Functional group detection

Functional Groups Detection in Soil Organic Matter 671... 

Second, an even more serious problem with this method is the critical nature of the filtration step (Holtzclaw and Sposito, 1979 Perdue, 1979 Perdue et al., 1980). Any moderately acidic functional groups (pKa 7-10) that are soluble in the equilibrium mixture (pH 6-7) will be titrated along with acetic acid when the filtrate is titrated to pH 9.8 (see Fig. 7). All the functional groups detected in that titration are simply assumed to be carboxyl groups. Thus, while the use of high concentrations of humic substances can lead to underestimation of carboxyl content, the complexation... 

Main FT-IR peaks (wavenumber, cm" ) and associated functional groups detected in the... 

Raman spectra arc similar to IR spectra in that they have regions useful for functional group detection and fingerprint regions that permit the idcntiflcaiion of specific compounds. Uaimay et al. have published a comprehensive treatment of Raman functional group frequencies,"... 

Nowadays, solid-state speciation or molecular identification of inorganic analytes is a hot topic in analytical chemistry. Molecular speciation allows individual components to be identified in mixtures, an impossible task for element or functional group detection methods. In fact, LMMS has been a forerunner in this field. Figure 3 illustrates the speciation scheme used in FT-LMMS. Basically, the miz difference between prominent signals from atomic ions and their adducts, the isotope patterns, and structural fragments such as oxide (adduct) ions in the case of oxysalts readily allow the molecular composition... 

In an extremely powerful technique, Dams et al. [540] separated 18 opiates and their derivatives (morphine, codeine, naloxone, hydrocodone, papaverine, dextromethorphan, noscapine, bupremorphine, methadone, heroin, thebacone, ethylmor-phine, 6-monoacetylmorphine, acetyldihydrocodeine, acetylcodeine, normethadone, normorphine, norcodeine) with baseline resolution in <12 min This was accomplished on a fast LC phenyl column 53 x 7 mm (2 = 280 nm) using a simple 100/0—>50/50 (at 10min)—> 0/100 (at 12min hold Imin) (90/5/5 water/ methanol/acetonitrile with 50 mM ammonium acetate)/(50/50 methanol/ acetonitrile with 50 mM ammonium acetate) gradient. The mobile phase components were adjusted to pH pp 4.5 with formic acid prior to use. The phenyl column was chosen ova- the conventional Cg or C g columns because of the increased selective interaction with analytes containing the planar phenyl functional group. Detection limits from 50 to 450ng/mL (analyte dependent) were reported. 

Ring perception is a routine task, a utihty to provide a description of cyclic pa of a structure in such a way as to complement other topologicad anadyses, such fragmentation, functional group detection, and topological indices. 

Colorimetric and Fluorimetric Analysis. The functional groups of amino acids exhibit Htde absorption of uv light from 210 to 340 nm where uv absorption spectrometry is most conveniently conducted. Thus color or fluorescence formation reactions are employed for amino acid detection (128). 

Some of the analytical methods utilize highly selective and sensitive detection techniques for specific functional groups of atoms in compounds, whereas others respond in a more universal manner, i.e., to the number of carbon atoms present in the organic molecule.- ... 

Microchemical reactions These can be carried out either with universal reagents [11] or with such substances which react with particular functional groups (group-characterizing reagents). If the separation process ensures that only one component occurs at a particular spot on the chromatogram, then this can be detected sub-stance-specifically . But specificity in an unequivocal sense can only be produced by a combination of the separation and the detection process. (The same is true of other forms of detection.)... 

Substances which do not exhibit such properties have to be transformed into detectable substances (denvatives) in order to evaluate the TLC separation Such reactions can be performed as universal reactions or selectively on the basis of suitable functional groups Substance-specific derivatization is practically impossible... 

Just like the physical and microchemical methods of detection, the indirect, biological-physiological detection procedures are very selective when apphed to thin-layer chromatography. Here it is not chemical functional groups or particular physical properties that are selectively detected but effects on highly sensitive biodetectors . The following detection techniques have been employed ... 

Further aspects, which come from special demands (e.g., multiple detection or samples with reactive functional groups), are also possible these are discussed later. 

In liquid chromatography, in contrast to gas chromatography [see Section 9.2(2)], derivatives are almost invariably prepared to enhance the response of a particular detector to the substance of analytical interest. For example, with compounds lacking an ultraviolet chromophore in the 254 nm region but having a reactive functional group, derivatisation provides a means of introducing into the molecule a chromophore suitable for its detection. Derivative preparation can be carried out either prior to the separation (pre-column derivatisation) or afterwards (post-column derivatisation). The most commonly used techniques are pre-column off-line and post-column on-line derivatisation. 

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