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A thin-layer chromatographic (TLC) method has been used for determination of phenolic compounds in two samples of wine commercially available in Croatia. Sample preparation was by liquid-liquid extraction with diethyl ether at pH 2.0. Extracts and standard solutions were applied to 20 cm × 20 cm silica gel 60 F 254 TLC plates. After treatment of the developed plates with ammonia vapor, phenolic compounds were detected on chromatograms by their colors or by fluorescence in UV light at λ = 244 nm and at λ = 366 nm before and after spraying with 1% ethanolic AlCl 3 . The efficiency of eleven mobile phases was tested by three mathematical techniques — calculation of the information content ( I ) derived from Shannon’s equation, determination of discriminating power ( DP ), and formation of clusters and dendrogram. It was shown that the best mobile phase for separation of phenolic compounds in the wine extracts was benzene-ethyl acetate-formic acid, 30 + 15 + 5 ( v / v ). Six phenolic compounds were identified in the tested samples.

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Abstract  

The possibility of preparation of comparison standards for activation analysis on a base of phenol-formaldehyde polymer has been shown. This polymer contains only a small amount of neutron-sensitive impurities. The suggested standards may be prepared in large amounts under laboratory conditions.

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Abstract  

The effect of phenols on the ion-pair extraction of chromium(VI) as chromate anion (HCrO 4 ) with tetraphenylarsonium cation (TPA+) has been investigated. By using TPACl, chromate is extracted as an ion-pair, TPA+·HCrO 4 , into organic solvents, but its extractability into nonpolar solvents such as carbon tetrachloride is very low. The addition of several phenols greatly enhances the extractability, e.g., the distribution ratio of chromium(VI) between carbon tetrachloride and water rises 5500-fold in the presence of 0.020M 3,5-dichlorophenol in the organic phase. The enhancement was larger when using more acidic phenols and less polar solvents. From the analysis of the extraction data for the 3,5-dichlorophenol-carbon tetrachloride system, it was shown that one molecule of chromate is extracted together with one TPA+ and 1–3 phenol molecules and the extraction constants were determined. The UV spectrum indicated the extracted species including chromate ester to the TPA+·ArOCrO 3 ·mArOH (m=1,2).

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Abstract  

We reported the synthesis and labeling of one tetradentate and two pentadentate amino-phenol ligands with technetium-99m by the direct pertechnetate addition and by ligand exchange methods. Labeling by direct pertechnetate addition was attended by adding pertechnetate eluate to the ethanolic solution of the amino-phenol ligands at pH 9. Stannous chloride dihydrate was used as reducing agent. Exchange studies were carried out via the use of the following 99mTc-chelates: 99mTc-DTPA, 99mTc-gluconate, 99mTc-tartrate and 99mTc-citrate complexes. Ligand exchange method was achieved by incubation the ligand solutions with 99mTc-co-ligands complexes in 0.05M bicarbonate buffer pH 9. At this pH value the 99mTc-co-ligands dissociated and the more stable new 99mTc-ligands were formed with high radiochemical yield 95%. The radiochemical yield of 99mTc-labeled amino-phenol ligands were estimated by solvent extraction, electrophoresis and HPLC methods. The produced technetium-99m amino-phenol complexes were neutral, lipophilic and stable during the period of 24 hours.

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Abstract  

The immersion enthalpies of modified activated carbons were determined, with commercial CarbochemTM–PS230 (CAG) as the initial activated carbon, which was modified by: chemical treatment with HNO3 7 mol L−1 (CAO) and thermal treatment under flow of H2 (CAR) in function of the adsorbed quantity of monohydroxilated phenols, catechol, resorcinol and hydroquinone at a pH of 7 in aqueous dissolutions in order to characterize the solid–solution interaction and evaluate the influence of the chemical characteristics of the activated carbon in the phenol adsorption. The results show a variation in the immersion enthalpy in function of the adsorbed quantity of phenol and the initial dissolution concentration; which shows that the intensity of the interaction changes in function of the composition of the liquid phase. The immersion enthalpies present the following arrangement: catechol > resorcinol > hydroquinone, with a −ΔHinm of 35.7; 30.8 and 24.6 Jg−1, respectively, at a pH of 7 for a 100 mg L−1 phenol monohydroxilated solution.

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Acta Alimentaria
Authors: J. Piljac-žegarac, S. Martinez, L. Valek, T. Stipčević, and K. Kovačević-Ganić

The Folin-Ciocalteu (FC) test and cyclic voltammetry (CV) at a glassy carbon electrode were used to quantify phenolic antioxidants in a set of 17 Croatian wines and express them in gallic acid (GAE) and catechin equivalents (CE). The total phenolic index (TPI) values for red wines expressed in GAE ranged from 18.851 to 26.905 mM, while TPI for white wines ranged from 1.722 to 2.869 mM. The levels of phenolics derived from CV measurements were markedly lower than those of TPI, since these values include only those phenolic compounds that get oxidised up to 500 mV and contain ortho -diphenol and triphenol groups.The free radical scavenging ability of the same set of wines was evaluated according to the Brand-Williams assay and expressed in equivalents of catechin, gallic acid, vitamin C and Trolox. Ivan Dolac barrique 2002 exhibited the highest antioxidant activity. The DPPH radical scavenging ability of the wines was also evaluated and correlated to the TPI values. Better correlation was observed between the TPI and the antioxidant activity for red wines (r 2 =0.826) as opposed to white wines (r 2 =0.686). The highest correlation (r 2 =0.970) was found between the TPI and the antioxidant activity measured when the whole set of samples was considered.

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Separation selectivity has been optimized in two-dimensional thin-layer chromatography (2D TLC) by connecting diol or silica plates (on which NP chromatograms were developed) to RP-18W plates (on which reversed-phase chromatograms were developed). Retention of test substances was investigated to select optimum chromatographic systems for separation of selected phenolic compounds by 2D TLC. Selection of optimal mobile phases was performed on the basis of plots of retention against mobile phase composition. The next step of the optimization was calculation of statistical data for correlation of R M values for pairs of chromatographic systems — NP diol-RP C 18 or silica-RP C 18 . Orthogonal chromatographic systems were selected on the basis of these correlations and used to separate phenolic compounds present in plant extracts. For example, extracts from Polygonum sp. and Verbascum sp. were separated by use of optimum 2D TLC systems.

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This study was designed to develop a simple, sensitive, selective, and precise high-performance thin-layer chromatography (HPTLC) fingerprint and quantitative estimation method for the analysis of three phenolic compounds from nine Leucas species. The developed HPTLC method was validated according to the International Conference on Harmonization guidelines. The method permits reliable quantification of one important phenolic acid (gallic acid) and two hydroxycinnamic acids (caffeic and ferulic acids) in 50% hydroethanolic extracts on silica gel with toluene—ethyl acetate—formic acid 8:2:1 (v/v) as the mobile phase. The system showed good resolution and separation of caffeic, ferulic, and gallic acids (at R f values 0.48, 0.60, and 0.30, respectively) from the other constituents of the extract. Densitometric scanning was done at 300 nm in absorbance mode. All the results obtained by the developed method were statistically compared for validation parameters, for accuracy and good precision. Caffeic, ferulic, and gallic acids were estimated in all the aforesaid nine Leucas species, but the quantity varied from species to species. Further, these phenolics were reported from the aforesaid Leucas species for the first time, except for Leucas lanata and Leucas urticifolia. However, Leucas biflora, Leucas decemdentata, and Leucas stricta were documented for their chemical constituents for the first time. The proposed HPTLC method can be used for routine quality testing of Leucas species.

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Dendrophthoe falcata (Linn. f.) Etting. is a stem parasite commonly known as ‘ Vanda ’ in the Ayurvedic system of medicine. A TLC method has been established for simultaneous identification and quantification of phenolic compounds in different parts of this plant. Chromatography was performed on silica gel with tolueneethyl acetate-formic acid 6:4:1 ( v/v ) as mobile phase, and characteristic bands of (+)-catechin, ellagic acid, quercetin, and ferulic acid were observed at R F 0.35, 0.41, 0.63, and 0.66, respectively. The method was validated for precision, repeatability, and accuracy. The method enables reliable quantification with good resolution and separation from other constituents of the plant extract. The accuracy of the method was checked by measuring recovery of all four phenolic compounds at three different concentrations and by matching the spectra of reference markers with those of the corresponding bands in the extract at three different positions, i.e. the start, apex, and end positions of the band. The presence and quantity of these phenolic compounds varies from part to part of this parasitic plant. For example, quercetin was present only in the leaves, ferulic acid in the stem, and ellagic acid and (+)-catechin in stem and root. More (+)-catechin and ellagic acid were found in the stem than in the root.

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Commelina benghalensis (Commelinaceae) is widely used as traditional and folklore medicine in India. In the present study, a reverse-phase high-performance liquid chromatography—photodiode array detection (RP-HPLC—PDA) method was developed for the separation, identification, and quantification of bioactive phenolics. Antioxidant potential was also accessed to validate the presence of identified markers. Method was developed on C18 column with 1% formic acid (in water) and acetonitrile as solvent system, and data acquisitions were achieved at wavelength of 285 nm. The developed method was also validated for accuracy, precision, robustness, limit of detection and quantification (LOD and LOQ), repeatability, and recovery according to International Conference on Harmonization (ICH) guidelines. In this method, five phenolics, viz., protocatechuic acid (0.033%), vanillic acid (0.262%), ferulic acid (0.365%), apigenin (0.126%), and kaempferol (0.544%), were quantified in linearity range of 0.2–1.0 μg with correlation coefficient of more than 0.9949. Relative standard deviation (RSD) (%), LOD, LOQ, and recovery (%) are within the acceptable limit. Besides that, methanolic extract shows the inhibition (%) range from 24.45 to 68.75% at 0.02–0.12 mg mL−1. IC50 of extract was observed at 46.75 μg mL−1, suggesting the promising activity in methanol extract. Hence, the proposed method for simultaneous quantification of five bioactive phenolics in the tuber of C. benghalensis using HPLC–PDA detection under the specified conditions is specific and accurate, and validation proves its selectivity and reproducibility.

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