Optimized and validated spectrophotometric methods for the determination of lisinopril in pharmaceutical formulations using ninhydrin and ascorbic acid

Abstract

Dois métodos espectrofotométricos, simples e sensíveis, são descritos para a determinação de lisinoprila pura e em preparações farmacêutica. O primeiro método é baseado na reação da droga com nihidrina, no solvente N, N'-dimetilformamida (DMF) a temperatura ambiente, a qual é acompanhada espectrofotometricamente pela medida do aumento da absorbância a 595 nm, em função do tempo. As técnicas de medida da velocidade inicial, da determinação da constante de velocidade e de medida em tempo fixo (10 min) foram adotadas na construção das curvas de calibração, para a determinação da concentração da droga. Os métodos de velocidade inicial e da medida em tempo fixo mostraram uma resposta linear no intervalo de concentração 10-50 μg mL -1 , enquanto o método de constante de velocidade tem resposta linear no intervalo 10-40 μg mL -1 . No segundo método, a droga reage com ácido ascórbico em solução de DMF, resultando num produto colorido com máximo de absorbância a 530 nm. A lei de Beer é obedecida no intervalo de concentração 5-50 μg mL -1 de linisoprila, com absortividade molar de 4,548×10 3 L mol -1 cm -1 . As variáveis que afetam o desenvolvimento da cor foram otimizadas, e o método foi validado estatisticamente e por estudos de recuperação. O método proposto foi usado com sucesso na determinação de lisinoprila em comprimidos comerciais.Two simple and sensitive spectrophotometric methods are described for the determination of lisinopril in pure form and pharmaceutical preparations. The first method is based on the reaction of the drug with ninhydrin in N,N'-dimethylformamide (DMF) medium at room temperature which is followed spectrophotometrically by measuring the increase in absorbance at 595 nm as a function of time. The initial-rate, rate-constant and fixed-time (at 10 minutes) procedures were used for constructing the calibration graphs to determine the concentration of the drug. The initial-rate and fixed-time procedures showed a linear response over the concentration range 10-50 μg mL -1 whereas rate-constant procedure was applicable in the range 10-40 μg mL -1 . In the second method, the drug reacts with ascorbic acid in DMF medium resulting in the formation of a coloured product, which absorbed maximally at 530 nm. Beer's law is obeyed in the concentration 5-50 μg mL -1 of lisinopril with molar absorptivity of 4.548×10 3 L mol -1 cm -1 . The variables affecting the development of the colour are optimized and the developed methods are validated statistically and through recovery studies. The proposed methods have been successfully applied to the determination of lisinopril in commercial tablets.Keyword: lisinopril, ninhydrin, ascorbic acid, dimethylformamideis an angiotensin converting enzyme (ACE) inhibitor. It is used in the treatment of hypertension and heart failure. The increasing use of this recently introduced drug, which is highly susceptible to the acidic degradation, needs simple, sensitive and selective method for the routine analysis in pharmaceutical formulations.Certain successful attempts have been...

New Method for Spectrophotometric Determination of Lisinopril in Pure Form and in Pharmaceutical Formulations

“…Five independent analyses [29] rt: Room temperature Alizarin is advantages over many of the reported methods. The methods are rapid, simple and have good sensitivity and accuracy.…”

“…Sodium hypochlorite-phenyl hydrazine [7], 1-fluoro-2,4-dinitrobenzene [28] and ascorbic acid [29]. Most of these methods employ organic solvents as reaction medium, require longer heating times, use expensive reagents, and/or are less sensitive (Table 1).…”

“…Of the various regents used in the assay of LNP in pharmaceuticals, ninhydrin has been employed by quite a few researchers. For example, Rehman et al [29] used ninhydrin in DMF medium for kinetic spectrophotometric determination of LNP by initial rate and fixedtime procedures. Both methods showed linear response over 50 µg/ mL LNP.…”

“…Rajashekaran and Udayavani [31] assayed LNP in the 10-40 µg/mL range by measuring the coloured product formed between ninhydrin and LNP in acetone medium at elevated temperature. The common feature of all the three methods using ninhydrin [29][30][31] is the use of organic solvent as the reaction medium which quite often is undesirable.…”

Development and application of spectrophotometric method for the determination of cefaclor in pharmaceutical formulations

“…13 It has been extensively used in the determination of the compounds of pharmaceutical importance. [14][15][16] …”