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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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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How would you examine samples of rocks using a handheld spectrometer?

My friend has an old spectrometer set that his father used to own and we are trying to figure out how to use it. Asking his father about it is not an option unfortunately. The box contains a handheld ...
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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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68 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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132 views

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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Do some particles get ionised to 2+ or higher in a mass spectrometer or do they only get ionised to 1+?

In a mass spectrometer the sample is vapourised, then ionised, then accelerated. My textbook says that the high energy electrons from the electron gun knock electrons off the sample molecules and ...
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218 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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55 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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27 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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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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107 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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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 ...
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26 views

Comparing collision energy formats in the NIST 17 MS/MS library

In the NIST 17 MS/MS library, collision energy can be represented as a positive integer (i.e. 1,2,3,...), a percentage (i.e. 35%), or a floating point number (i.e. 7.3 eV). How can I compare these ...
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37 views

Can catecholamines be quantified by HPLC-MS/MS at high pH?

It seems that most HPLC-MS/MS methods used for quantitation of catecholamines (epinephrine, norepinephrine and dopamine, specifically) operate at low pH (commonly 3.0), and therefore demand the ...
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75 views

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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326 views

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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48 views

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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31 views

Isotope labeled experiment analysis

I'm analyzing a dataset generated with LC-MS from cells that were fed $\ce{^13C}$-Glucose. There are 3 groups in total each with a different media conditions. My goal is to identify differences ...
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18 views

Finding Pressure of M in a Charge Exchange

Ar (RE = 15.5 eV) is the reagent gas in a charge exchange experiment. If Ar+ reacts with anisole with a rate constant of 2.26x10-10cm3 molecules-1/s-1 and 65% of the Ar ions react in 25 milliseconds, ...
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66 views

Kinetic Shift of Simple Cleavage

What is the kinetic shift for the simple cleavage fragmentation if the ion source residence time is 100 microseconds, the time to reach the detector after leaving the ion source is 10 microseconds? (...
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38 views

Impediments to GC-MS characterization of petroleum products

In an attempt to characterize, and sometimes to 'match' oil on feathers of birds, a laboratory utilize gas chromatographic - mass spectrometry. Persons likely to encounter oiled birds are advise to ...
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126 views

How does the “sample type” selection on the MassHunter software for Agilent 7900 ICP-MS affect the quantitative results?

I'm new to using the instrument, and recently I have tried to measure Cr in both the eluent(1% nitric acid) and a method blank (also 1% nitric acid, but after it has gone through the entire analytical ...
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47 views

What is the best way to illustrate the recovery of an extraction method?

I'm currently working on PFAS (perfluoroalkyl compounds) extraction from soils and their analysis by HPLC-MS/MS. I wonder what kind of graph can be the best to illustrate the recovery of the method. ...
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87 views

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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869 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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76 views

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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139 views

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 can mass spectrometry be used to determine concentration?

Which forms of mass spec will determine accurate concentrations of metal ions in a sample? Preferable not using GC/MS but can MALDI ToF or quadrupole do this somehow. Also, not relative concentration ...
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74 views

Explaining base peak for but-3-en-1-ol mass spectrum?

The mass spectrum for but-3-en-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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69 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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75 views

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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46 views

Ionisation of a gas - from gas to plasma

Is it possible to ionise a gas such as Carbon Dioxide? If you continue to heat up a gas eventually the electrons from the gaseous atoms are stripped away and those e- gain energy (endothermic reaction)...
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Mass spectrometry: systematic mathematic transformation for calibration

Given a NaI mass calibration in the m/z 300-2000 range on a QTOF instrument as shown below: and given any uncalibrated mass spectrum that has been measured with the same instrument settings. What ...
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47 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 ...