Determination of phenols in water using liquid phase microextraction with back extraction combined with high-performance liquid chromatography

Ionic Liquid-Based Magnetic Needle Headspace Single-Drop Microextraction Combined with HPLC/UV for the Determination of Chlorophenols in Wastewater

A magnetic needle headspace single-drop microextraction (MN-HS-SDME) method coupled to HPLC/UV has been developed. Trihexyl(tetradecyl)phosphonium chloride was employed as an ionic liquid (IL) solvent for the headspace extraction of some chlorophenol (CP) compounds from wastewater samples. Despite of the nonmagnetic character of the IL, a significant improvement in the extraction efficiency was obtained by the magnetization of the single-drop microextraction needle using a pair of permanent disk magnets. A simplex method for the fast optimization of the experimental conditions (e.g., stirring speed, ionic strength, pH, extraction time and temperature) was used. The coefficients of determination (R2) varied between 0.9932 and 0.9989, the limits of detection were from 0.004 to 0.007 μg mL-1 and the relative recoveries were in the range of 88-120% for the studied analytes. The developed MN-HS-SDME HPLC/UV method was successfully applied to the determination of CPs in industrial wastewater.

Determination of sulfonamide residues in animal foodstuffs by magnetic dispersive solid-phase extraction using magnetic carbon nanocomposites coupled with ion pair-dispersive liquid–liquid micro-extraction combined with HPLC-DAD

In this study, magnetic-dispersive solid-phase extraction coupled with ion pair-dispersive liquid–liquid micro-extraction (MSPE-i-DLLME) was used to the pre-concentration and extraction of five sulfonamides residues (sulfadiazine, sulfathiazole, sulfacetamide, sulfamethazine and sulfamethoxazole) in animal foodstuffs. The sulfonamides are extracted using magnetic carbon nanocomposite and then eluted with acetonitrile. In the DLLME step, the target analytes are collected in 1-octanol containing 10% Aliquat-336 (as extraction solvent). Finally, the compounds are quantified by HPLC with DAD detection. The extraction parameters optimized using the one at the time and central composite design methods. Under the optimized conditions: sample solution volume was 100 mL; initial pH: 12, amounts of MCNs: 30 mg; desorption solvent (ACN) volume, 1 mL; desorption condition, 10 min sonication at two step; extraction solvent (1-octanol + 10% aliquat) volume, 115 µL; pH of DLLME step, 3; salt effect, 24.6%, (w/v) NaCl; centrifuge, 5 min, 4000 rpm. In these extraction conditions, the proposed procedure represented good pre-concentration factors between 130 and 490; detection limits in the range from 0.01 to 5 μg kg−1 (at S/N = 3), and linear response in the 0.1–400 μg kg−1 concentration range. The method is successfully applied to the determination of sulfonamides residues in animal foodstuffs.

Simple magnetization of Fe3 O4 /MIL-53(Al)-NH2 for a rapid vortex-assisted dispersive magnetic solid-phase extraction of phenol residues in water samples

The present work describes a simple route to magnetize MIL-53(Al)-NH₂ sorbent for rapid extraction of phenol residues from environmental samples. To extend the applications and performances of the metal-organic frameworks in the field of adsorption materials, we combined the properties of metal-organic frameworks and magnetite to decrease the extraction time and simplify the extraction process as well. In this study, a simple and quick vortex-assisted dispersive magnetic solid phase extraction method for the extraction of ten United States Environmental Protection Agency's priority phenols from water samples prior to analysis by high-performance liquid chromatography with photodiode array detection was proposed. The developed method exhibits a rapid enrichment of the target analytes within 10 s for extraction and 10 s for desorption. Low detection limits of 1.8-41.7 µg/L and quantitation limits of 6.0-139.0 µg/L with the relative standard deviations for intra- and interday analyses less than 12% were achieved. Satisfactory recoveries in the range of 80-111% with the relative standard deviations less than 11% demonstrated that Fe₃ O₄ /MIL-53(Al)-NH₂ is promising sorbent in the field of magnetic solid-phase extraction for environmental samples.

A label-free electrochemical system for comprehensive monitoring of o-chlorophenol

o-Chlorophenol (OCP) is a priority pollutant that poses serious health threats to the public. The following study designs a simple electrochemical system to monitor the concentration and toxicity of OCP. This system was primarily characterized by the integration of both physicochemical and biological monitoring procedures that had a synergistic effect between the functionalized carbon nanotubes and rhodamine B. This resulted in excellent electrocatalytic activities toward OCP and cellular purine bases. The peak current of OCP was linear with concentrations ranging from 0.05-125.0 μM and the detection limit was 0.028 μM under optimal testing conditions. There was an enhanced voltammetric signal detected that was caused by the guanine/xanthine of human hepatoma (HepG2) cells. The cytotoxicity of OCP to HepG2 cells was assessed using the proposed system. The obtained IC₅₀ value was 512.86 μM. This study provided a fast, label-free, and low-cost platform for the comprehensive assessment of OCP. This is highly beneficial for simplifying the environmental monitoring process.

An ionic liquid loaded magnetically confined polymeric mesoporous adsorbent for extraction of parabens from environmental and cosmetic samples

Schematic illustration of MSPE procedure for paraben analysis using a new ionic liquid loaded magnetically confined polymeric mesoporous material.

Extraction of phenolic compounds from water samples by dispersive micro-solid-phase extraction

In this article, the use of magnetically separable sorbent polyaniline/silica-coated nickel nanoparticles is evaluated under a dispersive micro-solid-phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica-modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box-Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02-100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10-23 and 33-77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%.

Microextraction techniques used in the procedures for determining organomercury and organotin compounds in environmental samples

Due to human activities, the concentrations of organometallic compounds in all parts of the environment have increased in recent decades. The toxicity and some biochemical properties of mercury and tin present in the environment depend on the concentration and chemical form of these two elements. The ever-increasing demand for determining compounds at very low concentration levels in samples with complex matrices requires the elimination of interfering substances, the reduction of the final extract volume, and analyte enrichment in order to employ a detection technique, which is characterised by high sensitivity at low limits of quantification. On the other hand, in accordance with current trends, the analytical procedures should aim at the miniaturisation and simplification of the sample preparation step. In the near future, more importance will be given to the fulfilment of the requirements of Green Chemistry and Green Analytical Chemistry in order to reduce the intensity of anthropogenic activities related to analytical laboratories. In this case, one can consider the use of solvent-free/solvent-less techniques for sample preparation and microextraction techniques, because the use of the latter leads to lowering the quantity of reagents used (including solvents) due to the reduction of the scale of analysis. This paper presents an overview of microextraction techniques (SPME and LPME) used in the procedures for determining different chemical forms of mercury and tin.

Recent advances in application of liquid-based micro-extraction: A review

Liquid-based micro-extraction is a novel “green” sample preparation technique using micro-litre levels of organic solvent to extract target analytes from various sample matrices for subsequent instrumental analysis. This technique developed rapidly from its introduction in the mid-1990s. Micro-extraction methods can be conveniently combined with a wide selection of instruments commonly used in a chemical laboratory; they significantly reduce analysis time and costs of solvents’ use and waste disposal. This review focuses on recent advances in several liquid-based micro-extraction methods, including single-drop micro-extraction, hollow fibre-liquid phase micro-extraction, and dispersive liquid-liquid micro-extraction. Examples of application of these methods to environmental, food, and biomedical analysis are listed.

Photocatalytic Degradation of Phenol Using a Nanocatalyst: The Mechanism and Kinetics

The study of photocatalytic degradation of phenol was exploited with nano-ZnO as immobilized photocatalysts in a laboratory scale photocatalytic reactor. The photocatalytic degradation mechanism and kinetics of phenol in water were studied using the solid-phase microextraction (SPME) technique. Based on optimized headspace SPME conditions, phenol in water was first extracted by the fibre, which was subsequently inserted into an aqueous system with immobilized photocatalysts (nano-ZnO) exposed to an irradiation source (i.e., ultraviolet A (UVA) lamps). After different irradiation times (5–80 min), four main intermediates of photocatalytic degradation generated on the fibre were determined by GC-MS.

Hollow fiber liquid-phase microextraction with in situ derivatization combined with gas chromatography-mass spectrometry for the determination of root exudate phenylamine compounds in hot pepper ( Capsicum annuum L.)

Hollow fiber liquid-phase microextraction (HF-LPME) with derivatization was developed for the determination of three root exudate phenylamine compounds in hot pepper ( Capsicum annuum L.) by gas chromatography-mass spectrometry (GC-MS). The performance and applicability of the proposed procedure were evaluated through the extraction of 1-naphthylamine (1-NA), diphenylamine (DPA), and N-phenyl-2- naphthaleneamine (N-P-2-NA) in a recirculating hydroponic solution of hot pepper. Parameters affecting the extraction efficiency were investigated. The calibration curves showed a good linearity in the range of 0.1-10 μg mL(-1). The limits of detection (S/N = 3) for the three compounds were 0.096, 0.074, and 0.057 μg mL(-1), respectively. The enrichment factors reached 174, 196, and 230 at the concentration of 5 μg mL(-1), and relative standard deviations (RSD) of 9.5, 8.6, and 7.8% and 8.4, 7.6, and 6.2% were obtained at concentrations of 2 and 5 μg mL(-1) for 1-NA, DPA, and N-P-2-NA, respectively. Recoveries ranging from 90.2 to 96.1% and RSDs below 9.1% were obtained when HF-LPME with in situ derivatization was applied to determine root exudate 1-NA, DPA, and N-P-2-NA after 15 and 30 days of culture solution, respectively.

Low-density solvent-based dispersive liquid-liquid microextraction combined with single-drop microextraction for the fast determination of chlorophenols in environmental water samples by high performance liquid chromatography-ultraviolet detection

A new format of fast three-phase microextraction by combining low-density solvent-based dispersive liquid-liquid microextraction (DLLME) and single-drop microextraction (SDME) was for the first time developed for the determination of chlorophenols in environmental water samples. The extraction procedure includes a 2 min DLLME pre-extraction and a 10 min SDME back-extraction. A portion of low-density solvent (toluene) was used as organic phase and injected into the aqueous sample (donor phase) with methanol as disperser. The analytes were pre-extracted into the organic phase within 2 min. A thin layer of the organic phase formed on the top of the aqueous phase by a 2 min centrifugation. Then a drop of acceptor solution was introduced into the upper layer and SDME was carried out for the back-extraction. The stirring step typically involved in SDME and LLLME is avoided with the benefit of the high speed and efficiency of DLLME pre-extraction. After extraction, the acceptor drop was withdrawn and directly injected into a high performance liquid chromatography instrument with ultraviolet detection for analysis. Five chlorophenols, 4-chlorophenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol, were selected as model compounds for developing and evaluating the method. Factors affecting extraction efficiency were studied, including the organic solvent, the disperser solvent, the composition of donor phase and acceptor phase, the volume of acceptor microdrop, and the extraction time. At optimal conditions, the method showed low detection limit (0.016-0.084 μg/L) for the five chlorophenols, good linearity (from 0.2-250 to 1.0-250 μg/L, depending on the analytes) and repeatability (RSD below 8.2, n=5). The simple, fast, and efficient feature of the proposed method was demonstrated by the analysis of chlorophenols in environmental water samples.

Gas-purged headspace liquid phase microextraction system for determination of volatile and semivolatile analytes

In order to achieve rapid, automatic, and efficient extraction for trace chemicals from samples, a system of gas-purged headspace liquid phase microextraction (GP-HS-LPME) has been researched and developed based on the original HS-LPME technique. In this system, semiconductor condenser and heater, whose refrigerating and heating temperatures were controlled by microcontroller, were designed to cool the extraction solvent and to heat the sample, respectively. Besides, inert gas, whose gas flow rate was adjusted by mass flow controller, was continuously introduced into and discharged from the system. Under optimized parameters, extraction experiments were performed, respectively, using GP-HS-LPME system and original HS-LPME technique for enriching volatile and semivolatile target compounds from the same kind of sample of 15 PAHs standard mixture. GC-MS analysis results for the two experiments indicated that a higher enrichment factor was obtained from GP-HS-LPME. The enrichment results demonstrate that GP-HS-LPME system is potential in determination of volatile and semivolatile analytes from various kinds of samples.

Phenol determination on HDTMA-bentonite-based electrodes

The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.

Single-drop microextraction in bioanalysis

Bioanalysis usually requires a preparation procedure for sample cleanup or preconcentration. Conventional sample preparation techniques are often time consuming and labor intensive. Among recent progress in sample preparation, single drop microextraction (SDME) is one of the most efficient techniques providing both sample cleanup and preconcentration capabilities. In SDME, analytes are extracted from a sample solution into an acceptor drop and the drop is introduced to subsequent analysis. Since the volume of the acceptor drop is 1–10 µl or less, the consumption of solvents can be minimized and the preconcentration effect is enhanced. In this review, the basic principles of two-phase and three-phase SDME are described briefly and then recently developed modes of SDME, coupling with analytical instruments, and methods to enhance the drop stability are discussed. Recent applications of SDME to biological samples, including urine, blood and saliva, for the analysis of drugs, metal ions and biomarkers are reviewed.

Determination of sulfonamides in swine muscle after salting-out assisted liquid extraction with acetonitrile coupled with back-extraction by a water/acetonitrile/dichloromethane ternary component system prior to high-performance liquid chromatography

A salting-out assisted liquid extraction coupled with back-extraction by a water/acetonitrile/dichloromethane ternary component system combined with high-performance liquid chromatography with diode-array detection (HPLC-DAD) was developed for the extraction and determination of sulfonamides in solid tissue samples. After the homogenization of the swine muscle with acetonitrile and salt-promoted partitioning, an aliquot of 1 mL of the acetonitrile extract containing a small amount of dichloromethane (250-400 microL) was alkalinized with diethylamine. The clear organic extract obtained by centrifugation was used as a donor phase and then a small amount of water (40-55 microL) could be used as an acceptor phase to back-extract the analytes in the water/acetonitrile/dichloromethane ternary component system. In the back-extraction procedure, after mixing and centrifuging, the sedimented phase would be water and could be withdrawn easily into a microsyringe and directly injected into the HPLC system. Under the optimal conditions, recoveries were determined for swine muscle fortified at 10 ng/g and quantification was achieved by matrix-matched calibration. The calibration curves of five sulfonamides showed linearity with the coefficient of estimation above 0.998. Relative recoveries for the analytes were all from 96.5 to 109.2% with relative standard deviation of 2.7-4.0%. Preconcentration factors ranged from 16.8 to 30.6 for 1 mL of the acetonitrile extract. Limits of detection ranged from 0.2 to 1.0 ng/g.

Single drop microextraction--development, applications and future trends

Single drop microextraction (SDME) has emerged over the last 10-15 years as one of the simplest and most easily implemented forms of micro-scale sample cleanup and preconcentration. In the most common arrangement, an ordinary chromatography syringe is used to suspend microliter quantities of extracting solvent either directly immersed in the sample, or in the headspace above the sample. The same syringe is then used to introduce the solvent and extracted analytes into the chromatography system for identification and/or quantitation. This review article summarizes the historical development and various modes of the technique, some theoretical and practical aspects, recent trends and selected applications.