TFA related retention time variation

[Sahil]

I have been observing the shifting of Retention time from 12.0 to 7.5 in reverse phase column, on agilent 1200 series....i have checked the GPV but its okay as well as i have changed the lot of Acetonitrile also...as the Rt is shifting towards left hand side....now the problem is whether TFA addition is not proper...my mobile phase consists of 0.1% TFA in 50% ACN and the mobile phase B consists of 0.1% TFA in 95% ACN....so either ACN or TFA has to be culprit for low retention time..so what is a suggestion to resolve this issue..and how shall i add TFA? and how to determine the if TFA is culprit

[tom jupille]

Or, you may be hydrolyzing the bonded phase off your column. What happens if you try a new column?

[Sahil]

Or, you may be hydrolyzing the bonded phase off your column. What happens if you try a new column?

I also tried it with new column but same Rt shift was observed, thus we changed the gradient propotion valve..than we got consistency in Retention time. Now we got consistency but the Retention time was one minute less than that of reported value...our Rt should be about 12 minute, but we got 10.8 minutes consistently for 10 injections. So i have doubt either on acetonitrile and TFA....