UV-Vis at 190nm

[WK]

Hi All,
Can anyone give a reason why my equilibration step (time to get baseline stable) when using 190nm is so long (1 hour +) compared to (20mins) at 280nm?
I am using 1ml/min 0.15% phos acid in water / mecn (80/20) with RP-Bonus.
Deuterium lamp
WK

[vicentexxx]

Hello,
may it deal with CH3CN cutoff at 190 nm? or some contaminants? after conditioning column at 280 nm you notice the same thing?

I don't know exatly, theese are only imputs...what about it?

vincenzo

[Uwe Neue]

Don't forget that at 190 nm you will see everything, including column bleed...

[leadazide]

Also 190nm is at the edge of most UV lamps capability and even though there are many hours left of usage at higher nm, the lower nm can quite quickly get fuzzy..

[DR]

If you must run at that low a wave length, do a UV scan (220nm down to below 190, ideally) of a sample from every lot of MeCN available to you. Make your mobilr phase from the cleanest of them. Also - before you make the phosphate portion, filter the water through an Empore extraction disk - even if it's LC grade 18M-ohm-CM etc. etc. water. It will help, as will using a fresh lamp.

If you still have issues, then it is most likely column crud. That you will have to wait for or try a different column.