Gas chromotography-mass spec percent composition

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SUMMARY

This discussion focuses on using gas chromatography-mass spectrometry (GC-MS) to determine the percent composition of biodiesel in a diesel/biodiesel mixture. The user prepared four standard solutions and analyzed an unknown sample using a GC-MS instrument. The key method involves calculating the relative abundance of the biodiesel peak compared to the total relative abundance of all peaks in the chromatogram. While this method provides an approximation, it is effective when no additional data is available.

PREREQUISITES
  • Understanding of gas chromatography (GC) principles
  • Familiarity with mass spectrometry (MS) techniques
  • Knowledge of interpreting gas chromatograms
  • Basic skills in calculating relative abundances
NEXT STEPS
  • Research how to interpret gas chromatograms for quantitative analysis
  • Learn about mass spectrometry peak identification techniques
  • Study the principles of calibration curves in GC-MS analysis
  • Explore advanced methods for determining composition in complex mixtures
USEFUL FOR

This discussion is beneficial for chemists, laboratory technicians, and students involved in analytical chemistry, particularly those working with GC-MS for fuel composition analysis.

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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