Chromatography Forum

Hey ,
I am Lopa . I am using HPLC in gradient mode.My mobile phase solvents are water+TFA(0.2%) and methanol+TFA(0.2%).
But TFA makes the two solvents pH 1.56 and 0.67 respectively.
My column is a c18 column which has pH range up to 2-8 .Can i use this mobile phase?

Please suggest me

Hello, Lopa,

Most C-18 materials have the C-18 alkane chain attached covalently to a silica surface via a silane: Si-(CH2)17CH3. At pH 2.0 or less, the Si-C bond will start to hydrolyze. Consequently, sustained use of 0.1% TFA results in a steady loss of capacity of a C-18 column over a period of several months. With your 0.2% TFA the rate of loss will be even faster.

In Addition to Andy's comment please check if your column is a so called trifunctional or polymeric bonded packing material, or a monofunctional bonded Phase. Under acidic conditions trifunctional bonded phases in General have longer lifetime. But definitively C18 chains are stripped off faster with 0,2%TFA. What is the pK of your target compound?