Phenols detection methods

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). 

Stalikas C. 2007. Extraction, separation, and detection methods for phenolic acids and flavonoids. J Sep Sci 30(18) 3268-3295. 

Note The presence of p nloroglucinoi can be detected by ferric chloride(blue coloration) or by other phenolic reaction methods... 

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. 

An automated flow injection analysis (FIA) system for quantifying ethanol was developed using alcohol oxidase, horseradish peroxidase, 4-amino-phenazone, and phenol. A colorimetric detection method was developed using two different methods of analysis, with free and immobilized enzymes. The system with free enzymes permitted analysis of standard ethanol solution in a range of 0.05-1.0 g of ethanol/L without external dilution, a sampling frequency of 15 analyses/h, and relative SD of 3.5%. 

To improve the quality control process of gasohol and hydrated ethanol, an automated FIA system was developed using AOD and HRP enzymes, and addition of 4-aminophenazone and phenol. A colorimetric detection method was used in two different methods of analysis, with free (4) and immobilized enzymes. Both systems have shown good results when compared with established methods such as gas chromatography (GC) and high-performance liquid chromatography (HPLC) (4,7). 

The use of NCW as the mobile phase in liquid chromatography was recently reviewed. In this area, in addition to its green credentials, NCW is compatible with a range of detection methods flame ionization detection, mass spectrometry (MS) and UV (to short wavelengths). The reason for the recent growth in this area is the development of more thermally stable stationary phases. It has been used to analyse a growing number of analytes (alkylbenzenes, phenols, ketones, carboxylic acids, amino acids, carbohydrates and some pharmaceuticals). For example, carbohydrates (monosaccharides, disaccharides and sugar... 

The most common alternative to the phenol-hypochlorite method uses OPA. This technique was introduced in an automated version based on the conversion of NH4+ to NH3, which is then allowed to diffuse across a membrane into a flowing stream of OPA to form a fluorescent product (Jones, 1991). This final product is then analyzed fluorometricaUy with a detection limit of 1.5nM (Jones, 1991). Advantages of the method are that it requires only a single reagent and it has a lower detection limit than the standard phenol-hypochlorite method. Furthermore, the salt effect is relatively small (<3% over a salinity range of 0—35 %o) and there is no interference from primary amines. The technique has been modified to remove the gas diffusion cell, also with a reported detection hmit of 1.5 nM (Kerouel and Aminot, 1997) a manual version has also been published (Holmes et al, 1999). 

Two main objectives are pursued when analytes are derivatized before GC analysis Increasing volatility and attaining enhanced sensitivity when certain detection methods are used. Derivatization methods of phenolic compounds for GC analysis have been reviewed . ... 

A study was carried out for LEE by the Soxhlet method and microwave-assisted extraction for the determination of the priority phenols in soil samples. Recoveries varied from 67 to 97% with RSD between 8 and 14% for LEE, and >70% for the MAP, except for nitrophenols that underwent degradation when the latter method was applied. LOD was from 20 ngg for 2,4-dimethylphenol to 100 ngg for pentachlorophenol. The best detection method for EC was atmospheric pressnre chemical ionization MS (APCI-MS). The most abnndant ions obtained by this detection method were [M — H] for the lowly chlorinated phenols and [M — H — HCl] for tri-, tetra- and pentachlorophenols . 

Comparative studies were carried out to determine the efficiency of the various detection methods in the analysis of phenolic compounds. On-line SPE of sixteen priority phenol pollutants in water on polystyrene was followed by HPLC separation and detection. The sensitivity of ELD was higher than that of UVD. LOD down to the ppt level was attained by ELD on 100 mL samples for all the chorinated phenols however, nitrophenols could not be equally determined because they require working potentials different from those... 

HPLC with TSP-MS and ISP-MS detection methods was used to identify phenolic glycoside components of olive leaves, such as oleuropein (40), directly from crude extracts . Phenolic compounds in extracts from freeze-dried olives were cleaned up by SPE and subsequently analyzed by HPLC with both fluorescence and ESI-MS detection. Oleuropein (40) was the major phenolic component in the fruit. ... 

One of the phenol determination methods described in Standard Methods , the so-called phenol index nnmber, inclndes all, water stream distillable, phenolic compounds, which are detected photometrically after derivatization with 4-aminoantipyrine and extraction with chloroform . Here, only the total amonnt of phenols is measnred. It is impossible to distingnish between individnal phenols or to estimate the probable toxicity of the analyzed water sample. This method is important only for preliminary information about possible phenol pollution and to determine if further tests are necessary. 

In comparison to equivalent optical detection methods using whole cell biosensors for water toxicity detection, these results proved to be more sensitive and produce faster response time. Concentrations as low as 1% of ethanol and 1.6 ppm of phenol could be detected in less than 10 min of exposure to the toxic chemical, whilst a recent study [11] which utilized bioluminescent E.coli sensor cells, detected 0.4 M (2.35%) ethanol after 220 min. An additional study [1] based on fluorescent reporter system (GFP), enabled detection of 6% ethanol and 295 ppm phenol after more than one hour. Cha et al [12] used optical detection methods of fluorescent GFP proteins, detected 1 g of phenol per liter (1,000 ppm) and 2% ethanol after 6 hours. Other studies [13] could not be directly compared due to different material used however their time scale for chemicals identification is hours. 

Procyanidins can usually not be completely separated from each other, from phenolic acids and from accompanying flavonoids by sample clean up and/or chromatographic procedures. The differentiation between these individual compounds can therefore only by accomplished by the selectivity of a suitable detection method. UV-DAD (ultra violet diode array detection), electrochemical and mass spectrometry detection have been used for the identification and quantitative determination of procyanidins. 

The diamagnetic products are observed and can be characterized very well because the detection method is high-resolution NMR spectroscopy. On the other hand, the signal enhancement by the CIDNP effect mitigates the inherent low sensitivity of NMR. In consequence, even diamagnetic species that are unstable and thus present only in low concentration can be captured. An early example is the enol of acetophenone formed in the photoreaction of acetophenone with phenol [45], others are vinylamines in photoinduced hydrogen abstractions from aliphatic amines [46] (see Section V.B) and in the sensitized photoreactions of amino acids (Section V.G.l). 

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