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### Topic: Ketamine MS  (Read 1039 times)

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#### sharbeldam

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##### Ketamine MS
« on: September 04, 2020, 04:31:38 AM »
If i'm given 3 base peak (M,M+1,M+2,M+3) of the compound ketamine and i have the abundance AND m/e for

M (100 relative abundance , 237 m/e)
M+1 (14.3 relative abundance , 238 m/e)
M+2 (33.3 relative abundance, 239 m/e)

but i'm only given the m/e (240) of M+3 and im required to find the abundance of M+3.

what is the way to do it?
I know that the M+2 should be from chlorine atom since 1:3 relative abundance from M. but how can i figure out and predict the abundance of M+3, i tried using percentanges and molecular formula but its not working out.
Is it right to do this...

« Last Edit: September 04, 2020, 06:23:09 AM by sharbeldam »
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#### AWK

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##### Re: Ketamine MS
« Reply #1 on: September 04, 2020, 06:14:52 AM »
Can you calculate the expected intensity for peak 274 from the compound composition?
Do the same for peak 276 using peak 275.
AWK

#### sharbeldam

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##### Re: Ketamine MS
« Reply #2 on: September 04, 2020, 06:22:42 AM »
Is it too much to ask for the calculation? I'm not really sure how to calculate (I edited the original post)

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#### AWK

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##### Re: Ketamine MS
« Reply #3 on: September 04, 2020, 06:27:55 AM »
Peak 238 (M + 1) depends primarily on the number of carbon atoms in peak 237 (M).
The same relationship occurs between peaks 239 (M + 2) and 240 (M + 3).
AWK

#### sharbeldam

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##### Re: Ketamine MS
« Reply #4 on: September 04, 2020, 06:36:17 AM »
number of carbons = (abundance of M+1 ion/abundance of M ion) * (100/1.1)

t ketamine has 13 carbons, hence... solving for that, except putting M+3/M+2, in that equation?
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#### AWK

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##### Re: Ketamine MS
« Reply #5 on: September 04, 2020, 06:40:59 AM »
If M shows intensity 100 then M+1  ==> 13·1.1
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#### sharbeldam

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##### Re: Ketamine MS
« Reply #6 on: September 04, 2020, 06:44:29 AM »
yes but i need M+3,
so can i do

x/33.3*(100/1.1) = 13

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#### AWK

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##### Re: Ketamine MS
« Reply #7 on: September 04, 2020, 06:45:52 AM »
NO
0.333·13·1.1
AWK

#### sharbeldam

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##### Re: Ketamine MS
« Reply #8 on: September 04, 2020, 06:49:27 AM »
thank you sir AWK, i get it now
and tbh your " NO " kinda scared me, i heard it.
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