Is it better to use formic acid or potassium phosphate buffer for a reverse-phase method? - WKB123365

ENVIRONMENT

• Buffer selection
• Mobile phase
• Formic acid
• Potassium phosphate
• Reverse phase

ANSWER

Each buffer has its own benefits, depending on the method and pH range of the reverse-phase column.

ADDITIONAL INFORMATION

Phosphate buffer:

Benefits-  Better at low UV; pH is buffered at pH 2 (more stable pH)

Concerns- Not MS compatible; can precipitate out in high % organic (especially methanol); can’t add it to both the A and B lines of a gradient; takes time to make the buffer

Formic acid:

Benefits- MS compatible; easy to use/add to mobile phases; is a weak ion pairing reagent, which could be beneficial for proteins/peptides; compatible with organic solvents

Concerns- Higher UV cutoff; potential pH drift over time (not buffered)