Functional group derivatization

Analyte functional group Derivatizing agent Product Examples of derivatizing agents... 

Power A, Mathys G. 1992. Characterization of distillate fuel sediment molecules-functional-group derivatization. Fuel 71(8) 903908. 

The first involves a known functional group derivatization to quantify specific types of carbons found in humic substances, the derivatization being carried out by chemical reactions with l C-labeled reactants.( d-27) For example, methylation with C-labeled diazomethane or methyl iodide has been used to distinguish between and quantify hydroxyl functionalities in humic acids. The second labeling methodology involves the use of C-labeled reactants to follow the course of a complex reaction or association such as the interaction of pollutants with humic acids.(6-9,22,2J) The first structural evidence for the type of interaction of pollutants with humic substances was provided using and site specific labeling in combination with and NMR, respectively. 

Thermal Conductivity Detector. The TCD is based on the principle that addition of a compound to a gas alters the thermal conductance of the gas. It is used often with capil-laiy GC. The operating principle of the ECD is based on the reaction between electronegative compounds, such as fluorine, chlorine, bromine, and iodine, and thermal electrons. Because not all compounds contain these functional groups, derivatization with reagents containing polychlorinated or polyfluorinated moieties is a common practice used with an ECD. 

The chemical derivatization technique in combination with LC-MS/MS has also been used as an effective tool to facilitate the identification of metabolites, especially for unusual or unstable metabolites [277-279]. The MS detection sensitivity for poorly ionizable compounds can be increased by introduction of an easily ioniz-able functional group. Derivatization can reduce the polarity of very polar small molecular weight metabolites that elute very early together with many endogenous materials in the HPLC columns. As a result, the derivatized metabolite can be... 

This chapter focuses on the effects of anticoagulant activity caused by specific functional group derivatization of heparin, and on preliminary immobilization spacer group evaluations. The functional groups selected for immobilization are hydroxyl and carboxylic heparin groups. 

Functional Group Derivatization. Carboxylic Derivatization. Two grams of N -acetylated heparin and 2 mL of n-butylamine were dissolved in 40 mL of water, and the pH was adjusted to 4.75. A total of 0.8 g of l-ethyl-3-(3-dimethylaminopro-pyl)carbodiimide hydrochloride was added to the heparin/n-butylamine solution in approximately 10-mg portions over a 6-h period while the reaction was maintained at 4°C and pH 4.75. Periodic samples were withdrawn from the reaction vessel, dialyzed, and freeze-dried. In a separate reaction, 0.5 g of N-acetylated heparin and 1.0 g of 2-aminoethyl hydrogen sulfate were dissolved in 10 mL of water and adjusted to pH 4. 75. A total of 0.2 g of l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added to the reaction vessel in approximately 10-mg portions over a 4-h... 

For exact XPS quantification of the functional groups, derivatizations were performed using trifluoroacetic anhydride (TFAA) [62, 63] or m-trifluoromethylphe-nyl isocyanate (TMPl) for the OH groups, pentafluorobenzaldehyde (PFBA) or... 

Analyte functional group Derivatizing reagent Reference... 

Analyte functional group Derivatizing reagent Potential vs Ag/AgCl (mV) Reference... 

Table 1. Analyte Functional Groups and Chiral Derivatizing Reagents...

Another successhil strategy for derivatization of erythromycin employed modification of functional groups involved in intramolecular cyclizations. The C-9 ketone, C-6 hydroxyl group, C-8 proton, and/or C-ll,12-diol of erythromycin were converted into functional groups which participate poorly, if at all, in intramolecular cyclizations. Some derivatives which have been extensively evaluated in preclinical and clinical trials exhibit such desirable properties as better stabiUty under acidic conditions, greater oral bioavadabihty, and higher and more prolonged concentrations of antibiotic in semm and tissues. 

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... 

A large number of silylating agents exist for the introduction of the trimethylsilyl group onto a variety of alcohols. In general, the sterically least hindered alcohols are the most readily silylated, but are also the most labile to hydrolysis with either acid or base. Trimethylsilylation is used extensively for the derivatization of most functional groups to increase their volatility for gas chromatography and mass spectrometry. 

Accordingly, the resulting current reflects the rate at which electrons move across the electrode-solution interface. Potentiostatic techniques can thus measure any chemical species that is electroactive, in other words, that can be made to reduce or oxidize. Knowledge of the reactivity of functional group in a given compound can be used to predict its electroactivity. Nonelectroactive compounds may also be detected in connection with indirect or derivatization procedures. 

These few questions serve to demonstrate that there must be great interest in characteri2dng chemical compounds by means of their reactive functional groups. The most important group-specific reagents for postchromatographic derivatization are listed alphabetically in Table 4 below ... 

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