Elrasheed Ahmed Gadkariem

A stability-indicating LC method for the simultaneous determination of ramipril and hydrochlorothiazide in dosage forms

A simple, rapid and sensitive HPLC method has been developed for the simultaneous determination of ramipril and hydrochlorothiazide in their dosage forms. Acetonitrile: sodium perchlorate solution (0.1 M) adjusted to pH 2.5+/-0.2 with phosphoric acid (46:54 v/v), was used as the mobile phase, at a flow rate of 1.5 ml/min. A supelcosil LC-8 column (5 microm), 15 cm x 4.6 mm i.d. was utilized as stationary phase. Detection was affected spectrophotometrically at 210 nm. Clobazam was used as an internal standard. The method was also applied for the determination of ramipril in the presence of its degradation products. Linearity ranges for ramipril and hydrochlorothiazide were 4.5-45 and 0.6-14 microg/ml, respectively. Minimum detection limits (S/N = 2) obtained were 180 and 23 ng/ml for ramipril and hydrochlorothiazide, respectively. The proposed method was further applied to the analysis of tablets containing the two drugs, the percentage recoveries +/- S.D. (n = 5) were 100.45%+/-0.63 and 99.55%+/-0.78 for ramipril and hydrochlorothiazide, respectively.

Potentiometric and Visual Titrimetric Methods for Analysis of Captopril and Its Pharmaceutical Forms

Abstract Captopril, a new anihypertensive agent, has been assayed in authenitic as well as in tablet (Capoten((R))Manufacture: Squibb and Sons, Inc., Princeton, N.J., U.S.A. dosage forms by applying potentiometric visual, argentometric and oxidometric methods of idoine and cupric ion. Each method of assay involves the determination of captopril in a given weight of sample. Six samples were run for each method and the average percentages of recovery of captopril from its tablets were computed. For the potentiometric and visual silver methods the average percentages of recovery are 103.3 ± 1.2 and 102.3 ± 1.0 respectively. For the oxidometic methods of iodine and cupric ion, the average percentages of recovery are 103.8 ± 1.5 and 104.2 ± 1.4 respectively.

Liquid chromatographic determination of amoxycillin and clavulanic acid in pharmaceutical preparations

A liquid chromatographic method for the simultaneous determination of amoxycillin and potassium clavulanate in tablet and suspension preparations is presented. The method specifies reversed phase column and a buffered mobile phase (CH3OH + KH2PO4-buffer pH 6 + H2O, 15:1:84) isocratically at a rate of 1.0 ml min-1, with detection at 235 nm. The suitability of the chromatographic system developed is tested using replicate injections of the sample and standard preparations. The observed relative standard deviations (RSDs) were within 2%. Recovery experiments conducted utilizing the proposed method gives results of 101.5% +/- 1.72 (n = 6) and 101.22% +/- 1.93 (n = 6) for amoxycillin in tablets and powder for oral administration, respectively. Similarly, recovery experiments for clavulanic acid gave results of 100.33 +/- 1.90 (n = 6) and 99.61 +/- 1.32 (n = 6) in the tablets and suspension powder, respectively. Comparison of the proposed method with the USP method proved it to be satisfactory. The statistical F- and t-tests observed, indicated that there were no significant differences between the two methods regarding precision and accuracy.

A Selective Colorimetric Method for the Determination of Penicillins and Cephalosporins with α-Aminoacyl Functions

A simple, sensitive and selective colorimetric method is described for the assay of ampicillin, amoxicillin, cephalexin, cefadroxil and cefaclor in their pharmaceutical preparations. The method is based on measuring the color obtained when the alkaline degradation products of these agents are allowed to react with ascorbic acid. The factors affecting the color generation and determination were studied and optimized. The reaction is selective to β-lactam antibiotics having amino acid side-chains with free amino functions and thus allow interference-free quantitation of some preparations containing these agents in combination with other β-lactam agents. The procedure is also successfully adopted as stability-indicating method for cephalosporins. A tentative mechanism of the color reaction is proposed.

Colorimetric Method for the Determination of Ampicillin and Amoxicillin

A simple colorimetric procedure is described for the quantitation of ampicillin and amoxicillin in their pharmaceutical preparations. The color production is based on the reaction of the oxidation product of ascorbic acid, dehydroascorbic acid, with the corresponding penicillenic acids obtained by the degradation of the antibiotics after heating under acidic conditions. The reaction demonstrated selectivity towards the penicillins having amino acid side chains and thus allowed interference-free quantitation of ampicillin and amoxicillin in combination with cloxacillin or clavulenic acid. The procedure showed good accuracy and precision and offers advantages over the official and many other reported analytical procedures.

Simultaneous determination of amoxycillin and dicloxacillin in capsules by potentiometric titrimetry and high-performance liquid chromatography.

Direct potentiometric titration and two HPLC conditions for the simultaneous determination of amoxycillin and dicloxacillin in their capsules have been developed. One-run titration utilizing 0.05M acet. HClO(4) enables the quantification of both antibiotics. The HPLC-separation could be undertaken on reversed phase, LiChrosorb RP-18 (10 mum), and LiChrospher 100 RP-18 (5 mum), columns by using mobile phases containing acetonitrile + 1% aq, acetic acid, in proportions of 47:53 or 39:61 (v/v), respectively, at a flow rate of 1.5 ml/min with UV-detection at 240 nm. Recoveries of the individual drugs by the application of each described method were found to be fairly satisfactory.

Spectrophotometric Determination of Fluvoxamine in Tablets Based on Charge-Transfer Complex with Chloranil

Abstract Fluvoxamine was reacted with chloranil in aqueous ethanolic medium buffered at pH 9 to yield a complex with maximum absorption at 347 nm. The estimated molar absorptivity and stability constant of the complex were (1.30 ± 0.03) × 104 L mol−1 cm−1 and (1.7 ± 0.5) × 104 L mol−1 respectively. Absorbance at (δmax) was linearly related to concentration of fluvoaxamine over the range 2 to 25 μg ml−1 with a detection limit of 0.4 μg ml−1. The slopes of log-log plots of initial concentrations of fluvoxamine or chloranil vs. initial rate of color development were both unity. When the reaction was applied to commercial tablets (Faverin ρ −50) labeled to contain 50 mg of fluvoxamine maleate per tablet, the mean percentage found was 100.4 ± 1.0. Recovery experiments after standard additions and analysis of variance (ANOVA) were carried out to investigate the accuracy and precision of the proposed method. Reversed-phase high-performance liquid chromatography, (RP-HPLC), using μ-Bondapak C18 (30 cm × 3.9 mm, i...

Colorimetric determination of piperazine with p-benzoquinone.

Piperazine and its salts are reacted with aqueous alcoholic p-benzoquinone, buffered at pH 5.4, to give a coloured product with maximum absorption at 516nm. The piperazine base has a molar absorptivity of 0.96 x 10(4)l.mole(-1).cm(-1) and Beers law is obeyed over the range 2-10 mug ml . When applied to three commercial preparations, the proposed method gave mean recoveries within 1% of those obtained by the official gravimetric method. The relative standard deviation was less than 1%.

A STABILITY-INDICATING HPLC METHOD FOR THE DETERMINATION OF ISOXSUPRINE IN DOSAGE FORMS. APPLICATION TO KINETIC STUDIES OF ISOXSUPRINE

A simple, rapid, and stability-indicating HPLC method has been developed for the determination of isoxsuprine in the presence of its degradation products. Acetonitrile: potassium dihydrogen phosphate (0.01 M solution) adjusted to pH 2.2 ± 0.1 with phosphoric acid (18:82 v/v), was used as the mobile phase, at a flow rate of 2.5 mL/min. A μ Bondapak™ C18 10μm column (3.9 mm i.d. × 150 mm) was utilized as a stationary phase. Detection was affected spectrophotometrically at 275 nm. Methyl p-hydroxybenzoate was used as an internal standard. The method was applied for the determination of isoxsuprine in the presence of its main degradation products, namely: 4-hydroxy-benzaldehyde, 4-hydroxybenzyl alcohol, 4-hydroxybenzoic acid, and 4-hydroxyacetophenone. Linearity range for isoxsuprine was 2–40 μg/mL with correlation coefficient (r) of 0.9998 and minimum detectability was 0.2 μg/mL (∼6 × 10-7M). The proposed method was further applied to the analysis of commercial tablets containing the drug, the percentage recoveries ± SD were 99.60 ± 0.76 and 99.78 ± 0.88, and these values were in agreement with those given with the official methods. The method was also adopted to detect isoxsuprine in spiked human plasma at its therapeutic level of concentration (0.4 μg/mL). The proposed HPLC method was successfully applied to study the degradation kinetics of isoxsuprine. The photothermal degradation of isoxsuprine upon exposure to UV light was first-order with regard to its concentration.

Effects of alkali and simulated gastric and intestinal fluids on danazol stability.

The degradation kinetics of methanolic solution of danazol (0.020% w/v) in aqueous buffers and sodium hydroxide was investigated using stability-indicating HPLC method. The drug degrades in alkaline medium through a base-catalysed proton abstraction rather than via an oxidative mechanism involving oxygen species. The degradation followed pseudo-first-order kinetics. The rates pH-profile exhibited specific base catalysis. The stability of the drug was found to be dependent on pH, buffer concentration, buffer species (acetate, borate, phosphate) and temperature. The ionic strength did not affect the stability of the drug. The energy of activation according to Arrhenius plot was estimated to be 22.62 kcal mol(-1) at pH 12 and temperatures between 30 and 60 degrees C. The effect of simulated gastric and intestinal fluids on the drug stability was also investigated. Two major hydrolytic degradation products were separated and identified by IR, NMR and mass spectrometry and the degradative pathway suggested.