Setting SRS Suppressor Currents

Detector Control
Setting SRS Suppressor Currents

For optimal suppressor performance, it is important to use the recommended suppressor currents for the target applications. The Chromeleon Program Wizard (see The Control Program The Program Wizard) guides you in setting the recommended current for the Self-Regenerating Suppressors (SRS). The wizard supplies a recommended current based on the eluent concentration and flow rate settings (see the table below). Chromeleon automatically enters the recommended current into the Program and applies that current to the SRS.

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.

The maximum suppression capacity of the Self-Regenerating Suppressors varies, depending on the suppressor type and the flow rate. The table below indicates the absolute maximum suppression capacity for each SRS, regardless of flow rate. The required capacity for an application is calculated as [mN eluent][ml/min flow rate] and cannot exceed the absolute maximum dynamic capacity of the specific suppressor. For example, the 4-mm ASRS cannot suppress 200 mM at 2.0 ml/min.

Suppressor	Absolute Maximum Suppression Capacity
4-mm ASRS	200 meqv/min at 1.0 ml/min
2-mm ASRS	50 meqv/min at 0.25 ml/min
4-mm CSRS	110 meqv/min at 1.0 ml/min
2-mm CSRS	37.5 meqv/min at 0.25 ml/min

Tip:

For gradient applications, select the highest eluent concentration in the gradient when you enter the eluent concentration in the wizard.

Examples of Recommended Operating Currents for Self-Regenerating Suppressors:

Column	Eluent	Flow Rate (ml/min)	Current (mA)
4-mm AS4A-SC	1.8 mM Na2CO3/1.7 mM NaHCO3	2.00	26
2-mm AS4A-SC	1.8 mM Na2CO3/1.7 mM NaHCO3	0.50	7
4-mm AS9-HC	9.0 mM Na2CO3	1.00	44
2-mm AS9-HC	9.0 mM Na2CO3	0.25	11
4-mm AS14	3.5 mM Na2CO3/1.0 mM NaHCO3	1.20	24
2-mm AS14	3.5 mM Na2CO3/1.0 mM NaHCO3	0.30	6
3-mm AS14A	8.0 mM Na2CO3/1.0 mM NaHCO3	0.5	21
4-mm CS12A	22 mM MSA	1.00	65
3-mm CS12A-5 mm	20 mM MSA	0.50	59
2-mm CS12A	22 mM MSA	0.25	16
4-mm AS11	12 mM NaOH or KOH	1.00	30
2-mm AS11	12 mM NaOH or KOH	0.25	7
4-mm AS11-HC	30 mM NaOH or KOH	1.50	111
2-mm AS11-HC	30 mM NaOH or KOH	0.38	28
4-mm AS15	38 mM NaOH or KOH	1.20	113
3-mm AS15	40 mM NaOH or KOH	0.50	49
2-mm AS15	38 mM NaOH or KOH	0.30	28
4-mm AS16	35 mM NaOH or KOH	1.00	86
2-mm AS16	35 mM NaOH or KOH	0.25	22
4-mm AS17	15 mM NaOH or KOH	1.00	37
2-mm AS17	15 mM NaOH or KOH	0.25	9
4-mm CS14	10 mM MSA	1.00	29
2-mm CS14	10 mM MSA	0.25	7
4-mm CS15	10 mM H2SO4/9% Acetonitrile	1.25	74
2-mm CS15	10 mM H2SO4/9% Acetonitrile	0.30	18
4-mm CS16	30 mM MSA	1.00	88

For other conditions, the recommended current for the Self-Regenerating Suppressors can be calculated using the following equations.

For anion separations:

Current (mA) = 2.47 (mA*min /mN*ml) x [eluent (mN)] x flow rate (ml/min)

[eluent (mN)] = 2 x [CO32-(mM)] + [HCO3-(mM)] + [OH-(mM)]

For cation separations:

Current (mA) = 2.94 (mA*min /mN*ml) x [eluent (mN)] x flow rate (ml/min)

[eluent (mN)] = 2 x [H2SO4(mM)] + [MSA (mM)]

(Where: [ ] enclosing an ion or eluent indicates concentration.)

The following table lists the maximum operating currents for the suppressors under various column diameter and flow rate conditions.

Maximum Operating Currents for the Self-Regenerating Suppressors:

Suppressor	Maximum Current (mA)
4-mm ASRS	500
2-mm ASRS	150
4-mm CSRS	300
2-mm CSRS	110

Once the recommended suppressor current is determined, turn on the pump flow and apply the current to the suppressor.