Dear coleages,
I am using for my first time a microbore column. At the moment I am trying to separate three compounds with a mixture of acetonitrile/water (86:14). The problem that I have is that the pressure of the system keeps going up all the time event without injecting anything. Could anybody help me with this problem?
´Thank you in advanced.
Soledad

Hi Anon, what dimension of column do you use for microbore, a 2mmID or 1mmID. Your mobile phase should be ok, but what is the flow rate? Do you have a micro injection valve, and how did you optimized your HPLC system, like capillaries and detector flow cell? How long is your microbore column, and what particle size is packed into it? Do you have a micro pump system? First of all check all connections within your HPLC system. Use new ferrules and do all the connections new. Step by step we will sort it out and solve your problem. Gerhard

Dear Soledad, are you using an old column or a new one?

Creo que con ese nombre puedo hablarte en español, no?.Prueba a pasar un flujo bajo con alta proporción de agua primero durante un buen rato, no vaya a ser que si la columna no está bien lavada y alguien la usó con sales, las estés precipitando.Luego, prueba a ir subiendo el % de AcN. Si me he equibocado dímelo, y te lo cuento en ingles.

Tell me if you are not a spanish speaker...
Balto.

Assuming by 'microbore' you mean a 1 or 2mm column, it sounds to me like you are washing particles of some kind onto the column frit.

If your system has had buffer in it that has not been properly removed, you will see this problem. Or, if the system has not been well-maintained, and 'slime' has grown in the water lines, when you start the system up again you will see this problem as the slime is washed off the tubing walls and plugs the column frit.

Put a particle filter before the column if you haven't already ruined your column, and keep pumping. If it is a slime problem, it will go away in a few days. When the pressure goes up, backflush the particle filter, and continue pumping. You might want to use an old, known good (at least no pressure problems) column to generate 'normal' backpressure. It took me 2-3 days to clean up a seriously contaminated system, but eventually it worked fine again.

We have also seen this problem with damaged columns, or poor quality columns. I once had a problem where it appeared that small particles inside the column would move through the column and plug the frit on the exit end. If the column was reversed, it worked fine for a couple days, and then the pressure began to build again. It repeated this behavior over and over. I had a particle filter to keep anything from the pumping system or sample out of the analytical column.