What are the common buffers used in HPLC?
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Since the retention of ionizable compounds is very sensitive to the mobile phase pH, it is necessary to control the pH of the mobile phase by the addition of a buffer. A buffer maintains the pH when a small amount of acid or base is added. Many different substances have been used for buffering in HPLC.
The most popular buffers for HPLC with UV detection are phosphate and acetate. Phosphate and acetate are particularly useful buffers because they can be used at wavelengths below 220 nm.
When a mass spectrometer is used as the LC detector (LC-MS), the mobile phase must be volatile, because one of the functions of the LC-MS interface is to vaporize the mobile phase. This means that the most popular buffer for LC-UV work, phosphate, cannot be used. Several buffers are sufficiently volatile to qualify for LC-MS use. The most common HPLC Buffers for LC-MS applications are Acetate, TFA (0.1%), formic acid, ammonium formate and ammonium bicarbonate.