Noisy baseline - diagnostics question

[LCFan]

Hello,

what might cause such a baseline noise:

(Hypersil C8 / 150x4.6 / 3 µ / 22% AcN / Flow = 1.0 / 220 nm)



Thank you very much for every hint.

Florian

[aceto_81]

contaminated mobile phase?
Do you use HPLC water or a buffer solution?

Ace

[DSP007]

Solvent of sample= mobile phase? Or not? wavelength 210-220 nm?

At a wavelength of 210 nm, water and acetonitrile HPLC (such as kriohrom 0) have very low absorption. And in the the absorption of of the mobile phase contributes buffered salt.
The sample solvent can give a negative peak.


It's not noise, it is a real decrease absorbance of the mobile phase.

PS
Maybe the dirty water or acetonitrile mobile phase. Very bad proved to be acetonitrile Panreak 240 in a large packing

[LCFan]

Hello,

the mobile phase is:

HPLC-water / Acetonitrile 78:22

Might there be a seal problem and I record the consequent flow pulsation?

Regards

Florian

[Bull76]

Hi Florian,

Have you recorded the pressure trace also? Possible an issue with the pump. But you would need to see the pressure trace to confirm.

Bull76.

[tom jupille]

Possibilities (some of these have already been suggested; I'm just trying to be comprehensive):

- a mixing problem (if you are using on-line mixing). Diagnostic: try a pre-mixed mobile phase and see if the problem goes away.

- a pump problem on one head of a two-headed pump. Diagnostic: check the pressure and see if that varies synchronously with your baseline. Also, listen to the pump to find out if the fluctuation is tied to one head or the other.

- an electronic problem (this has low probability!). Diagnostic: shut off the flow and see if you get the same kind of fluctuation in the signal.

- A small air bubble or piece of particulate garbage in the flow cell that is moving in response to slight flow pulsations. No good diagnostic for this one aside from cleaning the flow cell as a last resort.

[LCFan]

@Bull76: Unfortunately, I didn't record the pressure

@Tom Jupille: Thank you very much for your hints and explanations; I will perform some trials

Regards

Florian