Molecular organic analytes

Molecular fluorescence and, to a lesser extent, phosphorescence have been used for the direct or indirect quantitative analysis of analytes in a variety of matrices. A direct quantitative analysis is feasible when the analyte s quantum yield for fluorescence or phosphorescence is favorable. When the analyte is not fluorescent or phosphorescent or when the quantum yield for fluorescence or phosphorescence is unfavorable, an indirect analysis may be feasible. One approach to an indirect analysis is to react the analyte with a reagent, forming a product with fluorescent properties. Another approach is to measure a decrease in fluorescence when the analyte is added to a solution containing a fluorescent molecule. A decrease in fluorescence is observed when the reaction between the analyte and the fluorescent species enhances radiationless deactivation, or produces a nonfluorescent product. The application of fluorescence and phosphorescence to inorganic and organic analytes is considered in this section. 

To further understand the molecular organization in humic systems at the level of covalent and noncovalent interactions, additional developments in the high-resolution analytical tools are needed. To achieve this level of resolution, techniques used to explore the complexity of humic materials must be coupled to separation methods that facilitate substantial reductions in the molecular heterogeneity of studied systems. 

The new field of molecular diversity raises three issues which need to be addressed by the organic analytical chemistry community (i) What tools can we use for following solid-phase reactions (ii) How can we analyze all these samples (iii) How much characterization of libraries is possible or appropriate This chapter deals with these problems and reviews the literature since a similar review written in June 1995 [2] (earlier seminal publications are described where appropriate). Other analytical issues such as decoding of combinatorial libraries or the applications of affinity separations and single-bead mass spectrometry for library deconvolution are dealt with in other chapters of this book. 

Gu, L. Q., Braha, O., Conlan, S., Cheley, S., and Bayley, H. (1999). Stochastic sensing of organic analytes by a pore-forming protein containing a molecular adapter. Nature 398, 686-690. 

Du W, Wang Y, Luo QM, Liu BF. Optical molecular imaging for systems biology from molecule to organism. Analyt. Bioanalyt. Chem. 2006 386 444-457. 

As measured by the dramatic increase in the number of publications in the area over recent years [1], the field of molecular imprinting has gained acceptance as a unique area of scientific endeavour, which lies at the cross-roads of polymer, organic, analytical, physical and bio-chemistries. Both the technique itself and its range of applications have been comprehensively reviewed [2-18]. 

In positive ion mode, M + H (M + 1) and M + Na (M + 23) ions may be formed from organic analytes. Since this is a very soft type of ionization, fragmentation is rarely seen, and the spectrum is dominated by these molecular ion species. 

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