Waters Amide Column Stability

[WillyOne]

About the increasing of Head pressure:
I'm working on wines, liquors, honey and soft drink sugars content.
Flow: 1 ml/min; eluent 80:20 ACN/ Water plus 0.2% Triethylamine. Samples at 25°C Column 35°C RI detector 35°C
I've destroyed two column because the increasing pressure.
Now, at the end of the day I clean up the column as follows:
First change to 80:20 ACN/water without Tryethylamine,
Then change to 50:50 60 min
then change to 50:50 ACN/Water plus 0.1% Trifluoroacetic acid and hold 60 min
New change to 50:50 ACN/Water 30 min abd finally store the column in 80:20 ACN/Water

I'm working like this three months and pressure increase has been no significant (Initially 1175psi, nowadays 1250 psi)
The column is 250 x 4.6 mm
Perhaps it can help
Guillermo

[carol]

Hi again,
I am trying to do lactose in milk by HPLC-MS/Ms, I know, there are better detector but this is the one they have and it is for a project so it will only be for a couple of months. The idea is also to be able to detected lactose in free lactose milk.
Any comments our suggestion will be great. The problem I am facing is that the peaks are wide if I use waters application so I had to increase the flow, but even though I get much better shape if I use a gradient. However, I started with 0.5 ml/min but do to the pressure problems I am now working at 0.125. I hope I will not have to reduce the pressure anymore!!
I milk sample I have only tried a few times because quantification was unsuccessful, concentration of lactose were lower than it should be. I was just diluting the milk by approximately 50000.
Thanks for your interest,
Carol