Spectrofluorimetric determination of clioquinol in pharmaceutical preparations

Summary The absorption spectrum of the nitrate radical (NO₃) in aqueous solution and the kinetic of the reactions with Cl^– and OH^– have been determined using laser-spectrometric techniques. The maximum absorption was found at 635 nm with a decadic absorption coefficient of =(530±110) l/mol·cm. At 298 K rate constants of k₁=(1.0±0.2)·10⁷ l/mol·s for the reaction with chloride and of k₂=(8.2±0.9)·10⁷ l/mol·s for the reaction with hydroxide were obtained.     

Spectrofluorimetric determination of fluoroquinolones in pharmaceutical preparations

Simple, rapid and highly sensitive spectrofluorimetric method is presented for the determination of four fluoroquinolone (FQ) drugs, ciprofloxacin, enoxacin, norfloxacin and moxifloxacin in pharmaceutical preparations. Proposed method is based on the derivatization of FQ with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in borate buffer of pH 9.0 to yield a yellow product. The optimum experimental conditions have been studied carefully. Beer's law is obeyed over the concentration range of 23.5-500 ng mL(-1) for ciprofloxacin, 28.5-700 ng mL(-1) for enoxacin, 29.5-800 ng mL(-1) for norfloxacin and 33.5-1000 ng mL(-1) for moxifloxacin using NBD-Cl reagent, respectively. The detection limits were found to be 7.0 ng mL(-1) for ciprofloxacin, 8.5 ng mL(-1) for enoxacin, 9.2 ng mL(-1) for norfloxacin and 9.98 ng mL(-1) for moxifloxacin, respectively. Intra-day and inter-day relative standard deviation and relative mean error values at three different concentrations were determined. The low relative standard deviation values indicate good precision and high recovery values indicate accuracy of the proposed methods. The method is highly sensitive and specific. The results obtained are in good agreement with those obtained by the official and reference method. The results presented in this report show that the applied spectrofluorimetric method is acceptable for the determination of the four FQ in the pharmaceutical preparations. Common excipients used as additives in pharmaceutical preparations do not interfere with the proposed method.     

Microbiological assay for cefoxitin sodium in dosage form

A microbiological assay applying the cylinder-plate method is described for determination of the activity of cefoxitin sodium in injectables. Using a strain of Staphylococcus epidermidis ATCC 12226 as the test organism, cefoxitin sodium was measured in concentrations ranging from 50.0 to 200.0 microg/mL. The validation showed that the method was linear (r = 0.9998), precise (RSD = 0.81%), and accurate. It was concluded that the microbiological assay is satisfactory for quantitation of cefoxitin sodium in injectables.     

Spectrofluorimetric determination of fexofenadine hydrochloride in pharmaceutical preparation using silver nanoparticles

A novel sensitive fluorimetric method was investigated for the assay of fexofenadine hydrochloride (FEX) using silver nanoparticles (NPs) as a fluorescence probe. The NPs, which were prepared by chemical reduction of silver nitrate with sodium borohydride (reducing agent) in aqueous solution (without organic stabilizers) were water soluble, stable and had narrow emission band. The addition of drug to NPs solution caused considerable quenching of the emission band of silver NPs, which was likely due to the complexation of the drug to silver NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the concentration of FEX in the range of 1 × 10^?7 to 2.5 × 10^?5 mol L^?1 (0.9985) with a detection limit of 1.2 × 10^?8 mol L^?1. The quenching mechanism of the studied drug on the emission band of silver NPs was explained by Stern–Volmer law. The developed method was applied to FEX determination in a pharmaceutical formulation (allegra tablets) and biological fluids (human serum and urine).     

Near infrared transmittance analysis for the assay of solid pharmaceutical dosage forms

The recent commercial availability of near infrared spectrometric instruments for the transmittance analysis of solids makes it possible to analyse solid drugs in their finished form. Application of the method to the control of the assay of the active ingredient in diphenhydramine tablets gave results comparable to those obtained in reflectance mode with whole and milled tablets.     

Application of pressurized liquid extraction technology to pharmaceutical solid dosage form analysis

The technique of pressurized liquid extraction has been evaluated for the extraction of active ingredients from pharmaceutical dosage forms using montelukast sodium oral chewable tablets as a model. The extraction method was optimized for the number of extraction cycles, extraction time, extraction solvent composition and temperature. Samples were extracted using two cycles of water for 2 min with a cell temperature of 40 degrees C and a pressure of 1.0 x 10(4) kPa, to disintegrate the tablet, followed by three cycles of methanol for 3 min at 70 degrees C and 1.0 x 10(4) kPa, to solubilize montelukast sodium. The method demonstrated an extraction efficiency of 98.2% of label claim and an RSD of 1.3% (n=10), as compared to 97.6% and an RSD of 0.9% obtained using a validated mechanical extraction method.     

General method for the analysis of pharmaceutical dosage forms by high-performance liquid chromatography

A reliable and simple method for the routine analysis of pharmaceutical dosage forms by high-performance liquid chromatography using a C18 Bondapak reversed-phase column with a binary solvent system consisting of acetonitrile and 0.05 M potassium dihydrogen phosphate has been developed. Standardised extraction procedures for drugs in various dosage forms have been developed and successfully applied to a wide range of current pharmaceutical formulations.     

Validation of a capillary electrophoresis method for analysis of rabeprazole sodium in a pharmaceutical dosage form

Rabeprazole sodium is an antisecretory agent that inhibits the enzyme H+/K+ ATPase present in the stomach parietal cells. There are few data about its quantitative determinations in laboratorial routines. Capillary electrophoresis is a method being used increasingly for analysis of pharmaceutical compounds, the main advantages of which are the simplicity of instrumentation, low consumption of sample and reagents, and fast analysis. The aim of this study was to develop and validate a capillary electrophoresis method for determination of rabeprazole sodium in coated tablets. The conditions used were a bare fused silica capillary with 48.0 cm length (39.5 cm effective) and 75 microm id; a 10mM, pH 9.0, sodium tetraborate run buffer; a diode array detector set at 291 nm; hydrodynamic injection (50 mbar/5 s); and a voltage of 20 kV. HP Chemstation CE rev. A.06.03 software was used for system control, data acquisition, and analysis. The method was demonstrated to be linear in the concentration range of 5.0-40.0 microg/mL (r = 0.9993), precise (interday relative standard deviation = 0.49), accurate (mean recovery = 103.1%), and specific. The limits of detection and quantitation were 1.29 and 3.91 microg/mL, respectively.     

HPTLC method for determination of nevirapine in pharmaceutical dosage form

A sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic method of analysis of nevirapine both as a bulk drug and in formulations was developed and validated. The solvent system consisted of toluene-carbon tetrachloride-methanol-acetone-ammonia (3.5:3.5:2.0:1.0:0.05, v/v/v/v/v). Densitometric analysis of nevirapine was carried out in the absorbance mode at 289nm. This system was found to give compact spots for nevirapine (R(f) value of 0.44+/-0.02). Nevirapine was subjected to acid and alkali hydrolysis, oxidation, dry heat and wet heat treatment and photodegradation. The drug undergoes degradation under acidic, basic conditions and oxidation. Also the degraded products were well resolved from the pure drug with significantly different R(f) values. Linearity was found to be in the range of 30-1000ng/spot with significantly high value of correlation coefficient. The linear regression analysis data for the calibration plots showed good linear relationship with r(2)=0.998+/-0.002 in the working concentration range of 300ng/spot to 1000ng/spot. The mean value of slope and intercept were 0.073+/-0.005 and 36.78+/-1.50, respectively. The method was validated for precision, robustness and recovery. The limit of detection and quantitation were 5 and 10ng/spot, respectively. As the method could effectively separate the drug from its degradation products, it can be employed as a stability indicating one. Moreover, the proposed HPTLC method was utilized to investigate the kinetics of acid degradation process. Arrhenius plot was constructed and activation energy was calculated.     

Voltammetric determination of coenzyme Q10 in pharmaceutical dosage forms

A simple and rapid voltammetric method has been developed for the quantitative determination of coenzyme Q(10) (CoQ(10)) in pharmaceutical preparations. Studies with differential pulse voltammetry (DPV) were carried out using a glassy carbon electrode (GCE) in a mixed solvent containing 80 vol.% acetic acid and 20 vol.% acetonitrile. A well-defined reduction peak of CoQ(10) was obtained at -20 mV vs. Ag/AgCl. The voltammetric technique applied provides a precise determination of CoQ(10) using the multiple standard addition method. The statistical parameters and the recovery study data clearly indicate good reproducibility and accuracy of the method. The accuracy of the results assessed by recovery trials was observed to be within the range of 101.1% to 102.5%. The detection and quantification limits were found to be 0.014 mM (12 mg L(-1)) and 0.046 mM (40 mg L(-1)), respectively. An analysis of real samples containing CoQ(10) showed no interferences with common additives and excipients, such as unsaturated fatty acids and soya lecithin. The method proposed does not require any pretreatment of the pharmaceutical dosage forms. A spectrophotometric determination of CoQ(10) in real samples diluted in mixtures containing ethanol and n-hexane was also performed for comparison.     

Gas chromatographic determination of parabens in various pharmaceutical dosage forms

Summary A specific, sensitive and general applicabla gas chromatographic method is described for the determination of parabens in various liquid pharmaceutical preparations: propylparaben and butylparaben in a liquid antacid dosage form (I); methylparaben, ethylparaben and propylparaben in a syrup (II); methylparaben and propylparaben in a solution for injection (III). Each time one of the parabens is used as internal standard. The parabens are extracted with diethylether and derivatized by silylation. Different columns are used for the analysis of the parabens: 3% SE-30 column, a 3% QF-1 column for different selectivity, a 2% OV-1 column for isothermal operation.Special attention is attributed to the standard: the parabens are dissolved in a minimal amount of 0.1 M sodium hydroxide and extracted in the same way as the pharmaceutical dosage form.     

Spectrofluorimetric study of the beta-cyclodextrin-ibuprofen complex and determination of ibuprofen in pharmaceutical preparations and serum

The inclusion complexation of ibuprofen in beta-cyclodextrin (beta-CD) has been examined by means of spectrofluorimetry at both acid and alkaline pH. The results suggest that stable 1:1 complexes are formed in both media. The analysis of the pK(a) values for ibuprofen in both the absence and presence of beta-CD (4.12 and 4.66, respectively) suggests that in the inclusion complex the carboxylic group is located outside the cyclodextrin (CD) but interacting with it. Further structural characterization of the complex was carried out by means of am1 semiempiral calculations. Based on the obtained results, a spectrofluorimetric method for the determination of ibuprofen in the presence of beta-CD at 10 degrees C was developed in the range of 4.7-58 mug ml(-1). Better limits of detection (1.6 mug ml(-1)) and quantification (4.7 mug ml(-1)) were obtained in this latter case with respect to those obtained in the absence of beta-CD. The method was satisfactorily applied to the quantification of ibuprofen in pharmaceutical preparations. A novel spectrofluorimetric determination of ibuprofen in the presence of beta-CD was also developed for serum samples at concentration levels between 5 and 70 mug ml(-1). It uses second-order fluorescence excitation-emission matrices coupled to an algorithm based on self-weighted alternating trilinear decomposition (SWATLD), and avoids resorting to separative instrumental analyses.     

Determination of Exemestane in bulk and pharmaceutical dosage form by HPTLC

An HPTLC method for analysis of Exemestane in bulk and pharmaceutical formulation has been established and validated. The analyte was separated on aluminium plates precoated with silica gel 60 F₂₅₄. The mobile phase was chloroform:methanol 9.2:0.8 (v/v). Quantification was done by densitometric scanning at 247 nm. Response was a linear function of Exemestane concentration in the range of 100–500 μg mL⁻¹. The limit of detection and quantification for Exemestane were 5.8 and 17.58 μg mL⁻¹, respectively. Average recovery of Exemestane was 100.1, which shows that the method was free from interference from excipients present in the formulation. The established method enabled accurate, precise, and rapid analysis of Exemestane in bulk as well as pharmaceutical formulation.     

Electroanalysis of antioxidants in pharmaceutical dosage forms: state-of-the-art and perspectives

Monatshefte für Chemie - Chemical Monthly - Recent developments and future trends in electroanalytical chemistry of antioxidants in pharmaceutical dosage forms are discussed. The advantages of...     

Microwave-assisted extraction of active pharmaceutical ingredient from solid dosage forms

The microwave assisted extraction (MAE) technique has been evaluated for the extraction of active pharmaceutical ingredients (API) from various solid dosage forms. Using immediate release tablets of Compound A as a model, optimization of the extraction method with regards to extraction solvent composition, extraction time and temperature was briefly discussed. Complete recovery of Compound A was achieved when samples were extracted using acetonitrile as the extraction solvent under microwave heating at a constant cell temperature of 50 degrees C for 5 min. The optimized MAE method was applied for content uniformity (single tablet extraction) and potency (multiple tablets extraction) assays of release and stability samples of two products of Compound A (5 and 25mg dose strength) stored at various conditions. To further demonstrate the applicability of MAE, the instrumental extraction conditions (50 degrees C for 5 min) were adopted for the extraction of montelukast sodium (Singulair) from various solid dosage forms using methanol-water (75:25, v/v) as the extraction solvent. The MAE procedure demonstrated an extraction efficiency of 97.4-101.9% label claim with the greatest RSD at 1.4%. The results compare favorably with 97.6-102.3% label claim with the greatest RSD at 2.9% obtained with validated mechanical extraction procedures. The system is affordable, user-friendly and simple to operate and troubleshoot. Rapid extraction process (7 min/run) along with high throughput capacity (up to 23 samples simultaneously) would lead to reduced cycle time and thus increased productivity.     

Spectrophotometric determination of tranexamic acid in pharmaceutical bulk and dosage forms.

In this study, a simple, fast, accurate and sensitive spectrophotometric method has been developed for the determination of tranexamic acid in bulk and pharmaceutical preparations. The method is based on the reaction of ninhydrin with the primary amino group of tranexamic acid in the basic medium at pH 8.0. The reaction produces a bluish-purple color which absorbs maximally at 565 nm. Beer's law was obeyed in the range of 3-40 microg ml(-1) with molar absorptivity of 5.093 x 10(3) L mol(-1) cm(-1). The effects of various factors such as temperature, heating time, concentration of reagent, color stability and interferences were investigated to optimize the procedure. The results have been validated analytically and statistically. The proposed method has been applied for the determination of tranexamic acid in bulk and pharmaceutical preparations with good results.     

Spectrophotometric determination of metronidazole in pharmaceutical pure and dosage forms using p-benzoquinone

A simple and accurate spectrophotometric method for the determination of metronidazole in pure and pharmaceutical dosage forms has been developed. The proposed method is based on the reduction of the nitro group to amino group of the drug. This can be achieved by heating a mixture of an alcoholic solution of metronidazole, zinc powder and dilute hydrochloric acid in a water bath at 90 ± 5 °C for 15 min. The cold and clear filtrate reacts with p-benzoquinone to develop a purple color, which absorbs maximally at 526 nm. The calibration graph is linear over the concentration range of 15–190 μg ml^?1 with a molar absorptivity of 1.09 × 10³ l mol^?1 cm^?1. The proposed method is applied to commercially available pharmaceutical dosage forms and the results are statistically compared with those obtained by the reference method.