Phenolic compounds measuring

Future plans call for the incorporation of a microprocessor into the spectrometer to provide instrument control and to act as an interface with a microcomputer that can be used for data storage and analysis. The objective is the development of portable, real-time instruments, such as a monitor for measuring phenolic compounds and/or alkyl naphthalenes in wastewater. 

Procedure. Dissolve the sample in distilled water and take an aliquot which should contain not more than 50 pg of phenolic compound. Use the aqueous ammonia to adjust the pH of the solution to 9.7-10.3 (pH meter), and then dilute to 500 mL with distilled water. Transfer the solution to a large separatory funnel, add 1.0 mL of solution A followed by 10 mL of solution B. Shake well to ensure thorough mixing, and then carry out three extractions with successive portions of 15 mL, 10 mL and 5 mL of chloroform (trichloromethane). Combine the chloroform extracts and make up the volume to 30 mL. Measure the absorbance of the extract against a blank of chloroform at a wavelength of 460 nm (blue filter), using 1 cm cells. The colour may tend to fade after 10 minutes and so speed is essential. 

The allelopathic effects of dominant plants on other plants in phytocoenosis are caused by phenolic phytotoxins present in all parts of plants, but the highest amount of these compounds is accumulated in the leaves. Leaves of dominant trees represent the main components of the litter in the forest, thus analysis of phenolic compounds and measurements of their content in leaves and leaf litter is considered as very important. 

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. 

Various analyzers have been used to analyze phenolic compounds. The choice of the MS analyzer is influenced by the main objective of the study. The triple quadrupole (QqQ) has been used to quantify, applying multiple reaction monitoring experiments, whereas the ion trap has been used for both identification and structure elucidation of phenolic compounds. Moreover, time-of-flight (TOF) and Fourier-transform ion cyclotron resonance (FT-ICR) are mainly recommended for studies focused on obtaining accurate mass measurements with errors below 5 ppm and sub-ppm errors, respectively (Werner and others 2008). Nowadays, hybrid equipment also exists, including different ionization sources with different analyzers, for instance electrospray or atmospheric pressure chemical ionization with triple quadrupole and time-of-flight (Waridel and others 2001). 

Several compounds can be oxidized by peroxidases by a free radical mechanism. Among various substrates of peroxidases, L-tyrosine attracts a great interest as an important phenolic compound containing at 100 200 pmol 1 1 in plasma and cells, which can be involved in lipid and protein oxidation. In 1980, Ralston and Dunford [187] have shown that HRP Compound II oxidizes L-tyrosine and 3,5-diiodo-L-tyrosine with pH-dependent reaction rates. Ohtaki et al. [188] measured the rate constants for the reactions of hog thyroid peroxidase Compounds I and II with L-tyrosine (Table 22.1) and showed that Compound I was reduced directly to ferric enzyme. Thus, in this case the reaction of Compound I with L-tyrosine proceeds by two-electron mechanism. In subsequent work these authors have shown [189] that at physiological pH TPO catalyzed the two-electron oxidation not only L-tyrosine but also D-tyrosine, A -acetyltyrosinamide, and monoiodotyrosine, whereas diiodotyrosine was oxidized by a one-electron mechanism. 

Meta-analysis of 48 tests, where induction of phenolic compounds after artificial or natural wounding was measured, revealed a marginally significant, positive mean effect size (Fig. 3.2a). Positive effect sizes indicate larger concentrations of phenolics in the wounded algae, i.e., induction of phenolics. The mean effect sizes... 

By careful choice of both the reaction conditions and the phenolic compound used, it may be possible to produce a colour that is characteristic of a particular carbohydrate or related group, so giving some degree of specificity to the method. Thus, Seliwanoff s test uses hydrochloric acid and either resorcinol or 3-indolylacetic acid to measure fructose with minimal interference from glucose. The colour produced by pentoses with orcinol (Bial s reagent) or p-bromoaniline is sufficiently different from that produced by hexoses to permit their quantitation in the presence of hexoses. However, none of the methods based on the formation of furfural or its derivatives can be considered to be entirely specific. 

PEPPERMINT PHENOLIC COMPOUNDS SEPARATED BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY (RT1 AND RT2 = RETENTION TIMES IN MIN MEASURED IN GRADIENTS 1 AND 2)... 

RP-HPLC has been employed for the determination of flavonoids and other phenolic compounds in cranberry juice. The neutral and acidic analytes were preconcentrated octadecyl silica SPE cartridges conditioned with distilled water (neutral analytes) or with 0.01 M HC1 (acidic compounds). Hydrolysis of samples was carried out in aqueous methanol solution acidified with 6 M HC1 at 35°C for 16h. Chromatographic separation was performed in an ODS column (150 X 4.6mm i.d. particle size 5/.an). Solvents A and B were water-acetic acid (97 3, v/v) and methanol, respectively. The gradient started with 0 per cent B (flow rate, 0.9 ml/min), reached 10 per cent B in lQmin (flowrate, 1.0 ml/min) and increased to 70 per cent B in 40min (flowrate, 1.0 ml/min). Analytes were detected at 280 and 360 nm. Some typical chromatograms are presented in Fig. 2.71. The concentrations of flavonoids and phenolic acids are compiled in Table 2.69. It was stated that the SPE-HPLC procedure makes possible the simultaneous determination of phenolic compounds and flavonoids, therefore, it can be employed for the measurement of these classes of analytes in other fruit juices [188],... 

It was suggested that the method can be used for the measurement of phenolic compounds not only in wines but also in other alcoholic beverages such as beers and liqueurs [193],... 

Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rates of phenol were 525 mg/kg of pine burned, 300 mg/kg of oak burned, and 434 mg/kg of eucalyptus burned. 

Lin et al. ( 6) measured the emulsion capacity of defatted sunflower seed products. Data in Table VII show that sunflower flour was superior in emulsifying capacity to all other products tested. The emulsions were in the form of fine foams and were stable during subsequent heat treatments. The diffusion-extraction processes employed to remove phenolic compounds dramatically reduced emulsion capacity, although isolating the protein improved emulsion capacity to some extent. 

A postchromatographic -glucuronidase procedure has been also used for the analysis of phenolic glucuronides, such as those produced from trimethoprim (274). The enzymatic analysis of these glucuronides provided the production of the corresponding phenolic compounds, which were measured by both UV and electrochemical detection. 

Several studies have described a relationship between the activity of PAL in iceberg lettuce leaf tissue and the development of RS symptoms [141-146]. Hyodo et al. [141] observed that an ethylene-induced increase in PAL activity parallelled the appearance of RS symptoms. These researchers also measured an increase in total phenolic compounds. It has been proposed that ethylene induces PAL activity and the resulting accumulation of phenolic compounds in cells leads to their discoloration and eventual death [141,143,145]. 

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