Spectrometric methods optical

In addition to the wet and optical spectrometric methods, which are often used to analyse elements present in very small proportions, there are also other techniques which can only be mentioned here. One is the method of mass spectrometry, in which the proportions of separate isotopes can be measured this can be linked to an instrument called a field-ion microscope, in which as we have seen individual atoms can be observed on a very sharp hemispherical needle tip through the mechanical action of a very intense electric field. Atoms which have been ionised and detached can then be analysed for isotopic mass. This has become a powerful device for both curiosity-driven and applied research. 

Table 8.31 Power of detection of optical atomic emission spectrometric methods...

Finally, it should be mentioned that, in the case of etching plasmas, any of the mass spectrometric or optical spectroscopic methods described in Sect. 2.1.4 could in principle be calibrated to measure the etch rate simply by monitoring the etch product. This approach, has been used for end-point detection in the etch process These methods may also be applicable to polymerizing plasmas where interesting correlations between the concentration of certain gas phase species and polymerization rate have been noted s . ... 

We have developed several new measurement techniques ideally suited to such conditions. The first of these techniques is a High Pressure Sampling Mass Spectrometric method for the spatial and temporal analysis of flames containing inorganic additives (6, 7). The second method, known as Transpiration Mass Spectrometry (TMS) (8), allows for the analysis of bulk heterogeneous systems over a wide range of temperature, pressure and controlled gas composition. In addition, the now classical technique of Knudsen Effusion Mass Spectrometry (KMS) has been modified to allow external control of ambient gases in the reaction cell (9). Supplementary to these methods are the application, in our laboratory, of classical and novel optical spectroscopic methods for in situ measurement of temperature, flow and certain simple species concentration profiles (7). In combination, these measurement tools allow for a detailed fundamental examination of the vaporization and transport mechanisms of coal mineral components in a coal conversion or combustion environment. 

Once the sample has been converted into gaseous atoms or elementary ions, various types of spectroscopy can be performed. We consider here optical and mass spectrometric methods. 

Atomic spectrometric methods of analysis essentially make use of equipment for spectral dispersion so as to isolate the signals of the elements to be determined and to make the full selectivity of the methodology available. In optical atomic spectrometry, this involves the use of dispersive as well as of non-dispersive spectrometers. The radiation from the spectrochemical radiation sources or the radiation which has passed through the atom reservoir is then imaged into an optical spectrometer. In the case of atomic spectrometry, when using a plasma as an ion source, mass spectrometric equipment is required so as to separate the ions of the different analytes according to their mass to charge ratio. In both cases suitable data acquisition and data treatment systems need to be provided with the instruments as well. 

In the course of the late 1970s new mass spectrometric methods, which made use of the plasma sources known from optical atomic spectrometry came into use. They will be treated in detail and consist in particular of ICP mass spectrometry (ICP-MS) and glow discharge mass spectrometry (GD-MS), which have contributed to a considerable portion of the progress that has been made in elemental analysis as compared with spark source mass spectrometry. 

Merten D., Broekaert J. A. C. and LeMarchand A. (1997) Application of a rapid sequential inductively coupled plasma optical emission spectrometric method for the analysis with linerich emission spectra by different means of sample introduction, J Anal At Spectrom 12 1387-1391. 

The sensitivity of the spectrometric methods are given by the composition of the flame and plasma.268 By coupling ICP with a mass spectrometer (MS) detector,269 the selectivity and sensitivity of the optical measurement is increased considerably. For ASV, the low level of concentration is not a problem because of the steps followed by the technique the first step is a concentration of the analyte on the surface of the electrode, and the second step is given by the redox reaction. As a result of the concentration step, the method can be used for very low concentration levels with high selectivity. 

Plsko E (1988) Analysis of water using optical emission spectrometry with arc and spark excitation. In Butler LRP and Strasheim A, section editors. Atomic-, mass-, X-ray-spectrometric methods, electron paramagnetic and luminescence methods. In West TS and Niimberg HW, eds. The determination of trace metals in natural waters. 

Photothermal spectroscopy is a class of optical analysis methods that measures heat evolved as a consequence of light absorption in an irradiated sample. In conventional spectrometric methods information is obtained by measuring the intensities of light transmitted, reflected, or emitted by the sample. In photothermal spectrometry, spectroscopic information is obtained by measuring the heat accompanying non-radiative relaxation. Because of the universality of the photothermal effect (e.g., heat evolution accompanies essentially all optical absorption), photothermal spectroscopy has diverse applications in chemistry, physics, biology, and engineering. Some applications and measurements in the analysis of solids are reviewed here. 

Detection methods applied in ion chromatography (IC) can be divided into electrochemical and spectrometric methods. Electrochemical detection methods include conductometric, amperometric, and potentiometric methods, while spectroscopic methods include molecular techniques (UVA is, chemiluminescence, fluorescence, and refractive index methods), and spectroscopic techniques such as atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and mass spectrometry (MS). ... 

In the course of the late 1970s new mass spectrometric methods, which made use of the plasma sources known from optical atomic spectrometry came into use. 

Optical atomic and mass spectrometric methods can be used for the determination of the light elements, which is an advantage over x-ray spectrometric methods. 

Atomic spectrometric methods of analysis essentially make use of equipment for spectral dispersion to achieve their selectivity. In optical atomic spectrometry, this involves the use of dispersive as well as nondispersive spectrometers, whereas in the case of atomic spectrometry with plasma ion sources mass spectrometric equipment is used. In both cases, suitable data acquisition and processing systems are built into the instruments. 

S-sulphonylglutathione and three other peptides. Mass spectrometric methods indicated that one of these was 8-(a-aminodipyl)-cysteinylvaline. The optical rotatory dispersion spectrum of the intact peptide and the circular dichroism spectra of the constituent amino acids enabled the stereochemistry to be assigned as 8-(L-a-aminoadipyl)-L-cysteinyl-D-valine. 

However, I is the emission intensity emitted over the whole space angle. Here, the % of space angle with which the radiation is collected into the optical system is to be considered, together with the transmittance of the spectrometer [according to Eq. (156) and the characteristics of the radiation detector, Eqs. (186-189)]. Evidently, in all the equations cited many constants are not exactly known and all types of atomic spectrometry are relative methods nevertheless, the intensities measured can be traced back to the concentrations of the analyte in the sample in a stringent way. This also applies to the other atomic emission, atomic absorption, atomic fluorescence, and mass spectrometric methods discussed here. 

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