The Dionex CDRS 600 or Dionex CERS 500e can be used for suppression of MPIC (ion-pairing) eluents by using the Auto Suppression External Water Mode or the MPIC Suppression Mode depending on the specific MPIC application. The MPIC Suppression Mode is a combination of the Auto Suppression External Water Mode augmented with a chemical regenerant if necessary, such as boric acid (H3BO3). When the Dionex CDRS 600 or Dionex CERS 500e is operating in this mode, it uses an applied current and a constant source of dilute boric acid solution from a pressurized bottle delivery system.
The separation of alkanolamines by ion-pairing using the Dionex CDRS 600 or Dionex CERS 500e requires adding 10 mM boric acid to the regenerant to increase the ionization of the ethanolamine’s, thereby increasing the conductivity of the alkanolamines. Boric acid regenerant should not be used for the separations of the fully ionized alkali and alkaline earth metals as the borate will displace the hydroxide counter-ion and reduce the conductance of these ions. The following table lists the eluent concentrations and flow rates of standard eluents used in cation MPIC separations and the current level and regenerant flow rate required to suppress them.
Eluent | Eluent Flow Rate | Current | Regenerant Flow |
|---|---|---|---|
0.1–2.0 mM Hexanesulfonic acid (HSA) | 0.5–1.0 | 50/100 | 3–5 |
2.0–5.0 mM Hexanesulfonic acid | 0.5–1.0 | 100/300 | 3–5 |
0.1–2.0 mM Octane sulfonic acid (OSA) | 0.5–1.0 | 50/100 | 3–5 |
2.0–5.0 mM OSA | 0.5–1.0 | 100/300 | 3–5 |
0.1–2.0 mM Nonafluoropentanoic acid | 0.5–1.0 | 50/100 | 3–5 |
2.0–5.0 mM Nonafluoropentanoic acid | 0.5–1.0 | 100/300 | 3–5 |
NOTE
For the lower eluent concentration in a given range, choose the lower corresponding current; for the higher eluent concentration, choose the higher current setting. Higher current settings require higher pressures applied to the pressurized regenerant delivery bottle to maintain adequate regenerant flow. Organic eluent solvents levels should be kept below 40%.