Questions tagged [mass-spectrometry]

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.

Filter by
Sorted by
Tagged with
17
votes
1answer
2k views

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, ...
15
votes
1answer
20k views

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 ...
15
votes
1answer
760 views

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 ...
15
votes
1answer
2k views

Why does 2-chloropropane's mass spectrum have a peak at 27?

I have noticed that all halogenoalkanes of the form 2-Xpropane seem to have a mass spec peak at 27, implying that a $\ce{C2H3+}$ ion is being formed. Forming a $\ce{C2H3+}$ ion, however, would mean ...
11
votes
3answers
715 views

Why are isotopes an issue in reading mass spectra?

It is my understanding that the isotope distribution for carbon and hydrogen, for example, are skewed heavily toward one species, i.e., one isotope accounts for ~99% of the abundance of the element in ...
11
votes
1answer
106 views

Would cerium(III) in solution be oxidized to cerium(IV) in ESI mass spectroscopy?

During ESI (assuming positive ion mode for now), we apply a strong voltage ($1.0{-}\pu{5.0 kV}$) to induce ionization. Therefore, it is common to see oxidation of metal ions (e.g. $\ce{Cu^{+I} -> ...
10
votes
2answers
3k views

Why is the probability for the signal at 160 in the bromine mass spectrum twice as high as for the signals at 158 and 162?

The mass spectrum in Bromine, with the molecules $\ce{^{158}Br2+}$, $\ce{^{160}Br2+}$ and $\ce{^{162}Br2+}$: As you can see, the $\ce{^{160}Br2+}$ is almost double in intensity compared to the $\ce{^{...
10
votes
2answers
8k views

Gas chromatography/mass spectrometry: Can I use peak ratios and molecular mass to derive quantity?

Can derive the quantity of a substance from a GC/MS report if I know: the ratio to another substance in the data, the quantity of that second substance, and the molecular mass of both substances. ...
10
votes
1answer
721 views

Why does alpha cleavage occur?

I am studying fragmentation patterns in mass spectrometry and I am confused about why alpha cleavage occurs. Why does the carbon-carbon bond adjacent to a functional group break instead of the bond ...
9
votes
3answers
589 views

How do I figure out how many hydrogens my compound actually has using a mass and NMR spectrum?

Question 3: It said $m/z = 122,$ and $m/z = 124$ is in a $3:1$ ratio, so I figured that meant that chlorine is present. Then I thought $m/z$ was the actual compound's molecular mass. So I used ...
9
votes
2answers
979 views

Can we recycle garbage with the principles of mass spectrometry?

'Mass Spectrometry (MS) is an analytical technique that sorts ions based on their mass (or "weight"). Mass spectrometry is used for many chemical analyses, ranging from the analysis of a complex ...
8
votes
1answer
1k views

What is the molecular structure of the fragment ion m/z 161 of rosmarinic acid?

Attached is an ESI-MS/MS spectrum of product ion scan of rosmarinic acid (m/z 359.10) (source). I'm trying to figure out the structure of the fragment m/z 161. It's not clear to me what the structure ...
8
votes
1answer
112 views

Continuous flow mass spectrometer for isotope analysis

If i took thousands of discrete samples of mineral fragments in a field study using a specialized drill, what mass-spectrometry techniques/equipment would allow me to analyse the samples as fast as ...
7
votes
2answers
838 views

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?
7
votes
2answers
5k views

How long does it take to run an MS/MS experiment

I am not planning to do these types of experiments but I would like to know the order of magnitude of the time it takes to run an LC-MS/MS experiment. Let's assume that I have the sample prep (protein)...
7
votes
1answer
4k views

How can I reverse engineer a commercial cleaning solution's “other ingredients”?

I have a commercial lens cleaning solution. The manufacturer of the solution claims it is not only distilled water and that the formula is confidential. I suspected it was only or mostly distilled ...
7
votes
1answer
558 views

What is the difference between a time of flight mass spectrometer and a spectrometer that uses a magnetic field?

Traditional mass spectrometers used electromagnets to deflect isotopes of different masses which allowed only a certain isotope to reach the detector. But how is the TOF MS different besides the fact ...
7
votes
2answers
4k views

Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques?

Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques? My book says this technique is efficient for detecting multiple elements, with exception of halogens and carbon. I found ...
7
votes
1answer
137 views

Heats of formation of neutral molecules and homolytic vs heterolytic bond dissociation in mass spectrometry

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: Great efforts have been ...
7
votes
0answers
71 views

Identifying Structure based off 1H-NMR & Mass Spectroscopy Data [closed]

I have almost the whole night trying to identify this structure with no avail as there is always one part that does not fit. The determined formula for this structure was $\ce{C13H17BrO}$ from the $m/...
6
votes
1answer
584 views

Which unit should I use for m/z?

I've written m/z 300 - 1100 Thomson in my paper, but the reviewer said that the Th is already deprecated. So in this case, should I write m/z 300 - 1100 Da? or something else?
6
votes
2answers
610 views

What is the relative size of the (M+2) peak?

The $(M+1)$ peak is often considered in the high-resolution mass spectra of organic molecules as it reveals the number of carbon atoms in the sample. In general, it is known that the ratio of the size ...
6
votes
1answer
134 views

Behavior of Natural Abundance and Mass Spec Ratios

The presence of sulfur in a mass spec is 96% and 4%. I believe this to be because the natural occurrence of sulfur isotopes are within these proportions. However, chlorine behaves in a 66%/33% ratio ...
6
votes
3answers
270 views

How is the distance between m/z axis values in mass spectrums called?

The output data of mass spectrometers is relative intensity (y axis) over m/z (x axis). How is the distance between m/z values on the x-axis called (in case of centroided data and profile/raw data ...
6
votes
1answer
2k views

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 ...
5
votes
3answers
7k views

How to retrieve Dalton value from m/z value?

As I understand, Dalton (Da) is the standard way for representing mass unit. As for $m/z$, which is a specific notation for mass spectrometry, quoting for wikipedia: This notation eases data ...
5
votes
2answers
1k views

How Does Benzyl Alcohol Produce a Peak at m/z = 79?

I have understood the mechanism for converting ion 1 (benzyl alcohol) to ion 2 (m/z = 107) but not the mechanism for the conversion of ion 2 to ion 3 (m/z = 79). Please elaborate the mechanism for ...
5
votes
1answer
206 views

Peak at m/z = 39 in mass spectrum of 3-chloropropene

I've noticed that in the mass spectrum of 3-chloropropene, there is a peak at m/z = 39, which to me, indicates the formation of the C3H3 ion. However, given that 3 bonds would have to be broken to ...
5
votes
1answer
890 views

How were the absolute masses of atoms calculated before the mass spectrometers?

I understand that true (non-relative) masses of atoms are calculated with a mass spectrometer. using this relationship: Centripetal Force = Force due to magnetic field(B) But I was wondering how ...
5
votes
1answer
2k views

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 ...
5
votes
1answer
169 views

Stronger ESI signal for deuterated substances

I observe a constant phenomenon in my ESI measurements, which indicates that deuterated substances give a stronger signal than the same substance in non-deuterated form. Unfortunately I can't make any ...
5
votes
1answer
4k views

What is 'Retention period' in chromatography and what is its importance?

I heard people quite often speak about retention time/retention period in Chromatography and Mass Spectrometry. I see somewhere that it is the time duration between the injection time and the target ...
5
votes
1answer
940 views

What is the substituent on this benzaldehyde? (MS attached)

I have no clue what the substituent may be. The molar mass of the unsubstituted benzaldehyde is 105 g/mol (subtracting one H, where the substituent will be). So the substituent is around 30–33 g/mol. ...
5
votes
1answer
122 views

Finding identities of diatomics from Spectroscopy and Mass Spec Data

Let's say I have a sample of 2 (assumingly different) diatomics A and B. Through spectroscopy I found the data below: For molecule A: $$\begin{align} B&\approx2.17690\ \mathrm{cm^{−1}}\\ D&\...
5
votes
2answers
220 views

Is is possible to do mass spectrometry without coupled liquid chromatography?

It's possible to identify a solution with several compounds* without the coupled liquid chromatography (LC) before to isolate the compounds? On the university where I study, the LC is broken, so all ...
5
votes
1answer
381 views

Tandem mass spectrometry: a1 and immonium ions

In tandem mass spectrometry of proteins one will usually end up with a mix of $b$ and $y$ fragments but also $a$ fragments and immonium fragments. My problem is that wouldn't an $a_1$ ion be the exact ...
4
votes
1answer
272 views

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 ...
4
votes
1answer
1k views

How does bombarding a molecule with electrons cause ionization?

I am a chemistry student, and my current are of study is mass spectrometry. In the ionization process, atoms are bombarded with electrons, but how does this work? I assume the flow of electrons ...
4
votes
3answers
6k views

Could someone please explain the difference between m/z and m/e in mass spectroscopy

The definition: The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number. It has long been called the mass-to-charge ratio ...
4
votes
1answer
136 views

How did Thomson calculate the momentum of electron when he didn't know the mass of electron?

This was proven in 1903 by J. J. Thomson who calculated that the momentum of the electrons hitting the paddle wheel would only be sufficient to turn the wheel one revolution per minute. source J. J. ...
4
votes
1answer
268 views

In TOF Mass Spectrometry how does the detector 'know' the difference between ions of different elements?

After the positive ions have been accelerated, I know that they travel through the drift zone at different speeds due to their masses. But surely, a heavier ion/element that enters the drift zone ...
4
votes
1answer
235 views

Base Peak Intensity different than higher value in Mass Intensity Map

I've been working with mass spectrum data analysis (but my field is computer science). I'm using a library that allows me to get the entire Mass Intensity of the MS1 scan (such as [time, intensity])....
4
votes
1answer
76 views

Stubborn CuAAC reaction as derivatization for ESI-MS

Problem description I have a substance that is extremely non-polar and therefore does not ionize in the ESI source, which makes it impossible to quantify small amounts. The substance contains only two ...
4
votes
0answers
86 views

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 ...
3
votes
1answer
1k views

What are compounds with the same mass called?

It may be that the answer is just "no" and that's why I can't find it, but is there any common name for compounds with the same mass? I'm thinking in the context of mass spectrometry where these ...
3
votes
3answers
4k views

Mass Spectrum and Molecular Ion peaks [closed]

If a molecule contains four chlorine atoms, how many molecular ion peaks will this compound show in its mass spectrum?
3
votes
4answers
3k views

Where does the characteristic peak for phtalic acid diethyl ester at m/z 149 originate?

Which fragmentation is possible at this m/z value for phthalic acid diethyl ester? I tried McLafferty but it didn't solve my problem.
3
votes
2answers
79 views

What is the difference in Da of ESI analytes with multiple charges?

This is a follow-up question to Why are isotopes an issue in reading mass spectra? A follow-up question: electrospray ionization (ESI) produces multiply charged species and charge can be >40 (for the ...
3
votes
1answer
300 views

Mass spectrum analysis [closed]

When finding ions which correspond to certain fragments on a mass spectrum; there are multiple possible ions that can correspond to the same fragment; How should I know which one is the correct one?
3
votes
1answer
2k views

Why is the molecular peak not observed in the mass spectrum of 2,2-dimethylbutane?

Why isn't the molecular weight of 2,2-dimethylbutane on the mass spectrum? I can tell that a $\ce{-CH3}$ group is removed just by the math, but I do not know the reason why. The molecular weight is 86 ...