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Hydrophilic-interaction chromatography (HILIC) is often used to analyze polar analytes, but it encounters challenges such as increased use of organic solvents, poor solubility of analytes in highly organic media, retention affects created by the sample matrix, and a limitation to the extent to which the retention of hydrophobic analytes can be controlled.
Ion-exchange chromatography can be used to retain charged molecules, but it fails to retain neutral analytes and can show poor selectivity for analytes of the same charge.
Mixed-mode chromatography is a method that uses more than one separation mode; mainly reversed-phase combined with ion-exchange interactions, which allows the retention and separation of both polar and nonpolar analytes in a single analysis.
The biggest benefit of this approach is that selectivity can be optimized by adjusting mobile-phase ionic strength, pH, or organic solvent. As a result, the selectivity can be finely tuned for the separation of compounds with widely different physico-chemical properties. For example, drug molecules and their counterions may be separated in a single analysis.
Mixed-mode chromatography requires no ion-pairing agents in the mobile phase for separating highly hydrophilic charged analytes, which simplifies the mobile phase and is compatible with mass spectrometry (MS).
Mixed-mode chromatography is an excellent choice for your method development and your everyday separation tasks. Unique selectivity combined with robust methods and columns will help you develop a reliable method. Never have co-elution or see peaks in the void unless you want it. Use mixed-mode columns when unique selectivity combined with mass spectrometry is required. The synergy of multiple interactions allows separating compounds which are very similar in nature. Multiple mechanisms can be applied to specific compounds independently letting you in one run to separate compounds with a drastic difference in properties.
