Enriqueta wrote:
Hello,
I am analysed a peptide with an important number of Lysines by LC-MS. To increase the retention on the column (CSH) I am working with HFBA. A gradient with mobile phase: HFBA (0.1%) in water /HFBA (0.1%) in acetontrile. The retention is Ok and the sensitivity as well, but the columns (CSH) have a short life. I think the additive is the cause of the problem, but I am not sure. Has anybody seen this problem before?
Any idea? I am thinking of adding ammonium formate to increase the pH.
Thanks a lot for your time!
Depending on the size of your peptide and number of basic groups you might be able to use mixed-mode column with some ACN/water/ammonium formate mobile phase, but the approach Andrew offered should work too. The only obstacle you might have is solubility of your peptide in high organic. If you sample is in water you want to avoid injecting high volume injection into high concentration of ACN to avoid peak disturbance. Since you will be exploring ion-exclusion and HILIC, more buffer/ions will mean more retention for peptide and less retention for your acidic counterions (if you have them)