Preconcentration Of Phenolic Compounds Research Articles

Development of magnetic dispersive micro-solid phase extraction based on magnetic adipic acid nanoparticles and deep eutectic solvents for the isolation and pre-concentration of phenolic compounds in fruit juice samples prior to determination by HPLC-UV

In this research, novel magnetic nanoparticles based on ultrasonic-assisted magnetic dispersive micro-solid phase extraction and deep eutectic solvent have been developed for the determination of phenolic compounds (naringenin, hesperetin, gallic acid) in fruit juice samples. For this purpose, for the first time, adipic acid-coated magnetic nanoparticles (AD@Fe3O4) as an efficient sorbent were synthesized and identified. In this study, deep eutectic solvents were prepared with available and less-toxic compounds and used as eluent solvent in the desorption step. These solvents are good options instead of conventional organic solvents to reduce hazardous waste products and improve the adsorption capacity. In addition, the extracted analytes were easily isolated from the media by an external magnet, and no special devices were required for phase separation. The screening of some important parameters on the extraction procedure was examined by fractional factorial design. Then, the central composite design was applied to optimize the effective parameters. The optimum conditions for the developed method were obtained as pH: 3.7, the amount of salt: 5% (w/v), the amount of adsorbent: 2 mg, and extraction time: 2 min. Under the optimal conditions, the proposed method demonstrated excellent linearity in the range of 1.0–500.0 µg L−1 for hesperetin and 5.0–500.0 µg L−1 for naringenin and gallic acid (R2 > 0.997). The extraction recoveries were obtained above 91.0%, and the intra-day and inter-day precision (RSD%) lower than 4.8%. Limit of detections (LODs) were in the range of 0.3–2.0 µg L−1. The results indicated that the suggested method is simple, fast, and eco-friendly. At the end, the new method was effectively applied for the determination of phenolic compounds in fruit juice samples.

Preconcentration of Phenolic Compounds on Carbon Sorbents and Their Chromatographic Determination in Aqueous Extracts of Medicinal Plants

A possibility of using carbon sorbents for the extraction, preconcentration, and chromatographic determination of phenolic substances of plant origin is investigated. A method is proposed for the preconcentration of biologically active substances from extracts of medicinal plants with carbon sorbents followed by the desorption of analytes with organic solvents at elevated temperature and pressure. Some sorption characteristics of carbon materials Supelclean ENVI-Carb and HyperSep Hypercarb in relation to phenolcarboxylic acids and flavonoids isolated from aqueous extracts of St. John’s Wort Hypericum perforatum L. are studied. The conditions of the sorption and desorption of analytes of various classes are optimized. A possibility of using carbon sorbents for the extraction and preconcentration of phenolic substances from aqueous extracts of various medicinal plants is shown using an examples of creeping thyme Thymus serpyllum L. and sage Salvia officinalis L.

Trace analysis of phenolic compounds in water by in situ acetylation coupled with purge and trap-GC/MS

The purge-and-trap preconcentration of phenolic compounds from waters after in situ acetylation was carried out in order to quantify them by Gas Chromatography/Mass Spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Using spiked natural surface water, various parameters including purge method, derivatization reagent (acetic anhydride), pH adjuster (Na2HPO4), temperature and time of derivatization reaction, amount of inert salt (NaCl) added, purge time and desorb temperature have been investigated. The final optimized preconcentration conditions were as follows: 10.0 g of NaCl, 0.40 g of Na2HPO4 and 400 μL of acetic anhydride were added to a 35 mL sample which then was heated at 55 °C for 20 min and purged for 20 min while the trap remained at room temperature. Once the purge step was over, the trap was desorbed at 260 °C for 2 min and then baked at 270 °C for 6 min. Under these optimized conditions, the precision and detection limits for all target compounds ranged from 1.3 to 7.0% (relative standard deviation, RSD) and from 0.06 to 0.12 μg L−1, and recoveries from the river water sample and wastewater sample ranged from 87.3 to 111% for all analytes. The response was found to be linear in the validated range, with the correlation coefficient (R2) better than 0.998. Finally, the method had been utilized for determination of phenolic compounds in natural surface water and wastewater samples, which suggested that it is a useful and effective method for the routine analysis of trace-level phenolic compounds in water.

Pre-concentration of phenolic compounds in water samples by novel liquid–liquid microextraction and determination by gas chromatography–mass spectrometry

Pre-concentration and determination of 8 phenolic compounds in water samples has been achieved by in situ derivatization and using a new liquid–liquid microextraction coupled GC–MS system. Microextraction efficiency factors have been investigated and optimized: 9 μL 1-undecanol microdrop exposed for 15 min floated on surface of a 10 mL water sample at 55 °C, stirred at 1200 rpm, low pH level and saturated salt conditions. Chromatographic problems associated with free phenols have been overcome by simultaneous in situ derivatization utilizing 40 μL of acetic anhydride and 0.5% (w/v) K 2CO 3. Under the selected conditions, pre-concentration factor of 235–1174, limit of detection of 0.005–0.68 μg/L (S/N = 3) and linearity range of 0.02–300 μg/L have been obtained. A reasonable repeatability (RSD ≤ 10.4%, n = 5) with satisfactory linearity (0.9995 ≥ r 2 ≥ 0.9975) of results illustrated a good performance of the present method. The relative recovery of different natural water samples was higher than 84%.

Extraction and Determination of Phenolic Derivatives in Water Samples by Using Polyoxyethylene Surfactants and Liquid Chromatography with Photodiode Array Detection

Methodology based on the cloud-point phenomenon was applied to the comparative study of 3 different polyoxyethylene nonionic surfactants in order to extract and preconcentrate a group of phenolic derivatives in water samples; these phenolic compounds, which were determined by liquid chromatography with UV detection, included 11 pollutants given priority by the U.S. Environmental Protection Agency. The optimum conditions for the extraction and preconcentration of phenolic compounds were established for each surfactant. The surfactant that gave the best extraction and preconcentration of the analytes under study was polyoxyethylene 6 lauryl ether (C12E6) with detection limits of <3.5 microg/L for all the phenolic compounds tested. The method was applied to seawater and depurated wastewater samples.

Use of non-ionic surfactant solutions for the extraction and preconcentration of phenolic compounds in water prior to their HPLC-UV detection.

A simple and rapid HPLC method with spectrophotometric detection to determine phenolic compounds in water, including the 11 priority phenolic pollutants, is described. As they are present in low concentrations, an extraction and preconcentration step is necessary prior to their determination. A methodology based on the cloud point phenomenon is applied using the non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) as extractant. The optimum conditions for the extraction and preconcentration of phenolic derivatives have been established and detection limits lower than 10 micrograms L-1 were obtained for all studied compounds. The method has been applied to their determination in sea water and depurated waste water samples.

High performance liquid chromatographic determination of phenolic compounds in seed exudates of Festuca arundinacea and F. pratense

Derivatives of benzoic and cinnamic (caffeic, protocatechuic, vanillic, ferulic, p-coumaric, p-hydroxybenzoic and syringic) acids and 3,4-dihydroxybenzaldehyde in seed exudates of Festuca arundinacea cv. “Kora” and F. pratense cv. “Otava” have been separated and quantified on a Zorbax SB C18 Rapid Resolution™ column with linear gradient elution using a mobile phase containing acetonitrile and 0.5% acetic acid. The USP tailing factors were less than 1.15 for all peaks. Strictly linear calibration curves (r > 0.9997) with limits of detection of 90–880 nM were obtained for all analytes in the concentration ranges from units or tenths up to 600 µM. RP 105 and OASIS™ HLB polymeric sorbents have been shown to be the best of the tested sorbents for the separation and preconcentration of phenolic compounds from both plant materials. The solid-phase extraction procedures have been compared with classical liquid–liquid extractions and consistent results were obtained. Copyright © 2000 John Wiley & Sons, Ltd.

Membrane solid-phase extraction with closed vessel microwave elution for the determination of phenolic compounds in aqueous matrices

Preconcentration of phenolic compounds was carried out with Empore C18 membrane disks, which were eluted with a closed-vessel microwave extraction system. The optimum microwave-elution conditions were obtained by optimizing the elution solvent, elution temperature, duration of elution and volume of elution solvent. The recoveries of eleven phenolic compounds spiked at 10 and 500 μg/L levels into water, using the optimum conditions, were all above 85% with relative standard deviations between 4.0 and 10.0%, except for phenol and 4-nitrophenol. Extraction of an industrial waste water sample suspected of containing phenolic compounds by SPE-CVME showed similar recoveries of phenol (the only phenolic compound detected) when compared with LLE and C18 SPE cartridge techniques. Analysis of phenolic compounds was carried out using liquid chromatography coupled to a UV detection system.