Determination of the dead time

[wiclef]

Good Afternoon,

I have tried to read some articles on the Theory of Chromatography and I want to
to determine the dead time.In literature, they say that you have to use methane for this determination.
I do not have methane that I can use.What chemical may I use instead of methane in GC?Do you have some further
information that you can suggest to me for this?Have you some documents which explain more on the theory of Chromatography?How can I check the efficiency of the column that I would like to use?

Regards

Wiclef Kagisha

[Johnny Rod]

What column and detector do you have?

[chromatographer1]

You have no availability of natural gas in your lab, building, or town?

If you are using a TCD you can use air.

Not the best choice but one that costs less than a dollar at a local store is to buy a butane lighter and sample from that for a FID.

best wishes,

Rod

[wiclef]

Dear Rod

Thanks for your advice.
I have the Agilent 6890 N and the column is a packed column PORAPAQ Q.
The detector I use is a FID.I was wondering how I can inject the butane and how I can
take it from the cylinder.What technique may I use?

Wiclef Kagisha

[chromatographer1]

butane is a VERY poor choice to make your determination using THAT column.

Even methane will be inaccurate as the fixed gases elute before methane on the column you have.

You can only inject hydrogen and see if you can detect a change in the response of the FID when H2 elutes. Even Hydrogen elutes after helium on the Porapak column. So there will be an error even with hydrogen.

The column you have does not meet the requirements to describe the classical calculations of a gas liquid chromatography.

Find another column or realize the futility of your endeavor.

best wishes,

Rod

[wiclef]

Dear Rod,

Thanks a lot for your positive advice.
I am starting to analyze the ethanol and methanol in alcoholic beverages
and I was trying to calculate the parameters that should give me
the best column that I can use.I would like stay in touch for other possible
problem that I can meet.

Regards,


Wiclef

[chromatographer1]

I believe you can find literature that describes a SP-20 capillary from Supelco which does an exceeding good job at the task about which you describe your efforts are directed.

best wishes,

Rod