Chromatography Forum

Hello all!

We have suddenly lost our ability to inject samples.

The observed signal is about 0.5% of what it ought to be for standards.

Here is the odd thing:

I can make a flow injection, no problem. It appears that I only cannot inject sample when a column (any column, tried several) is connected. We suspect that the increased backpressure is to blame.

When I try to make an injection with a column connected I can sometimes observe some "bubbling" in the vial and a meniscus of liquid is sometimes left on top of the vial septum.

Has anyone seen this before or has any idea on where to start troubleshooting?

There are no visible leaks.

Thank you for any and all advice!

Arne

see response below.

The problem was solved. A slight leak in the injector had developed that only had an effect when the system was under high (>1500 psi) pressure. We changed the rotor, which fixed the problem. Inspection under a dissection scope revealed slight scratches connecting the drilled holes and thus forming a channel between ports that allows for the injection loop to be bypassed.