\"Quiz 4\" - answer all questions in the space provided (or on the back if you n

Question

"Quiz 4" - answer all questions in the space provided (or on the back if you need more space) (this question will be scaled to be worth 10% of your final mark) Buckminsterfullerene is the soccer ball-shaped molecule C_60. (a) Calculate the relative size (percentage of total) of the M and M+1 peaks if^12 C has a natural abundance of 98.9% and for^13 C it is 1.1%. (b) The monounsaturated triglyceride fat with molecular formula C_45H_84O_6 has the same nominal mass as C_60. How would you distinguish between these two species in a MS experiment? Explain why a GC-MS is a simple interface but the HPLC-MS interface is not. Describe how an HPLC-MS interface might be accomplished.

Explanation / Answer

ans a) abundace of C12 = 98.9 %

abundance of C13 = 1.1 %

relative size of m+1 peak as compared to M can be given by---

abundance of C13 X 100 / abundance of C12

   or, 1.1 X 100 /98.9

   = 1.112 %

----------------------------------------------------------------------------------------------------------------------------------------------------------------

ans b) if the molecular ion is at m/z = 720. An ion representing loss of 32 mass units (methanol from the ester moiety) i.e. 720-32 and another of 74 units (both m/z = 74 per se and [M-74]+ ) from a rearrangement involving the ester moiety confirm that we really do have a methyl ester.but these peaks will missing in the spectra of C60.

------------------------------------------------------------

ans c)

one major difference between GCMS interface and HPLC MS interface is that GCMS interface is cost friendly as compared to LCMS interface which is costly. you can give a comparison between GCMS and HPLC ms -

1.Both LC-MS and GC-MS are methods to separate chemicals in a mixture or a sample. Both methods separate the chemicals first by chromatography and are further examined and identified by the mass spectrometer.
2.Both methods require a mobile phase and a stationary phase. The only difference is that LC-MS uses a solvent as a mobile phase while GC-MS uses inert gases (like helium) in the same capacity.
3.GC-MS is considered as the preferred standard for forensic identification, and it is also the preferred machine in terms of costs and operation

Read more: Difference Between GC-MS and LC-MS | Difference Between http://www.differencebetween.net/science/difference-between-gc-ms-and-lc-ms/#ixzz4fEVVSaE1

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.