The chromatographic separation of polar and ionic compounds remains a persistent challenge in analytical science. Conventional reversed-phase liquid chromatography (RP-LC) often fails to retain such analytes adequately, resulting in poor peak shapes, tailing, and compromised resolution, which limit reliable qualitative and quantitative analysis in pharmaceutical, biological, and environmental samples. This review critically evaluates ion-pair chromatography (IPC) as a versatile analytical strategy to enhance retention, selectivity, and separation efficiency for polar and ionic analytes across diverse application domains. A literature survey was performed using major databases, including Google Scholar, PubMed, Scopus, and Web of Science, focusing on IPC principles, ion-pair reagents, key chromatographic parameters, method development, and recent advances, with emphasis on MS-compatible and green analytical approaches. We found that, the ion-pair chromatography (IPC) enhances separation on reversed-phase columns via ion-pair formation, dynamic ion exchange, and partitioning. It is widely applied in pharmaceutical analysis, bioanalysis, and environmental/food monitoring. Recent advances such as volatile ion-pair reagents, mixed-mode columns, and IPC-MS workflows have improved sensitivity, reproducibility, and MS compatibility. We concluded that, ion-pair chromatography remains a powerful and complementary tool for the separation of polar and ionic analytes, with ongoing innovations ensuring enhanced performance, sustainability, and applicability across pharmaceutical, biological, and environmental matrices.
Simultaneous quantification of trace-level nitrosamines and high-concentration active pharmaceutical ingredients presents substantial analytical challenges due to extreme disparities in molecular mass, ionization efficiency, and dynamic concentration range. Herein, a unified UHPLC-APCI-MS/MS method was developed, systematically optimized, and validated for concurrent determination of edoxaban and stress-induced N-nitrosodimethylamine (NDMA) at trace levels within a single analytical run. Using an ACE Excel C18-PFP column coupled with APCI+-SRM detection and targeted mass spectrometric optimization enabled enhanced low-mass ion transmission. The method demonstrated excellent linearity (r 2 >=.9940) with sub-ng mL-1 sensitivity for NDMA. The limit of quantification (LOQ) for NDMA was 0.12 ng mL-1 based on a signal-to-noise (S/N) ratio of 10:1 and 0.39 ng mL-1 based on the standard error of the calibration curve. For edoxaban, the corresponding LOQ values were 0.93 ng mL-1 (S/N) and 1.05 ng mL-1 (standard error of the calibration curve). Forced degradation studies of edoxaban conducted in the presence of sodium nitrite demonstrated that oxidative stress was the predominant driver of NDMA formation under nitrosating conditions (31.0-35.5 ng mL-1). These results provide controlled laboratory insight into potential NDMA susceptibility, plausibly associated with oxidative modification of the N-methyl tetrahydrothiazolopyridine moiety of edoxaban, rather than evidence of intrinsic instability. The proposed strategy offers a robust, regulatory-aligned analytical framework that supports future investigations of susceptibility in structurally related pharmaceutical compounds.
