A sequential injection spectrophotometric method for the determination of penicillamine in pharmaceutical products by complexation with iron(III) in acidic media

A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA-iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the system's performance criterion. A linear dynamic range for the determination of PA of 25-300 ppm was obtained with a sampling frequency of 50 h⁻¹ and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.     

Gold electrodes from compact discs modified with platinum for amperometric determination of ascorbic acid in pharmaceutical formulations

A simple, rapid and precise amperometric method has been developed for quantification of ascorbic acid (AA) in pharmaceutical formulations using flow-injection analysis (FIA). A slice of recordable compact disc (CD) modified by electrodeposition of platinum was employed as the working electrode. The proposed flow system allows determinations in the 1 mumol l(-1) of the analyte and enables 90 determinations per h, employing only 150-mul sample. The method permits the direct quantification of ascorbic acid in many pharmaceutical products, avoiding cumbersome processes as previous separations, solvent extraction or sample filtration. This new procedure was applied to commercial pharmaceutical tablets and the results obtained were identical than the ones obtained by the classical iodometric method. The calibration plots for freshly prepared ascorbic acid standards were highly linear in the concentration range of 1-10 mumol l(-1) with a relative standard deviation (R.S.D.) <1%. For all real samples studied, the deviations were situated between 0.5 and 8.7%.     

A Simple and Rapid CZE Determination of Tiapride Hydrochloride and Related Impurities in Pharmaceutical Formulations

A simple, fast, inexpensive capillary zone electrophoresis method for the separation and determination of tiapride hydrochloride and its two related impurities in pharmaceutical formulations has been developed and validated. The successful separation of these compounds was achieved in less than 3 min using a fused silica capillary and photodiode array detector at 218 nm. The best conditions were obtained using a 10 mM sodium tetraborate (pH 8.0) as the running buffer. The linear responses covered the ranges from 1.0 to 100 μg mL^?1 (R = 0.9989) for tiapride hydrochloride. The detection (LOD) and quantitation limits (LOQ) for tiapride hydrochloride were 2.7 and 9.0 μg mL^?1, respectively. The intra- and inter-day relative standard deviations for migration times and peak areas were less than 0.47 and 5.7%, respectively. The method was validated for the determination of tiapride hydrochloride in commercial tablets.     

Simultaneous determination of atenolol and amiloride in pharmaceutical preparations by capillary zone electrophoresis with capacitively coupled contactless conductivity detection

Capillary zone electrophoresis coupled with a capacitively coupled contactless conductivity detector (CE‐C⁴D) has been employed for the determination of atenolol and amiloride in pharmaceutical formulations. Acetic acid (150 mm ) was used as background electrolyte. The influence of several factors (detector excitation voltage and frequency, buffer concentration, applied voltage, capillary temperature and injection time) was studied. Non‐UV‐absorbing L‐valine was used as internal standard; the analytes were all separated in less than 7 min. The separation was carried out in normal polarity mode at 28°C, 25 kV and using hydrodynamic injection (25 s). The separation was effected in an uncoated fused‐silica capillary (75 μm, i.d. × 52 cm). The CE‐C⁴D method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 5–250 μg/mL for the studied analytes. The relative standard deviations of intra‐ and inter‐day migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of atenolol and amiloride in different pharmaceutical tablet formulations. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous determination of atenolol,chlorthalidone and amiloride in pharmaceutical preparations by capillary zone electrophoresis with ultraviolet detection

Capillary zone electrophoresis methods for the simultaneous determination of the β‐blocker drugs, atenolol, chlorthalidone and amiloride, in pharmaceutical formulations have been developed. The influences of several factors (buffer pH, concentration, applied voltage, capillary temperature and injection time) were studied. Using phenobarbital as internal standard, the analytes were all separated in less than 4 min. The separation was carried out in normal polarity mode at 25°C, 25 kV and using hydrodynamic injection (10 s). The separation was effected in an uncoated fused‐silica capillary (75 μm i.d. × 52 cm) and a background electrolyte of 25 mm H₃PO₄ adjusted with 1 m NaOH solution (pH 9.0) and detection at 198 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 1–250 μg/mL for atenolol and chlorthalidone and from 2.5–250 μg/mL for amiloride. The relative standard deviations of intra‐ and inter‐day migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of atenolol, chlorthalidone and amiloride in various pharmaceutical tablets formulations. Copyright © 2010 John Wiley & Sons, Ltd.     

Green and efficient determination of ʟ-dopa in complex polypill formulations using a magnetic microplate

A high-throughput and selective method for the determination of ?-dopa (levodopa) in complex formulations was developed. The method is based on the oxidation of ?-dopa to yield dopachrome using tyrosinase-labeled magnetic nanoparticles (TYR-MNPs) as the oxidation catalyst. TYR-MNP activity was retained at 75% after 20 reuse cycles, which is superior to previously reported systems that employ other substrates or cross-linkers for the immobilization of tyrosinase. In addition, the precision (< 3%), accuracy (recovery?=?95–102%), and selectivity of the newly developed quantitative-analysis method for ?-dopa in complex polypill formulations meets the pharmaceutical industry’s quality-control requirements; consequently this method can be applied to the routine analysis of complex formulations. The quality-control assay uses 96-well microplates, which reduces the required volume of reagents, and the tyrosinase can easily be recycled and reused using an in-house-prepared magnetic microplate, thereby rendering the proposed method economical and less wasteful than existing methods.     

A New HPLC Method for the Simultaneous Determination of Acetaminophen,Phenylephrine, Dextromethorphan and Chlorpheniramine in Pharmaceutical Formulations

Abstract

Acetaminophen, phenylephrine, dextromethorphan, and chlorpheniramine are frequently associated in pharmaceutical formulations against the common cold. A new high performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of these active pharmaceutical ingredients in pharmaceutical formulations. The separation and quantitation were achieved on a 25 cm underivatized silica column using a mobile phase of methanol: water (containing 6.0 g of ammonium acetate and 10 ml of triethylamine per liter, pH adjusted to 5.0 with orthophosphoric acid), 95:5%(v/v). Detection was carried out using a variable wavelength UV-vis detector at 254 nm for acetaminophen, at 220 nm for phenylephrine, and at 227 nm for dextromethorphan and chlorpheniramine. The method showed linearity for the acetaminophen, phenylephrine, dextromethorphan, and chlorpheniramine in the 162.5–650, 2.5–10, 7.5–30, and 1–4 µg/ml ranges, respectively. The intraday and interday RSDs ranged from 0.92 to 1.52%, 1.00 to 1.76%, 1.21 to 1.74% and 1.26 to 1.80% for the acetaminophen, phenylephrine, dextromethorphan, and chlorpheniramine, respectively. Compounds were eluted in a run time of less than 12 min.     

Quality control of benserazide-levodopa and carbidopa-levodopa tablets by capillary zone electrophoresis

In modern practice, the treatment of Parkinson's disease and syndrome is carried out using pharmaceutical formulations containing a combination of levodopa and a decarboxylation inhibitor (carbidopa or benserazide). Two pharmaceutical formulations were quantified by capillary zone electrophoresis using two procedures which differed only in the kind of background electrolyte used. One procedure used a 25 mM phosphate buffer, pH 2.5, while the second one used a 25 mM borate buffer, pH 8.5. The electrophoretic analysis was carried out using an uncoated fused- silica capillary, a separation voltage of 20 kV with currents typically less than 60 microA, and spectrophotometric detection at 205 nm. Calibration curves were performed for levodopa (concentration range 1-100 microg/mL), for carbidopa and benserazide (1-50 microg/mL), and the plots of the peak area versus concentration were found to be linear with a correlation coefficient better than 0.9990. Satisfactory results were obtained when commercial tablets were analyzed in terms of accuracy (98-102%), repeatability (0.6-2.0%), and intermediate precision (1.1-2.6%).     

Development of Electrochemical Biosensor Based on Nanostructured Carbon Materials for Paracetamol Determination

This work describes the development of a biosensor for paracetamol (PAR) determination based on a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT) and laccase enzyme (LAC), which was immobilized by means of covalent crosslinking using glutaraldehyde. Voltammetric investigations were carried out by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The biosensor was characterized by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FT‐IR). The results showed that the use of MWCNT/LAC composite increased the sensor sensitivity, compared to bare glassy carbon electrode. Factors affecting the voltammetric signals such as pH, ionic strength, scan rate and interferents were assessed. Linear range, limit of detection (LOD) and limit of quantitation (LOQ) obtained were 10–320 μmol L^?1, 7 μmol L^?1 and 10 μmol L^{? 1}, respectively. The developed biosensor was successfully applied to PAR determination in urine and pharmaceutical formulations samples, with recovery varying from 99.96 to 106.20 % in urine samples and a relative standard deviation less than 1.04 % for PAR determination in pharmaceutical formulations. Therefore, the MWCNT‐LAC/GCE exhibits excellent sensitivity and can be used to PAR determination as a viable alternative in clinical analyzes and quality control of pharmaceutical formulations, through a simple, fast and inexpensive methodology.     

Fast determination of ethambutol in pharmaceutical formulations using capillary electrophoresis with capacitively coupled contactless conductivity detection

A method for the determination of ethambutol (EMB), a first‐line drug against tuberculosis, based on CE with capacitively coupled contactless conductivity detection is proposed. The separation of EMB and its main product of degradation were achieved in less than 3 min with a resolution of 2.0 using a BGE composed of 50 mmol/L histidine and 30 mmol/L MES, pH 6.30. By raising the pH to 8.03, the analysis time was reduced to 1.0 min, but with a significant loss of resolution (0.7). Using the best separation conditions, linearity of 0.9976 (R², five data points), sensitivity of 1.26×10^?4 V min μmol^?1 L, and LOD and quantification of 23.5 and 78.3 μmol/L, respectively, were obtained. Recoveries at four levels of concentration ranged from 95 to 102% and the concentration range studied ranged from 100 to 500 μmol/L. The results obtained for the determination of EMB in pharmaceutical formulations were compared with those obtained by using CE with photometric detection.     

Determination of Pentaerythritol Tetranitrate in Pharmaceuticals by High Performance Liquid Chromatography

Abstract

A high performance liquid chromatographic procedure for the analysis of pharmaceutical formulations containing pentaerythritol tetranitrate including the diluted bulk drug and finished products consisting of uncoated tablets and timed-release capsules and tablets was developed. The method employs a reversed-phase system with UV detection at 230 nm. Replicate analyses of 11 commercial formulations (5 diluted bulk drugs and 6 dosage forms gave precision values (CV) having a range of 0.17 to 1.80%. Recovery values obtained from these commercial preparations via fortification ranged from 98.8 to 102.0% while recoveries from 3 synthetic mixtures varied from 99.2 to 100.8%. The detector response for the analyte was observed to be linear over a 50-fold concentration range using nitroglycerin as the internal standard. The proposed HPLC method is specific, easy to perform and exhibits excellent accuracy and precision. Seven different brands of HPLC columns were evaluated for possible use with the method.     

Pharmaceutical formulation analysis of thalidomide by solid surface room temperature phosphorimetry

A rapid and simple method of analysis for thalidomide formulations has been reported based on solid surface room temperature phosphorimetry. Thalidomide phosphorescence was enhanced by Hg(II) ions deposited on paper substrates previously treated for background reduction. A calibration curve with a linear dynamic range of three orders of magnitude was obtained (1.37 × 10^–6 M – 10^–3 M) and a 1.8 ng absolute limit of detection was estimated. The recovery of the method was tested in pharmaceutical formulations containing thalidomide as the only active ingredient. The values obtained were 96.3 ± 6.6% (employing the calibration curve procedure) and 98.0 ± 5.3% (employing the standard addition procedure), which show the potential of the technique for the analysis of thalidomide in dosage forms.     

Microextraction by packed sorbent of N-nitrosamines from Losartan tablets using a high-throughput robot platform followed by liquid chromatography-tandem mass spectrometry

The development of a fast, cost-effective, and efficient microextraction by packed sorbent setup was achieved by combining affordable laboratory-repackable devices of microextraction with a high-throughput cartesian robot. This setup was evaluated for the development of an analytical method to determine N-nitrosamines in losartan tablets. N-nitrosamines pose a significant concern in the pharmaceutical market due to their carcinogenic risk, necessitating their control and quantification in pharmaceutical products. The parameters influencing the performance of this sample preparation for N-nitrosamines were investigated through both univariate and multivariate experiments. Microextractions were performed using just 5.0 mg of carboxylic acid-modified polystyrene divinylbenzene copolymer as the extraction phase. Under the optimized conditions, the automated setup enabled the simultaneous treatment of six samples in less than 20 min, providing reliable analytical confidence for the proposed application. The analytical performance of the automated high-throughput microextraction by the packed sorbent method was evaluated using a matrix-matching calibration. Quantification was performed using ultra-high-performance liquid chromatography-tandem mass spectrometry with chemical ionization at atmospheric pressure. The method exhibited limits of detection as low as 50 ng/g, good linearity, and satisfactory intra-day (1.38–18.76) and inter-day (2.66–20.08) precision. Additionally, the method showed accuracy ranging from 80% to 136% for these impurities in pharmaceutical formulations.     

Simultaneous Determination of Ezetimibe and Simvastatin in Pharmaceutical Formulations by Dual-Mode Gradient LC

A liquid chromatography method was developed and validated for the simultaneous determination of ezetimibe and simvastatin in pharmaceutical formulations. Optimum separation was achieved in less than 10 min using a C₈ column (200 mm × 4.6 mm i.d., particle size 5 μm) and elution was accomplished by the application of a dual-mode solvent and flow-rate gradient system. Detection was carried out using a diode-array detector set at 240 nm. Canrenone was used as internal standard. The method was economical in terms of the time taken and the amount of solvent used for each analysis. It was also validated with respect to system suitability, specificity, limit of quantitation and detection, linearity, precision, accuracy, and recovery, respectively. The limits of quantitation for ezetimibe and simvastatin were 0.2 and 3 μg mL⁻¹, respectively. Limits of detections were found to be 0.05 and 0.5 μg mL⁻¹, for ezetimibe and simvastatin, respectively. The developed method was successfully applied to the simultaneous determination of ezetimibe and simvastatin in pharmaceutical formulations.

     

Simultaneous separation and determination of process-related substances and degradation products of venlafaxine by reversed-phase HPLC

A simple and rapid gradient RP HPLC method for simultaneous separation and determination of venlafaxine and its related substances in bulk drugs and pharmaceutical formulations has been developed. As many as four process impurities and one degradation product of venlafaxine have been separated on a Kromasil KR100-5C18 (4.6 mm x 250 mm; particle size 5 microm) column with gradient elution using 0.3% diethylamine buffer (pH 3.0) and ACN/methanol (90:10 v/v) as a mobile phase. The column was maintained at 40 degrees C and the eluents were monitored with photo diode array detection at 225 nm. The chromatographic behaviour of all the compounds was examined under variable compositions of different solvents, temperatures, buffer concentrations and pH. The method was validated in terms of accuracy, precision and linearity as per ICH guidelines. The inter- and intraday assay precision was < 4.02% (%RSD) and the recoveries were in the range of 96.19-101.14% with %RSD < 1.15%. The correlation coefficients (r2) for calibration curves of venlafaxine as well as impurities were in the range of 0.9942-0.9999. The proposed RP-LC method was successfully applied to the analysis of commercial formulations and the recoveries of venlafaxine were in the range of 99.32-100.67 with %RSD <0.58%. The method could be of use not only for rapid and routine evaluation of the quality of venlafaxine in bulk drug manufacturing units but also for the detection of its impurities in pharmaceutical formulations. Forced degradation of venlafaxine was carried out under thermal, photo, acidic, basic and peroxide conditions and the acid degradation products were characterized by ESI-MS/MS, 1H NMR and FT-IR spectral data.     

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.     

Development and validation of a stability-indicating LC method for the assay of adapalene in bulk drug and pharmaceutical formulations

A simple and sensitive reverse phase HPLC method for the determination of adapalene (ADP) in bulk drug samples and pharmaceutical formulations has been developed and validated. The separation of ADP was achieved on an Inertsil ODS-3V (5 ??m, 15 cm ± 4.6 mm i.d.) column using UV detector at 230 nm. The mobile phase consisted of ammonium acetate (25 mM, pH 3.0), methanol and tetrahydrofuran (18: 42: 40 v/v). The linear range of detection was 2?C200 ??g/mL (R = 0.9991). Intra- and inter-day assay relative standard deviation values were less than 0.5%. The method has been successfully applied to the determination of ADP in pharmaceutical preparations. The excipients commonly present in formulations did not interfere with the assay of ADP. Analytical parameters were calculated and complete statistical evaluation was performed.     

High‐Performance Liquid Chromatographic Determination of Parecoxib in Human Plasma and Pharmaceutical Formulations

Abstract

A simple and sensitive RP‐HPLC method for the determination of parecoxib (PXB) in human plasma and pharmaceutical formulations has been developed and validated. The separation of PXB and the internal standard, ibuprofen (IBF) was achieved on a CLC C₁₈ (5 μ, 25 cm×4.6 mm i.d.) column using UV detector at 200 nm. The mobile phase consisted of acetonitrile‐water (92:8 v/v). The linear range of detection was found to be 0.9–18.4 µg/ml (r=0.9985). Intra‐ and inter‐day assay relative standard deviations were observed to be less than 0.3%. The method has been applied successfully for the determination of PXB in spiked human plasma and pharmaceutical preparations. Analytical parameters were calculated and complete statistical evaluation is incorporated.     

HPLC Analysis of Methoxamine in Rabbit Plasma and Pharmaceutical Formulations

Abstract

A rapid, selective and simple high performance liquid chromatographic (HPLC) assay for methoxamine HC1 has been developed. The analytical procedure involved the use of internal standardization method (1-norephedrine). It has been applied for the qualitative and quantitative determination of methoxamine HC1 in rabbit plasma and in pharmaceutical formulations using an adsorption column in an isocratic mode, with resulting relative standard deviations of 1.7% and 3.3%, respectively. The applicability of the assay procedure to pharmacokinetic studies was demonstrated. Detection limits were as low as 15ng for a 30 ul injection and the determination time was less than 6 minutes.     

Conductometric Determination of N-acetylcysteine in Pharmaceutical Formulations Using Copper(II) Sulphate as Titrant

Abstract

A simple, precise, rapid, and low-cost conductometric method for N-acetylcysteine determination in pharmaceutical formulations is proposed. N-acetylcysteine present in pharmaceuticals containing known quantities of the drug was conductometrically titrated in aqueous solution with copper(II) sulphate using a conductometric cell coupled to an autotitrator. No interferences were observed in the presence of common components of the tablets such as sodium monophosphate, saccharine, sodium benzoate, sucrose, and fructose. Recoveries of N-acetylcysteine from various tablet dosage formulations ranging from 98.3 to 102.0% were obtained.