Resolution peak deconvolution

A third problem with simulation of high resolution diffraction data is that there is no unique instrament function. In the analysis of powder diffraction data, the instalment function can be defined, giving a characteristic shape to all diffraction peaks. Deconvolution of these peaks is therefore possible and fitting techniques such as that of Rietveld can be used to fit overlapping diffraction peaks. No such procedure is possible in high resolution diffraction as the shape of the rocking curve profile depends dramatically on specimen thickness and perfection. Unless you know the answer first, you cannot know the peak shape. 

Ramos et al. [13] first separated the individual spectra of benzo[b]fluoranthene and benzo[k]fluoranthene or chrysene and benz[a]anthracene from each other in a purposely created co-eluting peak of mixtures of each of the two pairs of PAHs. They were then able to deconvolute the individual spectra from a mixture of the isomers benzo[e]pyrene, benzo[b]fluoranthene, and benzo[k]fluoranthene in a similar fashion. In all cases they purposely generated peaks with severe overlap (greater than 90 % of each peak co-eluting with the other components) to show the power of deconvolution. Tauler et al. described another algorithm to deconvolute the individual spectra in co-eluting peaks and reviewed similar efforts by others. Multivariate curve resolution has been used as an alternative approach for peak deconvolution. It can identify minor impurity peaks and yield the true retention times [14, 15]. 

In addition, even if peak area measurements are used, a separation of 4a will usually provide adequate accuracy and this is particularly so if computer data acquisition and processing is used with peak deconvolution software. In general, a resolution of 4a will be assumed whenever dealing with resolution or column design. In most column optimization procedures the effect of increasing the criteria for resolution can easily be accommodated if so desired. 

TOF-MS (time of flight MS), with its high mass-resolving power is capable of generating mass data of sufficient accuracy and precision to establish the elemental composition of an analyte. The high accuracy, fast response time, and ease of peak deconvolution capability make TOF-MS an ideal online detector to interface with high-resolution separation techniques. The hyphenation of TOF-MS with CE... 

It is still possible to enhance the resolution also when the point-spread function is unknown. For instance, the resolution is improved by subtracting the second-derivative g x) from the measured signal g x). Thus the signal is restored by ag x) - (7 - a)g Xx) with 0 < a < 1. This llgorithm is called pseudo-deconvolution. Because the second-derivative of any bell-shaped peak is negative between the two inflection points (second-derivative is zero) and positive elsewhere, the subtraction makes the top higher and narrows the wings, which results in a better resolution (see Fig. 40.30). Pseudo-deconvolution methods can correct for sym-... 

The relatively poor resolution of the XPS systems has lead to an extensive use of deconvolution techniques in order to prove the presence of shifted core levels of low intensity in the presence of unshifted levels (thin oxide layers on metal substrates). Deconvolution techniques should be used only in those cases where the presence of multi components is shown up by a shoulder in the intensity distribution. Interpretation of asymmetric peaks in terms of chemical shifts can be misleading in some cases because the asymmetry may change due to a change of the electron population at the Fermi level as was demonstrated for the metallic oxide Ir02 [23, 24],... 

Multidimensional GC with time of flight MS (ToF-MS) is increasingly being employed to examine complex mixtures. In this technique non-polar and polar GC stationary phases connected by a thermal modulator enable increased resolution of GC peaks. The fast scanning made possible by the ToF measuring system leads to many data points across peaks and the possibility of deconvolution of complex overlapping peaks. 

In summary such marked structural differences can be assumed to affect the structure of the initial nanoparticles in the solidification process. Improved peak resolution, deconvolution, Q1 ratio-possible ring structure matching, model calculations, and comparison with NMR and other structural data can make Raman a quite useful, inexpensive, and mobile accessory for studying the structure of silicates both in aqueous solutions and in solid phase. 

Registration of a metastable ion in the spectrum is rather useful, as it confirms realization of a certain fragmentation reaction. The fragmentation schemes are considered to be true if corresponding metastable peaks are detected. On the other hand, metastable peaks deteriorate spectral resolution. Depending on the amount of energy released, the forms of the metastable peaks may be quite different. These peaks are eliminated from the spectra as part of the computer deconvolution process. 

Chemometric methods can greatly increase the number of analyzable peaks in MDLC in particular, the generalized rank annihilation method (GRAM) can quantify overlapping peaks by deconvoluting the combined signal to those of each dimension. Standards with precise retention time are required, and there must be some resolution in both dimensions [60,61]. 

Fig. 11. High-resolution 29Si MAS NMR spectra of synthetic zeolites Na-X and Na-Y at 79.80 MHz (58). Experimental spectra are given in the left-hand columns Si(nAl) signals are identified by the n above the peaks. Computer-simulated spectra based on Gaussian peak shapes and corresponding with each experimental spectrum are given in the right-hand columns. Individual deconvoluted peaks are drawn in dotted lines.

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