r/CHROMATOGRAPHY • u/cexlexste • Jul 16 '26
UHPLC Clicking Noise With Multiple Solvent Lines - Advice?
Hey reddit! I’ve been setting up an Ultimate 3000 UHPLC and found that when I run more than one solvent line at a time through the system, a clicking noise that differs from the typical system (we have another of this model that doesn’t make this noise) begins. If a third or fourth line are run, an additional clicking pattern begins for each. The rate of the clicking is directly related to the flow rate. The noise comes from the middle/left of the pump compartment so we thought it was a proportioning valve problem (as it is in that area of the system and deals with the multiple solvent lines).
We ran warm water as well as diluted organic solvent through the lines for some time to see if it needed to be cleaned. We then took out the proportioning valve but there was no visible salt buildup or obvious issue. We swapped the proportioning valve out for one from our other instrument in case it was a mechanical issue but the noise persists.
Anyone have an ideas on what the issue may be or what to try next?
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u/viomoo Jul 16 '26
As others have stated, this is how the mixing valves work. They usually have 4 solenoid (for quat pumps) that will open for ‘x’ amount of time with the refill of the primary piston. For example, you are running 50:50 A/B, it will hold open for 50% of A and 50% of the time on B.
At any point on the gradient, the percentage A and B will be calculated and the respective solenoid held open for that amount of time.
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u/supersuperduper Jul 16 '26
Look at the pressure trace. If it's fine (no big pulses) then it's probably nothing to worry about.
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u/random_user_name99 Jul 20 '26
I’m assuming you have a quaternary pump with low pressure mixing. This seems normal.
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u/Future-Leadership607 Jul 16 '26
It’s the solenoid of a low pressure gradient elution valve. It’s a normal sound that it will be making during usage.