Chromatography Forum

Hi,
For the GC used in analysing natural gas, i use a standard gas imported and produced by Linde gas.
For the Gc used for liquid hydrocarbon, do i really need a standard liquid?i have an old printed chromatogram from another lab which can be used for peak identification. Is this ok?
Pls advice on standard practice and if there are other developed practices, let me know pls.

Thanks,
B

Standards are always a good thing. In going from one instrument to another, and even as the same instrument changes, things change. Thus a retention time that was good on one instrument may not be valid for identifying a compound on another instrument - it may not even be valid on the same instrument just days later.

If you are going to run the same mixture that was run on that other instrument and it has been carefully kept, it can be a standard. But be careful of the quality of that standard. The quality of your work is only as good as the quality of your standards.

If you need to identify several compounds and you know that all are in the mix, you may not need a standard that is suitable for quantitative analysis, but you need to be sure that the specific compunds are present and can not be confused with contaminants in the mixture.

Commercially prepared standards are well characterized, have been properly packaged, and have a known shelf life. Some of us bet our paychecks on the quality of those standards.

Purchase small quanities and prepare std in house.

This also allows for peak identification and dosing samples in the event of questions raised against peak identification in process samples.

Dave

Dave & Don thanks for your responses.
Pls, how can i prepare inhouse hydrocarbon liquid standards.

One more question, if I have no problems with peak identification in a multi-component hyrocarbon liquid i want to analyse, can i do without a standard in my quantification?

Many thanks for your response.

B

Whenever I help someone with a problem on their instrument it is always extremely useful for them to have a standard available as well as historical data (paper copy of their instrument method/conditions, chromatograms over time.)