Multi-component analysis

NMR spectroscopy is one of the most widely used analytical tools for the study of molecular structure and dynamics. Spin relaxation and diffusion have been used to characterize protein dynamics [1, 2], polymer systems[3, 4], porous media [5-8], and heterogeneous fluids such as crude oils [9-12]. There has been a growing body of work to extend NMR to other areas of applications, such as material science [13] and the petroleum industry [11, 14—16]. NMR and MRI have been used extensively for research in food science and in production quality control [17-20]. For example, NMR is used to determine moisture content and solid fat fraction [20]. Multi-component analysis techniques, such as chemometrics as used by Brown et al. [21], are often employed to distinguish the components, e.g., oil and water. 

Another aspect of modern analytical chemistry is the possibility of multi-component analysis. Especially spectroscopic and chromatographic methods are able to detect and determine a large number of species simultaneously. Therefore, such methods like ICP-OES, ICP-MS, TXRF, and chromatography are the work-horses in today s analytical chemistry. 

Y. Ermolenko, T. Yoshinobu, Y. Mourzina, K. Furuichi, S. Levichev, M.J. Schoning, Y. Vlasov, and H. lwasaki, The double K+/Ca2+ sensor based on laser scanned silicon transducer (LSST) for multi-component analysis. Talanta 59, 785—795 (2003). 

Figure 16. Opto-nose and multi-component analysis of nose output.

Most current automated measurement techniques focus on one or possibly two air pollutants. A survey of recent developments shows major advances in multi-component analysis. Examples include ... 

In process analytics, chemometrics can undergo a staling process during the early phases of implementation, the benefits of the technology are most apparent (e.g. interference rejection, multi-component analysis capabilities, and fault monitoring), but over time, as conditions change and new interferences appear, the models can lose their accuracy. This can lead to suspicions of bait and switch. ... 

Loos, R., G. Hanke, and S. Eisenreich. 2003. Multi-component analysis of polar water pollutants using sequential solid-phase extraction followed by LC-ESI-MS. J. Environ. Monit. 5 384-394. 

The intensities of the bands in the spectrum of a mixture are usually proportional to the concentrations of the individual components. It is thus possible to determine the concentration of one substance or to carry out a multi-component analysis. 

In the case of non-ideal systems, where overlapping of bands is combined with more pronounced deviations from the Lambert-Beer law, the procedures of quantitative analysis are considerably more complex. An introduction into these problems has been provided by Baumann (1962), Perkampus (1992) and Massart et al. (1988). Nonlinear multi-component analysis by IR spectrophotometry has been described by Maris and Brown (1983). 

The M018O52 phase found is non-crystalline, as the authors point out No additional diffraction peaks were found. In addition to the multi-component analysis of the XANES spectra the authors observed a significant change in the Mo—O and Mo—Mo distances at 573 K, where XANES suggested the formation of a M018O52 phase. 

Analysis strategies that use on-line ESI-LC/MS approaches provide an integrated format for natural product dereplication by combining traditional fraction collection, sample preparation, and multi-component analysis into a single step. In this way, crude extracts are screened without extensive purification and chemical analysis. Furthermore, less material is required due to the sensitivity of the technique and chromatographic resolution is retained. 

The substantial computing power of FTIR systems has also been an important factor in the success of FTIR spectroscopy. FTIR software packages provide a wide variety of data handling routines that facihtate spectral acquisition and interpretation and enhance the utiUty of IR spectroscopy as both a quahtative and a quantitative analysis tool. In the following section, we will discuss some data handling techniques. FTIR software for multi-component analysis will be covered in the subsequent section on quantitative analysis methods. 

When more than one component is present in the solution, the above approach will generally not be satisfactory as it cannot account for any contributions of additional components to Ay, nor can it model interactions between components. Therefore, more complicated mathematical approaches are required for multi-component systems. We will describe here the three techniques that are most commonly used in multi-component analysis. 

According to Beer s law, the measured absorbance of a solution of a single light-absorbing species is directly proportional to its concentration. For a solution containing a mixture of absorbing species, the measured absorbance is then simply the linear combination of the absorbances of all species in that solution, each measured at the same wavelength. When the different species in the mixture have different spectra, we can do a multi-component analysis and extract the concentrations of the individual species. 

M. Blanco, J. Coelho, H. Iturriaga, S. Maspoch, M. Redon, J. Riba, Multi-component analysis of concentrated solutions by flow-injection analysis with zone sampling and partial least-squares resolution, Anal. Chim. Acta 259 (1992) 219. 

Unified calcn. of titn. curves (for limited number of components) Multi-component analysis computations using Kalman filtering Titration assisted by microcomputers. Electro-activity treated similarly to pH... 

Vaihinger S. andGopelW, Multi-component analysis in chemical sensing, in A... 

Systems of highly correlated spectra can also be used for multi-component analysis. 

Multi-component analysis with dc polarography is based on completely separated polarographic waves. The separation of two polarographic waves is dependent on the reversibility of the electrode reaction, and also on the concentration of the electroactive compounds, and the number of electrons taking part in the electrode reaction. In Fig.8, schematic polarographic waves are shown when determining two compounds in the same solution, assuming that the components are present in the same concentrations and that the electrode reaction is either a reversible one-electron reaction or a reversible two-electron reaction. 

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