Mass spectrometry (MS) is an analytical technique which takes advantage of the mass-to-charge ratio of gas-phase ions in order to elucidate the composition of a sample.
Questions tagged [mass-spectrometry]
237 questions
16
votes
1 answer
Resolution in Mass Spectrometry
I have been reading about resolution in mass spectrometry and there are a few things I do not understand.
The resolving power is determined by $m/(m_2-m_1)$ at full width half height of a peak. The higher the value obtained the better. This is where…
Harpal
- 263
- 1
- 2
- 5
16
votes
1 answer
What do typical results from inductively coupled plasma mass spectrometry (ICP-MS) look like, and how do I interpret them?
I have a degree in chemical engineering and remember having seen a inductively coupled plasma mass spectrometer (ICP-MS) during the laboratory part of a chemistry course I took while at university, but it is many years ago. Now I would like to know…
anon
15
votes
1 answer
Understanding how mass spectroscopy works
I’m trying to get a deeper understanding of how mass spectroscopy works. Most tutorials and textbooks I’ve encountered omit certain details about the process and I’m hoping someone out there who understands the process can fill in the gaps. I’ll…
Amateur Math Guy
- 395
- 3
- 9
7
votes
2 answers
Why is a very small peak with larger m/z not considered to be the molecular ion?
With regards to the following spectrum:
When asked for the M/Z for the molecular ion, the peak at 58 was taken, not 59.
What causes the peak at 59, and why isn't it taken as the molecular ion?
George Tian
- 1,361
- 2
- 15
- 30
6
votes
1 answer
EI-MS: M-28 peak in aldehydes
I've noticed a phenomenon in the EI-MS spectra of aliphatic aldehydes. Many of them show a significant peak (sometime it's even the base peak) at $M-28$.
To my best understanding, the only thing that can explain this – and is common to all…
Oded R.
- 215
- 2
- 6
6
votes
1 answer
How to find polynomial factor of relative (M+n) peak when factoring more than 2 isotopes
I'd like to ask for an extension of Nicolau Saker Neto's answer here:
What is the relative size of the (M+2) peak?
I'm trying to calculate isotopic abundances of molecules with more than 2 isotopes. I've been experimenting calculating relative…
Estif
- 63
- 3
6
votes
0 answers
Why is the base peak of my MS spectra of 2,3,5-tribromothiophene at m/z=382?
I recently requested a ESI-MS analysis of 2,3,5-tribromothiophene and got this spectrum:
These are the analysis conditions:
Detector: ESI(+)
Source Tem: 150
Capillary voltage: 1.5 kV
Cone Voltage: 20 V
Mass range: 200 - 1000
Flow: 0.2…
Krang Lee
- 1,081
- 8
- 14
6
votes
1 answer
Prediction/computation of mass spectral ionisation intensity
There are quite a few approaches (ranging from empirical additive rules based on presence of functional groups to full blown in silico QM calculations) to predicting molecular properties such as UVmax absorption or IR vibrational frequencies. While…
NotEvans.
- 17,137
- 4
- 69
- 137
6
votes
1 answer
Difference between HCD and CID collision induced dissociations?
With the Thermo-Fisher Fusion Orbitrap mass spectrometer I can do both CID (collision-induced dissociation) and HCD (higher energy C trap dissociation) collision-induced dissociation studies.
When I apply HCD on inorganic molecules I observe more…
C.X.F.
- 1,849
- 12
- 25
5
votes
1 answer
Mass Spectrometry Resolving Power Normalization to Average Mass
The resolving power in MS is often defined as $m / \Delta m$, or the reciprocal of the smallest discernible mass difference $\Delta m$ normalized to average mass $m$.
I wonder why the normalization to the average mass $m$ makes sense. Is there a…
Selenimoon
- 197
- 4
4
votes
0 answers
Is there a kind of table about configurations similar to the example I gave below?
If MALDI is used as an ionization method, then TOF as an analyzer is suitable since the MALDI creates singly charged ions which have high m/z ratio and only TOF can analyze that ions, and multichannel plate should be used because the TOF is very…
gunakkoc
- 645
- 1
- 6
- 12
4
votes
1 answer
Why would the 2+ molecular ion of butane have a mass spectrum peak at 29?
Question 7 of Edexcel's June 2014 Unit 2 exam paper reads:
In a mass spectrum of butane, C4H10, where would a peak be seen for
the molecular ion if it had a charge of 2+?
The answer is 29.
My question is: why?
hello_there_andy
- 361
- 5
- 11
4
votes
1 answer
How to find the mass spectrum of Cl3+?
The setting of this problem is on the moon of Jupiter: Io.
Given that chlorine exists in two isotopes: $\ce{{}^{35}_{17}Cl}~(33.3\%)$ and $\ce{{}^{37}_{17}Cl}~(66.7\%)$, what is the mass spectrum of $\ce{Cl3+}$?
What I know now is that there are…
user9862
4
votes
1 answer
Resolution in mass
I'm pretty confused about mass resolution. The resolution of my instrument is 1000 and I have two masses at 85.0639 and 85.0651. So, the difference is 0.0012.
I know that (M1-M2)=M/R.
But, I'm not sure if my spectrometer will be able to separate…
user130197
3
votes
1 answer
What's the difference between mass spectrometry, mass spectroscopy, and mass spectrography?
It seems that the terms mass spectrometry, mass spectroscopy, and mass spectrography are mostly used like synonyms. Is this correct? Or is there a difference?
oefe
- 133
- 5