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.

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16
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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, ...
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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 ...
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1answer
747 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 ...
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1answer
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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 ...
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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
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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} -> ...
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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{^{...
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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
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1answer
696 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 ...
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563 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 ...
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959 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 ...
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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 ...
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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 ...
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746 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?
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How long does it take to run a 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
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1answer
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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
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491 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 ...
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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
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1answer
106 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 ...
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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/...
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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?
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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 ...
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264 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 ...
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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 ...
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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 ...
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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
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1answer
192 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
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1answer
876 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 ...
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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 ...
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1answer
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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 ...
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1answer
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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&\...
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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 ...
4
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1answer
245 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 ...
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1answer
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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 ...
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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
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1answer
165 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 ...
4
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1answer
52 views

What happens to the “leftover” Ions in the Mass Analyzer

I am very intrigued by what happens to the ions which do not make it to the detector in mass spectrometers, do they just pile up? I have never seen anyone clean our quadrupole, is this done? or do ...
4
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1answer
263 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
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1answer
233 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])....
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1answer
911 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. ...
4
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1answer
374 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 ...
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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 ...
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1answer
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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 ...
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3answers
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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?
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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.
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2answers
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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 ...
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1answer
299 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
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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 ...
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2answers
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How exactly are ions in a Mass Spectrometer accelerated?

After a molecule is ionised, the ion is accelerated by an electric plate up to a certain kinetic energy by the attraction of the ion to the electric plate. However, after the ion has passed the ...
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1answer
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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 ...