Quantitative analysis absorption-diffraction method

Vibrational Spectroscopy [Infrared (mid-IR, NIR), Raman]. In contrast to X-ray powder diffraction, which probes the orderly arrangement of molecules in the crystal lattice, vibration spectroscopy probes differences in the influence of the solid state on the molecular spectroscopy. As a result, there is often a severe overlap of the majority of the spectra for different forms of the pharmaceutical. Sometimes complete resolution of the vibrational modes of a particular functional group suffices to differentiate the solid-state form and allows direct quantification. In other instances, particularly with near-infrared (NIR) spectroscopy, the overlap of spectral features results in the need to rely on more sophisticated approaches for quantification. Of the spectroscopic methods which have been shown to be useful for quantitative analysis, vibrational (mid-IR absorption, Raman scattering, and NIR) spectroscopy is perhaps the most amenable to routine, on-line, off-line, and quality-control quantitation. 

The ASTM F 1185 designation specifies chemical and crystallographic requirements for hydroxyapatite applied to the surfaces of surgical implants. Elemental analyses for calcium and phosphorus will confirm the expected stoichiometry of hydroxyapatite. The calcium and phosphorus contents will be determined by a suitable method such as ion chromatography. A quantitative X-ray diffraction analysis will determine a hydroxyapatite content of at least 95%. The concentration of deleterious trace elements such as arsenic, cadmium, mercury and lead will be assessed for hydroxyapatite derived from natural resources. The analysis of other trace elements may be required, based on the conditions, apparatus or environments specific to the manufacturing techniques and raw materials. Inductively coupled plasma/mass spectroscopy (ICP/MS), atomic absorption (AAS) or the... 

X-ray fluorescence spectroscopy is the most widely used x-ray technique for quantitative analysis this chapter will be primarily concerned with this method of analysis. X-ray absorption and x-ray diffraction analysis are treated briefly at the end of the chapter. 

For quantitative analysis of largely amorphous composites, an analysis based on the diffraction-absorption method was also developed. In this approach, the intensity scale factor and the microabsorption parameter are obtained by a calibration procedure based on the diffraction data of different samples of pure crystalline and mixtures. This information is used to calculate the crystalline weight fraction. 

Quantitative analysis of phase in the multi-phase system has always been a problem. Although the XRD is the most studied technique in the past as quantitative analysis of phase, but because multicrystalline XRD has problems of bulk effect of different X-ray absorption factors, the peak-overlap and changes in the intensity of diffraction hkl is caused by difference of fine structure which cannot be solved by traditional method. Thus, the results are always unsatisfied and considered to be unreliable. Rietveld analysis has completely solved the problem. The basic equation is ... 

X-rays provide an important suite of methods for nondestmctive quantitative spectrochemical analysis for elements of atomic number Z > 12. Spectroscopy iavolving x-ray absorption and emission (269—273) is discussed hereia. X-ray diffraction and electron spectroscopies such as Auger and electron spectroscopy for chemical analysis (esca) or x-ray photoelectron spectroscopy are discussed elsewhere (see X-raytechnology). 

X-RAY ANALYSIS. X-rays occupy that portion of the electromagnetic spectrum between 0.01 and 100 angstroms (A). Their range of approximate quantum energy is from 2 x 10-6 to 2 x 10 10 erg, or from 106 to 100 eV. Important X-ray analytical methods are based upon (1) fluorescence (2) emission (3) absorption and (4) diffraction. These methods are used qualitatively and quantitatively to determine the element content of complex mixtures and to determine exactly the atomic arrangement and spacings of crystalline materials. See also Ion Microprobc Mass Analyzer. 

The trend in industrial hygiene work is to identify the particular species responsible for an occupational health problem, although assessment of exposures to inorganic materials previously has most often been based on elemental analysis When a solid inorganic compound is to be identified and quantified, X-ray diffraction should be among the approaches considered This paper has outlined the use of X-ray powder diffraction as a tool for the identification and quantitation of crystalline particulates It has been shown that the substrate standard method is the preferred quantitative procedure for several reasons (1) easy adaptability to most analytes (2) fast analysis time (as compared to the internal standard procedure) and (3) accurate determination of matrix absorption effects While there are a number of reasons why a given compound may not be amenable to this technique, it is likely that the list of analytes will be added to in the future ... 

Abstract This chapter deals with the analytical applications of synchrotron radiation sources for trace-level analysis of materials on microscopic and submicroscopic scales. Elemental analysis with X-ray fluorescence is described in detail. Two-dimensional (2D) and three-dimensional (3D) analyses are discussed in their quantitative aspects. Related methods of analysis based on absorption edge phenomena such as X-ray absorption spectrometry (XAS) and near-edge scanning spectrometry (XANES) yielding molecular information, computerized X-ray fluorescence microtomography (XFCT) based on the penetrative character of X-rays, and microscopic X-ray diffraction (XRD) providing structural data on the sample are also briefly discussed. The methodological treatment is illustrated with a number of applications. 

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