Spectrographic methods

Analytical Methods. Molybdenum contents in ore concentrates and technical oxide are most accurately deterrnined gravimetricaHy by precipitating lead molybdate. Molybdenum content is usually not determined on pure compounds or metal. Instead, spectrographic methods are used to measure impurity elements that must be controlled. Carbon and oxygen in metal products are measured by standard gas analysis methods. 

The purity of commercial tin is under strict control at the smelters. Photometric, chemical, atomic absorption, fluorimetric, and spectrographic methods are available for the determination of impurities (17). 

The agreement of the calculated and experimental values is as good as can be expected in view of the many approximations made, and it is better than can be obtained for most other spectrographic methods. 

The absorption bands measured by the flash spectrographic method are often assigned by (a) comparison with known singlet-singlet absorption spectra, (b) comparison of the lifetime of the species responsible for the absorption with the phosphorescence lifetime, (c) comparison with calculated energies and intensities of the various possible absorptions by semi-empirical molecular orbital methods, and (d) comparison with published triplet absorption spectra and decay kinetics of model compounds. 

The composition of a liquid phase reaction, 2 A => B, was followed as a function of time by a spectrographic method with the tabulated results. The initial concentration was A0 = 1.0 mol/liter. Check first and second orders. The rate equation is... 

Various spectrographic methods are described in Refs. Harris (Ref 4) recommended an image-orthicon spectrograph and an image-converter spectrograph,... 

Cook (1958), 38 (Spectrographic methods for determination of temperature of detonation) 9) Baum, Stanyukovich Shekhter (1959), 97 (Spectroscopic method of Alentsev Belyaev, proposed in 1945 for determination of flame temp of expls) 10) Andreev Belyaev (I960), 429 (Spectrographic method of A.Ya. Apin I.M. Voskoboinikov... 

Calculo de T de la explosion) 13) J-G. Fox, "Spectrographic Measurement of Detonation Temperature , NavOrdRept 200-45(1945) PB Rept 36957 (1945) (Detn of spectrographic, methods of temp developed on deton of military and other HE s) 14) Perez Ara (1945),... 

Table VII shows the analytical wavelengths chosen, the concentration ranges calculated to the whole coal, average relative standard deviations, and detection limits in ash determined by the spectrographic method.

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. 

Quantitative analyses were made on samples which originally contained ca lOOmg of Centr. The chromatographic-spectrographic method can detect quantitatively less than O.lmg of substance... 

Bedrosian et al. [123] have described a spectrographic method for the determination of down to 1 mg/kg of lead in 50 mg samples of soil. 

Landis FP, Coons MC. 1954. A rapid spectrographic method for the determination of beryllium in air dust. Appl Spectroscopy 8 71-75. 

The UV-absorption method, with which quantitative determination of DNA in tissue sections can be done, provided the inspiration for the development of x-ray spectrographic methods at the end of the 1940s. The quantitative x-ray analysis methods were developed to provide quantitative elementary analysis on a histochemical and cytochemical scale, that is, quantitative elemental analysis of tissues in situ and at a subcellular level. Engstrom1 formulated how the problem could be attacked in the following way ... 

This spectrographic method that allowed chemical elementary analysis of single mammalian cells was based on the selective absorption of monochromatic x-rays measured directly in the spectrometer... 

Waring, C. L., and H. Worthing A spectrographic method for determining trace amounts of lead in zircon and other minerals. Am. Mineralogist 38, 827 (1953). 

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. 

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]. 

The chemical method of accurately determining atomic weights involves the determination of stoichiometric ratios. The procedure is illustrated by the examples given below and the problems at the end of the chapter. In addition to this method, extensive use is made of the method of gas densities, and, in recent years, of the mass-spectro-graphic method. The gas-density method is discussed in Chapter 8, and the mass-spectrographic method in the section following this one. 

The great accuracy of modern mass spectrographs makes the mass-spectrographic method of determining atomic weights about as useful and important at present as the chemical method. 

Additional development work will make the economic picture even more favorable. It should be remembered that a few short years ago it took over a day to perform a semiautomated amino acid analysis on a protein hydrolysate, whereas it can now be performed in a highly automated way in less than 2 hours (Bl). We may even reach the point where it will be less expensive, faster, and more accurate to make a high-resolution analysis of a body fluid sample even when we are interested only in a few of the constituents. This has certainly been true for the somewhat analogous case of trace metal analysis by the newer spectrographic methods instead of the more specific, but now less acceptable, wet chemistry methods. 

The nicest possible summary of the transformation in instrumentation and objectivity can be read off a 1959 advertisement. In 1959 BA advertised their spectrometers by comparing analytical methods, wet chemistry, spectrographic methods, and direct reading (figure 6.1). An iconic summary was presented for each approach. As with any effective ad, the visual point is made quickly and clearly wet chemical analysis takes more steps than spectrographic analysis, which itself takes more steps than spectrometric analysis (using a direct reader). Furthermore, the steps involved are easier with spectrographic methods than with wet chemical analysis, and easier still with spectrometric methods. 

In the text inside the brochure BA acknowledges that wet chemical methods are more versatile than spectrographic methods, which, in turn, are more versatile than spectro-metric methods. But the decrease in versatility—if you can believe advertising—surely is compensated by the savings in money, person power, and time. Another advertising brochure for spectromet notes that one "regularly trained person, probably of shop origin, may operate Spectromet" (Baird Associates, 1956, p. 3). 

An analytical procedure (ASTM D-128) is available for the separation of grease into its component parts and their measurement. Spectrographic methods, such as flame photometry (ASTM D-3340), may also be used to determine the metal present as soaps or the wear elements in used grease, in conjunction with separation techniques to measure and identify the various types of fats, lubricating fluids, or additives present. The simpler tests that are more likely to be quoted are ash content, acidity and alkalinity, water, and dirt content. 

Analysis Identification The identity of the residues must be determined expensive chromatographic and mass spectrographic methods may be needed... 

---