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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373 views

Mechanism of formation of peak of mass spectrum of isobutane at m/z = 27

Here is the mass spectrum of isobutane: http://webbook.nist.gov/cgi/cbook.cgi?Spec=C75285&Index=0&Type=Mass Clearly the peak at $\mathrm{m/z} = 27$ corresponds to the species $\ce{C2H3+}$, ...
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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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252 views

Advantages of Travelling wave IMS and Drift tube IMS

I am learning Ion Mobility spectrometry. I am sorry for a very fundamental question. After reading different articles, I really did not understand what is the advantage of Travelling wave IMS over ...
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Influence of rotational degrees of freedom on gas phase stability of ions in CID

In mass spectrometry it is possible to determine the stability of an ion in the gas phase using e.g. collision induced dissociation (CID). In CID, we fragment an ion by colliding it with a neutral ...
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4k views

Mass chromatogram : Total Ion Chromatogram (TIC)

I am confused about what a Total Ion Chromatogram (TIC) means. The definition I have says: The total ion current (TIC) chromatogram represents the summed intensity across the entire range of ...
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60 views

How to evenly ionize in mass spectrometry

I know that in mass spectrometry they charge different molecules and then run them through a magnetic field and then see where they land. Depending on this, they calculate their masses relative to ...
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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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Why (abundance of M+1)/(abundance of M)=(number of carbon atoms)*(1.1/100)?

In mass spectrometry, why is this equation true? $\frac{A_{\mathrm{M1}}}{A_{\mathrm{M}0}} = n_\ce{C}\;\;\times\;\; \frac{1.1}{100}$ Here, $A_{\mathrm{M1}}$ is the abundance of the M+1 peak and $A_{\...
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In a mass spectrum, are there peaks corresponding to a combination of 13C and bromine isotopes?

I just began studying mass spectroscopy and I don't understand why certain peaks are not represented in the mass spectrum graph. Like let's say you have methyl or ethyl bromide. Usually, there are two ...
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87 views

Travelling wave ion mobility spectrometry: determination of size?

I performed an ESI / travelling wave ion mobility spectrometry / MS experiment and observe $\ce{M + H+}$ at $m/z ~701$ and $\ce{M + K+}$ ions with $m/z ~740$. The drift times are 6.75 ms for $\ce{M + ...
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Understanding mzML, specifically precursor mass

I'm a Biotechnologist and computer scientist, migrating into the field of Mass Spec. for my new position. Some things I know well, and others not at all. Please be patient :) I'm working with OpenMS, ...
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819 views

What is a “tube lens” in a mass-spectrometer ion source and what does it do?

I came across the Russian phrase "Transporting capillary voltage: 85 V" in a text I was translating. The paragraph was describing the operating parameters of an electrospray ionization-based ion ...
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237 views

Naming convention for adduct ions

In order for a compound to be analysed in mass spectrometry it must first be ionised, forming an adduct ion. In many papers (e.g 1 [PDF], 2) these adduct ions are described in the form: [M+H]+ [M+Na]+...
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82 views

How small a peak could one identify by GCMS

I'm trying to characterize the impurity profile of an organic liquid sample that is already described as 99.7% pure (Boiling Point 230 C). Would a GC-MS be a viable way to identify the smaller peaks?...
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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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96 views

How closely do GCMS spectra typically agree to conclude a match?

I have two unknown peaks on my GC (both with the same MW or rather highest M/Z ratio peak = 98) and I am trying to confirm their identity. Unknown-1 Unknown-2 Based on the expected chemistry I ...
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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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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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How to calculate peak ratios in mass spectometry for a polyatomic species from given isotope ratios? [closed]

Element Z has 2 isotopes, 55Z and 57Z with the abundance ratio of 2:1. It exists in nature as Z3. The ratio of the peaks at m/e ratios 165:167:169:171 is 8:x:y:1. What are the values of x and y? I ...
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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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806 views

GCMS Peak Identification: Online or Open Source / Free Programs?

Suppose I have a GCMS peak graph for a component, what are possible options to figure out what the molecule may be? Any tips about good software that will do this? I do know that for many compounds ...
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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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Fragmentations and rearrangements in n-(4-alkyl phenyl) alkanoic acids in mass spectrometry

I have this example exam question for which I don't have the answer. I have been working on it the whole morning but I can't figure it out. The question suggests three molecules, only one of which ...
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141 views

Minimum resolution to acquire exact mass on a spectra from m/z peak

I'm having a little difficulty with finding what the minimum resolution required to obtain the exact mass of a 400 $m/z$ peak in a mass spectrum. I would appreciate any help.
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What causes differences in limits of detection?

I'm wondering what causes the limits of detection (LOD) to vary between different compounds, when calculated from the data obtained from one sample. I've analyzed a 0,1 µg/ml sample, containing ...
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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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Pentabromophenol Mass Spectrum

I am working on analyzing the mass spectrum of pentabromophenol but am struggling to determine the fragment at 60 m/z. It could possibly be 5 carbons however that is too much positive charge to exist ...
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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 ...
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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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663 views

why do we denature proteins before mass spectroscopy?

I'm learning about mass spectroscopy in particular the use of it in analyzing protein structure. they said we have to use trypsinolysis to cut the protein to segments, but why does the protein have to ...
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982 views

What is the difference between TIC and TICC?

I have picked up a textbook on mass spectrometry, and I am finding it did not clearly distinguish between total ion chromatogram (TIC) and total ion current chromatogram (TICC) in the section (1.3 Ion ...
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666 views

How mass spec formate and acetate adducts masses are calculated?

If I look at any tables or calculators, I find that negative ion formate adduct has a monoisotopic mass of +44.9982 units. If I try to calculate myself, I get ...
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Mass Spec - What could a loss of 28amu as the first fragmentation be?

I guess 28 could be CO, C2H4 or N2. However I can't work out a mechanism by which CO could be the first fragmentation of any common organic compound. It seems like a diazonium salt could lose N2 as ...
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How to control the purity and quality of fatty acids or their CoA thioesters?

Background: We are looking into getting a series of cis-mono-unsaturated very-long-chain (C20-C32) fatty acids (with different, specific double-bond positions) — and/or the corresponding acyl-Coenzyme ...
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614 views

Predicting isotope patterns in mass spectrometry

Imagine you have a mixture of $\ce{^1H}$, $\ce{^2H}$ and $\ce{^3H}$ (hydrogen, deuterium and tritium) present as diatomic molecules and that the numbers of the atoms of the three species are the same. ...
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Possible ionization and fragmentation of chemicals

Is there any generic method where I can know/calculate/generate the possible ionization and fragmentation of a specific chemical, for example, hydrogen chloride and water? This question is actually ...
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432 views

What is the mechanism for electrospray ionization?

I've been asked to Descibe the ionization mechanism used in electrospray ionization I know that this is a desorption ionization source, which uses a high electrical field as the ionizing agent. ...
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244 views

Relative atomic mass

Is it possible for an element to have a calculated relative atomic mass that is higher than the relative isotopic mass of its most massive component isotope? The equation is: $\mathrm{Relative~...
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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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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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Fragmentation of phenyl radical cations in mass spectrometry

What are the main fragmentation pathways and products of a phenyl radical cation in mass spectrometry ? I notice sometimes that there's a m/z = 51 peak after the m/z = 77 for phenyl radical cation; I ...
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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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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 ...
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What is the significance of an organic compound's M peak?

Background On the topic of identifying an organic compounds using peaks generated in Mass Spectrometry, a rule of thumb expressed in the UK educational textbook, CGP, is that that "the M peak is the ...
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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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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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In a mass spectrum, how can the sum of relative abundances be greater than 100?

I apologise if this seems a very simple question, and also if I am overlooking something that is very simple. For part of my A Level course, we have to be able to interpret mass spectrometer readings ...
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GC-MS unexpected peaks during 1-octanol quantification

Note: This experiment was performed as part of a teaching lab experiment which has concluded, so I would not be able to alter any experimental conditions. I was also unable to modify any of the ...
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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 ...
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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 ...