SelexION® and Selexion®+ - How to Avoid Discharge Error

For research use only. Not for use in diagnostic procedures.

Issue Description

DMS (differential mobility spectrometry) discharge can have multiple causes. The discharge occurs between the electrodes of the SelexION® electrodes and will cause instrument failure.



A corresponding error message can be found in the event log in Analyst® (View - Event Log - Windows Logs - Application)



Possible Causes:

1. Separation Voltage (SV) is too high

• Discharge happens more likely at higher SVs. Lower the SV in case the action points listed below do not help.

2. DMS cell and electrodes are not properly installed

• Make sure the DMS cell is installed square to the orifice plate, both thumbscrews are tight against the DMS cell without visible gaps.
• Make sure the electrodes are installed correctly and the screws are tightened. Use the spacer tool and consider the correct alignment.

3. DMS cell and electrodes are dirty

• Use the routine cleaning procedure to clean the cell and the electrodes.
• Always clean after a DMS discharge error occurred.

4. High source temperature and/or ionization voltage (IS)

• Lowering those values will decrease the likelihood of DMS discharge.

5. Low probe positioning and high electrode protrusion

• Change the vertical probe to < 2 mm.
• Make sure the electrode protrusion does not exceed 0.5 mm.

6. LC flow

• Decrease the flow rate.
• Lower the percent of water as high water content facilitates DMS discharge.

7. Modifier

• Inspect the modifier lines with a flash light and make sure that you don't have bubbles or sputtering in the modifier liquid line or curtain gas line.
• Lower the modifier flow if you use the settings medium or high or lower the curtain gas as this will lower the modifier flow.

8. Equilibration

• Make sure to equilibrate the system for 40 minutes without modifier and LC flow.
• Allow further 10 minutes of equilibration with modifier and LC flow.

9. Source Gases (Gas 1 and Gas 2)

• SelexION® / SelexION®+ should not be operated with nitrogen for Gas 1 and Gas 2.

Resolution