The mass spectra of organic compounds

MS analysis is commonly used in arson investigations, engine exhaust analysis,petroleum product analysis, and for blood monitoring in surgery. MS identifiessubstances by electrically charging the specimen molecules, accelerating them through amagnetic field, breaking the molecules into charged fragments and detecting the differentcharges. A spectral plot displays the mass of each fragment. A technician canuse a compound's mass spectrum for qualitative identification. The technicianuses these fragment masses as puzzle pieces to piece together the mass of the originalmolecule, the "parent mass."

Basic Information for Mass Spectroscopy

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Mass Spectroscopy and Isotopes Tutorial - AUS-e-TUTE

Accelerator mass spectrometry (AMS) differs from other forms of mass spectrometry in that it accelerates ions to extraordinarily high kinetic energies before mass analysis. AMS is exceptional in its ability to sensitively and accurately analyze elemental and isotopic compositions

What Is Mass Spectroscopy Used for in Forensic …

Generally negative ions are created (atoms are ionized) in an ion source. It is preferable, but not necessary that the charges be the same for each atom. These ions are introduced to the gas phase and they enter an electrostatic accelerator that accelerates them to very high kinetic energy by presenting ever more positive electrical potentials. Half-way through the accelerator they impact a sheet of carbon. The impact strips off many of the ion's electrons, converting it into a positively charged ion. In the second half of the accelerator the now positively charged ion is accelerated away from the highly positive center of the electrostatic accelerator, which previously attracted the negative ion. When the ions leave the accelerator they are positively charged and are moving very fast. Next, the exact ion velocities must be filtered such that only a narrow selection of ion velocities is allowed to pass to allow for proper mass analysis. A device called a velocity selector, which utilizes both electric fields and magnetic fields to allow only ions of a specific charge and kinetic energy to pass, most frequently accomplishes this. The ions then pass through at least one mass analyzer, most often a magnetic or electric sector. For example with a magnetic sector, the atom, at its known velocity (relative to mass) and charge is released into a magnetic field perpendicular to it velocity. This field causes the particle's path to curve in a circular arc. The radius of this circular arc is related to the mass-to-charge ratio of the particle. Dedicated detectors for each isotope or element then detect the ions.

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Many ionisation methods are available and each has its own advantages and disadvantages ("Ionization Methods in Organic Mass Spectrometry", Alison E. Ashcroft, The Royal Society of Chemistry, UK, 1997; and references cited therein).

Mass Spectrometry Tutorial from a ..

The sample can be inserted directly into the ionisation source, or can undergo some type of chromatography en route to the ionisation source. This latter method of sample introduction usually involves the mass spectrometer being coupled directly to a high pressure liquid chromatography (HPLC), gas chromatography (GC) or capillary electrophoresis (CE) separation column, and hence the sample is separated into a series of components which then enter the mass spectrometer sequentially for individual analysis.

Mass Spectroscopy | Mass Spectrometry | Ion

Gas chromatography ("GC") and massspectrometry ("MS") make an effective combination for chemical analysis. This article serves to demonstrate tools for an effective attack or defense of GC/MSevidence. To effectively use GC/MS evidence one must understand the process. First, the GC process will be considered, then the MS instrument will be presented. After a background in GC and MS is obtained, the reader will learn how to analyze theevidence produced by these instruments. The focus of this article lies in presentingthe limitations to GC/MS analysis.