Christie Hunter


Methods for OPI electrode cleaning for Echo® MS system electrodes

Depending on the samples you are running on the system, it is possible for the Open Port Interface (OPI) electrode to become dirty or occluded over time. Below are two different cleaning strategies that can help you maintain your Echo® MS system and keep your OPI electrodes running well.

Quick cleaning protocol

This protocol is easy to perform between running your sample plates:

  • Stop the mobile phase flow.
  • From the Maintenance menu, select Replace OPI Electrode Assembly to open the door and raise the OPI.
  • Disconnect the OPI by loosening the finger-tight red nut and pulling straight up, slowly, to prevent an OPI leak.
  • Place the end of the OPI electrode into solvent. With the MS system still active and well equilibrated, the draw created from the GS1 flow will draw solvent through the OPI into the MS source. Set the ISV to 0 V to prevent ions entering the MS system, but ensure the GS1 stays set at 90.
  • Wash with Milli-Q water for 1 min.
  • Wash with 20% acetonitrile with 0.1 M formic acid (0.4% FA) for 20 min.
    • Drawing speed is about 450 µL/min based on the consumption of 20% acetonitrile with 0.1 M formic acid
  • Wash with Milli-Q water for 1 min.
  • Reattach the OPI to the system and tighten the red nut to finger-tight.
  • Restart the mobile phase flow and check the maximum supported flow (MSF).


Intensive cleaning protocol

This protocol is an offline protocol that can be used periodically for a more intensive wash of the OPI electrode or to recover electrodes that are becoming occluded:

  • Connect the OPI electrode to a small union (1/16 to 1/32 with 1/32 nut).
  • Flow 50% methanol through the OPI at a flow rate of 2–5 mL/min.
  • Flow at least 200 mL of solvent through.
  • Test on the Echo® MS system for droplet linearity, reproducibility and peak shape.

Some electrodes may not be recoverable, but we have had good success with this method on many.

Here is an example of a good union to use:

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1 Comment

  1. Jahangir Alam

    Thanks Christie! It will be very helpful.

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