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.     

Fabrication of Potentiometric Sensors for the Selective Determination of Ketoconazole

Abstract

The fabrication and analytical applications of two types of potentiometric sensors for the determination of ketoconazole (KET) are described. The sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair as electroactive material. The fabricated sensors include both polymer membrane and carbon paste electrodes. Both sensors showed a linear, stable and near Nernstian slope of 57.8 mV/decade and 55.2 mV/decade for PVC membrane and carbon paste sensors respectively over a relatively wide range of KET concentration (1 × 10^?2 ? 5 × 10^?5and 1 × 10^?2 ? 1 × 10^?6). The sensors showed a fast response time of < 30 sec and < 45 sec. A useful pH range of 3–6 was obtained for both types of sensors. A detection limit of 2.96 × 10^?5M was obtained for PVC membrane sensor and 6.91 × 10^?6 M was obtained for carbon paste sensor. The proposed sensors proved to have a good selectivity for KET with respect to a large number of ions. The proposed sensors were successfully applied for the determination of KET in pharmaceutical formulations. The results obtained are in good agreement with the values obtained by the standard method.     

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.     

Determination of Mefenamic Acid and Paracetamol by First Derivative Spectrophotometry

Abstract

A direct and simple first derivative spectrophotometric method has been developed for the determination of mefenamic acid and paracetamol in pharmaceutical formulations. A methanolic hydrochloric acid solution was used as solvent for extracting the drugs from the formulations and subsequently the samples were evaluated directly by derivative spectrophotometry. Simultaneous determination of both drugs can be carried out using the zero-crossing and the graphical methods. The methods do not require simultaneous equations to be solved. The calibration graphs were linear in the ranges from 1.8 × 10^?6 to 1.6 × 10^?4 M of mefenamic acid and from 4.1×10^?6 to 1.4 × 10^?4 M of paracetamol. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets.     

A Rapid,Simple, and Sensitive Spectrophotometric Determination of Traces of Vanadium (V) in Foodstuffs,Alloy Steels,and Pharmaceutical,Water, Soil,and Urine Samples

Abstract

A rapid, simple, sensitive, and selective spectrophotometric method is investigated for the determination of traces of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples in aqueous DMF medium. The metal ion forms a green colored complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) in an acidic buffer of pH 6.0. The green colored solution, having an absorbance maximum at 380 nm, is stable for more than 72 hours. Beer's law is obeyed in the range of 0.051–2.037 µg ml^?1. The molar absorptivity and Sandell's sensitivity of the method are found as 2.75 × 10⁴ l mol^?1 cm^?1 and 0.0018 µg cm^?2, respectively. The green colored complex has 1:2 [V(V)-HMBATSC] stoichiometry. The stability constant of the complex is determined as 3.267 × 10¹¹ by Job's method. The optimum reaction conditions and other analytical parameters are studied. A sensitive and selective second-order derivative spectrophotometry has also been proposed for the determination of V(V). The interference of various cations and anions are studied. The present method is successfully applied to the determination of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples.     

Development of Nalbuphine‐Selective Membrane Electrode and Its Applications in Pharmaceutical Analysis

Abstract

A nalbuphine ion‐selective PVC membrane electrode based on ion‐pair complex of nalbuphine with tetra phenyl borate was prepared with di‐butyl sebacate as a plasticizer. The electrode exhibits a linear response with a Nernstain slope 59.6 mV decate^?1 at 25°C with the concentration range of 1×10^?6?1×10^?2 M nalbuphine. The electrode response was not sensitive to pH changes from 3.5–7 and not affected by possible interfering species such as common inorganic cations, sugars and amino‐acids. The electrode shows good stability, reproducibility and fast response. These characteristics of the electrode enable it to be used successfully for the determination of nalbuphine hydrochloride in pure form and in pharmaceutical preparations.     

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.     

Indication Ion Square Wave Voltammetric Determination of Thiamine and Ascorbic Acid

Abstract

Cd²⁺ ion was used as an electrochemical indicator to detect V_B1 or Vc using square ware voltammetry (SWV) at a mercury film‐coated glassy carbon (GC) electrode. At pH=10 NH₃‐NH₄Cl buffer, a new cathodic peak was found at ?0.360 V (vs.SCE) by addition of thiamine, and the peak current of SWV was linear with the concentration of thiamine in the range of 1×10^?6 to 4×10^?3 M. On the other hand, the SWV peak current of Cd²⁺ at ?0.856 V linearly decreased with addition of ascorbic acid in the range of 6×10^?6～10^?3 M. The effects of interference, such as citric acid, DL‐malic acid, and calcium panlothenate, on thiamine or ascorbic acid determination were investigated. This method was successfully applied to the determination of thiamine or in pharmaceutical preparation.     

Differential Pulse Voltammetric Determination of Sildenafil Citrate (Viagra®) in Pharmaceutical Formulations Using a Boron-Doped Diamond Electrode

The determination of sildenafil citrate using differential pulse voltammetry and a cathodically pre-treated boron-doped diamond electrode is described. The obtained analytical curve is linear in the sildenafil concentration range 7.3 × 10^?7 ? 7.3 × 10^?6 mol L^?1 in a 0.1 mol L^?1 H₂SO₄, with a detection limit of 6.4 × 10^?7 mol L^?1. The proposed method, which is fast and simple to carry out, was successfully applied in the determination of sildenafil citrate in Viagra® pharmaceutical formulations, with results in close agreement (at 95% confidence level) with those obtained using a comparative HPLC method.     

The Determination of Perphenazine by a New Simple Flow‐Injection Chemiluminescence Method

Abstract

A rapid and simple flow‐injection chemiluminescence (CL) method is described for the determination of perphenazine, which is based on the CL intensity that generated from the redox reaction of Ce (IV)-perphenazine in HNO₃ medium is proportional to the perphenazine concentration without any sensitizers. The proposed method allows the determination range within 1.0×10^?7–7.0 ×10^?5 g mL^?1 with a detection limit of 8.0×10^?8 g mL^?1, and it has been successfully applied to the determination of the perphenazine in pharmaceutical tablet compared well with the official method.     

Simultaneous Determination of Ibuprofen and Pseudoephedrine Hydrochloride in Pharmaceutical Tablets by Reversed-Phase HPLC

Abstract

An isocratic HPLC method was developed and validated for the simultaneous determination of ibuprofen (IBU) and pseudoephedrine hydrochloride (PSE). Chromatography was carried out on an Apex phenyl column using 0.025 M acetic acid, triethylamine solution (pH 4.5) – acetonitrile (80:20, v/v) as mobile phase at a flow rate of 1 mL · min^?1. UV detection was performed at a wavelength of 210 nm. The method was validated for specificity, linearity, accuracy, precision, and was successfully applied to pharmaceutical tablets of Rhinadvil®.     

Electrochemical Behavior of Dopamine at a Mercury Electrode in the Presence of Citrate: Analytical Applications

Abstract

Dopamine can be determined by voltammetric methods using a mercury electrode, previously oxidized at +0.30 V. The oxidation product formed is stabilized in the presence of citrate and undergoes reduction at ?0.31 V. This work describes the electrochemical behavior of dopamine at a mercury electrode in the presence of citrate and its application in the development of a square‐wave voltammetric method for the dopamine determination in pharmaceutical formulations. The method was in‐house validated for determination of dopamine in injectable formulations. The detectability of the method was 0.02 µg ml^?1.     

Electrochemical Reduction and Voltammetric Determination of Metronidazole Benzoate at Modified Carbon Paste Electrode

Abstract

A metalloporphyrin incorporated carbon paste sensor has been developed for the determination of metronidazole benzoate (MTZB). Zn(II) complex of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was used as the active material. The MTZB gave a well-defined reduction peak at?0.713 V in 0.1 mol l^?1 phosphate buffer solution of pH around 7. Compared with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode significantly enhanced the reduction peak current of MTZB as well as lowered its reduction potential. Under optimum conditions the reduction peak current was proportional to MTZB concentration over the range 1 × 10^?3 mol l^?1 to 1 × 10^?5 mol l^?1. The detection limit was found to be 4.36 × 10^?6 mol l^?1. This sensor has been successfully applied for the determination of MTZB in pharmaceutical formulations and urine samples.     

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.     

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.     

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.     

Simultaneous Spectrofluorimetric Determination of Paracetamol and Caffeine in Pharmaceutical Preparations in Solid‐Phase Using Partial Least Squares Multivariate Calibration

Abstract

Partial least‐squares algorithm (PLS)‐1 was used for the solid‐phase spectrofluorimetric determination of paracetamol (PA) and caffeine (CF) in pharmaceutical formulations. In despite of the closely overlapping spectral bands, the method allows the simultaneous quantification and sample preparation prior to analysis is not required. The calibration set consisted of 96 samples with 100–400 mg/g^?1 PA plus 10–65 mg/g^?1 CF; another set of 25 samples was used for external validation. Agreement between predicted and experimental concentrations was fair (r=0.993 and 0.964 for PA and CF models). Prediction performance was evaluated in terms of the coefficient of variability (CV), relative predictive determination (RPD), and ratio error range (RER). The PLS‐1 model was used for the determination of PA and CF in pharmaceutical formulations.     

Spectrophotometric Determination of Sparfloxacin in Pharmaceutical Preparations by Ternary Complex Formation with Pd(II) and Eosin

Abstract

A simple, sensitive, and direct spectrophotometric method has been developed for the assay of sparfloxacin in bulk and pharmaceutical preparations. The proposed method is based on the formation of ternary complex between an investigated drug, palladium(II) ion and eosin in the presence of methylcellulose as surfactant and acetate buffer of pH 4.2. Spectrophotometrically, under the optimum conditions, the ternary complex showed absorption maximum at 550 nm, with apparent molar absorptivity of 2.69×10⁴ l mol^?1 cm^?1, Sandell's sensitivity of 0.01458 µg ml^?1 and linearity in the concentration range 1.6–16 µg ml^?1. The composition of the ternary complex was studied by Job's method of continuous variation and the result indicated that the molar ratio of SPFX: Pd: eosin is 1∶1∶1. The optimum reaction conditions and other analytical parameters are evaluated. The proposed method was successfully applied for the determination of SPFX in its pharmaceutical product with mean percentage recoveries of 99.71%. The observed data has been subjected to statistical analysis, which revealed high accuracy and precision.     

A Direct Chemiluminescence Method for the Determination of Prulifloxacin Using Tris-(4,7-Diphenyl-1,10-Phenanthrolinedisulfonic Acid) Ruthenium(II)–Cerium(IV) System

Abstract

A simple, rapid, injection chemiluminescence method is described for the determination of prulifloxacin, a commonly used antibiotic. A strong chemiluminescence signal was detected when a mixture of the analyte and tris-(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)ruthenium(II) was injected into cerium(IV) sulfate. The chemiluminescence signal is proportional to the concentration of prulifloxacin in the range 4.0 × 10^?8–9.0 × 10^?6 mol L^?1. The detection limit is 1.0 × 10^?8 mol L^?1, and the relative standard deviation is 2.2% (n = 11) for the determination of 8.0 × 10^?7 mol L^?1 prulifloxacin. The proposed method was successfully applied to the determination of prulifloxacin in pharmaceutical preparations in capsules, spiked serum, and urine samples.     

Development and Validation of a Stability Indicating LC Method for the Determination of Faropenem in Pharmaceutical Formulations

A simple, selective and sensitive stability indicating LC method has been developed and validated for the determination of faropenem in bulk drug and pharmaceutical formulations in the presence of degradation products. The separation was achieved by using an isocratic mobile phase mixture of acetate buffer of pH 3.5 and methanol (65:35, v/v) and 250 mm × 4.6 mm I.D., 5 μm particle size SGE make Wakosil C-18 AR column at flow rate of 1.0 mL min^?1 with detection at 305 nm. The retention time of faropenem is 6.63 min and was linear in the range of 5–75 μg mL^?1 (r = 0.9999). The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation and was found to be unstable in all the stress conditions. The proposed method was successfully employed for quantification of faropenem in bulk drug and its pharmaceutical formulations.