JEOL Resources

JEOL Gas Chromatograph – Mass Spectrometer (GC-MS) Primer

Mon, 06 Feb 2023 16:15:44 GMT

What is a Gas Chromatograph – Mass Spectrometer (GC-MS)? Learn more in this guidebook written by our experts. Click on the link below.

Examining detection sensitivity of EI-FI and PI ion sources using nitrogen as a GC carrier gas MSTips 299

Tue, 17 May 2022 11:45:15 GMT

Abstract

The global helium shortage is a very serious issue that is affecting a variety of scientific research organizations that utilize this gas for their work. In particular, gas chromatography-mass spectrometry (GC-MS) is a widely used analytical technique that traditionally uses helium as the GC carrier gas. Consequently, it has become critical to identify other carrier gases for GC-MS in order to minimize the effects of the helium shortage. Previously, we changed the GC-MS carrier gas from helium (He) to nitrogen (N2) to determine how this affects sensitivity when using the dedicated EI ion source. The results showed that the detection sensitivity for N2 as the GC carrier gas was 1/18 of the level when compared to He. In this work, we compare sensitivity levels when using the combination EI/FI and EI/PI ion sources when He and N2 are used as the GC carrier gas.

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Tandem Mass Spectrometry (MS/MS)

Mon, 27 Jul 2020 20:08:20 GMT

Mass spectrometers are commonly combined with separation devices such as gas chromatographs (GC) and liquid chromatographs (LC). The GC or LC separates the components in a mixture, and the components are introduced, one by one, into the mass spectrometer. MS/MS is an analogous technique where the first-stage separation device is another mass spectrometer.

MS Elemental Composition Calculations and Their Interpretation

Mon, 27 Jul 2020 20:05:12 GMT

Accurate mass measurements are frequently used to determine the elemental composition for molecular and fragment ions. These measurements are normally obtained by acquiring a high resolution mass spectrum so that the masses are measured for a single species and not measured for unresolved or partially resolved peaks.

Mass Spectrometers - A Short Explanation for the Absolute Novice

Mon, 27 Jul 2020 20:01:56 GMT

What does a mass spectrometer do? What are mass spectrometers used for? What does the mass tell us? How does a mass spectrometer work?

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How Resolution Is Defined

Mon, 27 Jul 2020 19:58:55 GMT

Several different definitions of resolution are used in mass spectrometry. It is useful to understand the distinctions between the different definitions to understand the characteristics of different mass spectrometers.

Summary of the characteristics of different mass analyzers

Fri, 06 Mar 2020 06:29:58 GMT

All mass spectrometers combine ion formation, mass analysis, and ion detection. This discussion is concerned with how various mass analyzers are used to separate ions according to their massto- charge ratio. Each mass analyzer has its own special characteristics and applications and its own benefits and limitations. The choice of mass analyzer should be based upon the application, cost, and performance desired. There is no ideal mass analyzer that is good for all applications. For an excellent and more complete discussion of mass analyzers, see "The Ideal Mass Analyzer: Fact or Fiction?" (Curt Brunnee, Int. J. Mass Spectrom. Ion Proc. 76 (1987), 125-237.

Ionization Methods in Organic Mass Spectrometry

Fri, 06 Mar 2020 06:23:33 GMT

A mass spectrometer works by using magnetic and electric fields to exert forces on charged particles (ions) in a vacuum. Therefore, a compound must be charged or ionized to be analyzed by a mass spectrometer. Furthermore, the ions must be introduced in the gas phase into the vacuum system of the mass spectrometer. This is easily done for gaseous or heat-volatile samples. However, many (thermally labile) analytes decompose upon heating. These kinds of samples require either desorption or desolvation methods if they are to be analyzed by mass spectrometry. Although ionization and desorption/desolvation are usually separate processes, the term "ionization method" is commonly used to refer to both ionization and desorption (or desolvation) methods. The choice of ionization method depends on the nature of the sample and the type of information required from the analysis. So-called 'soft ionization' methods such as field desorption and electrospray ionization tend to produce mass spectra with little or no fragment-ion content.

About Magnetic Sector Mass Spectrometers

Fri, 06 Mar 2020 06:16:27 GMT

Slits are placed in the ion path to define the positions and energies of the ions that strike the detector. In general, decreasing the slit widths increases the mass resolution but reduces the number of ions that are detected. Additional electrostatic lenses are commonly used to shape and deflect the ion beam to optimize peak shape and maximize ion beam transmission from the source to the detector. JEOL uses octapole and quadrupole focusing lenses to simplify the ion optical design.

Collision chambers in the first field-free region (just after the ion source) and second field-free region (just after the magnet and before the electric sector) are used to induce ions to fragment in collision-induced-dissociation experiments (MS/MS).