Chromatography Forum

I am running an agilent 1200 and the other night the solvent ran to dryness. Since then I am not able to achieve and maintain proper pressure with the injection valve at the mainpass position. When in the bypass position I have the proper pressure so it seems as though there is something going on in the flow path from the injection valve to the needle seat. I have flushed all lines and get get the proper flow rate thorugh this path, just not the proper pressure. Also primed the pump after dryness. Any thoughts?

Doesn't sound like a pump problem from what you describe. Is there any leakage around the needle seat in the mainpass setting, like using a tissue to see any?

Sorry for the very delayed response in posting the solution. It was in fact a leak at the needle seat. replaced this part and back to normal operation.