Gas chromotography-mass spec percent composition

AI Thread Summary
To determine the percent composition of biodiesel in the unknown sample using gas chromatography-mass spectrometry (GC-MS), the relative abundance of the biodiesel peak can be compared to the total relative abundance of all peaks in the chromatogram. The mass spectrum aids in identifying which peaks correspond to biodiesel and diesel by providing structural information. While this method offers an approximation, it is a valid approach if no additional data is available. Understanding the chromatogram and mass spectrum is essential for accurate peak identification. This analytical technique allows for effective estimation of biodiesel content in mixtures.
Puchinita5
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So I conducted a lab where I prepared 4 standard solutions of diesel/biodisel mixtures and then analyzed a diesel/biodeisel sample of unknown composition.

We put all the samples into a GC-MS instrument (gas chromotograph-mass spectrograph).

I have a gas chromatogram for all samples and then a mass spectrum of the highest two peaks in each chromatogram.

Both the chromatograms and mass specs are in terms of relative abundance.

I am supposed to determine (i was told I could estimate) the percent composition of biodiesel in the unknown.


Can someone help me understand how I can use the gas chromatograms and mass specs to figure this out?

Can I just take the relative abundance of (whatever I determine to be) the biodiesel peak over the sum of the relative abundances of all other peaks?

What can the mass spec tell me? Is it just to help me figure out which peak is biodiesel and which is diesel?

I am not understanding this!
 
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Puchinita5 said:
Can I just take the relative abundance of (whatever I determine to be) the biodiesel peak over the sum of the relative abundances of all other peaks?

That's only an approximation, but should work if you have no other data.
 
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