Hi,
I am completly desperate for help with my instrument. I am developing method to analyse fatty acids (part of E&L, pharma company) using 6230 series Agilent Dual AJS ESI-ToF. I have tried tens of different methods, finally I have one that separates all compounds (Palmitic, Oleic, Stearic, Linoleic, Elaidic, Arachidic, Myristic).

But! I only managed to make it work few times and I don't understand what is going on. I am doing recommended maintenance. Once I make it work, I'm trying to run calibration, no compounds found, then I have 90 compounds visible in just blank, all sorts palmitates, some plastics etc. Then I am spending ages cleaning everything and situation repeats. I am running blanks between samples to clean the system but no luck.

I only work in -ve mode, I've seen some people had problems with suppression of ionisation, but I am not sure how to solve it since I need to have different tunning mix for negative/positive mode so I can't really try to alternate blank in opposite mode. Did any of you had similar problems?

Full details of method are:
Mobile phase: A: ACN + 5% IPA+0.1% ammonium formate; B: water+formic acid

gradient elution 1mL min-1 over 21 min.
Column C18 Poroshell 2.7um at 40C
injection 10uL
ESI source: VCap 4000V, Nozzle 500V, Gas T 250C, Gas Flow 13 L min-1, Nebuliser: 40V, Sheath Gas 11 L min-1 at 350C, Fragm: 170V.

PLEASE help I am losing hope!

Joanna