Chromatography Forum

Detailed Hydrocarbon analysis is new to me so forgive me if this is an obvious question.

In the method it has a list of compounds with Kovats Retention indexes

But instead of names some have a letter with a sequential number making a unique ID within each letter.

It this series it looks like:

I = isoparafin
A = Aromatic
N = Napthene (Cyclic Alkane)
O = olefin

and if there was an P series (which there is not it would be N-Alkanes...

So the class of those compounds are known... But are the structures, or at least their formulas or carbon numbers known?

Some others are just named "diolefin" or "Cyclic diolefin or triolefin"

I assume the classes were determined long ago by doing prep separation before GC injection...

But I would think that with the technology available these days, that the formulas, even if not structures, would be known by now.

Is more information on those unnamed compounds available someplace?

Of course I assume those named "?" are totally unknown peaks.

Thanks,
Karen

Those are all generic names. It is likely that they state it that way in the standard because for that "class" of compounds, there are many many structural isomers. I looked up "isoparaffin" and it came up with a mixture of C13-C14 hydrocarbons. There are just too many ways to make discrete hydrocarbons in that molecular weight range to call them out individually - although they can be named discretely.

A fairly detailed solutions for DHA analysis can be found here http://unichrom.com/dha/dha2e.shtml and http://unichrom.com/dha/petrol-report.shtml

Best regards,
Siarhei

Usually, DHA applications are used for PIONA (or PiONA, PONA, PNA) analysis. For almost all users, the most important information get from a DHA analysis is group quantification (n-paraffins, iso-paraffins, naphtenes, olefins, iso-olefins, aromatics). Even using a long column (100 m) and a long time analysis, a simple gasoline sample can have more than 500 different molecules.
For example, paraffins (n- and iso) with 10 carbons have 75 isomers, olefins (n- and iso) more than 1000, that is almost impossible to separate and identify properly each isomer. Then, the solution was use a generic identification, because even a column with 100m it's not capable to separarate all compounds.

Leonardo.