VDSpher® Ion-Exchange Phases
The product line VDSpher PUR is completed with ion-exchange phases based on silica gel.
The phase VDSpher PUR 100 NH2, known as a normal phase material, can be applied in the ion-exchange mode equally. Additionally, the amino phases VDSpher Classic 100 AP and VDSpher Classic 100 DAP are available for ion-exchange chromatography (IEX). Another option offered as weak anion-exchanger is the phase VDSpher PUR 100 PEI. For this, VDSpher PUR basic silica gel is modified with polyethylenimine via a spacer. VDSpher PUR PEI achieves the optimum anion-exchange capacity in the range of pH = 4-7. For the chromatographic separation, ionic strength and changes in pH value of the mobile phase are responsible for the adsorption and desorption of the analytes. The ion-exchange capacities of the available VDSpher 100 anion-exchange phases are shown in the Table.
Ion-Exchange Capacities: VDSpher® 100 Anion-Exchanger
| Phase | Ion exchange capacity [mmol/g] |
|---|---|
| NH₂ Classic & PUR | 0.95 |
| AP Classic | 0.85 |
| DAP Classic | 1.4 |
| PEI PUR | 2.1 |
A phase for cation-exchange is also offered with VDSpher PUR 100 OA-1, whereby H+ serves as counterion for the functional group. The phase has an exchange capacity of 0.5 mmol/g and silanophilic activity as well. The separation of organic acids without buffer addition in particular, is enabled by VDSpher PUR OA-1.
Ion-exchange phases are available with a pore size of 100 Å and a particle diameter of 5 µm. VDSpher Classic 100 AP is only available with particle diameter of 15 µm, 30 µm or 55 µm.