Agilent 1100 and Qtrap it work with MeOH but not with ACN

[carol]

Dear all,

I really hope somebody could come with one idea because I don’t know what else can I do!!
I have use a method for the detection of 15 compounds for four months. But the other day, I don’t know why it stops working.
I thought it was the MS but the MS work as when I infuse the standard with a syringe using the same HPLC method it work. If a put 100 % MeOH with formic cid the system Works perfectly, however if I use 100 % ACN with formic cid it doesn’t work…I mean I don’t detected anything.

I change the mobile phase locations, canals, I have changed the columns, I have injected without columns and without pre-columns, but the system only Works with MEOH. I have check if there are leak but there are not. ….So I don’t know what else to do or what else to try . I will really appreciate any comments or suggestions.


Carol

[lmh]

did it ever work with acetonitrile? I have occasionally come across things that don't ionise in ACN in electrospray, but do in MeOH.

[carol]

Hi,

Thanks for your replay Imh. Yes, it has always work with ACN...I just tried MeOH because it didn't work with ACN.

What can it be? Somebody told me that it could be the pump...but I don't know.

[Ron]

I would not think it is the pump, if the system worked previously I would inspect and claen the probe. You may have some contamination built up on the probe, but I don't know why it would affect ACN more than methanol.

[aysal]

Hi,
just try to infuse std prepared in another ACN, you may use old std which prepared old lot ACN. If you changed your ACN bottle (using new ACN lot), new ACN can supress the ionisation. Just check the ACN purity.
You also try infusion std (prepared in MeOH, you saw signal) diluting with problematic ACN for 1:5 fold. for example 1 ml std in MeOH, add 4 mL of ACN (both inc formic acid) and infuse also std in MeOH. Then compare results. Do your standarts stable in ACN for long time?

Ayhan