Today, Welch brings you the introduction of our two core liquid chromatography columns – ion exchange and hydrophilic analysis columns. Mainly from the type of bonded phase, pH tolerance range, and the characteristics of the chromatographic column to bring you closer to our two core chromatographic columns.
Principles of Ion Exchange Chromatography
Ion exchange chromatography refers to some charged groups in the stationary phase in ion exchange chromatography that bind to oppositely charged ions through electrostatic interactions. If other oppositely charged ions are present in the mobile phase, according to the law of mass action, these ions will exchange with the oppositely charged ions bound to the stationary phase.
There are two types of stationary phases in ion exchange chromatography: cation exchange functional groups and anion exchange functional groups. The cation exchange functional group has a negative charge and is used for the separation of cations; the anion exchanger functional group has a positive charge and is used for the separation of anions. The most commonly used cation exchange functional group is sulfonate type, and the most commonly used anion exchange functional group is quaternary amine type.
The mobile phase for ion exchange chromatography is usually a buffered aqueous solution containing salt. In order to meet different separation needs, sometimes an appropriate amount of organic solvents that are compatible with water, such as methanol, acetonitrile, tetrahydrofuran, etc., are added to improve the solubility of the sample, improve selectivity, and improve separation.
In ion chromatography with aqueous solution as the mobile phase, the concentration of the buffer solution directly affects the ion balance. When the buffer concentration increases, the concentration of counter ions in the mobile phase increases, which enhances its ability to compete with sample ions for ion-exchange functional groups, thereby weakening the affinity of sample components for ion-exchange resins. The type of ions in the mobile phase has a significant effect on the retention of sample molecules.
Welch ion exchange column product features
Introduction to HILIC Columns
In 1990, Professor Alpert proposed a new concept: Hydrophilic Interaction Chromatography (HILIC). This chromatographic method is used to separate highly polar and hydrophilic compounds such as nucleosides and nucleotides, amino acids, sugars, and more. It uses a polar stationary phase and a polar mobile phase, and generally uses a solution with a lower polarity than the stationary phase, such as acetonitrile/water.
The difference between HILIC chromatography and reversed-phase chromatography is that the greater the polarity of the mobile phase, the stronger the elution ability, but the water-phase ratio should not exceed 40%, not less than 3%. , the most widely accepted statement is the distribution of analytes between the mobile phase and the stationary phase surface enriched water layer, but also includes weak electrostatic interactions, hydrogen bonds and molecular bipolar interactions.
Welch HILIC Column Product Features
|Bonded Phase Type||Column||Tolerant pH range||Features of chromatographic columns|
|2.0-8.0||➩ Silica gel matrix is specially treated, so that it has good life and strong stability in the separation of strong polar substances in high water phase|
➩Multiple retention mechanisms in HILIC mode to obtain different selectivity and separation effects
|2.0-8.0||➩ The silica matrix has better stability and reproducibility for mixed monosaccharides than XB-NH2 under the action of multiple forces such as special hydrophilic treatment, weak anion exchange force, and hydrophilic separation and distribution force.|
|Amide polyacrylamide bonded silica column||Ultisil®|
|2.0-8.0||➩ Similar separation force to HILIC-NH2, but different selectivity|
➩ On ELSD, MS has lower bleed and longer lifetime than NH2
|Amphion Zwitterionic Columns||Ultisil®|
|2.0-8.0||➩Patented covalent bonding technology bonds zwitterionic functional groups, eliminating the need for ion-pairing reagents|
➩ With extremely strong hydrophilicity, it can effectively retain strong polar ionic compounds and basic drug molecules that are weakly or not retained in RP-LC