Mohammad A. Abounassif

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.

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.

Photodegradation kinetic study and stability-indicating assay of danazol using high-performance liquid chromatography

A selective high-performance liquid chromatographic procedure for the stability-indicating determination of danazol in the presence of its photolytic degradation products is demonstrated. The photolysis was carried out in glass vials and quartz cell under UV light at 254 nm. Satisfactory results were obtained for the assay and recovery testing with RSD values less than 2%. Kinetic parameters evaluated comprise the order of reaction and the rate constants of the degradation of the danazol irradiated in glass vials or quartz cell.

Spectrophotometric determination of amoxycillin and clavulanic acid in pharmaceutical preparation.

A spectrophotometric procedure for the simultaneous determination of amoxycillin and clavulanic acid in some pharmaceutical preparations has been developed. As the absorption bands of amoxycillin (274 and 227 nm) and clavulanic acid (270 nm) overlap, both Vierordts method and derivative spectrophotometry have been investigated and evaluated. The first-derivative spectrophotometric method was found to be more accurate, direct and reproducible.

D1-Differential Potentiometric and 1H-NMR Spectrometric Determinations of Ketoconazole and its Formulations

Abstract Two rapid and direct quantitative assays have been investigated for ketoconazole alone and in tablet form. the first one is a non-aqueous potentiometric titration in which the equivalence point has been located graphically using its distinct and sharp D1differential (peak-shape) potentiograph. the second is based on 1H-NMR spectrometry and involves the integration of the methyl protons-signal of ketoconazole (at 2.07 δ) relative to that of benzocaine (at 1.30 δ) which is used as internal standard. the obtained results were in good agreement with regard to accuracy, precision as well as sensitivity and reproducibility. However, by comparison with the official USP procedure, the two methods were significantly more accurate and more sensitive. the validity of the two methods were confirmed using the authentic addition technique.

Ratios of first-derivative maxima and compensated derivative absorption curves

General procedures are outlined for the detection of the presence of interferences during spectrophotometric analysis using first-derivative absorption spectra. These involve (i) ratios of first-derivative maxima, which are independent of concentration, and (ii) the compensated derivative curves. Thus, selecting two suitable maxima at λ1 and λ2, D11/D12, |D11–D12|/D11 and D1(corr.)1/|D11–D12| are used to reveal the shape of the interference curve and the possibility of eliminating its effect. These ratios are highly reproducible with coefficients of variation of less than 1%. The methods are illustrated by the determination of phenol in a pharmaceutical preparation. The results obtained were in good agreement with those of the official bromimetric method.

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.

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.

PHOTODEGRADATION KINETIC STUDIES AND STABILITY-INDICATING ASSAY OF DILOXANIDE FUROATE IN DOSAGE FORMS USING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

ABSTRACT The effect of different conditions on the photostability of diloxanide furoate (DF) was investigated. To perform stability studies on DF, a specific stability-indicating high-performance liquid chromatographic (HPLC) method was established using an ultraviolet detector set at 258 nm. The accuracy, precision, and reliability of the method for the assay of DF in its tablets dosage form were established. Assay results were within RSD values less than 2%. The stability-indicating power of the HPLC method was validated by UV-degraded DF solution in a mixture of acetonitrile:water (55 : 45 v/v) contained in quartz cells and glass bottles. The resultant chromatogram indicated that the degradation products were well separated from the parent drug. Photostability of DF was studied under different light exposures, i.e., UV-irradiation, room artificial light, and sunlight. Using the HPLC method, the photodegradation kinetics of the drug was studied in both a quartz cell and glass bottle. In both cases the photodegradation process followed first-order kinetics. The effects of different solvents on the UV-irradiation of DF are also reported. One of the three major degradation products observed was identified.

Spectrophotometric Method of Determination for Cycloserine Using Chlornil

Abstract Cycloserine has been determined by a spectrophotometric method based on n → charge-transfer complex formation with chloranil. The method involves addition of cycloserine solution to chloranil reagent in borate buffer of pH 9; and heating at 65°C for 45 min. The complex formed exhibits absorption maximum of 348 nm; and Amax is linearly related to concentration over the range 2–8 μg/ml. The mean percentage found for the authentic sample is 100.32 ± 0.70. When applied to commercial capsules claimed to contain 250 mg each, the mean percentage found is 102.45 ± 1.05. These results have shown good agreement when compared with those obtained by the pharmacopoeial (B.P.) methods.