A Simple and Rapid Analytical Method to Detect and Quantify the N‐Nitroso Desmethyl Diltiazem Impurity by Liquid Chromatography‐Tandem Mass Spectrometry in Diltiazem Hydrochloride

ABSTRACT N‐nitroso desmethyl diltiazem is a known genotoxic impurity in the cardiovascular drug product diltiazem hydrochloride, raising significant concerns due to its potential carcinogenicity. Detection of such impurities at trace levels is crucial to ensure drug safety and regulatory compliance. Thus, an effective and robust analytical method has been developed and validated with improved specificity, sensitivity, and separation efficiency using multiple reaction monitoring acquisition mode to detect and quantify the traces of N‐nitroso desmethyl diltiazem in diltiazem hydrochloride. Achieved an excellent separation and quantification of N‐nitroso desmethyl diltiazem and diltiazem hydrochloride in a short run time of 24 min by using a C18 Atlantis T3 column with a gradient composition of 0.1% formic acid in water as mobile phase A and 100% acetonitrile as mobile phase B, 0.5 mL min −1 flow rate, and a 10 µL injection volume. Mass spectrometric conditions comprised 1.00 kV interface and focus voltage through positive polarity in multiple reaction monitoring mode, with precursor ion at 429.90 m / z and product ion at 283.25 m / z . This method demonstrated excellent specificity, achieving baseline separation of N‐nitroso desmethyl diltiazem from matrix components, and exhibited linearity within a concentration range of 0.0025–0.1 µg mL −1 . Validation parameters, including accuracy, precision, and robustness, are obtained within acceptable limits as per International Council for Harmonization guidelines, ensuring the method's reliability. This study addressed the limitations of previous techniques and underscored the method's potential for routine analysis to meet regulatory compliance requirements.