Chromatography Forum

Hello,
We have a GC Thermo Trace with Triplus AS autosampler.
I am trying optimizing an injection method with various washing options, because of interferences appears in the chromatogram after sample injection. I need to discriminate if these interferences come from deficient syringe washing or by column memory of the analytes.
For that reason I want to obtain a chromatogram of the methods I used but without Triplus injection (that is to get the “instrument baseline” with the run method). But I can do this only manually. I need to implement an instrument baseline “sample” for quality control in the analytical batch. But I can´t found an option to put this run in the sequences of sample in a way that it run automatically. The best I have until now is: (1) to inject an “air sample” (empty vial), but this option introduce oxygen to de column and also syringe washing interferences. (2) To do the instrument base line by manual start, but in that way I can´t include it in the sequence to be run automatically.
Can anybody help me with this problem?

Thank you in advance!

Hello,
We have a GC Thermo Trace with Triplus AS autosampler.
...

More relevant than instrument model is your software version.
Check in help of your software how to make blank injection ie. run a method without injection.

Hello,
We have a GC Thermo Trace with Triplus AS autosampler.
...

More relevant than instrument model is your software version.
Check in help of your software how to make blank injection ie. run a method without injection.

Thank you for your answer.
I tried in the help but there no information abour programated blank runs. The software version in 4.2.

Regards,

...Thank you for your answer.
I tried in the help but there no information abour programated blank runs. The software version in 4.2.

Regards,

To be exact, I meant the brand name of the software.
Seems that yours is not Chromeleon.
If you have the manual of your software in pdf you may use search function to find "blank" injection, and how to execute it.

Sorry, is ChromQuest 4.2 (previuos version of Chomoloen).

I looked for many option (blank run, blank instrumernt, instrument baseline and others in the manuasl...) but I did noy found an option to do a blank run automatically in the middle of a samples sequence.

Regards,

Sorry, is ChromQuest 4.2 (previuos version of Chomoloen).
...

In Chromeleon sequence table has a field "sample type" in which you may declare sample, calibration, validation and at the end blank. When sample type is declared as blank there will be no injection in this particular sequence line - at least in Chromeleon for LC, but I think this behaviour is typical for GC as well.
Try to leave vial position empty in the sequence table - this works for ChemStation.

I don't know exactly what chromeleon will do, but when using xcalibur to run a sequence the sample type has no effect on the analysis. it is only used when processing so the software knows what to use as e.g. calibration points and QC.

can you make a special instrument methode with a 0µl injection and a needle depth in the injector that is hardly piercing the septum? This way you only need to change the instrument methode for that line in te sequence.

I know it is not a pretty solution, but if it works, ..... -

Just to clarify, Chromquest has nothing to do with Chromeleon. Chromquest 4.2 is basically Thermo's version of EZChrom. It's also in no way even remotely similar to Excaliber. EZChrom was purchased by Agilent, and is now part of 'OpenLab.' You can buy OpenLab with ChemStation or EZChrom. So those familiar with EZChrom may be able to help here.

You cannot conveniently do a 0 uL injection with EZChrom. It will generate an error. You can have the sequence by-pass errors, but that's asking for trouble.

As others have suggested, I'll look into this more as time permits, but I would just write a method with no washes and do an air inject. Assuming you're doing a split injection, the amount of air introduced onto the column is neglible.

How about just cutting the needle off an old syringe? That will give 0 ul injection.

How about just cutting the needle off an old syringe? That will give 0 ul injection.

That would require one to change syringes in the middle of a run.