Volatile Buffers for LC-ESI-MS

A table of ESI-MS compatible volatile additive and buffer systems, taken from "Optimizing Reversed Phase HPLC Separations for High Throughput Applications," a technical report at http://www.mac-mod.com/tr/04041-tr.html.

A concentration of 1 to 10 mM for any of these is recommended.  The use of TFA in concentrations above 0.1% should be avoided in ESI-MS due to ion suppression effects.

Additive or Buffer	pKa	Buffer range
TFA	0.5	-----
Formic Acid	3.8	-----
Ammonium Formate	3.8	2.8 – 4.8
Acetic Acid	4.8	-----
Ammonium Acetate	4.8	3.8 – 5.8
4-Methylmorpholine	~8.4	7.4 – 9.4
Ammonium Bicarbonate	6.3/9.2/10.3	6.8 – 11.3
Ammonium Acetate	9.2	8.2 – 10.2
Ammonium Formate	9.2	8.2 – 10.2
1-Methylpiperidine	10.1	9.1 – 11.1
Triethylamine (acetate salt)	11.0	10.0 – 12.0
Pyrrolidine	11.3	10.3 – 12.3