[yas]

Hi,
I am trying to quantify compounds after GC analysis using internal standard method. I do not have experience in cases like that
1. There is no authentic standard I can buy
2. I did not identify the compound (for example, I know it is a sterol, but I do not know exact structure, it might be a mixture)

I would really appreciate all suggestions

thank you,

yas

[JGK]

How are you quantifying if you do not have a standard? 

An internal STD (IS) method utilizes the peak area (or height) ratio (analyte/IS) as the  Y parameter plotted against analyte concentration (x parameter) in a regression.

Without a standard of your analyte, and therefore values for x, how can you begin to quantify?

[yas]

Hi JGK,
thanks for reply. I think I confused you. I am analyzing cuticular wax composition, there are like 55 different compounds, I used the internal standard method to quantify majority of the compounds as standards are available. There are 3 compounds of the same class for which I can not find standards.   So, my question is if there is a way to quantify these compounds or what people do in this case?

thank you very much,

yas

[JGK]

The I would say that without a standard, there is no way to accurately quantify your results.

[gericox]

Do your known standard compounds give similar response factor?

[Rivet]

If you can be certain that your unknown is a sterol and that you do not have a mixture, you might use the strategy employed in this paper, where they did not use an authentic standard for every individual compound:

Lo Presti et al 2008.  Flavour and Fragrance J. 23(4) 249 - 257.