amschneider
Registered: 10/09/09
Posts: 4
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Reply with quote | #1 |
On question 4, where it is asking how to determine if a peak in the MS is the molecular ion. If M, M+1, M+2 correspond to the highest peaks, unless there is significant fragmentation, how is it that you determine if a molecular ion is prone to easily fragment? What aspect of the molecule is that based on? |
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sthaker
Registered: 09/27/09
Posts: 15
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Reply with quote | #2 |
I had another question which I guess relates somewhat to this topic, but I was wondering for question 5, for example, all of the relative intensities for M also happen to be the base peaks. I know from question 3 that M is not always necessarily the base peak, since fragmentation determines the height of the peaks, but how would we know when fragmentation occurs and M is not the basepeak because it seems that this is often the case, at least according to the problems in question 5.
Thank you!
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sameerpatel
Registered: 10/03/09
Posts: 7
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Reply with quote | #3 |
Hello,
As for when to know that a molecule has been fragmented and therefore the base peak is not the m/z, look for the tallest peak to the most right of the spectrum. According to the TA that filled in for Oscar on Wednesday, if you look at page 96 of your Thinkbook for example, the tallest peak is around 44, but the M is at 78. That is because there's a pocket of readings between the 75-80, 60-65, 35-45 marks and so on. So if you look to the right-most pocket of readings, the ones around the 75-80 mark, the peak at 78 is the tallest peak and to the most right of the spectrum, therefore, that is the M.
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