Columns

Typical buffers and additives for reversed-phase HPLC

  pKa Buffer range Standard Concentration Volatility*
TFA <1.0   0.01~0.1% Yes
H3PO4 2.1   0.01~0.1% No
NH4H2PO4-H3PO4
[NaH2PO4-H3PO4, KH2PO4-H3PO4]
2.1 1.1~3.1 5~50 mM
(<20 mM recommended)
No
HCOOH 3.7   0.1~1.0% Yes
HCOONH4-HCOOH
[HCOONa-HCOOH, HCOOK-HCOOH]
3.7 2.7~4.7 5~50 mM NH4 salt:Yes
[Na, K salt:No]
CH3COOH 4.8   0.5~5.0% Yes
CH3COONH4-CH3COOH
[CH3COONa-CH3COOH, CH3COOK-CH3COOH]
4.8 3.8~5.8 5~50 mM NH4 salt:Yes
[Na, K salt:No]
(NH4)2HPO4 -NaH2PO4
[Na2HPO4-NaH2PO4, K2HPO4-KH2PO4]
7.2 6.2~8.2 5~50 mM
(<20 mM recommended)
No
Triethylamine-CH3COOH (TEAA)   4.6~6, 10~11 <20 mM Yes
HCOONH4-NH3, CH3COONH4-NH3 9.2 8.2~10.2 <20 mM Yes
Na3PO4-Na2HPO4, K3HPO4-K2HPO4 12.3 11.3~13.3 <10 mM No
NH4HCO3-NH3   8.5~10.5 <10 mM Yes

* Usable for LC/MS and preparative separation