Chromatography Forum

Thanks indeed my dear HW Mueller i will do that and see

i am really gratefull for all advice and contribution that i gain from those great people and great forum .

Thanks carls i am sure that no contaminated sources .

2- unknown peak from methanol

Did I misinterpret the above? From your oirignal post I got the impression you believe methanol (your sample solvent?) was the source of interfering peak #2 (unknown from methanol).

1) Is the interfering peak present when pure water, pure methanol or mobile phase are injected ?
2) Were the chromatograms shown run on a 150x4.6mm column?
3) What detector are you using, UV? If UV, what wavelength?

ok thanks

So you do not see the peak when you switch your injection valve from load to inject, but you do see it when you actually inject mobile phase?

Do you see the peak if you leave out the buffer constituents, and just mix a water:methanol mobile phase and inject that? Can you inject water, water plus buffer, water plus methanol, and methanol plus buffer to see if you can pinpoint where the peak is coming from?

ok thanks

ok thanks

I doubt that any amount of ACN you use will be large enough to exacerbate any shortage. ACN is more costly than it used to be, but it's still available. Your time has value.

By the way, the same comment applies to alternative columns.

ok thanks

I can!

A quick Google search turned up HPLC-grade ACN at $75/liter. That's 7.5 cents per mL (US). A 20-minute isocratic run at 2 mL/min of a 50% ACN mobile phase will consume 20 mL of ACN. That's about a buck fifty US (or just under a pound in the UK). How many minutes of your time does a pound pay for (don't answer! ).

We put together a quick video dealing with this a couple of years ago (in case your boss is interested). The economics are covered in the first four minutes:
http://www.lcresources.com/more_resourc ... /ACN1.html

thanks