Spectrographic method emission

Even in relatively large programs, few laboratories will justify the initial expense and calibration effort required for development of the emission spectrographic method. As reported by Scott etal. [3], sample preparation will generally not differ significantly from that required for AAS. Instrumental neutron activation analysis (INAA) is only attractive where a reactor is already available, and multielement analysis by this technique requires the use of high resolution Ge(Li) crystals and multiple irradiations for elements with differing activation product half-lives. The key elements, cadmium, nickel and lead still require analysis by AAS because of limitations of the INAA method [4]. 

Physical Techniques, i) Spectrographic determination. The arc emission spectrographic method for the determination of iron is particularly suitable for samples which are insoluble or available only in quantities of a few milligrams. The high sensitivity of the iron lines at 3720 A and 3020 A enables the metal to be detected in concentrations of the order of 1 p.p.m. For quantitative analysis an internal standard technique is used and the precision obtainable is about per cent. 

Analysis of refined germanium products is done in a wide variety of ways, including several methods that have become ASTM standards (47). Electronic-grade Ge02 is analyzed using an emission spectrograph to determine its spectrographic purity. Its volatile content is measured in accord with ASTM F5 and its bulk density with F6. Other ASTM standards cover the preparation of a metal biHet from a sample of the oxide (F27), and the determination of the conductivity type (F42) and resistivity (F43) of the biHet. 

Although the standard deviations in Table 7-4 are larger than those for the most painstaking analyses by conventional Wet methods, the x-ray emission spectrograph has the great advantage that an operator in one day has made twice as many x-ray determinations as are listed... 

Ultimately, all quantitative analytical methods rely upon standards, whose composition is determined by the classical techniques of wet chemical quantitative analysis. Obviously, the preferred techniques for analyzing art objects are nondestructive, such as x-ray fluorescence, neutron activation, electron microprobe (both dispersive and nondispersive techniques), and so forth. Emission spectrographic analysis is not suit-... 

Analytical methods employed in soil chemistry include the standard quantitative methods for the analysis of gases, solutions, and solids, including colorimetric, titrimetric, gravimetric, and instrumental methods. The flame emission spectrophotometric method is widely employed for potassium, sodium, calcium, and magnesium barium, copper and other elements are determined in cation exchange studies. Occasionally arc and spark spectrographic methods are employed. 

The amounts of 16 elements (see also Tab. 7-1) were determined with the above mentioned method of emission spectrographic analysis in a total of 170 samples of sedimented airborne particulates from three urban areas (Gera, Jena, and Greiz) in Thuringia (Germany) during one year of investigation. 

Before the 1960 s, the analysis of toxic elements in airborne materials employed separations and colorimetric determination for single-element problems, or spectrographic methods for multielement, multisample studies. Variable matrices in most aerosols sampled had prevented sensitive, but interference-prone, flame-emission methods from attaining much usage. The increased concern over the environmental effects of toxic elements in the late 1960 s resulted in a need for greater sensitivity and ease of operation in measurements of these elements. The many laboratories with increased responsibilities found AAS most useful because of its accuracy, sensitivity, and relative lack of matrix effects, plus the low cost of the equipment. 

The advent of instrumental methods changed this. Now, for example, a substance with relatively little preparation could be sparked in an emission spectrograph, and its elemental composition could be read off dials. The work of the analytical chemist came in the design of instrumentation to exploit the physical properties of the substances under investigation and with the administration and use of an array of instruments, each exploiting different physical properties for identification. 

A three-phase extraction system has been described. The method depends on the separation of a mixed organic solvent into two phases when diantipyryl-methane is present as the extracting agent 489). In one phase, the so-called third phase, the extracting elements are concentrated to 95-98% yield. The small volume of this third phase permits it to be transferred quantitatively and directly to the electrodes of the emission spectrograph. The system was described for the separation and analysis of Hg, Se, Sn, Cd, B, Zr, and Hf. 

The analysis of solid materials by their direct insertion into an ICP has been utilized as a method for compositional determination without the need for sample dissolution. The technique involves the packing of 10—30 mg of finely pulverized and homogenized (to ensure satisfactory subsampling statistics) sample into a depression or cavity in the end of a high-purity graphite rod. Often conventional direct current arc emission spectrograph-ic electrodes can be used for this purpose. 

A large laboratory ought to have both kinds of spectrographic equipment. Any laboratory that now has equipment modifiable for x-ray emission spectrography should proceed with the modification. A small laboratory that needs diffraction equipment and can afford only one spectrograph should buy x-ray equipment. A laboratory similarly situated that haa no need of diffraction should select its spectrograph after a careful survey of its needs. We believe that all spectroscopists should become familiar with the x-ray methods described in this book. 

The Aluminum Company of America alone carries out some millions of determinations annually on its Applied Research Laboratories Quantometers, which are automated spectrographs for the visible and ultraviolet regions. It is not surprising that any method as successful as x-ray emission spectrography should be influenced by the trend toward automation. This trend is logically following two directions, as follows. 

When analyses are done by the use of x-rays at intensities so low that quanta are counted, the reliability of x-ray methods involves considerations foreign to classical analytical chemistry, The reliability of x-ray emission spectrography will consequently be discussed in some detail. To illustrate the discussion, an error analysis of a laboratory spectrograph will be undertaken. This analysis can serve as a basis for corresponding examinations of larger instruments. 

Analysis. Atomic absorption, emission, and mass spectrographic separation are the most sensitive methods for the analysis of Si. Electrothermal atomization-atomic absorption spectroscopy ETAAS has a sensitivity of 10 ppb, ICPAES 1 ppb, and ICPMS 10 ppb. Colorimetric agents permit spectrometric analysis down to about 10 ppb. 

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