A stability indicating RP HPLC method for quantification of nitroglycerin in semisolid formulations

The method was validated according to the ICH guideline Q2(R2) and included the system suitability, specificity, linearity, accuracy, homogeneity, robustness and forced degradation studies. The study presents a robust and stability-indicating RP-HPLC method developed for the quantification of Nitroglycerin in 4 mg/g ointment formulations. Chromatographic separation was achieved using an Hypersil BDS C18 column (150 mm × 4.6 mm, 5 μm) with an isocratic mobile phase consisting of water and methanol in a 60:40 (v/v) ratio at a flow rate of 1.0 mL/min, and detection was carried out using an UV detector set at 220 nm with a run time of 15.0 min. The method demonstrated excellent system suitability and specificity without interference from excipients or matrix components. Linearity was observed over the concentration range of 40–120 µg/mL. The % recovery values ranging from 99.3% to 100.1%, confirming reliability of the method. A photodiode array detector verified the peak purity and homogeneity of the NTG peak under stress conditions, indicating uniform distribution across formulation layers. Robustness studies further confirmed the reliability of method under small deliberate variations in analytical parameters. Forced degradation studies confirmed the ability of the method to distinguish NTG from its degradation products under acid, base, oxidative, thermal, humidity, and photolytic conditions. The greenness of the method was evaluated using Analytical Eco-Scale, Analytical GREEnness metric, and Green Analytical Procedure Index tools. The Eco-Scale score was 87, Analytical GREEnness score was 0.63, and GAPI pictogram indicated a balanced green analytical profile. Therefore, the method is suitable for regulatory compliance and routine quality control analysis of Nitroglycerin formulations.