By DelphineG on Wednesday, December 18, 2002 - 02:04 am:
Hello everybody!
Just one question concerning mobile phase for LC-MS/MS, and particularly buffers.
I do not work with this technique for a long time and I am not a specialist in MS/MS.
First anaytical methods I developed in LC-MS/MS used ammonium acetate buffer 10mM(pH about 6.9) with acetonitrile, or formic acid 0.05% with acetonitrile, as mobile phase.
I would like to known what is the interest of working with ammonium formiate as buffer solvent because I see a lot of method using this buffer for mobile phase?
Is it only to adjust and controled pH of buffer, or is there another impact on ionization in MS/MS?
Thanks in advance for your precious answer.
By Michele on Wednesday, December 18, 2002 - 07:26 am:
You have a very limited range of buffers to use, since they have to be volatile. As a general rule, lowering the pH will increase ionization efficiency in positive ion mode. However, there are exceptions. Optimum ionization pH is analyte specific, and if you are trying for maximum sensitivity, you have to play with pH and buffer/acid concentrations a bit.