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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7 views

Explaning base peak for 3-buten-1-ol mass spectrum?

The mass spectrum for 3-buten-1-ol shows 42 as the base peak, but I don't know how this fragment ion is generated. I would expect the most favorable fragmentation to occur between C1 and C2, but ...
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What are the fragments that result from taking the Mass Spectrum of o-fluronitrobenzene?

I am doing my online lab, and we are on mass spec right now. I am having a very tough time figuring out the shape of the fragments of o-fluronitrobenzene, especially the large peaks. Especially the ...
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30 views

1/8 instead of 1/12 of mass of carbon atom as relative atomic mass [closed]

If we consider that 1/8 in place of 1/12 mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will: (1) Decrease by 1.5 times (2) Increase by 1.5 times ...
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Confused on the peak intensities in this mass spectrometry problem

A problem from Introduction to Spectroscopy by Pavia et al. [1, p. 137]: *4. An unknown hydrocarbon has a molecular ion peak at $m/z = 84,$ with a relative intensity of $31.3.$ The $\ce{M + 1}$ peak ...
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79 views

Using the right equipment for successful detection of Novichok [closed]

Apparently, Navalny’s biomaterials were flown to Moscow's Nii Sklif lab which didn't find any traces of the poison. But they used an American Agilent Technologies GC-MS [1], while Bundeswehr ...
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115 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 ...
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57 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 ...
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47 views

Meaning of “MS1 and MS2 resolution” and “MS1 and MS2: Unit” in a tandem mass-spectrometry parameter list

I'm translating a Certificate of Suitability that very briefly describes procedures used to measure several impurities in a drug substance. There is a short description of the parameters of a Gas ...
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191 views

Differences in Novichok agent mass spectra

As we have all heard, in 2018, a series of poisonings with a nerve agent alleged to be of the Novichok series was carried out on British soil. It is claimed that the agent used was A-234. However, a ...
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167 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 ...
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1answer
38 views

On the detection of molecules in electrospray ionisation (ESI)

Of the ESI spectra that I have encountered, positive & negative mode, the detected species always have charge (positive or negative) corresponding to the charge mode that the machine is in. Is it ...
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67 views

How can I simulate chromatograms and spectra?

Is there a tool which allows to generate simulated chromatogramms and spectra and export it into a mzML file? There is e.g. psims which allows to write mzML on a ...
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51 views

Identifying unknown compound using mass spectrum

I am currently studying the textbook Mass Spectrometry - A Textbook, third edition, by Jürgen Gross. In chapter 1.4.5 Statistical Nature of Mass Spectra, there's a following example: It is important ...
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26 views

Relative intensities are basically independent from the absolute ion abundances registered by the detector?

I am currently studying the textbook Mass Spectrometry - A Textbook, third edition, by Jürgen Gross. Chapter 1.4.4 Mass Spectrum says the following: The most intense peak of a mass spectrum is called ...
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1answer
57 views

Why do we subtract the mass of one proton in mass spectrometry (negative mode)?

This is probably very basic, but I have been given the understanding that we subtract the mass of only one proton when looking for our compound in a mass spectrometry (negative mode). I dont really ...
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67 views

Peak broadness and artifact peaks in intact antibody MS?

I am having an issue where the MS for my antibody (intact/nonreduced, deglycosylated by PNGase) shows multiple clusters of what appear to be ghost peaks after deconvolution, and the main peak is ...
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28 views

Disadvantages of SIM vs TIC in GC-MS [closed]

In GC-MS what are the relative advantages/disadvantages of using Selected-Ion Monitoring (SIM) vs using Total Ion Chromatograms (TIC)? I know that SIM offers a better S/N ratio, however if the S/N is ...
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21 views

How does the mass composition affect the empirical formula? [closed]

I have to do an assignment of empirical formula, and how different percentage mass compositions affect the formula obtained, from experimental data. We did three trials and 2 of which of the same ...
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1answer
31 views

Conversion factor for chemical to physical scale of atomic masses

Before the 1960s chemists and physicists used to have different atomic mass tables. The main difference was that the physicists assigned the $^{16}$O as the O=16 from mass spectrometry. Chemists on ...
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84 views

Why we need the average atomic mass? [closed]

I know , Average Atomic Mass of an element is - the sum of the Masses of its isotopes,each multiplied by its Relative Abundance percentage (in decimal notation). But what confusing me is, what is ...
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1answer
48 views

Cause of m/z = 56 peak in 4-methyl-1-pentanol

This is the mass spectrum for 4-methylpentan-1-ol: From its structural formula, what could be the fragmentation which results in a peak at $m/z = 56?$ I was considering a few possibilities; could it ...
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27 views

Why doesn't laser ablation decompose sample

I was reading up on LA-ICP-MS and MALDI. All the sources I read for LA-ICP-MS simply say that when the laser hits the sample immediately goes into the gas phase. Why doesn't the laser immediately ...
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1answer
105 views

Why does the heat of formation of organic radicals and positive ions decrease with their size and degree of branching at the radical or ionic site?

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: The heat of formation ...
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193 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 ...
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42 views

Amide fragmentation of salicylamide

I want to ask a question about the fragmentation of the $\ce{M_17}$ peak of Salicyclamide to a phenolic fragment. I was reading the following paper giving a profile about salicyclamide. I want to ...
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110 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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2answers
73 views

How do we weigh one C atom? [closed]

As far as I get it, we did weigh one carbon (12,6-isotope) atom. Then we said that electrons have nearly zero weight and protons weight nearly the same as neutrons. Hence we took the weight of that ...
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49 views

Calculate the mass of iron in the original mixture!

I seemingly can't solve the following problem, I've spend over 30 mins on it, no progress, can any of you geniusses give a step by step solution to me? Thank you so much Problem: A mixture of ...
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1answer
101 views

Conditions for choosing quantifying and qualifying ion in LC-MS/MS

In my PhD-work, we are trying to develop LC-MS/MS methods for targeted analysis. Usually, I determine my quantifying ion/fragment based on a few different criteria: If there is a 13C internal ...
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2answers
154 views

How can the formula of WD-40 remain a trade secret?

Wikipedia says WD-40's formula is a trade secret How can it remain a secret today? Can't mass spectrometers, NMR and other equipment be used to determine the structure of the compounds that go ...
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471 views

Mass Spectra: 1-pentanol vs 3-pentanol

In mass spectrometry, 1-pentanol can be observed to have no peak at $m/z = 59$, whilst 3-pentanol can be observed to have a peak at $m/z = 59$. Clearly the 3-pentanol peak at $m/z = 59$ is due to the ...
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1answer
47 views

How does a mass spectrometer treat ions? [closed]

I always thought that in a mass spectrometer all the ionized fragments were going in the quadrupole at the same time, and then this quadrupole was sorting them by ratio. But last week I learn that a ...
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1answer
109 views

Software platforms with integration of multi vendor mass spectrometer device data?

I know about ACD/Spectrus Processor which is a software platform to integrate analytical chemistry data from multiple mass spectrometer device vendors (e.g. Agilent Technologies, Bruker, Waters) to ...
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265 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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568 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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70 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/...
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2answers
784 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 ...
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1answer
132 views

Choosing LC-MS modifier - why only acids?

During method selection our chromatographists have options like NH4, TFA, Formic Acid. What's the point of choosing only between acid? Why not use the strongest that guarantees ionization? The sample ...
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52 views

Increasing concentration of acetylcholine via SPE

I am trying to increase the final yield of acetylcholine (ACh) in my biofluid samples. I need to get the yield high enough for high confidence annotation of ACh (currently all I can really say is that ...
3
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1answer
113 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. ...
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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 ...
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1answer
36 views

Ensuring constant ionisation of transition metals using plasma ionisation for accurate mass spec

Mass spectrometry depends on separation of the analyte based on mass to charge (m/z). ICP-MS is used to detect metals, but under the plasma conditions many of these metals could be ionised multiple ...
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37 views

Why do impacting electrons have a low probability of causing ionization?

In a section on ionization efficiency and ionization cross section, my mass spectrometry textbook, Mass Spectrometry by Jürgen Gross [1, pp. 38–39], says the following: The ionization energy ...
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2answers
75 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 ...
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I need to identify the peaks in this boron mass spectrum

As part of a bigger project we were given this image. Its a mass spectrum produced in an accelerator with a Boron cathode. It was implanted in diamond. I assume the first peak is just $B^-$ but I have ...
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Calculating Sensitivity in Mass Spectrometry

My mass spectrometry textbook gives the following example: Calculating sensitivity Magnetic sector instruments are specified to have a sensitivity of about $4 \times 10^{-7} C \ \mu g^{-1}$ for the ...
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710 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 ...
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1answer
625 views

why do atoms need to be ionised in a mass spectrometer? [closed]

why do atoms need to be ionized in a mass spectrometer? why can't you determine the mass of the atoms when they are not ionised? Also what is the mass-to-charge ratio
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122 views

What do we learn from an isotope peak (or M+2 peak) in a mass spectrum?

Mass spectrum of a molecule showed molecular ion peak and its isotopic peak in 1:1 ratio. What is the possibility of the atom present in the molecule? Since it is mentioned that it has a ...
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2answers
106 views

What am I doing incorrectly with this IR/ Mass spec data? [closed]

Hello, I am trying to determine the chemical formula for the following compound. From the IR spec, I see there is a carbonyl present. Moving on to the mass spec, I see an M+ peak of 142, with what ...