Phenols functional group analysis

A derivatization technique is commonly applied to an agrochemical with certain reactive functional groups (e.g., carboxylic acid, amine, phenol) to make the compound amenable to either gas chromatography (GC) or LC analysis. An in-depth discussion of derivatization reactions used in the analysis of agrochemicals is beyond the scope of this article. For more information on this topic, the reader is referred to Knapp. °... 

Photodiode array detection has three major advantages for HPLC analysis (26) (a) multiple-wavelength detection, (b) peak identification, and (c) peak-purity determination. Since PDA can record the characteristic UV spectra of the different phenolics as they elute from the column, characterization and peak-purity information can be facilitated through comparison of the spectra at the front, the apex, and the tail of each peak. Furthermore, the rapid calculation of absorbance ratios between different wavelengths is possible, which can be used to classify the spectra by functional groups or by other criteria (Table 1). 

Figure 5.3. A humic acid macromolecule interacting with a surface of a clay mineral. The proposed macromolecular structure of the soil humic acid (HA) is based on the following common average characteristics of humic acids MW 6386 Da elemental analysis (%) C, 53.9 N, 5.0 H, 5.8 0,35.1 S, 0.5 C/N, 10.7 NMR information (%) aliphatic C, 18.1 aromatic C, 20.9 carbohydrate C, 23.7 metoxy C, 4.9 carboxylic C, 8.4 ketone C, 4.5 phenolic C, 4.2 functional groups (cmol/g) carboxyl, 376 phenol, 188 total acidity, 564. The structure was created using the ACD/ChemSketch program. [HA-clay complex Chen s group, unpublished (2008). Individual HA molecule Grinhut et al., 2007.]...

TMS production involves one specific functional group (-OH, -COOH, =NH, -NH2, or -SH), which loses an activated hydrogen and is replaced by a trimethylsilyl group (Proestos et ah, 2006). To achieve silylation, some authors have used BSTFA (N,0-hA(trimethyl-silyl)trifluoroacetamide) and TMCS (trimethylchlorosilane) successfully in several matrices (e.g. aromatic plants, cranberry fixiit) (Zuo et ah, 2002 Proestos et ah, 2006). Using silylated derivatives is advantageous for several reasons phenols and carboxylic acids are prone to silylation, these compounds can be derivatized in the same part of the process, and the minor products do not impede analysis and are well documented (Little, 1999 Stalikas, 2008). A two-step methylation procedure was used to analyze catechins and tannins in plant extracts. The first step used trimethylsilyl diazomethane (TMS-diazomethane) to pre-methylate the sample, and the second step used thermally assisted hydrolysis and methylation (THM). The pre-methylation step with TMS-diazomethane stabilized the dimer molecule m/z 540) by minimizing isomerization and reducing reactivity. (Shadkami et ah, 2009). 

SBSE can be successfully used in the analysis of environmental samples [93-97] and for food analysis [98, 99]. PDMS is the most commonly used polymer, primarily because of its thermal stability and durability. SBSE has been modified by application of derivatization with different reagents (acetic anhydride, BSTFA, etc) [100-104]. This approach is suitable for the extraction of compounds requiring derivatization. The use of multistep derivatization with several extraction elements (each reaction is performed on a different stir bar) allows efficient extraction, desorption, and chromatographic analysis of compounds with different functional groups (e.g., phenols, steroids, amines, thiazoles, ketones). Acetic anhydride (ester formation), ethyl chloroformate (reaction of acids and amines), tetraethyloborane, and sodium bis-trimethylotrifluoroacetamide have been used for extraction and simultaneous derivatization [105]. 

There are many hundreds of published reports on the use of achiral lanthanide tris(/3-diketonates) as NMR shift reagents. Essentially any substrate with an oxygen, nitrogen or sulfur atom is a potential candidate for analysis with lanthanide shift reagents. These include sulfur- and phosphorus-containing functional groups that have oxygen atoms. Carboxylic acids and phenols were observed to decompose lanthanide chelates of dpm, whereas solutions with chelates of fod were stable for several days and suitable for study. 

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