of ion associates with isooctane-dichloroethane mixtures attains a maximum at pH 9–11 and dye concentration of (5–7) × 10^?5 M. The Beer law is fulfilled in the range 2.0–21.0 μg/mL; the detection limit for mefenamic acid is 0.72 μg/mL. A method is developed for the extraction-spectrophotometric determination of mefenamic acid in pharmaceutical preparations.     

Simultaneous Differential Pulse Voltammetric Determination of Ascorbic Acid and Caffeine in Pharmaceutical Formulations Using a Boron‐Doped Diamond Electrode

A cathodically pretreated boron‐doped diamond electrode was used for the simultaneous anodic determination of ascorbic acid (AA) and caffeine (CAF) by differential pulse voltammetry. Linear calibration curves (r=0.999) were obtained from 1.9×10^?5 to 2.1×10^?4 mol L^?1 for AA and from 9.7×10^?6 to 1.1×10^?4 mol L^?1 for CAF, with detection limits of 19 μmol L^?1 and 7.0 μmol L^?1, respectively. This method was successfully applied for the determination of AA and CAF in pharmaceutical formulations, with results equal to those obtained using a HPLC reference method.     

P‐Dimethyl Amino Benzaldehyde as a New Chromogenic Reagent for the Determination of Nonsteroidal Anti‐Inflammatory Drug by First‐Order Derivative Spectrophotometry

Abstract

Mefenamic acid reacts with P‐dimethylamino benzaldehyde to give a bluish‐green complex in acidic media after heating for 90 s at 90°C, having maximum absorbance at 597.5 nm. The reaction is selective for mefenamic acid with 0.02 mg/10 mL as visual limit of quantitation and provides a basis for a new spectrophotometric determination. The reaction obeys Beer's Law from 0.02 mg to 2.5 mg/10 mL of mefenamic acid and the relative standard deviation is 0.50%. The quantitative assessment of tolerable amounts of other drugs not interfering has also been studied. First‐order derivative spectrophotometric procedure was applied for the determination of mefenamic acid in pharmaceutical preparations.     

Zeolite-Modified Carbon-Paste Electrode as a Selective Voltammetric Sensor for Detection of Tryptophan in Pharmaceutical Preparations

Abstract

Several synthetic zeolites such as mazzite, mordenite, zeolite L, zeolite beta, and MCM-41 were tested as electrode modifiers in voltammetric determination of tryptophan. It was found that addition of zeolite beta to the carbon paste would generate the peak current of Trp because of its catalytic effect. The anodic peak currents were proportional to Trp concentrations in the range of 5.0 × 10^?7 to 5.0 × 10^?3 M. The detection limit was 1.0 × 10^?7 M. The influence of several species, especially other amino acids, were tested. The proposed method was applied successfully to the determination of tryptophan in pharmaceutical formulations.     

Electrochemical Oxidation of Pentoxifylline and its Analysis in Pure and Pharmaceutical Formulations at a Glassy Carbon Electrode

Abstract

The oxidative behavior of pentoxifylline was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetry. The oxidation process was shown to be irreversible over the pH range (3.0–9.0) and was diffusion controlled. The possible mechanism of the oxidation of pentoxifylline was investigated by means of cyclic voltammetry and UV-Vis spectroscopy. An analytical method was developed for the determination of pentoxifylline in phosphate buffer solution at pH 3.0 as a supporting electrolyte. The anodic peak current varied linearly with pentoxifylline concentration in the range 2.0 × 10^?8 M to 6.0 × 10^?7 M of pentoxifylline with a limit of detection (LOD) of 4.42 × 10^?10 M. The proposed method was applied to the determination of pentoxifylline in pure and pharmaceutical formulations.     

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

A new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312?nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5?×?10^?6–1?×?10^?4?mol?L^?1 with limit of detection 0.39?×?10^?6 and 0.77?×?10^?6?mol?L^?1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94?±?4.20%. The green barley appeared to be the richest source of LA.     

Quantitative Analysis of Irbesartan in Pharmaceuticals and Human Biological Fluids by Voltammetry

Abstract

A differential pulse (DP) and square wave (SW) voltammetric techniques were developed for the determination of irbesartan. The electrochemical behavior of irbesartan was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) at the hanging mercury drop electrode (HMDE). Different parameters were tested to optimize the conditions of the determination. It was found that in the range of 8 × 10^?6–1 × 10^?4 M, the currents measured by both of methods presented a good linear property as a function of the concentration of irbesartan. In addition, validation parameters, such as reproducibility, sensitivity, and recovery were evaluated as well. The slope of the log Ip- log ν linear plot was 0.58 indicating the diffusion control for 0.5 M sulphuric acid without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances.

The methods were successfully applied to the analysis of irbesartan in the pharmaceutical tablet formulations and in human serum samples.     

Study of Fluorescence System of Gmanylic Acid-Tb3+ and the Determination of Gmanylic Acid

Abstract

It was found that gmanylic acid (GMP) can be selectively completed with Tb³⁺ at pH 6.0-6.6, which then emits strong fluorescence characteristic of Tb³⁺. This reaction can be used for the determination of GMP in presence of adenylic acid (AMP), uridylic acid (UMP) and cylidylic acid (CMP). A linear relationship is obtained between the fluorescence intensity and GMP concentration in the range of 2.0×10^?7 - 1.0×10^?4M. The detection limit is 2.0×10^?8 M. The results showed that the composition ratio and apparent stability constant of GMP-Tb complex were 1:1 for GMP Tb³⁺- and 2.3×10^?5, respectively.     

Fourth Order Derivative Spectrophotometric Determination of Benzyl Alcohol in Piroxicam Injections

Piroxicam is a drug with analgesic and anti‐inflammatory properties. It is present in numerous pharmaceutical preparations. Injectable forms usually contain benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4–10%). In this work, spectrophotometric methodology was used in order to determine benzyl alcohol in piroxicam injectable formulations by applying the fourth derivative method adopting the zero‐crossing technique. The results obtained show that the method has significant advantages over other reported methods and is appropriate for routine pharmaceutical analysis. The method showed excellent linearity in the range of 2–100 μg mL^?1 with limit of detection (S/N = 3) 0.07 μg mL^?1 (6.47 × 10^?7 M). The proposed method could be applied successfully for the determination of benzyl alcohol in injectable formulations with average % recovery of 100 ± 0.61.     

Salicylate Ion‐Selective Electrode Based on a Calix[4]arene as Ionophore

A salicylate‐selective electrode based on calix[4]arene derivative was developed and its response characteristics were investigated. The optimum membrane composition was 1 % ionophore, 30 % PVC, 69 % DOS. The electrode exhibited a Nernstian slope of 58.8±0.5 mV/pSal in the range of 1.0×10^?5–1.0×10^?1 M with a detection limit of 4.3×10^?6 M at pH 4.0, 20±1 °C. The potentiometric response of the electrode in the presence of different anions was investigated by the separate solution method. The lifetime was found at least 4 months, and its response time was 5–10 s. It was successfully used for the potentiometric determination of salicylate in pharmaceutical preparations.     

Voltammetric determination of theophylline in pharmaceutical formulations using aligned carbon nanotubes (ACNTs) film modified electrode

A novel rapid, convenient and sensitive electrochemical method has been described for the determination of theophylline in pharmaceutical formulations, based on the extraordinary properties of an aligned carbon nanotubes (ACNTs) thin film. The voltammetric results suggest that the ACNTs-coated glass carbon electrode can exhibit excellent electrochemical activity for direct electrochemical oxidation of theophylline. Various experimental parameters such as solution pH value, amount of ACNTs suspension, accumulation conditions and scan rate were optimized for the determination of theophylline. Furthermore, it was found that the peak current increased linearly with the concentration of theophylline in the range of 8.0 × 10^?8?1.0 × 10^?5 M and the detection limit was 1.6 × 10^?8 M using differential pulse voltammetry. This newly proposed method has been applied successfully to the determination of theophylline in drugs.     

Colorimetric Determination of Some N-Substituted Phenothiazine Derivatives Using 2-Iodoxybenzoate

Abstract

A new, sensitive colorimetric method has been described for the quantitative determination of six N-substituted phenothiazines. the method depends on the formation of stable phenothiazine free radical by the use of 2-iodoxybenzoate as chromogenic reagent. the drug in 50% sulphuric acid is treated with reagent (5×10^?4 M). the produced red or purple color possesses characteristic absorption maximum for each of the drugs tested. Beer's law is obeyed over the concentration range 2-30 μg.ml^?1 with apparent molar absorptivities ranging from 9.4-12.4×10^?3 for the studied phenothiazine derivatives. the average % recovery is 99.5±0.96 - 101.6±1.01. the method was applied successfully to the microdetermination of promazine. HCl, chlorpromazine, HCl, promethazine. HCl, perphenazine, levomepromazine HCl and mesoridazine besylate either in pure form or incorporated in their representative pharmaceutical preparations. the stoichiometry of the reaction was assumed and a reaction mechanism was suggested. the precision of the assay was comparable with the official ones.     

Evaluation of the Analytical Potentialities of a Composite Electrode Modified with Molecularly Imprinted Polymers

Abstract

The preparation of a methacrylate polymer molecularly imprinted (MIP) with paracetamol (APAP) was performed. After extraction of the APAP template molecule, the MIPs were incorporated into a graphite–polyurethane (GPU) matrix, and the resulting composites were used to prepare modified electrodes intended to be used in APAP determination. The best results were found using a 2.5% MIP in the GPU electrode and a 500-µm MIP particle size. This electrode was used in the determination of APAP in pharmaceutical formulations, reaching a 6.7 × 10^?8 mol L^?1 limit of detection. The 2.5% MIP-GPU-modified electrode showed better sensitivity than the nonimprinted methacrylate GPU-modified electrodes. Interference of phenacetin in the APAP response decreased remarkably when the proposed electrode was used.     

Preconcentration of Rutin at a Poly Glutamic Acid Modified Electrode and its Determination by Square Wave Voltammetry

Abstract

The voltammetric determination of rutin in 0.04 mol l^?1 B‐R buffer (pH 4.0) by square wave voltammograms (+0.41 V vs. Ag/AgCl_(sat.)) at a poly glutamic acid modified glassy carbon electrode was found to be several orders of magnitude lower than that on a bare glassy carbon electrode. Rutin can be preconcentrated on the films of poly glutamic acid and presented linear relationship from concentration of 7×10^?7 to 1×10^?5 mol l^?1 in 0.04 mol l^?1 B‐R buffer pH 4.0. The method was successfully applied to the determination of rutin in pharmaceutical formulation without any pretreatment.