Development and validation of sensitive high‐performance liquid chromatography‐photodiode array method for determination of three sulfonated esters and N‐methyl‐O‐phenyldiamine dihydrochloride as potential genotoxic impurities in Amlodipine and Telmisartan fixed‐dose combination

Abstract

Several regulatory organizations encourage the quantitative analysis of potentially genotoxic impurities in finished pharmaceutical preparation. For the first time, a sensitive, accurate, and reliable reversed phase‐high‐performance liquid chromatography method was developed and validated for two antihypertensive drugs, three genotoxic impurities of Amlodipine namely methyl benzene sulfonate, ethyl benzene sulfonate, and ethyl‐p‐toluene sulfonate, as well as N‐methyl O‐phenylenediamine dihydrochloride as genotoxic impurities of Telmisartan that is marketed in a single pill combination. reversed phase‐high‐performance liquid chromatography method was developed using a C18 column Agilent (Zorbax C18; 250 × 4.6 mm internal diameter, 5 μm) along with 50 mM ammonium acetate (pH 4.5) and ACN as a mobile phase in gradient mode to achieve the retention of all analytes. The new method's sensitivity allowed the quantification of namely methyl benzene sulfonate, ethyl benzene sulfonate, and N‐methyl‐O‐phenylenediamine dihydrochloride at test concentrations as low as 0.025%. Amlodipine and Telmisartan each had a test concertation of 100 and 800 μg/ml, respectively. The developed analytical method was validated for different applications, that is, for assay and related substance methods. The calibration curves for genotoxic impurities were linear in the range of the Limit of quantitation to 1.2% of the test concentration of the respective drugs. Forced degradation investigations were conducted on selected drugs, and targeted analytes were then quantified. The stability of both drugs in acid and basic hydrolysis was improved compared to when they were evaluated separately, although Amlodipine showed an inverted degradation pattern in a more recent investigation when combined with Telmisartan under oxidative degradation conditions. The validated method was successfully applied for the quantification of the genotoxic impurities of Amlodipine and Telmisartan in finished pharmaceutical preparation.