unstable baseline and baseline drops

Question

Hello all 
 
 I am experiencing an unstable baseline problem increasing with increasing MeOH in the gradient and sudden drops in baseline. 
 This is a typical plasma metabolome profiling experiment with 1290 UHPLC and 6546 Q-TOF in NEGATIVE ION MODE 
 A: H20 (0.1 %Acetic acid) B: MeOH ( %0.1 Acetic acid) 
 Column ins HSS T3 Xbridge 
 
 As you see this is more like a IR spectra. Nebulizer and system temps are all OK. 
 Would incrasing AcA to 1% help? 
 Spectrum:

The gradient program is:

and method parameters are: 
 
 Any help and suggestions are much aprreciated. 
 
 Basri

p.altiero · Accepted Answer

Hi Basri, 
 To me, this looks like suppression from late eluting matrix components ( I am thinking lipids). The baseline is dropping out so much as it's actually showing negative peaks, this is a classic indication of matrix suppression.

unstable baseline and baseline drops

Top Replies