HEPES vs TRIS - Least Worst Option?

Question

I typically try to clean up and buffer exchange samples into ammonium acetate or (worst case) PBS; however, I need to compare some results with either 50mM HEPES or 20mM Tris. 
 Wondering if anyone has suggestions as to which one is worse in terms of contamination and/or buildup? 
 To give some extra detail: 
 
 This is on a 1290/6545XT LC/MS w/ AJS 
 Running intact protein MS with Water:ACN+FA 
 I use a PLRPS column and inject ~1 uL. 
 I divert the first 1 min to waste, in order to help "wash" the sample

MS2N · Answer

Sorry for the delayed response. I've found that either works fine. I typically try to keep injection volume low (0.2-1 uL for 1uM protein). I've mostly been using 50mM HEPES 150mM NaCl and get great deconvolution results, even with a 3 min short method. I run at roughly 384 well plate throughput and have not had any long term issues, though I'm pretty diligent about sending everything to waste that is not my protein peak. Tris is supposedly better for the system but I haven't found much of a difference. 
 The NaCl isn't great but necessary in most cases. It will increase NaCl adduct formation but it's fine for less complicated, smaller proteins (homogenous ptms and <150kDa). Surprisingly, our source/nebulizers is usually almost spotless (just a bit of ion burn) after 1000s of samples.

HEPES vs TRIS - Least Worst Option?

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