Isotopic analyses magnetic sector

Applications Sector instruments are applied for niche applications such as high-resolution measurements and fundamental ion chemistry studies. Magnetic sector mass spectrometers remain the instrument of choice in areas of target compound trace analysis, accurate mass measurement and isotope ratio measurement. 

The most widely used method for ionization is electron impact (El). In an El source the sample is placed in the path of an electron beam. Although many newer kinds of ion sources have been developed, El is the method commonly used in classical isotope-ratio mass spectrometers (IRMS), i.e. mass spectrometers designed for precise isotopic analysis. In this type of spectrometer the ions, once formed, are electrostatically accelerated, and then ejected through a slit into a magnetic field held perpendicular to the ion trajectory. In the magnetic sector part of the instrument the particles are deflected in an arc described by ... 

Blichert-Toft J, Chauvel C, Albarede F (1997) Separation of Hf and Lu for high-precision isotope analysis of rock samples hy magnetic sector-multiple collector ICP-MS. Contrih Mineral Petrol 127 248-260 Cameron AE, Smith DH, Walker RL (1969) Mass spectrometry of nanogram-size samples of lead. Anal Chem 41 525-526... 

Magnetic sector ion microprobes are becoming increasingly important in isotopic analysis of extratenestrial materials as spot size decreases and the precision and accuracy of the measurements improve. The first of the commercially available ion microprobes used in cosmochemistry were the Cameca ims 3f-7f series machines, which initially became available in the mid-1980s. These multipurpose instruments are able to measure isotopic compositions of most elements of interest in cosmochemistry and can also be used to measure trace element abundances. Their main drawback is that the relatively small mass spectrometer can only be operated at mass-resolving powers below about 9000, and at this mass resolving power, the transmission of the mass spectrometer is very low. 

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. 

Modem mass spectrometers are usually one of four types magnetic sector, quadrupole, time-of-flight, or ion trap. A brief introduction to each is provided. Classical applications are discussed to illustrate how these devices have shaped the landscape of elemental and isotopic chemical analysis. 

CV-AAS, Cold Vapour Atomic Absorption Spectrometry ETA-AAS, Electrothermal Atomization Atomic Absorption Spectrometry FAAS, Flame Atomic Absorption Spectrometry FIG-AAS, Flydride Generation Atomic Absorption Spectrometry ICP-AES. Inductively Coupled Plasma Atomic Emission Spectrometry ID-MS, Isotopic Dilution Mass Spectrometry HR-ICP-MS, Magnetic Sector High Resolution Inductively Coupled Plasma Mass Spectrometry NAA, Neutron Activation Analysis Q-ICP-MS, Quadrupole Inductively Coupled Plasma Mass Spectrometry Z-ETA-AAS, Zeeman Electrothermal Atomization Atomic Absorption Spectrometry... 

Most mass spectrometers measure one m/z value at a time. A single channel ion detector is used for these instruments, either an electron multiplier or a Faraday cup. TOF, ion trap, and FTICR mass spectrometers have the ability to extract ions with many m/z values simultaneously, so simultaneous detection of these ions is desirable. One approach to multiple ion detection has been to use multiple detectors. Multiple detectors are also used for high-resolution magnetic sector MS instruments designed for very precise isotope ratio determination and for quantitative analysis using isotope dilution. Instruments with... 

The ICP/MS is an elemental and isotopic analysis method that was first developed in the early 1980s. The ICP had been used only as a source for emission spectroscopy until it was adapted for producing ions for a mass analyzer (Douglas and French, 1981 Houk et al., 1980 Houk et al., 1981 Houk and Thompson, 1982). Since 1983, several manufacturers have sold ICP/MS instruments that incorporate various mass analyzer systems, such as quadrupole mass filter, magnetic sector field, time-of-flight, Paul ion trap, and ion detection systems such as the electron... 

At the heart of the TIMS ion source are one or more hot filaments that serve to vaporize and ionize atoms or molecules of interest. Once generated, the ions are accelerated, focused, and directed into the mass analyzer for measurement. The classic TIMS instrument consists of an ion source, a single magnetic sector mass separator, and an ion detector. Such an instrument is capable of measuring isotope ratios as small as 1 x 10 6, sufficient for the isotopic analysis of most elements. For radionuclide analysis, smaller isotope ratios are often encountered. Specialized mass spectrometers include multiple magnetic and electric sectors and sector instruments with retarding quadrupole lenses (Smith, 2000) to measure down to the 10-9 range. 

A major attraction is the ability to perform isotope ratio measurements, e.g., in many geological applications to determine the age of rocks, biological and geological fractionation of elements, anthropogenic origin, stable isotope tracer studies, and isotope dilution analysis. In this respect, magnetic sector... 

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