Derivatization methods

Minganti V, Capelli R, Depellegrini R (1995) Evaluation of different derivatization methods for the multielement detection of Hg, Pb and Sn compounds by gas chromatography-microwave induced plasma-atomic emission spectrometry in environmental samples. Fresenius Journal of Analytical Chemistry, 351 (4-5) 471 77. 

While most amino acids are not electroactive at analytically usable potentials at carbon electrodes, much work is currently directed at general methods of LCEC amino acid detection by electrode surface modification or derivatization of the amino acid. Kok et al. have directly detected amino acids at a copper electrode. Several derivatization methods for amino acids have also been reported 227.228)... 

The development of new fiber coatings in the near future should further improve the specificity of SPME and overcome some of the observed matrix effects. Quantification by stable isotope dilution gas chromatography/mass spectrometry (GC/MS) may assist in improving analytical performance. Along with the possible application of micro LC and capillary LC columns to in-tube SPME, the development of novel derivatization methods and the potential for the analysis of fumigant pesticides, SPME appears to be a technique with a future in the analysis of pesticide residues in food. 

T. Toyo oka, Modern Derivatization Methods for Separation Sciences, John Wiley Sons Ltd, Chichester (1999). 

The y-initiated oxidation of polyolefins produces a product mix which is less complex than that resulting from photo-or thermally initiated degradation. This results from the mild conditions in the Y-cell, where the major initial oxidation product, the -OOH group, is stable. Although the derivatization methods are applicable to all types of oxidation, for simplicity only the y-irradiated systems will be considered here. 

Eudy, L. W. Analytical pyrolysis and derivatization methods combined with gas chromatography-mass spectrometry for the characterization of bacteria and other nonvolatile materials. Univ. South Carolina, Columbia, SC, USA (1983), 197 pp. From Diss. Abstr. Int. B 1984, 45(1), 171. 

A. Asperger, W. Engewald and G. Fabian, Thermally assisted hydrolysis and methylation a simple and rapid on line derivatization method for gas chromatographic analysis of natural waxes, J. Anal. Appl. Pyrol., 61, 91 109 (2001). 

In the last decade modifications to the pyrolysis process have been developed to improve analytical efficiency and increase detectability. In the same way as in conventional GC, derivatization reagents may be used to improve the chromatographic separation and response of polar compounds. In order to reduce the time required for the analysis, the risk of contamination and of losing part of the sample, on-line derivatization methods should be preferred and those based on quaternary ammonium hydroxides are certainly the most widely used. 

More recently on-line pyrolysis with HMDS has been performed successfully even if the pyrolysis interface was kept at 250°C. In fact, Domenech-Carbo and colleagues [57,58] have obtained very good results on a variety of art materials and on real paint samples as well. They have applied Py-GC/MS with on-line trimethylsilylation to the characterization of diterpenoid resins and, in contrast to previous literature data, the derivatization method enabled not only the identification of resinous carboxylic acids in the form of TMS esters, but also an efficient conversion of hydroxyl groups to TMS ethers. 

Many of the chemical derivatization methods employed in these strategies involve the use of an activation step that produces a reactive intermediary. The activated species then can be used to couple a molecule containing a nucleophile, such as a primary amine or a thiol group. The following sections describe the chemical modification methods suitable for derivatizing individual nucleic acids as well as oligonucleotide polymers. 

Fluorescent probes containing sulfhydryl-reactive groups can be coupled to DNA molecules containing thiol modification sites. The chemical derivatization methods outlined in Section 2.2 (this chapter) may be used to thiolate the oligo for subsequent modification with a fluorophore. Appropriate fluorescent compounds and their reaction conditions may be found in Chapter 9. The protocol discussed in the previous section can be used as a general guide for labeling DNA molecules. 

SWNTs have attracted growing interest due to their potential applications in the fields of cancer diagnosis and therapy. To trace and diagnose the effects of the treatment in single cells or tissues, SWNTs need to be derivatized covalently or noncova-lently with fluorescent tags. The main derivatization method has... 

Some derivatization methods mentioned in other sections of this review include chemical ionization by nitric oxide (MS) or epoxidation (MS), formation of jr-complexes for NMR (shift agents) etc. Also, the Diels-Alder reaction, which was mentioned several times as a tool for derivatization of conjugated dienes and polyenes, was extensively described and reviewed in the literature. 

Fluorescence detection can be up to four orders of magnitude more sensitive than UV absorbance, especially where laser induced excitation is used, mass detection limits being as low as 10-20—10 21 mole. Pre- and post-column derivatization methods are being developed to extend the applicability of fluorescence detection to non-fluorescent substances. Several types of electrochemical and mass spectrometric detector have also been designed. Detector characteristics are summarized in Table 4.21. 

The two most commonly used derivatization methods for exohedral functionalization are the nucleophilic cyclopropanation with malonates (Bingel, 1993) and the formation of fulleropyrrolidines (Maggini et al., 1993). Both of these protocols have been used extensively to produce water-soluble fullerenes for biomedical applications. Other stable water-soluble fullerene adducts have also been reported (Hirsch and Brettreich, 2005). Sections 3.2.2-3.2.5 will give a short overview on the state-of-the-art of water-soluble fullerene derivatives and outline some general trends for designing such molecular structures. 

As mentioned earlier, the response of each protein will vary. This is especially apparent with colorimetric assays or derivatization methods requiring a chemical reaction. These protein-to-protein reactivity differences mean that a protein assay suitable for one protein may not be suitable for another. Even for a given protein and a specific protein determination method, results may still vary based on limitations of the assay. Methods requiring extensive sample preparation including protein concentration, buffer exchange, and time-sensitive reactions are liable to be less reproducible than direct measurement techniques, which have fewer variable parameters. The application will determine the suitability of the method. 

Extending the utility of fluorescence to various nonfluorophores is achieved via chemical derivatization methods, also termed labeling or tagging methods (Reaction 11.2). Numerous commercial fluorescent tags are available with disparate reactive functional groups. For example, derivatives of fluorescein, fluorescein isothiocyanate (FITC) are reactive toward nucleophiles such as amines and sulfhydryl groups. 

---