Determination of inorganic pharmaceutical counterions using hydrophilic interaction chromatography coupled with a Corona® CAD detector

Simultaneous determination of positive and negative pharmaceutical counterions using mixed-mode chromatography coupled with charged aerosol detector

“…The columns that exhibit both reversed-phase and ion-exchange (anionic, cationic or zwitterionic) behavior are most common type of mixed-mode columns [14][15][16][17][18][19]. Recently, mixed-mode columns with HILIC (hydrophilic interaction liquid chromatography) behavior have become increasingly popular in the separation of highly polar molecules including ions being weakly or not retained by conventional reversed-phase LC systems [20][21][22][23][24]. HILIC is a special type of normal-phase chromatography, where the stationary phase is more polar than the mobile phase.…”

Development of a simple method for quantitation of methanesulfonic acid at low ppm level using hydrophilic interaction chromatography coupled with ESI-MS

“…Both columns offer retentivity for organic acids due to the cationic nature of their stationary phases, and are claimed to reduce "column bleed" as a result of ligand desorption, which minimizes LC-MS noise levels. Since sulfonic acids possess both acidic and hydrophobic functional groups, mobile phase containing buffer of relatively low pH value (3.5) was selected to enhance the retentivity of sulfonic acids based on previously-gained experience with HILIC separation of ions [26]. Under these chromatographic conditions, all eight species of alkyl sulfonic acids (MSA, ESA, PSA, BSA, PTSA, HAS, HPSA and OSA) were retained and separated in less than 8 min on Cosmosil HILIC or Unison UK-Amino columns (Fig.…”

Ion-pair reversed phase liquid chromatography with ultraviolet detection for analysis of ultraviolet transparent cations

“…Indirect UV detection was used to quantitate UV-transparent charged molecules [25,26] based on the addition of ionic chromophore in mobile phase. Mix-mode LC with CAD and HILIC with ELSD methods were reported on the separation and detection of multiple cations and anions in pharmaceutical formulations [18][19][20][21][22]27,28]. CAD has been found to have better sensitivity and repeatability than ELSD [29].…”

“…As the separated ions migrate past the detector window, they are measured as negative peaks relative to the high baseline. A few publications addressed the use of IPR to enhance the detection of ionic compounds by evaporative light scattering detection (ELSD) or charged aerosol detection (CAD) [19][20][21][22]. TFA was found to significantly improve the detection of volatile amines.…”