Phenolic compounds detection methods

Country Extraction Method Phenolic Compounds Detection Method Method... 

In the 1990s hplc has become widely used in the flavor and fragrance industry to measure vanillin and other phenolic compounds. Routine methods have been developed that are particularly adapted to thermosensitive products, such as vanillin and its derivative products, with elution gradient and uv detection at given wavelengths. Certain critical impurities can thus routinely be traced to very low (10 ppm) concentrations. 

Current official analytical methods for phenolic compound detection imply separation steps (liquid-liquid extraction or solid-phase extraction for liquid samples and Soxhlet extraction for solid samples) followed by chromatography using different detection devices, where they may require also a derivatization step. Unfortunately, these methods may require expensive and hazardous organic solvents, which are undesirable for health and disposal reasons in addition, the analysis is labour intensive and takes long time. Hence, there is a general trend to find alternatives that may also be utilizable for on-site 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). 

Phenolic compounds of dominant plants (donor plants) in plant community have inhibitory effects on photosynthesis of target plants. Methods of the photosynthetic efficiency (Fv/Fm) measurement, the extraction, detection and measurement of chlorophyll (a, and b) are described. 

New detection methods of phenolic compounds are being developed. Based on the principle of the enzyme-linked immunosorbent assay (ELISA), a method has been developed to quantify phenolic compounds such as isoflavones (Vergne and others 2007). 

The Environmental Health Laboratory Sciences Division of the National Center for Environmental Health, Centers for Disease Control and Prevention, is developing methods for the analysis of endrin and phenolic compounds in urine. These methods use high resolution GC and magnetic sector MS which gives detection limits in the low parts per trillion (ppt) range. 

The retention times, limit of detection and repeatabilities of the analytes are compiled in Table 2.59. It has been concluded from the results that this easy-to-carry-out method can be used even in routine laboratories for the quantitative analysis (UV detection) and for the identification (ESI-MS) of this class of phenolic compounds in various complicated matrices [164]. 

Until recently, most of the chemical research on the contents of these structures was directed at the identification of the constituents of castoreum. In the late 1940s Lederer [72, 73] identified 36 compounds and some other incompletely characterized constituents in castoreum of uncertain origin. Other constituents were subsequently identified in the material [74-77]. In a reinvestigation aimed specifically at the phenol content of the material, Tang et al [69] identified 10 previously unreported phenols in the castoreum from the North American beaver, Castor canadensis. Of the 15 phenols reported elsewhere, only five were confirmed in this analysis, in addition to 10 phenolic compounds that were not reported elsewhere. It was concluded that the 10 previously identified phenols that were not found in the study by Tang et al. were either absent or were not volatile enough to be detected by the methods employed. This was most probably because a relatively low maximum column temperature of only 210 °C was employed in the GC-MS analyses. The compounds identified by Lederer,... 

Methods used for the detection of PAs in cmde or partially purified extracts can also be adapted for post-column analysis after fractionation (see below). Direct quantitative analysis of PAs in crude grape phenolic extracts is often impossible due to the complex sample matrix. Thus, fractionation or purification is often necessary before analysis. The Folin-Ciocalteu and Pmssian Blue assays are widely used for the quantification of total polyphenols in plants [27,28]. These methods are not specific for PAs due to the reaction of other phenolic compounds with these reagents. 

Phenolic compounds in Sicilian wines were directly detected by La Torre et al. [373] using an HPLC with a DAD coupled on-line with a MS system equipped with ESI source operating in the negative-ion mode and a quadruple mass analyzer. The structure was elucidated by recording MS spectra at different voltages, in addition to the molecular mass information. The method allowed both the identification and determination of 24 phenolic compounds in 22 different commercial Sicilian red wines by direct injection without any prior purification of the sample. Figure 19.10 reproduced an HPLC trace obtained in this work. 

A rather sensitive RP-HPLC method combined with UV (270 nm) and ESI-MS detection has been established for the determination of flavonoids and other phenolic compounds in various biological matrices.LODs based on UV data of flavonoids in onion and soybean were 6 to 42 pmol injected, which corresponded with analyte concentrations of 0.08 to 0.63 mg/... 

The variety of detection modes available for HPLC analysis that provide additional information about the eluent as it exits the column greatly facilitates unknown characterization. The majority of analytical methods for phenolic compounds includes HPLC with spectrophotometric-based detection techniques (UV absorption, fluorescence, photo diode array—PDA) as well as HPLC with electrochemical detection. 

P Hayes, MR Smyth, I McMurrough. Comparison of electrochemical and ultraviolet detection methods in high-performance liquid chromatography for the determination of phenolic compounds commonly found in beers. Part 1. Optimization of operating parameters. Analyst 112 1197-1203, 1987. 

Freon-113 (l,l,2-trichloro-l,2,2-trifluoroethane) was employed as a reagent gas in a NICI investigation on phenolic compounds in order to detect the phenolic acid fractions of coal-derived liquids. These fractions were evaporated into the ion source through a direct inlet probe. The method is based on the chloride attachment reaction leading to the almost exclusive formation of the [M + Cl]- adducts, which allow the relative molecular mass profiles to be obtained336. 

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