Over voltage/current issues

Issue

Over voltage

Environment

Ion Chromatography Suppressors

Resolution

To test to see if there is just a bubble, start the eluant flow for a 2-5 minutes before applying current. This will allow the bubble to be flushed out before current is applied. You may need to repeat.

If the above problem is encountered on a routine basis particularly with samples containing high levels of metals or solvents, the chemical mode of operation is recommended.

Analysis

The Dionex ERS 500e Suppressor Dionex ERS 500 Carbonate Suppressor operates in the constant current mode. The Dionex DRS 600 is a Dynamically Regenerated electrolytic Suppressor. It is designed to operate in constant voltage mode in addition to the traditional constant current mode.

As per the suppressor manual, Dionex DRS 600 Suppressor Dionex ERS 500e Suppressor Dionex ERS 500 Carbonate Suppressor, 031956 Revision 13 • March 2018

“Alarm state indicates that there is high electrical resistance or an open circuit in the suppressor device typically in the regenerant channel or there is an issue with the connectivity of the suppressor to a power supply.”

The old Chromatography term was bubble effect and occurs in the conductivity cell as well as the suppressor. This can be understood by applying Ohm's law to the circuit consisting of have two plates, positive and negative. If water is between the plates, you have resistance that is stable with no air.

If an air bubble exists between the plates, the resistance goes up, so for a constant current the voltage must go up. The air bubble does not need to be very large to cause the effect as the difference in the resistance to water is huge, (Air =3.3 × 10^16Ω-m vs. Water 1.8x 10^9 MΩ – cm).

Cause

In the Constant current mode of suppression over voltage may occur if the suppressor is the not hydrated completely or bubbles may occur due to outgassing after being down over night or the weekend.