Buckminsterfullerene is the soccer ball-shaped molecule C_60. (a) Calculate the

Question

Buckminsterfullerene is the soccer ball-shaped molecule C_60. (a) Calculate the relative size (percentage of total) of the Mand M+1 peaks if 12^C has a natural abundance of 98.9% and for 13C 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? Question 2 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

1)Relative size of the M and M+1 peaks in Buckminsterfullerene (C60):

Let molecular ion peak (M+) assign 100 % size, then relative to M+ we can assign % intensity to (M+1) peak.

Formula,

%(M+1) = 1.1 x Number of C atoms + 0.36 x Number of N atoms.

In Buckminsterfullerene (C60) number of C atoms = 60. No N atoms.

Hence,

%(M+1) = 1.1 x Number of C atoms.

%(M+1) = 1.1 x 66

%(M+1) = 72.6

Hence relative size M: M+1 is 100 : 72.6

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2)For monounsaturated triglyceride with molecular formula C45H84O6.

Let us find out M : M+1 peak size ratio.

Number of carbon atoms = 45

%(M+1) = 1.1 x 45

%(M+1) = 49.5

Hence, M:(M+1) peak size ratio will be 100 : 49.5

This molecpattern will distinguish the MS of Buckminsterfullerene and monounsaturated triglyceride fat.

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