A stability-indicating QTRAP LC-MS/MS method for identification and structural characterization of degradation products of indapamide

Abstract

A selective and sensitive stability-indicating liquid chromatography tandem mass spectrometry (LC-MS/MS) method, operated in electrospray ionization (ESI) and quadrupole linear ion trap (QTRAP) modes, has been developed for the identification and structural characterization of stressed degradation products of indapamide. In this study, comprehensive stress testing of indapamide has been carried out according to the International Conference on Harmonization (ICH) guidelines Q1A (R2). Indapamide was subjected to forced degradation studies under hydrolytic (acid, base and neutral), oxidation, photolysis, and thermal stress conditions. The drug showed instability to alkaline hydrolysis at 50 °C (29.55% degradation), while it remained slightly stable to light, acidic, neutral, oxidation and thermal stress (ranged from 0.50% to 8.25% degradation). The drug and its degradation products were resolved with time programmed gradient elution on a Phenomenex® Synergi Fusion-RP 80A column (50 × 4.6 mm, 4 μm) using methanol and 0.2% acetic acid aqueous solution as the mobile phase components. Structural characterization of the degradation products was performed using the Information Dependent Acquisition (IDA) method. The IDA with dynamic background subtraction (DBS) was configured to trigger a sensitive EPI scan when the EMS survey scan signal exceeded the defined criteria. The enhanced product ions of the degradation products were compared with the enhanced product ions of the protonated indapamide to assign most probable structures for the observed degradation products. The limit of detection (LOD) and limit of quantification (LOQ) for indapamide were 0.04 and 0.13 ng mL⁻¹, respectively. The intra- and inter-day precisions were lower than 1.95% while the accuracy ranged from 100.97% to 101.78%.