HPLC Baseline Noise at 214 but not 250 or Higher

[lawless2020]

I am developing an HPLC peptide analysis method. I would like to use a wavelength of 214. However, I see a great deal of cyclic baseline noise at 214. I am using RO water and HPLC grade Acetonitrile as mobile phases (both with 0.5% Formic Acid). I do not see this noise when using a wavelength of 250 or higher. I have replaced the flow cell and switched columns, and I am still seeing this noise. I do not see this noise at 214 when I remove the flow cell from its compartment. Could it be that the detector lamp is going bad and that is only evident at the shorter wavelength? Or, do I have contamination somewhere in my system? Thoughts and suggestions are appreciated...

[sbrand]

Hi

Your problem is well known. Simply increase your mixing performance with a bigger mixer (means higher volume) and your problem will be solved.

Wish you success and best regards

[tjbr]

It's likely a gradient mixing issue, try an inline mixer and it should improve.