Chromatography Forum

Columns like the Acclaim WAX-1 and Obelisc columns give alot of bleed under ESI(+) conditions right out of the box. Conditioning these columns at 35C for several hours using 20 mM Ammonium Acetate buffer and acetonitrile (tried 10, 50 and 80% B) still does not seem to make much of an impact on the column bleed. Also tried 50mM AmAc for about 1 hr but still higher background under ESI(+) mode than is typical for a reverse phase column. Last I looked the Obelisc columns were QC's using TFA - a double whammy - aahh!

Does anybody else have these same experiences and how do you solve this problem - condition overnight, conditions for days or just give up with these types of columns for MS work? Any better MS compatible alternatives for mixed mode? BTW, I do not want to use any ion pairing reagents such a HFBA or TFA.

Just an update. The Obelisc N column bleed has two prominant (~300K counts) peaks in ESI(+) at m/z 423.34 and a peak at m/z 481.38 which happen to be 58.04 mass units apart that is consistent with C3H6O. At higher ACN an ion at m/z 300.24 is prominant (1.5 million counts). These observation were made using 50 mM AmAc and CH3CN. Coumn at 35C.