Subtraction technique, effect

This paper contributes to the literature by quantifying anionic polymer adsorption onto the clay minerals kaolinite, feldspar, mica and quartz by X-ray photoelectron spectroscopy (XPS). XPS measures the sorbed amount directly rather than by a subtraction technique. This enables an insight into how effective selective flocculation is for obtaining kaolinite from a mineral mixture. Atomic force microscopy (AFM) is also used to image polymer adsorption onto mineral surfaces and the effectiveness of this technique applied to mineral surfaces is discussed here. 

The effect of the subtraction technique on the appearance of the difference spectra can be investigated by plotting the frequency of significant bands in the difference spectra (such as the v, CH2 band mentioned above and the vs S-O band discussed frirther below) as a function of the subtraction scalar, X. Table m shows... 

Figure 3.26 Subtraction technique for elimination of effect of sample heat capacity change. The endotherm from the DTA trace represents both the latent heat of transformation as well as a shift in heat capacity of the sample during the transformation. The baseline (which is the sample temperature lag relative to the reference) shifts most rapidly near the center of the endotherm, where the conversion of reactant to product is most fervent. The right-hand trace represents a DTA endotherm with the effects of sample heat capacity changes subtracted out. Note that in this case, where the total heat capacity of the product is less than the reactant, this subtraction has resulted in an endotherm of larger area.

Typical features of the spectra of polymers are the changes introduced when the polymer chains are oriented by strain. When observed with polarized radiation the changing orientation of the molecular chains is visible by pleochromism of the infrared bands or the changes of the polarizability in the Raman spectra. Stress relaxation and the effects of fatigue and fracture may be observed, especially when the spectral subtraction technique is applied. These methods are well described by Siesler and Holland-Moritz (1980). In the Atlas of polymer and plastics analysis by Hummel and Scholl (1991) the methods of polymer analysis are described exhaustively and the spectra of plastic material and its constituents are collected. 

Methods that monitor ions at nominal mass [23, 43, 55, 63, 64] have interferences from higher PCBs, toxaphene, and chlordane-related compounds, all of which have similar GC-retention times to PCAs and similar molecular masses to PCAs (i.e., 350-500 Daltons) [14]. Reiger and Ballschmiter [43] have applied a simple subtraction technique to compensate for the effects of these interferences, but it is unclear how this procedure compromises the accuracy of their quantitation method. 

We scan the telescope normal to the spectrograph slit, and record separate frames from each position of the telescope. Each frame has as axes wavelength and one spatial coordinate the stack of successive frames provides the second spatial coordinate and thus generates a data cube (strictly, cuboid). From that cube we extract monochromatic images. Continuum subtraction is effected by differendng nei bouring wavelengths. We refer to this technique as ima g spectroscopy. 

SPC techniques are hardly affected by additive noise and multiplicative noise is absent. However, subtractive noise due to the collection efficiency and transmission of optics and the quantum efficiency of the detector do play a role. In addition, at high count rates, the efficiency goes down due to pileup effects. 

---