Hi. I am new with GC. My question is: How can I know that my GC performing well? What is the acceptable reproducibility percentage of 1st and 2nd injection of a sample?

Thanks.

Good question anon,

what are You using: manual or sampler injections?
Solvent, injector, sample...

With other words: You can get a range of 1%...

manual injections with standard sample. I calibrated my sample eg. dodecane and internal standard - tetradecane.

my RSD 4.6% Is that bad?

Thanks.

It is not the best. Bad? is depends upon what RSD you NEED. But with good technique and with a good syringe, 1% RSD should be attainable without undue effort. 2% RSD using a splitter.

Most analysts do not know how to inject reproducibly with manual injection.

We dinosaurs died off when the big meteor called autosamplers hit the planet.

Good luck.

My RSD was ~5% (no internal std) if I remember correctly when I was new to GC. Though my injection technique wasn't the greatest.

Also keep in mind, the error (especially with a internal standard) is also a reflection of the GC conditions/program and not just injection speed/vol. delivery. This becomes especially sensitive when compounds are eluting at longer retention times.

Diesel fuels primarily have a pyramid like pattern of n-alkanes. Successive injections with my autosampler could show a differnent alkane as the apex of the pyramid.

In quantitative GCMS analysis, which parameter is most reliable and most reproducible? Is it the peak area or the peak height? why?