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- Posts: 16
- Joined: Fri Apr 24, 2015 2:44 am
Column temperature: 30 C
Detection: UV 227 nm
flow rate = 1 ml/min:
flow rate = 1.5 ml/min:
flow rate = 2 ml/min:
What can be the causes of the noisy baseline at 2 ml/min?
Thanks for any help
Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.
M Farooq wrote:
It seems that whoever made those method, also changed the sampling frequency and time constants. At high flow rates, you need high sampling frequency and small time constants to capture narrow peaks eluting at high speed. Check the detector settings in all 3 methods.
Peter Apps wrote:
Rather a wild guess, but the very high frequency of the noise points strongly to electrical or electronics rather than anything to do with fluid flows, and at 2 ml/min the pump is working harder, so mayber you have some kind of electrical interference between pump and detector ??
Peter
Fernando wrote:
Hi kaavie0801
What is the height of your peaks?. If you inject an amount of sample that is for example 200 mAu of height your noisy baseline is not that important. Your lamp is new? Or is old, that is a very important fact, you may need to replace it.
A certain amount of noise is unavoidable, check your equipment manual for limits and evaluate the noise.
Best luck!
Fernando
Peter Apps wrote:
Rather a wild guess, but the very high frequency of the noise points strongly to electrical or electronics rather than anything to do with fluid flows
Peter
kaavie0801 wrote:Peter Apps wrote:
Rather a wild guess, but the very high frequency of the noise points strongly to electrical or electronics rather than anything to do with fluid flows
Peter
Peter, I noticed the noise level is not affected by the pump flow as long as the detector flow cell is not flushed through.
kaavie0801 wrote:
Thank you for your informative advice, Peter.
So if you disconnect the detector from the column the noise is reduced ?
Yes
If the tubing between the column and detector is metal, try replacing it with PEEK.
A stainless steel tubing is used between the column and detector. Did you mean the steel tubing led to an "electrical interference?"There is a possibility that a stainless tube would conduct electrical interference as well as carrying mobile phase. To check this you need to allow mobile phase to flow, but stop electrical conduction by using a non-conductive tube. I have to admit that this is a long shot
What instrument are you using ?
An HPLC system from SHIMADZU: LC-20AB (pump), SIL-20A (autosampler), CTO-20A (oven), SPD-M20A (DAD), and CBM-20A (Communications bus module)
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