Colorimetric determination of zidovudine in bulk and tablet dosage forms using potassium dichromate

A colorimetric method involving the oxidation of zidovudine (ZDV) using potassium dichromate in sulphuric acid has been developed for the determination of ZDV in bulk and tablet dosage forms. The wavelength of maximum absorption (λmax) of the oxidation product was determined and concentrations of sulphuric acid, potassium dichromate and amount/duration of heat were optimized. Beers plot was constructed at the λmax and used in the recovery studies for pure drug sample. Two methods (acid and methanol extraction) were used to extract ZDV from tablet samples. The developed method was then used to determine the percentage content of the drug in the tablets. The method was validated using the International Council for Harmonization of Technical Requirement for registration of Pharmaceuticals for Human Use (ICH) guideline. The λmax of the oxidation product was found to be 602 nm. The optimized conditions were as follows: 0.083M (potassium dichromate), 12 M (sulphuric acid) and heating at 90ºC for 30 mins. The regression equation for the Beer’s plots is: A = 0.4313C + 0.0018 (R2=0.9995) for ZDV. The recovery of ZDV from standard solutions was 100.36%±0.36. Thus the developed method was accurate and precise. The percentage contents determined for different brands of ZDV tablets were 99.07%±0.83, 98.70%±0.76, 93.46%±0.72 for the three brands of ZDV. These values compared well with results obtained with use of another method of assay. These values are within the specifications of the British Pharmacopoeia (90-110%). The limits of detection and limits of quantification were 0.004 and 0.014 mg/ml respectively. The developed method is simple, accurate, and utilizes readily available chemicals and equipment, and is inexpensive. It could therefore be used for the routine determination of ZDV.Keywords: Zidovudine, Oxidation, Colorimetric, Absorbanc

Pharmacognostic evaluation of the leaves of Mitracarpus scaber Zucc (Rubiaceae)

Purpose: The methanolic extract and isolated constituents of Mitracarpus scaber Zucc have been reported to exhibit hepatoprotective, antibacterial and antimycotic activities. Establishment of Pharmacognostic profile of the leaves will assist in standardization for quality, purity and sample identification. Method: Evaluation of the fresh, powdered and anatomical sections of the leaves were carried out to determine the macromorphological, micromorphological, chemomicroscopic, numerical and phytochemical profiles. Results: Macro - and microscopical studies indicated presence of simple leaf whorled arrangement, an entire margin with lanceolate shape, acute apex and base, parallel venation, thin and wavy anticlinal walls with numerous calcium oxalate crystals. Stomata arrangement was anomocytic with numerous covering trichomes on both surfaces. Chemomicroscopic characters present include lignin, starch, cellulose, mucilage and calcium oxalate crystals while phytochemical evaluation revealed the presence of alkaloids, tannins, cardiac glycosides and saponins. The investigations also included numerical and quantitative leaf microscopy. Conclusion: These findings should be suitable for inclusion in the proposed Pharmacopoeia of Nigerian Medicinal plants

Rapid titrimetric and spectrophotometric determination of ofloxacin in pharmaceuticals using N-bromosuccinimide

One titrimetric and two spectrophotometric methods have been described for the determination of ofloxacin (OFX) in bulk drug and in tablets, employing N-Bromosuccinimide as an analytical reagent. The proposed methods involve the addition of a known excess of NBS to OFX in acid medium, followed by determination of unreacted NBS. In titrimetry, the unreacted NBS is determined iodometrically, and in spectrophotometry, unreacted NBS is determined by reacting with a fixed amount of either indigo carmine (Method A) or metanil yellow (Method B). In all the methods, the amount of NBS reacted corresponds to the amount of OFX. Titrimetry allows the determination of 1-8 mg of OFX and the calculations are based on a 1:5 (OFX:NBS) reaction stoichiometry. In spectrophotometry, Beer's law is obeyed in the concentration ranges 0.5-5.0 µg/mL for method A and 0.3-3.0 µg/mL for method B. The molar absorptivities are calculated to be 5.53x10(4) and 9.24x10(4) L/mol/cm for method A and method B, respectively. The methods developed were applied to the assay of OFX in tablets, and results compared statistically with those of a reference method. The accuracy and reliability of the methods were further ascertained by performing recovery tests via the standard-addition method.<br>Descrevem-se métodos, um titulométrico e dois espectrofotométricos, para a determinação de ofloxacino (OFX) na matéria-prima e em comprimidos, empregando a N-bromossuccinimida (NBS) como reagente analítico. Os métodos propostos envolvem a adição de excesso conhecido de NBS ao OFX, em meio ácido, seguida de determinação do NBS que não reagiu. Na titulometria, o NBS que não reagiu é determinado iodometricamente e na espectrofotometria, o NBS que não reagiu é determinado pela reação com quantidade fixa de índigo carmim (Método A) ou amarelo de metanila (Método B). Em todos os métodos, a quantidade de NBS que reagiu corresponde à quantidade de OFX. A titulometria permite a determinação de 1-8 mg de OFX e os cálculos se baseiam na estequiometria de reação de 1:5 (OFX:NBS). Na espectrofotometria, a Lei de Beer é obedecida nas faixas de concentração de 0,5-5,0 µg/mL, para o método A, e de 0,3-3,0 µg/mL, para o método B, respectivamente. Os métodos desenvolvidos foram aplicados para o teste de OFX em comprimidos e os resultados foram comparados estatisticamente com aqueles do método de referência. A precisão e a confiabilidade dos métodos foram, posteriormente, verificadas por meio dos testes de recuperação via método de adição de padrão