Simultaneous determination of clopamide-pindolol combination in tablets by zero-crossing derivative spectrophotometry

A first-derivative spectrophotometric method, using a 'zero-crossing' technique of measurement has been used for determining clopamide-pindolol mixture in tablets. In the first-derivative mode the zero-crossing points of clopamide and pindolol occur at 272.6 and 262.4 nm, respectively. The relative ease offered by this technique for the quantification of these drugs with closely overlapping bands was demonstrated. The linearity of the calibration curves was satisfactory (r = 0.9998) and the precision (RSD%) better than 1.89. Detection limits were 0.50 and 0.44 μg ml-1 for pindolol and clopamide, respectively. No spectral interferences from tablet excipients were found. Applications are given for the assay of commercial tablets and content uniformity test. The procedures proved to be suitable for rapid and reliable quality control. © 1994

Determination of captopril and captopril-hydrochlorothiazide combination in tablets by derivative UV spectrophotometry

Assay procedures based on derivative spectrophotometry have been developed for the determination of captopril alone or in combination with hydrochlorothiazide in tablets. Captopril (5.0-25.0 μg/ml) can be determined by measuring the amplitude of the maximum D2,258nm of the second-order derivative spectrum. Combinations of captopril (6.0-14.0 μg/ml) and hydrochlorothiazide (3.0-7.0 μg/ml) in a ratio of 2:1 can be determined using the simultaneous equations method with measurements of the amplitudes of the maximum-minimum of the first-order derivative spectrum D1,278-260nm and D1,213nm. The linearity of the calibration curves was excellent (r>0.9997), the precision (RSD) better than 1.6% and the relative errors (Er) less than 2.6%. The methods were succesfully applied to commercial tablets containing captopril alone or captopril in combination with hydrochlorothiazide. © 1992

Simultaneous determination of benazepril hydrochloride and hydrochlorothiazide by micro-bore liquid chromatography

A micro-bore liquid chromatographic method was developed for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical dosage forms. The use of a BDS C-18 micro-bore analytical column, results in substantial reduction in solvent consumption and increased sensitivity. The mobile phase consisted of a mixture of 0.025 M sodium dihydrogen phosphate (pH 4.8) and acetonitrile (55:45, v/v), pumped at a flow rate of 0.40 ml min(-1). Detection was set at 250 nm using an ultraviolet detector. Calibration graphs are linear (r better than 0.9991, n = 5), in concentration range 5.0-20.0 mu g ml(-1) for benazepril hydrochloride and 6.2-25.0 mu g ml(-1) for hydrochlorothiazide. The intra- and interday R.S.D. values were < 1.25% (n = 5), while the relative percentage error (E-r) was < 0.9% (n = 5). The detection limits attained according to IUPAC definition were 0.88 and 0.58 mu g ml(-1) for benazepril hydrochloride and hydrochlorothiazide, : respectively. The method was applied in the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control. (C) 1999 Elsevier Science B.V. All rights reserved

Second-derivative spectrophotometric determination of naproxen in the presence of its metabolite in human plasma

A second-derivative spectrophotometric method for the determination of naproxen in the absence or presence of its 6-desmethyl metabolite in human plasma is described. The method consists of direct extraction of the non-ionized form of the drug with pure diethyl ether and determination of the naproxen by measuring the peak amplitude (mm) in the second-order derivative spectrum at a wavelength of 328.2 nm. The efficiency of the extraction procedure expressed by the absolute recovery was 94.6 ± 0.7% (mean ± s) for the concentration range tested, and the limit of quantification attained according to the IUPAC definitation was 2.42 mg l-1. The linear dynamic range for naproxen was 5.0-100.0 mg l-1, the correlation coefficient for the calibration graphs was excellent, r = 0.99993 (n = 6), the precision (S r) was better than 4.58% and the accuracy was satisfactory (E r < 2.32%). The results obtained by the proposed method were in good agreement with those found by an HPLC method

Determination of hyoscine N-butyl-bromide, lidocaine hydrochloride, and paracetamol in injection forms using solid-phase extraction, high-performance liquid chromatography, and UV-Vis spectrophotometry

A solid phase extraction procedure using strong cation exchange (SCX, benzenesulfonic acid) cartridges followed by a reversed-phase HPLC assay was applied to the analysis of hyoscine n-butylbromide and lidocaine hydrochloride in injection forms. The chromatographic separation was performed on a BDS C-18 column. The mobile phase consisted of a mixture of acetonitrile: ammonium acetate 0.2M, (30:70, v/v) pumped at a flow rate 1.2 mL/min. The UV detector was operated at 254 nm. A UV-Vis spectrophotometric method was also developed for the determination of paracetamol in the injection forms. The method consists of subsequent dilution of the injection forms and measure of the absorbance value at 242.7 nm. Relative standard deviation was less than 0.95% for HPLC and less than 0.78% for the spectrophotometric method. Detection limits were 1.05, 0.96 and 0.67 μg/mL for hyoscine n-butylbromide, lidocaine hydrochloride and paracetamol, respectively

Determination of clopamide-pindolol combination in tablets by fourth-order derivative UV spectrophotometry

A fourth-derivative spectrophotometric procedure for the simultaneous determination of clopamide and pindolol in binary mixtures, in tablets, is described. Calibration graphs are linear (r = 0.9999), the precision (RSD%) better than 2.22 and the percentage relative error (Er%) less than 0.12. No spectral interference from tablet excipients was found. Applications are given for the assay of commercial tablets and content uniformity test. The procedure proved to be suitable for rapid and reliable quality control. © 1993

Use of cyclodextrins as chiral selectors for direct resolution of the enantiomers of fluoxetine and its metabolite norfluoxetine by HPLC

The goal of this work is to investigate the direct chromatographic separation of the enantiomers of fluoxetine and its active metabolite norfluoxetine. The liquid chromatographic retention behavior of these enantiomers on a β‐cyclodextrin bonded‐phase column was investigated with respect to mobile phase composition, pH, ionic strength, and solvent selectivity. Relationships were established between these factors and the three most important chromatographic parameters: retention time, resolution, and selectivity. Most of the evidence suggests that the unique selectivity of this column isdue to inclusion complex formation, which provides the physical basis for enantiomeric resolution. After these studies a set of optimum chromatographic conditions was chosen for the simultaneous separation/determination of a mixture of the four enantiomers using fluorescence detector. © 1993 Wiley‐Liss, Inc. Copyright © 1993 Wiley‐Liss, Inc

Enantiomeric separation of zopiclone, its metabolites and products of degradation on a β-cyclodextrin bonded phase

In this paper the separation of zopiclone (ZP) enantiomers, its degradation products and chiral metabolites, has been investigated on a β-cyclodextrin bonded phase. The liquid chromatographic behavior of the enantiomers of zopiclone, zopiclone-N-oxide (OXZP) and N-desmethyl-zopiclone (DMZP) has been studied with respect to mobile-phase composition, pH, ionic strength and the nature of the organic modifier. Based on the results, conditions were chosen for the separation of the enantiomers of zopiclone, its chiral metabolites and its related degradation products. The separation selectivity of a β-cyclodextrin (β-CD) bonded-phase column was examined. Further, based on crystallographic data, a computer model of the ZP molecule has been designed by using the HyperChem program in order to estimate the possibility of the different groups to interact with the β-CD and to give a plausible explanation of the mechanism of chiral discrimination

Evaluation of the chromatographic behaviour of fluoxetine and norfluoxetine using different cyclodextrins as mobile phase additives and fluorimetric detection

The principal goal of this work was to investigate the liquid chromatographic retention behaviour of fluoxetine and norfluoxetine using HPLC with respect to mobile phase composition, pH, flow rate and the amount of the native β-cyclodextrin (β-CD) or the β-hydroxypropyl-cyclodextrin (HP-β-CD), added to the mobile phase. Further, it was of interest to evaluate the effectiveness of β-CD and HP-β-CD to enhance fluorescence detection of these compounds. Another purpose of this study, was to calculate the formation constants of the inclusion complexes (K(f) of fluoxetine and norfluoxetine within the HP-β-CD, in different mobile phase compositions. Based on these findings, the log K(f) values of these two compounds referred to pure aqueous mobile phase (log K(fW), can be determined by extrapolation

Development and validation of a reversed-phase HPLC method for the determination of pindolol and clopamide in tablets

A high-performance liquid chromatographic method was developed for the simultaneous determination of pindolol and clopamide in pharmaceutical dosage forms. The use of a β-cyclodextrin bonded-phase column results in satisfactory separation of both of the compounds. The mobile phase consisted of a mixture of 1.0% w/v triethylamine acetate buffer (pH = 5.5) and methanol (90:10, v/v), pumped at a flow rate 0.8 mL/min. The UV detector was operated at 245 nm. Calibration graphs are linear (r better than 0.99997, n = 5), in concentration range 1.0-3.0 μg/mL for pindolol and 0.5-1.5 mg/mL for clopamide. The intra- and interday R.S.D. values were less than 2.97% (n = 5), while the relative percentage error Er was less than 2.0% (n = 5). Detection limits were 0.12 and 0.16 mg/mL for pindolol and clopamide, respectively. The method was applied in the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control