Ignoring response factors, can you just use the area of one peak divided by the total of all peaks excluding solvent *100 to determine the % amount of each component in the detected mixture?
Hi Louis,
you can do this if all compounds in the chromatogram have the same or similar response factor (e.g. analysis of hydrocarbons with an FID). In all other cases you only have an estimation of the % amount of your desired compound.
Regards
Markus
Thanks for the quick answer! Ok so if you wanted to calculate the yield of compound A then couldn't you just use the peak area of the starting material at t=0h and say that the theoretical yield would therefore be equal to that peak area. Then just divide the area of compound A peak by this theoretical yield to get the yield of compound A (assuming the same response factors)?
Hi Louis,
to calculate a kinetic of compound via GC I would use the peak area or height.
Providing you always inject the same amount. This is only possible with an autosampler. Manual injection is ruled out.
Regards
Markus
Usually in organic synthesis the percentage distribution of peak areas (expresssed as Total Ion Current) in GC-MS is used as a good estimate of the reaction conversion rate. This implies that response areas are similar between main product or reagent and by-products. This assumption is not ususally valid, because, as an example, oxidised compounds can have very different response respect to their parent. Furthermore, oxidised by-products could not abe nalysed in GC because they are too polar or less volatile, and on the consequence thay will be lost.
Yes, you can use it IF every compound you see give the same response on the detector such as 10 ng of any analyte gives the same peak area. I analyzed fatty acid methyl ester in cottonseed oil with GC/FID
ok brilliant. thanks for all your answers. i understand its not a perfect method as it is assuming response factors are the same but as a rough estimate it will do.
For fast approx. quantification you can use a simple normalization. For FID (GC) or RID (LC) for isomers or similar compounds the error will be not that big. But remember- all compounds of the mixture must be detected.
Regards
G
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