Chromatography Forum

When running a sequence of samples, I want the last samples to run an oven ramp method without injecting anything. Is this possible? It's an Agilent 7890/5975 GC/MS using chemstation.

Easiest thing to do it just tell the instrument to use an empty vial, though that still will be an injection. Some regulatory regimes may want to count those.

It is tricky to manage two configurations, one that has an autosampler and one that does not. I am not sure if it can be done. I think you end up with one configuration or the other, as it may not be method specific.

If you just want the oven to be at something over your starting temp, just make sure the method on the screen is that kind (a standy method is how I refer to it), and that method will be reloaded once your sequence ends. Note - I am refering to the G1701 series of MSD chemstations here, the GC/LC type may behave differently.

I routinely setup a a method to inject 5 or so solvent runs after a sequence, then let the instrument reload the startup or standby method at the end. Note that this forces whatever junk got onto the column even farther, but I would need a newer system with a back flush option to avoid that.

I thought about an empty vial, but then I would essentially be injecting air onto a hot column, yeah? Not great.

When running a sequence of samples, I want the last samples to run an oven ramp method without injecting anything. Is this possible? It's an Agilent 7890/5975 GC/MS using chemstation.

It is possible, althou not so straightforward as with GC ChemStation. And more elegant way is possible than empty vial method.

When running a sequence of samples, I want the last samples to run an oven ramp method without injecting anything. Is this possible? It's an Agilent 7890/5975 GC/MS using chemstation.

The easiest way to do this would be editing the method of your samples, and add your last oven ramp without injection to that. Call that method 2 and run the last sample in your sequence with method 2.

Or just inject a solvent blank.

One more option: make your injection-less method with 'manual' injection. Then you can make it a seperate "sample" without injecting anything, but you have to manually click on 'start run'.

I thought about an empty vial, but then I would essentially be injecting air onto a hot column, yeah? Not great.

Not if you start your oven method at a normal, low temperature (~50°C). By the time the column is hot the air will have passed trough your system. It's not great for your MS, but 1µL of air every now and then is nothing to worry about in my opinion.

Can't you just have your last row in the Sequence Table with "nothing"/empty cell in the box for number of injections. Called a blank run.

Do a search for "non-injection" on this site (You need the quotation marks), and you will see an answer to an earlier request for the same problem.

Gasman

Depending if the software fits for your need you might want to have a look at the latest OpenLAB 2 software. There you can make an injection free run by specifying as ALS source "No Injection".

Our last injection is or a blanc or just a vial with clean solvent.