Phenolic compounds spectrometry analyses

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

Canini A, Alesiani D, D Arcangelo G and Tagliatesta P. 2007. Gas chromatography-mass spectrometry analysis of phenolic compounds from Carica papaya L. leaf. J Food Comp Anal 20 584-590. 

Mass spectrometry applied to characterization of phenolic compounds has been widely reviewed (Fulcrand and others 2008 Harnly and others 2007 de Rijke and others 2006 Prasain and others 2004). Therefore, here we describe the most common mass spectroscopic methods used for the analysis of phenolic compounds. 

Im HW, Suh BS, Lee SU, Kozukue N, Ohnisi-Kameyama M, Levin CE and Friedman M. 2008. Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes. J Agric Food Chem 56(9) 3341-3349. 

S. Perez-Magarino, I. Revilla, M.L. Gonzalez-SanJose and S.Beltran, Various applications of liquid chromatography-mass spectrometry to the analysis of phenolic compounds. J. Chromatogr.A, 847 (1999)75-81. 

The Environmental Health Laboratory Sciences Division of the Center for Environmental Health and Injury Control, Centers for Disease Control, is developing methods for the analysis of cresols and other phenolic compounds in urine. These methods use purge and trap methodology and magnetic mass spectrometry which gives detection limits in the low ppt range. 

ANALYSIS OF PHENOLIC COMPOUNDS WITH MASS SPECTROMETRY... 

Analysis of phenolic compounds with mass spectrometry 199... 

Tandem mass spectrometry or MS/MS is frequently used for structural elucidation of phytochemicals to provide more detailed information about the structure and composition of a molecule. This involves two mass spectral steps and fragmentation of the compound occurs between the steps. The two steps may be separated in space or in time depending on whether two distinct separation elements are used (space) or two different separations occur in the same place over time. As described previously, an IT analyzer can be used to successively fragment a molecule to provide MS" spectra, an example of separation in time. A triple quadrupole mass spectrometer is a form of tandem mass spectrometry in space in which two quadrupoles serve as mass filters while a third, positioned in the middle, allows for collision-induced dissociation. Triple quadrupoles are common in phytochemical analysis, and have been used to characterize phenolic compounds in fruit juices (Abad-Garcia et ah, 2009) and procyanidins and alkaloids in cocoa (Ortega et ah, 2010), among others. 

Hu R. Lu Y. Dai X. Pan Y. 2010. Screening of antioxidant phenolic compounds in Chinese Rhubarb eombining fast counter-eurrent chromatography fractionation and liquid chromatography/mass spectrometry analysis. J. Sep. Sei. 33 1595-1603. 

Mertz, C. Cheynier, V. Brat, P. 2007. Analysis of phenolic compounds in two blackberry species (Rubus glaucus and Rubus adenotrichus) by high-performance liquid chromatography with diode array detection and electrospray ion trap mass spectrometry. J. Agric. Food Chem. 55 8616-8624. 

Besides alkoxides, acetylacetonates are also used as the starting materials for the synthesis of oxides. Titania (anatase) is obtained by decomposition of titanium oxyacetylacetonate (TiO(acac)2) in toluene at 300°C. Similarly solvothermal treatment of Fe(lll) acetylacetonate in toluene yields microcrystalline magnetite. One of the drawbacks of the use of acetylacetonate may be formation of various high boiling point organic by-products via aldol-type condensation of the acetylacetone. Actually more than 50 compounds are detected by gas chromatography-mass spectrometry (GC-MS) analysis of the supernatant of the reaction, some of which are phenolic compounds and are hardly removed from the oxide particles by washing with acetone. ... 

Traditionally, flavonoids have been separated and analyzed by HPLC and gas chromatography (GC). However, recent developments of SFC may permit a more accurate and complete analysis of plant phenolic compounds. Supercritical fluid chromatography brings together the advantages of both HPLC and GC techniques because it may be readily employed in the analysis of nonvolatile and thermolabile compounds and provides facile coupling to detector technologies such as mass spectrometry and Fourier transform infrared (FT-IR) spectroscopy. In recent years, SFC has been used to separate flavonoid compounds, most of which are polymethoxylated flavones and polyhydroxylflavonoids. 

The detection and identification of phenolic compounds, including phenolic acids, have also been simph-fied using mass spectrometry (MS) techniques on-hne, coupled to the HPLC equipment. The electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) interfaces dominate the analysis of phenohcs in herbs, fmits, vegetables, peels, seeds, and other plants. In some cases, HPLC, with different sensitivity detectors (UV, electrochemical, fluorescence), and HPLC-MS are simultaneously used for the identification and determination of phenolic acids in natural plants and related food products.In some papers, other spectroscopic instmmental techniques (IR, H NMR, and C NMR) have also been apphed for the identification of isolated phenolic compounds. 

Williams DT, Tran Q, Fellin P, et al. 1991. Evaluation of gas chromatography-Fourier transform infrared spectroscopy-mass spectrometry for analysis of phenolic compounds. J Chromatog 549(1-2) 297-311. 

As mentioned above in the context of the analysis of hgnin degradation products, gas chro-matography/mass spectrometry and related methods have been developed as extremely powerful tools for the identification of phenolic compounds. Use of high-pressure liquid chromatography in combination with mass spectrometry adds to the analytical arsenal with respect to the detection of polar, non-volatile compounds but, in particular, the advent of modem ionization techniques, such as ESI and MALDI mass spectrometry, have continued to broaden the analytically governable field of organic chemistry. The latter methods diminish the need of derivatization of polar phenolics to increase the volatility of the analyte. In this section, a more or less arbitrary selection of examples for the application of mass spectrometric techniques in analytical chemistry is added to the cases already discussed above in the context of gas-phase ion chemistry. 

J. Kronholm, P. Revilla-Ruiz, S.P. Porras, K. Hartonen, R. Carabfas-Martfnez and M.-L. Riekkola, Comparison of gas chromatography-mass spectrometry and capillary electrophoresis in analysis of phenolic compounds extracted from solid matrices with pressurized hot water, J. Chromatogr. A. 1022, 9, 2004. 

Alarcon-Flores, M. L, Romero-Gonzalez, R., Garrido-Frenich, A., and Martfnez-Vidal, 1. L. 2012. Analysis of phenolic compounds in olive oil by solid-phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry. Food Chem. 134 2465-2472. 

The role of advances in chromatographic techniques has been a step point in the development of phytochemistry [67]. Because of the complexity of crude herbal extracts, various online hyphenated techniques have been developed for the analysis of the complex mixtures. These techniques include liquid chromatography (LC), mass spectrometry (MS), LC nuclear magnetic resonance (NMR), and LC-NMR-MS [68]. They facilitate the structure determination of unknown constituents in crude extracts. For example, they are of great applicability in the analysis of flavonoids and other phenolic compounds [69, 70]. 

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