ABSTRACT
A simple, extraction-free spectrophotometric method is proposed for the analysis of some beta-blockers, namely atenolol, timolol and nadolol. The method is based on the interaction of the drugs in chloroform with 0.1% chloroformic solutions of acidic sulphophthalein dyes to form stable, yellow-coloured, ion-pair complexes peaking at 415 nm. The dyes used were bromophenol blue (BPB), bromothymol blue (BTB) and bromocresol purple (BCP). Under the optimum conditions, the three drugs could be assayed in the concentration range 1-10 microg ml(-1) with correlation coefficient (n = 5) more than 0.999 in all cases. The stoichiometry of the reaction was found to be 1:1 in all cases and the conditional stability constant (K(F)) of the complexes have been calculated. The free energy changes (DeltaG) were determined for all complexes formed. The interference likely to be introduced from co-formulated drugs was studied and their tolerance limits were determined. The proposed method was then applied to dosage-forms the percentage recoveries ranges from 99.12-100.95, and the results obtained were compared favorably with those given with the official methods.
Subject(s)
Adrenergic beta-Antagonists/analysis , Adrenergic beta-Antagonists/chemistry , Chemistry, Pharmaceutical/methods , Spectrophotometry, Ultraviolet/methods , Atenolol/analysis , Bromcresol Purple/pharmacology , Bromphenol Blue/pharmacology , Bromthymol Blue/pharmacology , Chemistry Techniques, Analytical/methods , Chloroform/chemistry , Coloring Agents/analysis , Coloring Agents/pharmacology , Dose-Response Relationship, Drug , Ions , Kinetics , Models, Chemical , Nadolol/analysis , Tablets , Thermodynamics , Timolol/analysisABSTRACT
The application of direct current differential electrolytic potentiometry to an aqueous titration of L-cysteine hydrochloride, captopril and D-penicillamine has been investigated. The basic character of thiol compounds in nitric acid is enhanced to permit their direct titrations with silver nitrate. A pair of silver amalgam electrodes was used as an indicating system. Titration curve shapes obtained are almost symmetrical with sharp peaks. The optimum current density for those titrations was found to be 0.2-2 microA/cm2. The procedure was applied successfully to the determination of certain thiol compounds in drug formulations and the results were favorably compared statistically with those obtained from official methods.
Subject(s)
Electrolysis , Sulfhydryl Compounds/administration & dosage , Sulfhydryl Compounds/analysis , Dosage Forms/standards , Electrolysis/standards , Potentiometry/methods , Potentiometry/standards , Sulfhydryl Compounds/standardsABSTRACT
2-Hydroxy-1-naphthaldehyde (HNA) was investigated as a derivatizing reagent for the fluorescence detection of histidine, methionine and tryptophan at 385 and 265 nm. The separation of HNA-derivatized amino acids on a conventional reversed-phase column was achieved in less than 40 min. This method was compared with the reported o-phthaldialdehyde (OPA) method. The procedure was successfully applied to the assay of the pure amino acids in a mixture and their pharmaceutical dosage forms.
Subject(s)
Amino Acids/analysis , Chromatography, High Pressure Liquid , Indicators and Reagents , NaphthalenesABSTRACT
A simple and rapid colorimetric method for the determination of some amino acids containing a sulfur group is described. The studied compounds are cysteine, cystine and methionine. The method is based on the formation of ferroin, from the reaction of the studied drugs with a mixture of iron(III) and 1,10-phenanthroline and measurement of the absorbance at 512 nm. The procedure has been successfully applied to the assay of the pharmaceutical preparations of the studied drugs after thin-layer chromatographic separation and the results of the studied compounds compare favourably with the official methods.
