Chromatography Forum

Hi,

Could anyone tell is it possible to do HPLC pump gradient accuracy test while using MS detector? If yes, which standards or solutions are used?

Thanks in advance!

In principle, you can use anything for which you have wide linear range. In practice, the imprecision associated with the MS interface may be too big to be useful. If it were my problem, I would pick up a used UV detector on eBay (there are several available at the moment for around $150 if you're in the US) and use that.

Thank you for your reply!
So it's better not to try to do gradient accuracy test using MS detector, isn't it?

Thanks again!

the key word is "linear". In electrospray, a lot of things give a response that tails off with increasing concentration, and they're really only linear with the eye of imagination. For many applications it doesn't matter terribly much, but if you're doing a pump test, any non-linearity will mess up your step-sizes. Also you don't want anything in your system that will subsequently cause contamination issues or ghost peaks.

I would never calibrate a pump gradient based on an MS detector but I could see a point getting a rough idea if the gradient is working or not..

Mobil phase to use could a A: 50/50 H20/MeOH + 0.1% Formic b: 50/50 H20/MeOH +0.1% Formic plus a dash of caffeine. How much caffeine would depend on your mass spec.. You would have to do some tests to determine the right concentration.. Please report back here if you do try and fine something that works.

Caffeine will not stay long or linger as back ground for long, it's easy to ionise with ESI and it's cheap.. (Plus wonderful in coffee!)

Thank you all for your responses! They were helpful!

Dear leadazide I will post back whenever we will try your suggestion.

Thanks!