Detector Control
Setting SRS-MPIC Suppressor Currents   

The Chromeleon Program Wizard (see The Control Program  The Program Wizard) displays the valid current settings for Self-Regenerating Suppressors (SRS) operating in the MPIC (mobile phase ion chromatography) Suppression Mode. For optimal suppressor performance, it is important to use the recommended suppressor currents for the target applications. The sections below indicate the recommended current for anion and cation applications, based on the eluent concentration and flow rate.

These settings are also used to set basic equilibration conditions for the suppressor (see Control  The SmartStartup Wizard) or to select suppressor settings for shutdown or standby mode (see Control The SmartShutdown Wizard.

 Caution:

It is possible to override the recommended current settings in the wizard by entering an alternate current value in the program file. However, to ensure the optimal performance of the suppressor, avoid applying excess current to it. Excess operating current leads to excess heat generation, which can reduce the suppressor lifetime and cause higher chromatographic baseline noise.

ASRS-MPIC Suppressor

The ASRS-ULTRA can be used for suppression of MPIC (ion-pairing) eluents when operating in the MPIC Suppression Mode. The MPIC Suppression Mode is a combination of the AutoSuppression External Water Mode augmented with a chemical regenerant, such as, sulfuric acid.

During operation in the MPIC Suppression Mode, the ASRS-ULTRA uses an applied current and a constant source of dilute sulfuric acid solution from a pressurized bottle delivery system. The table below lists the concentrations and flow rates of standard eluents for anion MPIC separations and the current levels and regenerant flow rates required to suppress them.

 

4-mm ASRS-ULTRA in the MPIC Suppression Mode:

Matching the Current Setting and Regenerant Flow Rate

Eluent

Eluent Flow Rate
(ml/min)

Current (mA)

Regenerant Flow Rate (ml/min)*

Sulfuric Acid Regenerant Concentration (mN)

0.1-2.0 mM Tetrabutylammonium Hydroxide

0.5-2.0

50/100

3-5

5-10

2.0-5.0 mM Tetrabutylammonium Hydroxide

0.5-1.0

100/300

5-8

10

 

1.1-1.5

300/500

5-8

10

* The flow rate is measured volumetrically with a graduated cylinder (with the power on).

 

 Tip:

For the lower eluent concentration in a given range, choose a correspondingly lower current setting; for a higher eluent concentration, choose a higher current setting. Higher current settings require the application of higher pressure to the pressurized regenerant delivery bottle to maintain adequate regenerant flow.

For complete operating instructions, refer to the manual for the 4-mm ASRS-ULTRA.

CSRS-MPIC Suppressor

The CSRS-ULTRA can be used for suppression of MPIC (ion-pairing) eluents when operating in either the AutoSuppression External Water Mode or the MPIC Suppression Mode; the appropriate mode depends on the specific MPIC application. The MPIC Suppression Mode is a combination of the AutoSuppression External Water Mode augmented with a chemical regenerant, if necessary (for example, boric acid). During operation in the MPIC Suppression Mode, the CSRS-ULTRA uses an applied current and a constant source of regenerant from a pressurized bottle delivery system.

The separation of alkanolamines by ion-pairing using the CSRS-ULTRA requires the addition of 10 mM boric acid to the regenerant. This increases the degree of ionization of the alkanolamines, thereby increasing their conductivity. Do not use boric acid regenerant for the separations of the fully-ionized alkali and alkaline earth metal salts; the borate ion will displace the hydroxide counter ion and lower the conductivity response. The table below lists the concentrations and flow rates of standard eluents for cation MPIC separations and the current levels and regenerant flow rates required to suppress them.

 

4-mm CSRS-ULTRA in the MPIC Suppression Mode:

Matching the Current Setting and Regenerant Flow Rate

Eluent

Eluent Flow Rate (ml/min)

Current (mA)*

Regenerant** Flow
Rate (ml/min)***

0.1-2.0 mM
Hexanesulfonic Acid

0.5-1.0

50/100

3-5

2.0-5.0 mM
Hexanesulfonic Acid

0.5-1.0

100/300

5-8

1.1-2.0 mM
Octanesulfonic Acid

0.5-1.0

50/100

3-5

2.0-5.0 mM
Octanesulfonic Acid

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

* For optimal results, choose a current setting of 300 mA or less. Operating the 4-mm CSRS-ULTRA at current settings over 300 mA can shorten the life of the suppressor.

** The regenerant is deionized water or boric acid.

*** The flow rate is measured volumetrically with a graduated cylinder (with the power on).

 

 Tip:

For the lower eluent concentration in a given range, choose a correspondingly lower current setting; for a higher eluent concentration, choose a higher current setting. Higher current settings require the application of higher pressure to the pressurized regenerant delivery bottle to maintain adequate regenerant flow.

For complete operating instructions, refer to the manual for the 4-mm CSRS-ULTRA.