USEFUL/ACCEPTABLE SOLVENTS:

• Water
• Acetonitrile
• Methanol
• Ethanol
• Propanol
• Isopropanol
• Dichloromethane – if mixed with methanol
• Toluene – if mixed with methanol or acetonitrile

TOLERABLE SOLVENTS IN SMALL AMOUNTS:

• Dimethylformamide (DMF)
• Dimethylsulphoxide (DMSO)

ACCEPTABLE ADDITIVES TO AID PROTONATION/DEPROTONATION:

• Acetic acid
• Formic acid
• Ammonium hydroxide
• Ammonium formate (10 mM)
• Ammonium acetate (10 mM)
• Ammonium bicarbonate (10 mM)

SOLVENT MODIFIERS/ADDITIVES NOT COMPATIBLE WITH ESI:

• Non-volatile salts (phosphate, borate, citrate, chloride, etc.)
• Surface-active agents (surfactants/detergents like SDS)
• Inorganic acids
• Trifluoroacetic acid (TFA)
• Ethylenediaminetetraacetic acid (EDTA)
• Plastics leaking/contamination
• Any particulates, however fine – filter your samples!