Some applications of ligand-exchange-II Separation of phenolic compounds

The separation of phenol, 2-nitrophenol, 2,4-dichlorophenol and pentachlorophenol by ligand-exchange chromatography was studied with Chelex 100 resin in the Fe(3+) form as stationary phase and sodium hydroxide solution (pH 7.5, 11.5, 12) as the mobile phase.     

Extraction and concentration of phenolic compounds from water and sediment

Continuous liquid—liquid extractors are used to concentrate phenols at the μg l^-1 level from water into dichloromethane; this is followed by Kuderna—Danish evaporative concentration and gas chromatography. The procedure requires 5 h for 18 l of sample water. Overall concentration factors around 1000 are obtained. Overall concentration efficiencies vary from 23.1 to 87.1%. Concentration efficiencies determined by a batch method suitable for sediments range from 18.9 to 73.8%.     

Extraction of phenolic compounds from environmental water samples using oil-in-water emulsions

A fast, sensitive and simple oil-in-water emulsion (OWE) method was developed for extraction of four phenolic pollutants in environmental water samples followed by gas chromatography and flame ionization detection. In this method, the density of a binary organic solvent (one heavier and one lighter than the sample) was balanced with the density of the sample solution. A stable emulsion was formed at room temperature under vigorous stirring using a Teflon-coated magnetic stirring bar. After addition of 10 µL of the heavier organic solvent and centrifugation, phase separation occurred. The influence of several important parameters on the extraction efficiency of phenolic compounds was evaluated. Under optimized experimental conditions, the calibration graphs were linear in the concentration range 0.025–20 mg L^?1 with coefficients of determination more than 0.9994. The limits of detection and quantification were in the range 19.2–76.0 and 64.1–251.0 μg L^?1, respectively. Intra-day and inter-day precisions were less than 5.0 %. The procedure was used for the determination of phenolic compounds in spiked water samples with good results. Recoveries range from 96.5 to 103.0%, and relative standard deviations are <2.5% (for n?=?3).     

Various applications of liquid chromatography-mass spectrometry to the analysis of phenolic compounds.

Different options of liquid chromatography-mass spectrometry were used to establish the most suitable ion source and conditions to analyse or detect some low-molecular mass phenols, flavan-3-ols, and apply such conditions to a complex sample (wine). Data presented in this work confirm the great utility of atmospheric pressure-ionisation electrospray mass spectrometry coupled to HPLC for analysis of phenolic compounds, under negative mode in the case of low-molecular mass phenols, and under both positive and negative modes in flavan-3-ol compounds. A fragmentor voltage of 60 V could be the most suitable for analysing the compounds under study.     

Recovery of phenolic compounds from grape seeds: effect of extraction time and solid-liquid ratio

The aim of this research was to study the recovery of phenolic compounds from grape seeds, by-products from winemaking industries, using ethanolic solid-liquid extraction. For such a purpose, the combined effects of the extraction time (9, 19 and 29?h) and the solid-liquid ratio (0.10, 0.20 and 0.30?gdw?mL(-1)), were investigated (where dw?=?dry waste). Results demonstrated that Pinot Noir seeds had high levels of both total polyphenols (73.66?mg(Gallic Acid Equivalent)?gdw(-1)) and flavonoids (30.90?mg(Catechin Equivalent)?gdw(-1)), being the optimum extraction time 19?h approximately. The main phenolic compounds analysed with high performance liquid chromatography were catechin and quercetin with a maximum extraction yield obtained at 29?h (362.23 and 339.35?mg/100?gdw, respectively). Concentration of the polyphenols and their antiradical powers are demonstrated to have a significant linear correlation.     

Two new phenolic compounds from Artemisia sphaerocephala

Two new phenolic compounds were isolated from whole plant of Artemisia sphaerocephala. The structures were elucidated on the basis of spectroscopic methods as 4-(1-hydroxylethyl)-phenol-1-O-b-D-glucopyranoside and 4-O-acetophenone-b-D-gluco- pyranosyl-(1-3)-b-D-glucopyranoside.     

Two new phenolic compounds from Ardisia gigantifolia

Two new compounds were isolated from the 60% ethanol extract of the dried rhizome of Ardisia gigantifolia Stapf. The structures were elucidated on the basis of spectroscopic methods as （＋）-5-（1,2-dihydroxypentyl）-benzene- 1,3-diol and （-）-5-（1,2- dihydroxypentyl）benzene- 1,3-diol.     

Ultrasound assisted extraction of phenolic compounds from grapes

A new ultrasound-assisted extraction method was developed for the determination of phenolic compounds present in grapes. Several extraction variables including extraction temperature (0–75 °C), output amplitude (20, 50 and 100%), duty cycle (0.2 s, 0.6 s and 1 s), the quantity of sample (0.5–2 g), and the total extraction time (3–15 min) were evaluated. One of the most widely used extraction methods of polyphenol extraction has been used as reference method. Three parameters were compared: total amount of phenolic compounds, total amount of anthocyanins and total amount of tannic components. The resulting method produced similar or higher recoveries for these three parameters; however a much shorter extraction time was needed: 6 min (ultrasound assisted extraction method) instead of 60 min (reference method).     

Microwave-assisted extraction of phenolic compounds from grape seed

A microwave-assisted extraction technique was developed to optimize the extraction of phenolic compounds from grape seeds. The microwave power (300-150W) and time of extraction (20-200s) were varied during the optimization process. The polyphenol content of the resulting extracts were measured as mg of tannic acid equivalent per gram of crude extract (mg TAE/g of crude extract), using a Folin-Ciocalteau reagent. In general, neither the time nor the power had a significant effect on the overall % yield (average of 13.5%) and on the polyphenol content (392 mg TAE/g of crude extract) of the extracts. However, when the solvent polarity was changed by the addition of 10% water, the yield increased to 15.2% and the polyphenol content increased to 429 mg TAE/g of crude extract.     

Determination of phenolic compounds in waste water by solid-phase micro extraction

The solid-phase micro extraction technique (SPME) using a polyacrylate coated fibre has been examined with the aim to determine phenolic components in strong contaminated waste water. Considering the high contents and the great variety of accompanying organic material, the feasibility of SPME-GC-MS analysis has been tested. In this connection the influence of matrix components on the SPME results are discussed. EPA-604 phenols and some other phenolic components have been sampled by a polar fibre under standard conditions and in original waste water. The effects of defined concentrations of humic acids and surfactants on the recovery of phenols have been studied. The influence of other organics, e.g. hexachlorocyclohexane isomers, on the recoveries of phenols are discussed. Finally, a comparison between results of a liquid-liquid extraction and SPME describes the performance of SPME regarding the phenol analysis of strong-loaded water. Received: 13 October 1995 / Revised: 6 March 1996 / Accepted: 9 March 1996     

Determination of phenolic compounds in water using membrane inlet mass spectrometry

Two membrane inlet mass spectrometric (MIMS) methods for determining phenolic compounds in water are described and compared, namely direct analysis and analysis after acetylation of the phenolic compounds. Direct analysis of phenolic compounds in water is a very simple and rapid method and detection limits are relatively low (from 30 mug 1(-1) for phenol to 1000 mug 1(-1) for 4-nitrophenol). Analysis of phenolic compounds after aqueous acetylation is also a very simple and rapid method, and the detection limits are even two orders of magnitude lower than in the direct analysis. For example the detection limit of phenol acetate is 0.5 mug 1(-1) and that of 4-nitrophenol is 10 mug 1(-1). The acetylation method was also tested in the analysis of phenolic compounds from contaminated surface water samples.     

Determination of phenolic compounds in waste water by solid-phase micro extraction

The solid-phase micro extraction technique (SPME) using a polyacrylate coated fibre has been examined with the aim to determine phenolic components in strong contaminated waste water. Considering the high contents and the great variety of accompanying organic material, the feasibility of SPME-GC-MS analysis has been tested. In this connection the influence of matrix components on the SPME results are discussed. EPA-604 phenols and some other phenolic components have been sampled by a polar fibre under standard conditions and in original waste water. The effects of defined concentrations of humic acids and surfactants on the recovery of phenols have been studied. The influence of other organics, e.g. hexachlorocyclohexane isomers, on the recoveries of phenols are discussed. Finally, a comparison between results of a liquid-liquid extraction and SPME describes the performance of SPME regarding the phenol analysis of strong-loaded water.     

Improvement of on-line solid-phase extraction for determining phenolic compounds in water

Summary Modifying the most common design for the on-line coupling of a precolumn to reversed phase LC with diode array detection has resulted in reduction of the broadening of the peaks which results when the compounds of interest are strongly retained by a highly hydrophobic sorbent. The modification consists of the desorption of the analytes trapped on the precolumn solely by the organic solvent used to modify the solvent strength of the mobile phase. Results obtained using this design were compared with those obtained with the conventional design, with C₁₈ and PLRP-S precolumns. The performance of the system was also tested with a highly cross-linked styrene-divinylbenzene copolymer (ENVI-chrom P) precolumn for the determination of phenolic compounds in real samples. The advantages and disadvantages are discussed. Ion-pair solid phase extraction is used in order to increase the breakthrough volumes of more polar compounds, mainly phenol. The use of the new design enables phenolic compounds to be determined at the low μg L⁻¹ level with limits of detection ranging between 0.1 and 2 μg L⁻¹ in tap water when a 10 mL sample was analyzed.     

New phenolic compounds from the leaves of Artocarpus heterophyllus

One new 2-arylbenzofuran derivative, artocarstilbene B(1), one new benzaldehyde derivative,(E)-3,5-dihydroxy-4-(3-methylbut-1-enyl)benzaldehyde(2), as well as 18 known compounds(3–20) were obtained from the leaves of Artocarpus heterophyllus. Their structures were elucidated on the basis of extensive spectroscopic techniques including 2D NMR and HR-ESIMS. Many compounds exhibited moderate to weak inhibitory activity against the proliferation of the PC-3, NCI-H460, and A549 cancer cell lines.