Suppressor design - ERD 500 - ERS 500e - ERS 500 Carbonate - DRS 600 - Suppressor design - ERD 500 - ERS 500e - ERS 500 Carbonate - DRS 600

The Dionex DRS 600 and Dionex ERS 500e design comprises of three channels defined by two ion exchange membranes. The central channel is the eluent channel and the two side channels are regenerant channels. The regenerant flow is arranged to be counter-current to the eluent flow. This orientation ensures complete regeneration of the device.

Electrodes are placed along the length of the regenerant channels to completely cover the eluent channel. In operation, when a DC voltage is applied across the electrodes and the voltage exceeds the standard potential for the electrolysis of water (approximately 1.5 V), water is electrolytically split to form electrolysis ions.

At the anode: H₂O → 2H⁺ + 1/2O₂ + 2e^-

At the cathode: H₂O + 2e^- → 2OH- + H₂

The electrolysis ions are then available for the suppression reactions. The Dionex DRS 600 suppressor design allows facile transport of cations or anions depending on which type of suppressor is used for the application. For example, when pursuing anion analysis with a Dionex ADRS 600, cation exchange functionality extends across the electrodes. The function of this is to lower the resistance and aid in the transport of ions in and out of the eluent channel. In the Dionex DRS 600, the eluent channel is filled with ion exchange resin and provides a static capacity which is particularly useful when eluent is pumped into the device with the power off.

In operation, the electrolytically generated hydronium ions in the Dionex ADRS 600 are driven towards the cathode along with eluent cations by the applied voltage. The membrane allows hydronium ions to pass into the eluent chamber resulting in the conversion of the electrolyte of the eluent to a weakly ionized form. For each hydronium ion entering the eluent channel one hydronium or a cation exits the device and is driven towards the cathode. At the cathode, the cations combine with the electrolytically generated hydroxide ions to form water or base. Overall, the current dictates the concentration of hydronium and hydroxide ions.

The eluent suppression process for the ADRS 600 is as follows:

1. The water regenerant undergoes electrolysis to form hydroxide ions on the cathode surface along with hydrogen gas while hydronium ions are formed in the anode surface along with oxygen gas.
2. In the Anion Suppressor, cation exchange materials such as screens, membranes, and resins allow hydronium ions to move from the anode chamber into the eluent chamber to neutralize the hydroxide eluent.
3. Sodium ions or eluent or sample counter-ions in the eluent are driven by the applied electric potential towards the cathode and combine with the hydroxide ions generated at the cathode to form sodium hydroxide waste. Hydronium ions can also travel all the way to the cathode to form water, thus effecting suppression of the eluent and conversion of the analyte to typically a more conductive acid form.

The eluent suppression process for the CDRS 600 is as follows:

1. The water regenerant undergoes electrolysis to form hydroxide ions in the cathode surface along with hydrogen gas while hydronium ions are formed in the anode surface along with oxygen gas.
2. In the cation suppressor, anion exchange materials such as screens, membranes, and resins allow hydroxide ions to move from the cathode chamber into the eluent chamber to neutralize the acid eluent.
3. MSA ions or eluent or sample counter-ions in the eluent are driven by the applied electric potential towards the anode and combine with the hydronium ions generated at the anode to form methane sulfonic acid waste.

The Dionex DRS 600 (2 mm) suppressor is optimized for MS detection; the suppressor has been designed to have minimal interference for MS applications and is compatible with operation in external water mode. The 2-mm suppressor is recommended for applications that use MS detection due to the improved efficiency, and compatibility with lower operational flow rates typically employed with MS detection.

The Dionex Anion Electrolytically Regenerated Suppressor for Carbonate Eluents (Dionex AERS 500 Carbonate) is optimized for use with carbonate or carbonate/bicarbonate-based eluents. The Dionex AERS 500 Carbonate operates similarly to the Dionex ADRS 600 suppressor using electrolysis derived regenerant ions; however, it uses a three-electrode design for the electrolysis function. The cathode electrode is segmented into two portions with an electrical gap. These two portions are connected via a resistor thus resulting in a lower applied current across the outlet section of the suppressor relative to the inlet section of the suppressor. This design results in decreased gas production at the outlet, and as a consequence, results in less variation in the suppressed background and is able to achieve low noise.