Development of Validated Specific Stability Indicating HPTLC Method for Simultaneous Estimation of Enalapril Maleate and Losartan Potassium in its Combined Dosage Form

Abstract

The objective of current study was to develop a validated, specific stability indicating normal-phase high performance thin layer chromatographic method for simultaneous estimation of enalapril maleate and losartan potassium in their combined dosage form. The forced degradation studies were performed on pure enalapril maleate and losartan potassium and also on their combined dosage form using acid, base, neutral, oxidation, thermal and photo stress to show the stability indicating capability of the developed method. Significant degradation products of enalapril maleate were observed in acidic, basic and thermal stress whereas losartan potassium were degrade in photo stress. No degradation products were obtained after neutral and oxidation stress conditions. The chromatographic method was optimized using samples generated in forced degradation studies. Good separation between the peaks corresponding to the active pharmaceutical ingredients, enalapril maleate and losartan potassium and degradation product from the analyte were achieved on silica gel 60F₂₅₄ TLC plate using toluene: ethyl acetate: methanol: acetic acid in ratio 5:2.5:2.5:0.1 (v/v) as mobile phase. Densitometric quantification was performed at 213 nm by reflectance scanning. The R_F values of enalapril maleate and losartan potassium were 0.49 ± 0.03 and 0.66 ± 0.03, respectively. Validation of the developed method was conducted as per ICH requirements. Response were a linear function of concentration of enalapril maleate over the range 50-400 ng/band by peak area with correlation coefficient 0.99523 and losartan potassium over the range 250-2000 ng/band by peak area with correlation coefficient 0.99030. The limit of detection of enalapril maleate was 4.58 ng/band for peak area and the limit of detection of losartan potassium was 7.26 ng/band for peak area. Results from analysis of a commercial tablet formulation were 100.17 ± 1.170 % and 98.97 ± 0.6243 % for enalapril maleate and losartan potassium, respectively. Recoveries were 98.69 ± 1.3373 % and 100.15 ± 0.5016 % for enalapril maleate and losartan potassium, respectively.