Phenolic analytical fractionation

Analytical Fractionation of the Phenolic Substances of Grapes and Wine and Some Practical Uses of Such Analyses... 

Singleton, V.L. 1974, Analytical fractionation of the phenolic substances of grapes and wine and some practical uses of such analyses. In Chemistry of Winemaking (A.D. Webb, ed.) pp. 184-211. American Chemical Society, Washington, D.C. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

SEC in combination with multidimensional liquid chromatography (LC-LC) may be used to carry out polymer/additive analysis. In this approach, the sample is dissolved before injection into the SEC system for prefractionation of the polymer fractions. High-MW components are separated from the additives. The additive fraction is collected, concentrated by evaporation, and injected to a multidimensional RPLC system consisting of two columns of different selectivity. The first column is used for sample prefractionation and cleanup, after which the additive fraction is transferred to the analytical column for the final separation. The total method (SEC, LC-LC) has been used for the analysis of the main phenolic compounds in complex pyrolysis oils with minimal sample preparation [974]. The identification is reliable because three analytical steps (SEC, RPLC and RPLC) with different selectivities are employed. The complexity of pyrolysis oils makes their analysis a demanding task, and careful sample preparation is typically required. 

Sample preparation is included in sample handling and is rapidly becoming a science in itself. The initial treatment of the sample is a critical step in chemical and biochemical analyses it is usually the slowest step in the analysis. In the case of food and plant samples, the number and diversity of analytes is very high and efficient pretreatment is required to obtain enriched phenolic fractions. 

Analytical studies of the tergal secretions of male B. germanica have identified a number of volatile compounds, none of which has so far been subjected to behavioral assays on females. Brossut et al. (1975) found p-hydroxybenzyl alcohol, o-hydroxybenzyl alcohol, di- and tri-methylnaphthalene, benzothiazole, two isomers of nonyl phenol, and myristic, palmitic, and oleic acids. The fatty acids constituted > 92% of the volatile fraction given their abundance in feces and frass, and their role as putative aggregation pheromones (Wileyto and Boush, 1983 Fuchs et al., 1985 Wendler and Vlatten, 1993 Scherkenbeck et al., 1999),... 

An alternative cleanup procedure is the partition of the raw extract, which often contains considerable amounts of lipid material, between an organic and an aqueous sodium hydroxide phase. With this partitioning scheme, the analytes are further fractionated into estrogens and nonestrogens. The presence of phenolic groups in the molecules of estrogens such as diethylstilbestrol and zeranol ensures their complete extraction from organic phases such as chloroform or tert.-butyl methyl ether into the aqueous sodium hydroxide phase (435, 438, 447). Further purification could be accomplished by neutralization of the sodium hydroxide solution and back-extraction of the contained diethylstilbestrol into diethyl ether (435), or adjustment of the pH of the sodium hydroxide solution to 10.6-10.8 and back-extraction of the contained zeranol into a chloroform phase (447). 

Jhe distribution of hydrogen types in coals continues to be a subject of considerable interest in coal structure studies. Published data indicate that the fraction of aromatic hydrogens usually increases with increasing rank, but the absolute values depend on the specific analytical method used (7). Hydrogen type analysis of a single coal based on the application of NMR spectroscopy to the soluble fraction from depolymerization with phenol-BFa has been reported by us (3). The conversion of coal to soluble fragments in substantial yields under very mild conditions permits a reliable determination of the hydrogen types by NMR analysis, and these results can be extrapolated to the parent coal with considerable confidence. 

Methods of analysis are needed to determine total phenolic content and the relative content of phenolic fractions by means of their different characteristics. Many analytical methods used for phenols have been empirical and not easily reproduced or rationalized (I). Procedures that are based on sound chemical principles and that are sufficiently verified deserve wider application. We are concerned here with recent work on such analyses for phenols in wines. Application cf these results may help solve a major problem in phenol research—the many different, too empirical, unrelatable values (ml KMn04, vanillin-to-leucoantho-cyanin ratio, etc.) obtained in different ways by different researchers. Uniform use of verified methods and uniform standards and methods of expressing results will aid in developing an understanding in this field. 

Analytical pyrolysis with field ionization mass spectrometry (online Py-FIMS) or in combination with GC/MS (Curie point Py-GC/MS) led to a significant increased number of identified subunits (e.g., Bracewell et al., 1989 Schulten et al., 2002). In addition, the application of tetramethylammonium hydroxide (TMAH) methylation, followed by GC/MS, was successfully applied. The most abundant pyrolysis products identified are benzene, phenol and furan derivatives, aliphatic and carboxylic compounds, and indene derivatives (Schulten et al.,2002). New approaches have been used for the quantification of n-alkyl fatty acids of DOM and isolated fractions in the form of individual compounds after solvent extraction followed by derivatiza-tion with TMAH. 

Aliphatic stretching, FTIR of vitrinite, 103-12 Alkyl phenols, Py-MS, 153f Analytical analyses of demineralized coals, density fractions, 71t Aromatic adjacent hydrogen in... 

In an analytical experimental series (Fig. 1), the effluent was collected in fractions. These fractions were analyzed with respect to pH, fermentable sugars, furan aldehydes, phenolic compounds, aliphatic acids, sulfate, and ultraviolet (UV) absorption at 280 nm. 

Six different detoxification treatments were performed using both weak and strong anion-exchange resins (Table 1) in an analytical experiment (Fig. 1) and a preparative experiment (Table 2, Fig. 2), in which the fermentability of the fractions was assayed. Figure 1 shows how the pH and the concentrations of glucose, furan aldehydes, phenols, aliphatic acids, and sulfate varied in hydrolysate fractions collected from columns packed with the six different resins in the analytical anion-exchange experiment. 

Extensive reviews of analytical methods for anthocyanins (Francis, 1982 Jackman et al., 1987b Strack and Wray, 1994) and other flavonoids (Williams and Harbome, 1994) as well as phenolic acids (Herrmann, 1989) have been published. In these reviews, extraction procedures, methods for fractionation of groups of polyphenols and the identification and quantification of individual components are presented. Here, a brief presentation of more recently published methods for grape and berry polyphenolic analyses is given with respect to their relationship to antioxidant activity and health benefits. 

Samples with particulate matter may present quite serious problems, and it may be desirable to remove particles, for example, by centrifugation, and examine this fraction by procedures applicable to solid phases which are discussed in Section 2.2.5. Tangential-flow high-volume filtration systems have been used for analysis of particulate fractions (>0.45 jum) where the analytes occur in only low concentration (Broman et al. 1991). Attention has already been drawn to artifacts resulting from reactions with cyclohexene added as an inhibitor to dichloromethane. It has also been suggested that under basic conditions, Mn2+ in water samples may be oxidized to Mn(III or IV) which in turn oxidized phenolic constituents to quinones (Chen et al. 1991). Serious problems may arise if mercuric chloride is added as a preservative after collection of the samples (Foreman et al. 1992) since this has appreciable solubility in many organic solvents, and its use should therefore be avoided. 

Pear Phenolics. The same HPLC analytical system gave good resolution of pear juice phenolics and enabled peak assignments and quantitation to be made in a similar manner to that described for apple phenolics (3,7). It was also necessary to isolate the procyanidins and catechins using the Sephadex clean-up procedure (4) in order to measure their concentration. Figure 6A shows the HPLC separation of cinnamics, flavonols, and arbutin in pear juice while Figure 6B is a HPLC chromatogram of the pear juice procyanidin fraction. 

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