Qualitative analysis, multidimensional

Multidimensional gas chromatography has also been used in the qualitative analysis of contaminated environmental extracts by using spectral detection techniques Such as infrared (IR) spectroscopy and mass spectrometry (MS) (20). These techniques produce the most reliable identification only when they are dealing with pure substances this means that the chromatographic process should avoid overlapping of the peaks. 

K. A. Rrock and C. L. Wilkins, Qualitative analysis of contaminated environmental extracts by multidimensional gas cliromatography with infrared and mass specti al detection (MDGC-IR-MS) , pp. 167-178, copyright 1996, with permission from Elsevier Science. 

The two examples discussed show the bioanalytical applicability of LC/MS, both in qualitative analysis and in target compound analysis. Although the moving belt interface owing to its El capabilities is ideally suited for the identification of unknown compounds and is used often for that purpose, identification problems can sometimes also be solved with thermospray LC/MS, for instance by applying repeller-induced fragmentation, and LC/MS/MS. The PSS approach is an example that indicates that LC/MS still can be improved. A more elaborate discussion on the so-called multidimensional approaches in LC/MS is given elsewhere (14). 

Factor analysis techniques and the power of their graphical representation permit rapid Identification of anomalous behavior in multidimensional water quality data. In addition, the techniques permit qualitative class distinctions among waters with different geologic... 

Multidimensional and multihyphenated techniques may become increasingly useful, particularly for the analysis of drugs in biological fluids where LC-GC interfacing has a great deal of promise with respect to sample cleanup and preparation timeJ GC-MS applications continue to grow in number from the qualitative structural identification point of view, for quantitative analysis that uses and for other... 

The fragmentation rate can be enhanced by either increasing the scanning speed of the instalments or by reducing the complexity of peptide mixtures prior to MS detection. Scan rate has significantly evolved during recent years, and the current generation of MSs reaches scan rates around 100 Hz, which represents a qualitative improvement compared to older models. Similarly, sample preparation has also been refined, and multidimensional separation at the level of proteins, proteolytic peptides, or both have made it possible to achieve a comprehensive analysis of nearly the entire human proteome... 

Multidimensional fluorescence analysis is well suited for routine qualitative separation and identification of complex mixtures of PAHs in environmental samples. The separation and extraction of the individual component spectra of PAH mixtures affords valuable information about these hazardous compounds. Such information may allow for a detailed study of the means to remove their influence from the environment. The differences in the intensity contributions from a mixture of PAHs in a multicomponent system could be related to the differences in concentrations of the individual components and their respective quantum efficiencies. The problem is exacerbated by the fact that most solutions containing mixtures of PAHs display broad fluorescence spectral bands at room temperature, resulting in significant overlap and limited specificity for multicomponent analysis. This makes the success of multidimensional fluorescence measurements for complete spectral resolution of a complex multicomponent mixture dependent upon the degree of spectral overlap among the individual components and their fluorescence... 

There is a way of putting the questionnaire to qualitative use. The analysis then is not aimed at spanning a multidimensional space and projecting cases into it. The responses are used to generate themes, which are used in subsequent (qualitative) research (for example, see Guldenmund 2008). 

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