Mass spectrometry magnetic focusing

Resolution does not affect the accuracy of the individual accurate mass measurements when no separation problem exists. When performing accurate mass measurements on a given component in a mixture, it may be necessary to raise the resolution of the mass spectrometer wherever possible. Atomic composition mass spectrometry (AC-MS) is a powerful technique for chemical structure identification or confirmation, which requires double-focusing magnetic, Fourier-transform ion-cyclotron resonance (FTICR) or else ToF-MS spectrometers, and use of a suitable reference material. The most common reference materials for accurate mass measurements are perfluorokerosene (PFK), perfluorotetrabutylamine (PFTBA) and decafluorotriph-enylphosphine (DFTPP). One of the difficulties of high-mass MS is the lack of suitable calibration standards. Reference inlets to the ion source facilitate exact mass measurement. When appropriately calibrated, ToF mass... 

A quite different type of mass spectrometer - the first 180° magnetic sector field mass spectrometer (see Figure 1.7), with directional focusing of ions for isotope analysis, was constructed by Dempster, independently of other instrumental developments in mass spectrometry, in 1918. 

Because of polydisperse nature of HS, the importance of separation methods increased as the science evolved. Various separation methods were widely used for conventional fractionation and characterization of components based on differences in component solubility, charge, molecular weight, and/or size, polarity, hydropho-bicity, and so on (Janos, 2003). More recent research focused on advanced molecular-level analyses of humic mixtures (Hertkorn and Schmitt-Kopplin, 2007), in which a combination of separation techniques, mostly, chromatography, or capillary electrophoresis) were coupled with high-resolution instrumental analysis [e.g., mass spectrometry (MS) or nuclear magnetic resonance (NMR) spectroscopy]. Several examples appeared in the literature, including those that used size exclusion chro-... 

The focus of this edition remains the same as that for the first, namely, to make electrochemistry an attractive, useful characterization methodology for chemists [comparable to infrared (IR), nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS)]. The goal is to outline the basic principles and modem methodology of electrochemistry in such a way that the uninitiated may gain sufficient background to use electrochemical methods for the study of chemical systems. Thus chemical problems that are amenable to an electrochemical approach are introduced as representative examples. 

Mass Spectrometry — The mass spectrometers and associated equipment have been described in detail (9). In brief, an LKB 9000 GLC-MS (a magnetic sector instrument) was utilized with a modified accelerating voltage alternator (AVA) (12). For A 9-THC the mass spectrometer was set to focus alternately on the ions... 

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