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Abstract  

The influence of polysorb on the quantitative characteristics of stationary extraction for phenol and guayacol with mixtures of tributylphosphate (TBP) and organic solvents of different classes (distribution coefficients, synergecity) was studied. Solvation numbers and constants of entering of TBP into mixed solvates were calculated both for extraction and extraction-sorption systems. Comparative study of selectivity for a mixture of extracting agents has been made relative to phenol and guayacol in the extraction and extraction-sorption systems for variable composition of mixture of solvents. Separation of phenol and guayacol is possible when applying the columns with mixed stationary phases at the stage of the extraction sorption.

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The flowering tops of Hypericum hirsutum, H. montanum, H. perforatum subsp. angustifolium, H. perforatum subsp. perforatum , and H. perforatum subsp. veronense , collected from different locations in Croatia, were investigated to determine their flavonoid, phenolic acid, and amino acid composition. Thin-layer chromatography (TLC) on silica gel was used for separation and identification of the flavonoids and phenolic acids and TLC on cellulose was used for investigation of the amino acids. By use of these procedures ten flavonoids, three phenolic acids, and sixteen amino acids were detected and identified in the samples investigated. The composition of these compounds depended on the taxa investigated and the locality. Spectrophotometric analysis of the flavonoid content indicated that the three subspecies of H. perforatum are richer in flavonoids than H. hirsutum and H. montanum. H. perforatum subsp. perforatum is the richest in flavonoids, phenolic acids, and amino acids. This is the first time these biologically active compounds have been identified in the some Hypericum taxa.

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Acta Chromatographica
Authors: A. Machalska, K. Skalicka-Woźniak, J. Widelski, K. Głowniak, G. Purevsuren, Z. Oyun, D. Khishgee, and B. Urjin

Summary

Five species of Iris commonly used in Mongolian traditional medicine (Iris dichotoma Pall., Iris flavissima Pall., Iris bungei Maxim., Iris lactea Pall., and Iris tenuifolia Pall.) were analyzed for the presence of phenolic acids. This was the first study of the phenolic acid content of these species. Samples containing the phenolic acids were prepared by the method of Świcatek and then analysed by HPLC with UV-visible diodearray detection (DAD). Identification was performed by comparing retention times with those of standards. Quantitative determination was performed at the absorbance maximum of each phenolic acid (320 nm for ferulic, p-coumaric, and caffeic acids, 280 nm for trans-cinnamic, syringic, and gallic acids, and 254 nm for vanillic, m-hydroxybenzoic, p-hydroxybenzoic, and protocatechuic acids). As the result of our study ten phenolic acids, both free and liberated by alkaline and acid hydrolysis, were identified by HPLC. Chromatographic investigation revealed the presence of vanillic acid, protocatechuic acid, trans-cinnamic acid, p-hydroxybenzoic acid, p-coumaric acid, ferulic acid, gallic acid, syringic acid, m-hydroxybenzoic acid, and caffeic acid. Quantitative analysis of these acids was also performed. Finally, the presence or absence of some phenolic acids after alkaline or acid hydrolysis was also observed.

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TLC and HPLC have been used for preliminary evaluation of the phenolic acids occurring in the leaves, inflorescences, and rhizomes of Silphium perfoliatum L. Free phenolic acids and those released after acidic and basic hydrolysis were subjected to chromatographic analysis. Qualitative TLC analysis was performed by one- and two-dimensional ascending development on plates coated with cellulose, polyamide 11 F 254 , and silica-gel 60 F 254 . Reversed-phase HPLC was performed with photodiode-array detection.Seven phenolic acids were present, in the free and bonded forms, in the raw material studied. Caffeic and protocatechuic acids occurred in all the fractions analyzed. p -Coumaric and p -hydroxybenzoic acids were identified in all the free phenolic acid fractions. Ferulic acid was found in inflorescences and rhizomes and vanillic acid in leaves and inflorescences. After acidic hydrolysis chlorogenic acid was identified in leaves and p -hydroxybenzoic and vanillic acids in inflorescences. After basic hydrolysis phenolic acid fractions isolated from leaves also contained p -coumaric acid; those isolated from inflorescences contained p -coumaric, ferulic and p -hydroxybenzoic acids. It was found that caffeic acid was the most predominant phenolic acid in S. perfoliatum (from 67.8% in the leaves to 94.4% in the rhizomes).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Macášek, V. Mikulaj, P. Rajec, R. Čech, L. Mátel, R. Kopunec, J. Kuruc, and A. Švec

Abstract  

Radiolytical decomposition of phenol was investigated at60Co gamma irradiation (1–2 Gy·s–1, 10 kGy) of pre- and continuously aerated aqueous solutions at concentrations of phenol 1–100 mg· ·dm–3 and in the presence of sodium hydroxide, sulphuric acid, sodium and ferrous sulphate, formaldehyde, 2-propanol,n-hexane, xylene, benzene, and commercial gasoline. From the decomposition rate at doses 50–400 Gy, a phenomenological model of linear relation between the dose acquired for 37% decomposition (D 37), initial concentration (g·m–3) of phenol (p 0) and of an admixture (s 0) was confirmed in the formD 37=52f tr(p 0+f eq s 0), wheref's are constants which can be attributed to the relative transformation resistance of phenol towards the OH radicals in given matrix (f tr, for pure waterf tr=1) and relative acceptor capacity of competing substrate (f eq). In real wastewaters, the efficient decrease of phenols content may be substantially lower than that in model solutions, obviously due to radiation oxidation of aromates, as proved by irradiation of aqueous solutions of benzene. Technical and economical feasibility of the process is discussed.

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Summary

Pomegranates (Punica granatum) have been known for centuries for their healing properties. The phenolic components of pomegranate are believed to be responsible for their antioxidant activities, hence playing a major role in reducing oxidative stress-related disease, such as cardiovascular diseases, cancer, and neurodegenerative diseases. In this study, thin-layer chromatography (TLC) was used to, first, separate and identify the phenolic constituents of pomegranate juice and, second, to assess the antioxidant efficacies of the identified compounds. Different oxidant and hydroxyl radical generating systems (Fe3+, Cu2+, H2O2, Fe2+-H2O2, and Cu2+-H2O2) were used in assessing the efficacies of phenolic compounds found in pomegranate juice. A 10 × 10 cm and 20 × 20 cm sized silica gel 60 F254 TLC plates with toluene-ethyl acetate-formic acid (60:40:10 v/v/v) as a mobile phase were used for the chromatographic separation. Two compounds, ellagic acid and gallic acid, were separated and identified. When pomegranate juice was challenged with the oxidant systems, it was observed that the phenolic compounds slowly disappeared in a concentration- and time-dependent manner. From the results, it was concluded that gallic acid had a higher antioxidant efficacy than ellagic acid. TLC has been applied for the first time to outline the antioxidant profile of pomegranate juice and assess the efficacies of phenolics using different oxidant systems, including redox-active metals and H2O2.

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New rocket insulator compositions have been studied by adding various types and amounts of fillers, such as graphite and asbestos fibres, Al2O3, MgZrO2, Cr2O3, SiC, carbon powders and phenolic resin to the base EPDM gum and graphite, kevlar,E type glass fibres to the base phenolic resin in order to improve thermal and ablative efficiency. The degradation of the insulators has been investigated by thermogravimetry (TG) analysis to 900°C and DSC analysis to 500°C. Conversion curves of the insulators at different heating rates were performed and maximum degradation temperatures were found as 646 and 661°C for EPDM P and phenolic resin, respectively. The kinetic parameters for degradation have been evaluated and the lifetime of the rocket insulators has been estimated. Thermal analysis has been conducted on the insulators and the indepth temperature distribution was evaluated in order to find optimum insulation thickness.

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The chromatographic behavior of some phenolic compounds has been studied with the objective of understanding the role of cyano groups in the processes of chromatographic separation on thin layers of CN-silica gel. For this purpose separations were performed on thin layers of CN-silica gel, unmodified silica gel, and polyacrylonitrile adsorbent (PANS) using fourteen mobile phases, nine of which resulted in normal-phase systems. On the basis of the results obtained the effect of compound structure (i.e. properties of ortho substituents of the compounds separated) on their retention is discussed. The dependence of the order of retention of the phenols on the properties of the adsorbent was also considered. Plots of retention data ( R M against R M ) determined by use of different chromatographic systems were used to characterize the systems used. The results enabled hypotheses to be formulated about possible mechanisms involved in the separations of the phenols on these adsorbents.

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Abstract  

The effect of the ionic environment on the adsorption of phenol from aqueous solutions was investigated in a microporous carbon and in an oxidized carbon. It was found that not only the pH of the solution but also the method of its setting affects the adsorption capacity. Thermal desorption of phenol exhibits an even stronger dependence on the method of pH setting than adsorption. The TG response, the position and the corresponding TG steps are also influenced by the surface chemistry. Thermogravimetry is found to be outstandingly useful and informative technique for the studying sorption interactions.

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Abstract  

Cumene hydroperoxide (CHP) being catalyzed by acid is one of the crucial processes for producing phenol and acetone globally. However, it is thermally unstable to the runaway reaction readily. In this study, various concentrations of phenol and acetone were added into CHP for determination of thermal hazards. Differential scanning calorimetry (DSC) tests were used to obtain the parameters of exothermic behaviors under dynamic screening. The parameters included exothermic onset temperature (T 0), heat of decomposition (ΔH d), and exothermic peak temperature (T p). Vent sizing package 2 (VSP2) was employed to receive the maximum pressure (P max), the maximum temperature (T max), the self-heating rate (dT/dt), maximum pressure rise rate ((dP/dt)max), and adiabatic time to maximum rate ((TMR)ad) under the worst case. Finally, a procedure for predicting thermal hazard data was developed. The results revealed that phenol and acetone sharply caused a exothermic reaction of CHP. As a result, phenol and acetone are important indicators that may cause a thermal hazard in the manufacturing process.

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