Hello everyone,

I recently encountered a noise problem in my patch clamp experiments. I happened to observe a small current and a noise when the electrode holder was in the open circuit. The observed current was 20 pA in the open circuit and 8 pA when the reference electrode was immersed in bath. The observed noise was at 50 Hz in both instances. (Image 1: open circuit without bath) (Image 4; when both the reference and recording electrodes are immersed in bath)

All the devices are grounded in a common earth/ground line, in which all the equipment and cage around the system are grounded to the grounding bus, which is then connected to the Axopatch 200B signal ground.

My RMS (pA) values are around 9 during the membrane test, and they are between 2-6 pA during the episodic scope run. (Image 2: Episodic scope)

I use a microperfusion system without a vacuum suction unit to aspirate the perfusion out of the bath. And I use the help of gravitation to make the solutions flow.

I’ve tried grounding the microscope to the rear gold connector of the head stage, but unfortunately, it wasn’t helpful.

I checked to locate the source of noise by turning it off and unplugging them one by one, but the RMS value remained around 9 all the time. I’ve covered the light source on the roof with copper mesh that’s used to make Faraday cages. I’ve attached two more images for your kind reference of noise when only the reference electrode is in the bath (Image 3; Reference electrode only in bath) and when both the reference and recording electrodes are in the bath (Image 4; when both Reference and recording electrodes are immersed in bath)

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I’m currently focused on endogenous currents of ligand-gated and voltage-gated ion channels using a whole-cell voltage clamp configuration.

Please help me figure out the problem, and I’m grateful for your kind responses.

Thank you very much.

Nirujan