From Spectra to Qualitative and Quantitative Results

the different methods available for quantitative analysis will be reviewed. The problem of determining one or two or more components can be solved with the usual methods based on the absorbance measurement at one or several wavelengths, if the optical response of the solution is free of interferences. Unfortunately, for water and wastewater analysis, there is always either physical (diffuse absorption of particles, for example) or chemical interference (e.g. overlapping peaks due to competitive absorbance of compounds), so that more robust methods have to be chosen. The simpler of them are probably the derivative techniques, because they offer to the user the possibility to 

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UV examination has been proved to be a relevant method for the study of water and wastewater quality using deconvolution methods of UV spectra. The absorbency spectrum of water can be decomposed from a few number of characteristic spectra (reference spectra). Therefore, a given spectrum can be reconstructed with a linear combination of reference spectra and all additive parameters can be computed with the same linear combination. Qualitative and quantitative results in terms of classical parameters such as TOC, COD, BOD5, TSS, nitrate,... can be provided. 

Polyethylene. The action of ozone on polyethylene was studied in the temperature range from 25° to 109° C. The reaction was followed qualitatively and quantitatively by infrared spectra. The products appeared to be of the same nature as those of O2 oxidations of polyethylene 2)—i.e., the formation of aldehydic and ketonic groups as indicated by the appearance of a strong absorption band in the region of 5.9 microns, and the existence of hydroxyl groups as shown by the 2.9-micron band. Polyethylene is readily oxidized in the presence of ozone, as even short period ozonizations carried out at temperatures as low as 25° C. yielded considerable concentrations of carbonyl and hydroxyl groups. Pure O2 oxidations did not yield comparable results until the reaction temperature was raised approximately... 

As could be recognized from the review of the more recent applications, the use of UIC has been abandoned in favour of GIC. Since GIC treatment would lead to qualitatively and semi-quantitatively similar results, the forthcoming section summarizes the original achievements based on UIC with reference to future utilization of the correlation maps or spectra, which will then be computed according to GIC. 

Abstract In this chapter the reader can find an overview on the UV-vis absorption spectroscopy technique. A very brief introduction on the nature and formation of the electronically excited states is functional to the following discussion on the characteristics, and interpretation of UV-vis absorption spectra. The typical instrumentation is also schematically described, and a particular emphasis is devoted to the possible qualitative and quantitative information that can be obtained with this kind of measurements. Practical indications to obtain accurate and reliable experimental results were introduced with the aim to help the readers that will approach for the first time this fundamental experimental technique. The chapter ends with the discussion of a few examples, taken from the literature, with the aim to make clear the investigative great potentialities of this spectroscopy in different fields. 

The amount of information, which can be extracted from a spectrum, depends essentially on the attainable spectral or time resolution and on the detection sensitivity that can be achieved. Derivative spectra can be used to enhance differences among spectra, to resolve overlapping bands in qualitative analysis and, most importantly, to reduce the effects of interference from scattering, matrix, or other absorbing compounds in quantitative analysis. Chemometric techniques make powerful tools for processing the vast amounts of information produced by spectroscopic techniques, as a result of which the performance is significantly... 

Perhaps more valuable over time than the quantitative predictions of spectra, structural parameters, and relative enthalpies and entropies of RIs, which can be obtained from electronic structure calculations, are the qualitative models of the electronic structures and reactivities of RIs that emerge from the computational results. Any model, to be successful, must do two things. 

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