How I clean a flow cell?

[koko]

Hello everyone!

I have problems with the detector Waters 2487, the signal is unstable, I cleaned it backflushing water at 0.2ml/min all night but the signal still unstable, the recommendation of Waters is that remove and cleaned it with Nitrogen but I have no nitrogen in the lab. What can you recommend?

[tedinelkgrove]

you could flush it with a dilute nitric acid solution, or clean the lenses with IPA and kim wipes.

[danko]

Hi Koko,

In my terminology “unstableâ€

[grzesiek]

have you seen it? I mean the flow cell?

[koko]

danko:

Yea, when I said unstable I tried to meant varying, so, what you recommend?

grzesiek:
No, I have seen the flow cell!

tedinelkgrove:

Do you mean that I remove the flow cell and only clean the exterior?

[grzesiek]

"No, I have seen the flow cell! " - you mean you have not seen it?

the problem as recognized by danko doesn't have to be dirty flow cell, can be for example air in the detector, mixing problems etc

"I cleaned it backflushing water at 0.2ml/min all night" - purging strong solvent through could be a better option

[danko]

Hi Koko,

In order for me/us to suggest potential solutions, it is important for you to describe the problem in more unequivocal manner.
F. ex.:
1. How does the signal instability manifest its self?
2. Do you see fluctuating, edgy baseline?
3. Or do you experience varying peak area (i.e. height, width or both) when running your analyte?
In any case, until further notice, you don’t need to attempt any flow-cell cleaning procedures. Because dirty cell would result in lower signal and potentially more pronounced noise. But it’s quite unlikely to cause variations as such.

Best Regards

[koko]

I will use THF as a strong solvent to flush the cell. Before I flush the flow cell I had no response of the sample, after flush it I have response but the baseline is fluctuating.
Today I flush it with HNO3 6N and then water like the manual said. And the baseline still fluctuating.

[danko]

Hi again,

As mentioned earlier, I don’t think flushing the flow-cell will bring you any closer to the desired situation i.e. stable baseline. Actually if you have an air bubble in the flow-cell (it’s easy to determine, by the look of the baseline) a reasonably hydrophobic liquid, such as ACN, or THF for that matter, would easily remove it. So, unless you’re getting found of flushing for the fun of it, you may consider some other explanations of the problem you’re dealing with.
One such might be flow/pumping problems. But if you make the effort to post a couple of data examples (a chromatogram and a baseline alone) it may help a lot.

Best Regards

[HW Mueller]

Weird . . . ., don´t the detectors have selftests anymore? Unstable with flow and/or no flow? Anything systematic possible here? What do you mean with unstable anyway? What is the nitrogen you don´t have?

[vofelyp]

Hi Koko

What do you mean unstable? Is it cyclic or not? What is the cycle time? Short cycle time noise come from the pump, long cyclic noise come from other source most frequently from the aircondition device or the online degasser. Non cyclic noise dirty eluent, not good gradient mixing.

You can check the lamp hours and number of ignition (Shift + 1). After 2000 hours the lamp energy decrease quickly.
The lamp energy check:
Fill the cell with MeOH, and set 230 nm. In the diagnostics menu choose the Sample & ref energy menu. The reference energy should bigger 40, if not the lamp and/or optics has failed.

[koko]

Thank you everyone, I found the problem, the lamp had 2800 hours.