Applications background correction

Chapters 5 and 6 discuss the application of new techniques such as atomic absorption spectrometry with and without graphite furnace and Zeeman background correction, inductively coupled plasma mass spectrometry, X-ray fluo-... 

The need for improved background correction performance has generated considerable interest in applying the Zeeman effect, where the atomic spectral line is split into several polarised components by the application of a magnetic field. With a Zeeman effect instrument background correction is performed at, or very close to, the analyte wavelength without the need for auxiliary light sources. An additional benefit is that double-beam operation is achieved with a very simple optical system. 

E. H. Van Veen and M. T. C. De Loos-Vollebregt, Application of mathematical procedures to background correction and multivariate analysis in inductively coupled plasma-optical emission spectrometry, Spectrochim. Acta, Part B, 53(5), 1998, 639-669. 

Ag, At, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn ETAAS Metals are measured by ETAAS using the manufacturer s recommended conditions and an injection volume of 20 pL Applicable to surface, ground, tap, and waste water. A high CE concentration interferes. To minimize the matrix effect, the chemical modification, standard addition method, and background correction systems may be used. 105... 

Zeeman background correction also depends upon line splitting, but in this instance most commonly the absorption line profile (the n component) is split into two or more components (the a components) by the application of an intense... 

Zinc. AAS analysis of zinc by P CAM 173 is a standard application of the method as seen in NIOSH PAT. Zinc in the divalent state has been analyzed by dithiozonate (13). This colorimetric method suffers interferences from many other dithi-zone complexing metals. Zinc is easily determined after nitric acid wet ashing with an oxidizing air-acetylene flame using the 213.9 nm analytical line and background correction. The AAS analysis for Zn is as sensitive as more complex activation or plasma techniques. 

For each Bragg reflection, the raw data normally consist of the Miller indices (h,k,l), the integrated intensity I(hkl), and its standard deviation [ a[I) ]. In Equation 7.2 (earlier), the relationship between the measured intensity / [hkl] and the required structure factor amplitude F[hkl) is shown. This conversion of I hkl) to F hkl) involves the application of corrections for X-ray background intensity, Lorentz and polarization factors, absorption effects, and radiation damage. This process is known as data reduction.The corrections for photographic and diffractometer data are slightly different, but the principles behind the application of these corrections are the same for both. 

Fig. 2. Flow diagram showing the application of the background and shade correction processes to the sample images. (A) shows the background correction of the images used for shade correction. (B) shows the application of the shade correction process to sample images.

Trace analysis requiring background correction can usually be achieved by computer control displacement of the entrance slit or by rotation of a quartz refractor plate behind the entrance slit. Using this technique allows the application of slew scan methods which allow scans from different samples to be superimposed with solutions of samples, dissolution solvent(s), etc. 

Fig. 4 Predictive capacity of the test battery approach of the feasibility study of the EU project ReProTect. The combination of letter and color background in each cell indicates the correspondence between the results of the FS and the available animal data. Whiter, no effect in vivo medium grey, positive effect in vivo light grey, in vivo effect dependent on the route of application. V. correctly predicted (Z) partly correctly predicted (in vivo effect dependent on the route of application) X not correctly predicted. Modified from Schenk et al. [22]...

A limited improvement in this context may be possible by the use of more stable proteins, e.g. from thermophilic bacteria. However, many principles demonstrated by nature could be transposed to sensor development. For example, biomimetic channel and carrier molecules could be used in conjunction with stabilized lipid membranes to prepare sensitive and selective electrochemical transducers which embodied the principle of intrinsic amplification by depolarization. The use of artificial receptor sites would probably result in a substantial reduction of the desired selectivity coefficients, but this could easily be compensated by the application of array processing for background correction. 

Applications considerations are included in many chapters in Vol 3 of Dean and Rains (1975) devoted to the determination of specific elements, and in various natural and manufactured materials. Methods for analytical atomic spectroscopy, 8th edition (ASTM 1987) contains a wealth of information based on evaluation and approval deliberations by the respected ASTM, including various computation practices, general laboratory practices, practices and methods for analysis of metallurgical and inorganic materials by spectrochemical techniques including flame atomic emission. Dawson et al. (1993) have published a tutorial review on background and background correction in analytical atomic emission spectrometry. 

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