Hemimicelle-based solid-phase extraction of estrogens from environmental water samples

Hemimicelles and admicelles of sodium dodecyl sulfate (SDS) on alumina and cetyltrimethyl ammonium bromide (CTAB) on silica were evaluated for the concentration and purification of the priority estrogens estrone (E(1)), 17beta-estradiol (E(2)) and ethynylestradiol (EE(2)) from sewage and river samples. Retention was based on analyte-sorbent hydrophobic and cation-pi interactions. Parameters affecting the SPE of estrogens on both types of sorbents were comparatively investigated. Adsolubilization was quantitative for SDS hemimicelles/admicelles and CTAB admicelles. SDS hemimicelle-coated alumina was the sorbent selected on the basis of the lower elution volume required and the higher sample flow rate allowed. Combination of estrogen adsolubilization-based SPE with liquid chromatography-diode array/fluorescence detection permitted the quantification of the target compounds with detection limits ranging from 20 to 100 ng l(-1). The relative standard deviation ranged from 3 to 8%. The approach developed was applied to the determination of estrogens in raw and treated sewage and river samples. The recovery found for estrogens in these environmental matrices was between 85 and 105%.     

Preparation of functionalized magnetic nanoparticulate sorbents for rapid extraction of biphenolic pollutants from environmental samples

A new solid-phase extraction coupled with magnetic carrier technology was developed for extraction of bisphenol A (BPA) and diethylstilbestrol (DES) from water samples. The SPE sorbents, functionalized magnetic nanoparticles (Fe₃O₄@SiO₂/β-CD, core/shell), were synthesized in a two-stage system. The material was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and a vibrating sample magnetometer. SPE extraction parameters, such as volume and pH of sample, adsorption time, and desorption conditions were optimized. Under selected conditions: 250 mL of water sample, 0.1 g of sorbents and elution with methanol (3 mL with 1% acetic acid), the extraction was completed in 25 min. SPE followed by HPLC was employed to determine BPA and DES in environmental samples. The developed method provided spiked recoveries of 80–105%, relative standard deviations of less than 7%, and LOD of BPA (20.0 ng/L) and DES (23.0 ng/L), respectively. The proposed method offered easy preparation of sorbents, rapid analysis, high enrichment yields, and reliable quantitative assay.     

Magnetic retrieval of graphene: extraction of sulfonamide antibiotics from environmental water samples

A new technique of retrieving graphene from aqueous dispersion was proposed in the present study. Two-dimensional planar graphene sheets were immobilized onto silica-coated magnetic microspheres by simple adsorption. The graphene sheets were used as adsorbent material to extract six sulfonamide antibiotics (SAs) from water samples. After extraction, they were conveniently separated from the aqueous dispersion by an external magnetic field. Under the optimal conditions, a rapid and effective determination of SAs in environmental water samples was achieved. The limits of detection for six SAs ranged from 0.09 to 0.16 ng/mL. Good reproducibility was obtained. The relative standard deviations of intra- and inter-day analysis were less than 10.7% and 9.8%, respectively.     

Preparation of alumina-coated magnetite nanoparticle for extraction of trimethoprim from environmental water samples based on mixed hemimicelles solid-phase extraction

In this study, a new type of alumina-coated magnetite nanoparticles (Fe₃O₄/Al₂O₃ NPs) modified by the surfactant sodium dodecyl sulfate (SDS) has been successfully synthesized and applied for extraction of trimethoprim (TMP) from environmental water samples based on mixed hemimicelles solid-phase extraction (MHSPE). The coating of alumina on Fe₃O₄ NPs not only avoids the dissolving of Fe₃O₄ NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory concentration factor and extraction recoveries can be produced with only 0.1 g Fe₃O₄/Al₂O₃ NPs. Main factors affecting the adsolubilization of TMP such as the amount of SDS, pH value, standing time, desorption solvent and maximal extraction volume were optimized. Under the selected conditions, TMP could be quantitatively extracted. The recoveries of TMP by analyzing the four spiked water samples were between 67 and 86%, and the relative standard deviation (RSD) ranged from 2 to 6%. Detection and quantification limits of the proposed method were 0.09 and 0.24 μg L⁻¹, respectively. Concentration factor of 1000 was achieved using this method to extract 500 mL of different environmental water samples. Compared with conventional SPE methods, the advantages of this new Fe₃O₄/Al₂O₃ NPs MHSPE method still include easy preparation and regeneration of sorbents, short times of sample pretreatment, high extraction yields, and high breakthrough volumes. It shows great analytical potential in preconcentration of organic compounds from large volume water samples.     

Preparation of a graphene-based magnetic nanocomposite for the extraction of carbamate pesticides from environmental water samples

A graphene-based magnetic nanocomposite was synthesized and used for the first time as an effective adsorbent for the preconcentration of the five carbamate pesticides (metolcarb, carbofuran, pirimicarb, isoprocarb and diethofencarb) in environmental water samples prior to high performance liquid chromatography-diode array detection. The properties of the magnetic nanocomposite were characterized by scanning electron microscopy and X-ray diffraction. This novel graphene-based magnetic nanocomposite showed great adsorptive ability towards the analytes. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid some of the time-consuming experimental procedures related to the traditional solid phase extraction. Various experimental parameters that could affect the extraction efficiencies have been investigated. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 474 to 868. A linear response was achieved in the concentration range of 0.1-50 ng mL(-1). The limits of detection of the method at a signal to noise ratio of 3 for the pesticides were 0.02-0.04 ng mL(-1). Compared with the dispersive liquid-liquid microextraction and the ultrasound-assisted surfactant-enhanced emulsification microextraction, much higher enrichment factors and sensitivities were achieved with the developed method. The method has been successfully applied for the determination of the carbamate pesticides in environmental water samples.     

Hemimicelle capped functionalized carbon nanotubes-based nanosized solid-phase extraction of arsenic from environmental water samples

The end functionalization of CNTs can introduce oxygen-containing negatively functional groups such as -COOH, -OH, or -CO on their surface site. If cationic surfactant such as cetyltrimethylammonium chloride (CTAC) was added to the functionalized CNTs, then interactions such as hydrophobic and ionic may lead to formation of hemimicelle/admicelle aggregates on the CNTs, a new kind of adsorbents, namely, the hemimicelle capped CMMWCNTs, is obtained. The application of the hemimicelle capped carbon nanotubes-based nanosized solid-phase extraction (SPE) adsorbents in environmental analysis is reported for the first time using arsenic as model target. The effect of adsorption and desorption conditions for arsenic including the amount of surfactant, initial pH of sample solution, the ultrasonic time of sample solution, the amount of electrolyte, flow rate, eluent and its amount were investigated and optimized prior to its determination by atomic fluorescence spectrophotometry (AFS). Arsenic can be quantitatively retained on the hemimicelle capped CMMWCNTs at pH 5-6 from sample volume up to 500 mL and then eluted completely with 2 mol L⁻¹ HNO₃ in the presence of 10 mg L⁻¹ CTAC. The method detection limit for arsenic determination with AFS detection was 2 ng L⁻¹, and the relative standard deviation (RSD, n = 11) was 5.3% at the 0.5 μg L⁻¹ level. The recoveries of arsenic in the spiked environmental water samples ranged from 94% to 104.29% with 500 mL of water sample. The proposed method has been applied successfully to the analysis of arsenic in aqueous environmental samples, which demonstrates the hemimicelle capped CMMWCNTs can be an excellent SPE adsorbents for arsenic pretreatment and enrichment from real water samples.     

Effective extraction of triazines from environmental water samples using magnetism-enhanced monolith-based in-tube solid phase microextraction

This article reports on the effective extraction of triazines from environmental water samples using magnetism-enhanced monolith-based in-tube solid phase microextraction (ME-MB/IT-SPME). Firstly, monolithic poly (octyl methacrylate-co-ethyleneglycol dimethacrylate) capillary column doped with magnetic nanoparticles was synthesized inside a fused silica. After that, the monolithic capillary column was placed inside a magnetic coil that allowed the exertion of a variable magnetic field during adsorption and desorption steps. The effects of intensity of magnetic field, adsorption and desorption flow rate, volume of sample and desorption solvent, pH value and ionic strength in sample matrix on the performance of ME-MB/IT-SPME for triazines were investigated in details. Under the optimized conditions, the developed ME-MB/IT-SPME showed satisfactory quantitative extraction efficiencies of the target analytes between 64.8% and 99.7%. At the same time, the ME-MB/IT-SPME was combined with high-performance liquid chromatography with diode array detection to detect six triazines in water samples. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were in the ranges of 0.074–0.23 μg/L and 0.24–0.68 μg/L, respectively. The precision of the proposed method was evaluated in terms of intra- and inter-assay variability calculated as relative standard deviation, and it was found that the values were all below 10%. Finally, the developed method was successfully applied for environmental water samples such as farmland, lake and river water with spiked recoveries in the range of 70.7–119%.     

Preparation of flower-like molybdenum disulfide for solid-phase extraction of N-nitrosoamines in environmental water samples

In this paper, a flower-like molybdenum disulfide material was prepared by hydrothermal method and was first used as adsorbents in the solid-phase extraction process for enriching N-nitrosoamines. Molybdenum disulfide exhibited three-dimensional petal-like microspheres with about 500 nm in diameter. The relevant analyte extraction and elution parameters (sample volumes, solution pH, washing solvents, elution solvents, and elution volumes) were optimized to improve the solid-phase extraction efficiency. The solid-phase extraction process coupled with high-performance liquid chromatography-tandem mass spectrometry for determining N-nitrosoamines in environmental water samples was established. The limits of detection were in the range of 0.01–0.05 ng/mL. The satisfactory recoveries (68.9–106.1%) were obtained at three different spiked concentrations (2, 5, and 8 ng/mL) in water samples, and the relative standard deviations were between 1.96 and 8.38%. This proposed method not only showed high sensitivity and good reusability but also provided a new adsorbent for enriching trace N-nitrosoamines in environmental water samples.     

Development and characterization of an immunoaffinity monolith for selective on-line extraction of bisphenol A from environmental water samples

Matrix interference and contamination from analytical procedures are two major issues in the detection of trace level of bisphenol A (BPA) in environmental water. In this paper, we report a highly selective and efficient method for on-line extraction of BPA from water samples followed by quantification with liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI/MS/MS). Poly(ethylene dimethacrylate-glycidyl methacrylate) monolith was synthesized in 50 mm × 4.6 mm i.d. stainless steel cartridges and the epoxy-groups on the surface of the monolith were hydrolyzed and oxidized to aldehyde functions. Antibodies against BPA were covalently immobilized onto the monolithic column via Schiff base reaction. The optimum application buffer and elution buffer were found to be pH 5.5 phosphate buffered saline (PBS) and methanol–water (70:30, v/v), respectively. The obtained immunoaffinity monolithic columns were on-line coupled to LC–MS/MS using column-switching valves and the system was applied to analyze BPA in real environmental water samples. The method achieved a detection limit of 0.3 ng L⁻¹ using a sample volume of 100 mL. The linear calibration range was 1.0–160 ng L⁻¹. Samples including tap water, lake water and effluent from municipal sewage treatment plant were all measured with satisfactory results.     

Preparation of silica-magnetite nanoparticle mixed hemimicelle sorbents for extraction of several typical phenolic compounds from environmental water samples

A novel type of superparamagnetic silica-coated (Fe3O4/SiO2 core/shell) magnetite nanoparticle modified by surfactants has been successfully synthesized and was applied as an effective sorbent material for the pre-concentration of several typical phenolic compounds (bisphenol A (BPA), 4-tert-octylphenol (4-OP) and 4-n-nonylphenol (4-NP)) from environmental water samples. Compared with pure magnetic particles, a thin and dense silica layer would protect the iron oxide core from leaching out in acidic conditions. In order to enhance their adsorptive tendency towards organic compounds, cetylpyridinium chloride (CPC) or cetyltrimethylammonium bromide (CTAB) were added, which adsorbed on the surface of the Fe3O4/SiO2 nanoparticles (Fe3O4/SiO2 NPs) and formed mixed hemimicelles. Main factors affecting the adsolubilization of analytes were optimized and comparative study on the use of CPC and CTAB-coated Fe3O4/SiO2 NPs mixed hemimicelles-based SPE was also carried out. CPC-coated Fe3O4/SiO2 NPs system was selected due to lower elution volume required and more effective adsorption of the target compounds. Under selected conditions, concentration factor of 1600 was achieved by using this method to extract 800 mL of different environmental water samples. The detection limits obtained for BPA, 4-OP and 4-NP with HPLC-FLD were 7, 14, and 20 ng/L, respectively.     

Supported liquid membrane extraction with single hollow fiber for the analysis of fluoroquinolones from environmental surface water samples

In this work, the simple analytical method for the determination of four fluoroquinolone antibiotics: ciprofloxacin, enrofloxacin, norfloxacin and danofloxacin, in environmental surface water samples is described. Sample pretreatment step was performed by the application of a technique based on supported liquid membrane extraction with the configuration of single hollow fiber (HF-SLM). The HPLC system with diode array detection was used for final analysis of studied analytes. Various parameters affecting the extraction efficiency during HF-SLM enrichment, such as type of membrane diluent, pH of donor (sample) and acceptor phases, as well as an enrichment time and salt content of sample were studied. Using the presented hollow-fiber extraction high recovery (70–80%) was achieved. It gave enrichment factor above 100. The detection limits in surface water samples, for the four target antibiotics, were at range 0.01–0.02 μg/l, when 10 ml samples were processed. The obtained results demonstrate the applicability of presented method for the selective extraction of fluoroquinolones in environmental water samples at ultratrace level. Errors, expressed as relative standard deviation (RSD) were below 8%, for all tested concentration levels.     

Rotating-disk sorptive extraction of nonylphenol from water samples

In this study the sorption of nonylphenol was implemented on a rotating Teflon disk coated with a PDMS film on one of its surfaces. In this way, the disk, which has a high surface area, contacts only the liquid sample, which can be stirred at higher velocity than with the stir bar used in stir-bar sorptive extraction (SBSE), without damaging the phase while at the same time facilitating analyte mass transfer to the PDMS surface. We refer to the procedure as rotating-disk sorptive extraction (RDSE). Extraction variables such as disk rotational velocity, extraction time, and surface area of PDMS film were studied to establish the best conditions for extraction. With increasing rotational velocity, the amount of extracted analyte significantly increases because the stagnant layer concomitantly decreases. On the other hand, the extracted amount concomitantly increases with extraction time, reaching equilibrium at approximately 20 min, which can be reduced to 10 min when the surface area of PDMS increases from 1.74 to 6.97 cm². Precision of the method was determined by using the same disk (n = 6) and different disks (n = 3), showing relative standard deviations for the analyte of 3.7% and 10%, respectively. The detection limit of the method was 0.09 μg/L NP, defined at a signal to noise ratio of 3. The method was applied to a real sample, achieving quantitative recovery. The PDMS phase on the disk could be used for at least 50 experiments. In any case, replacement of the PDMS film on the disk is very easy and inexpensive, as compared to the commercial alternative SBSE.     

Development and application of a polar coating for stir bar sorptive extraction of emerging pollutants from environmental water samples

In the present study, a stir bar coated with hydrophilic polymer based on poly(N-vinylpyrrolidone-co-divinylbenzene) was prepared for the sorptive extraction of polar compounds. The main parameters affecting the polymerisation of the coating were investigated.The new stir bar was applied successfully in stir bar sorptive extraction with liquid desorption followed by liquid chromatography–mass spectrometry in tandem with a triple quadrupole for the determination of a group of polar pharmaceuticals and personal care products (PPCPs) in environmental water matrices. Different variables affecting extraction and desorption such as agitation speed, temperature, ionic strength and extraction time were optimised. The results showed that the stir bar is able to enrich the selected analytes effectively.The developed method was applied to determine a group of PPCPs in different complex environmental samples, including river, effluent and influent waste water.     

环境样品中双酚类化合物的固相萃取研究进展

双酚类化合物作为一类内分泌干扰物广泛存在于环境介质中,经过多种途径迁移至人体后,可对人体产生内分泌毒性、细胞毒性、基因毒性、生殖毒性、二噁英毒性和神经毒性,已被加拿大政府风险评估识别为进一步优先控制名录。随着环境领域对双酚类化合物的广泛关注,相关研究工作逐渐向水、沉积物、灰尘和生物样品等多介质开拓。但是,由于不同环境样品在基质复杂性和污染物浓度水平等方面存在显著差异,开发提取效率高、净化选择性好、普适性强、操作简单、高通量的提取和净化方法,有助于实现环境介质中双酚类化合物的高灵敏、批量检测。近年来,新型前处理技术发展迅速,尤其是固相萃取技术,在双酚类化合物提取与净化方面取得了长足的发展,不仅在一定程度上克服了传统提取净化方法存在的耗时、耗力和耗溶剂等不足,而且为新型污染物分析提供了更多的技术支持。该文简述了典型双酚类化合物的理化性质、用途用量和环境危害,重点围绕新型固相萃取吸附剂开发和固相萃取模式转变两个方面,总结了固相萃取在双酚类化合物提取净化方法方面取得的进展。商品化固相萃取产品普适性强,在环境监测领域应用范围较广,适用于双酚类化合物的产品种类有限;新型吸附剂研发聚焦吸附容量(如介孔硅材料、碳纳米材料、金属-有机框架材料、环糊精)和选择性(如分子印迹聚合物和混合模式离子交换聚合物)两个方面,种类多样化可满足不同检测需求;越来越多的高灵敏分析仪器不断推向市场,为适应新的发展形势,固相萃取模式正逐渐向微型化、自动化、简易化等方向发展,如QuEChERS、固相微萃取、磁固相萃取等。     

Sulfhydryl-functionalised magnetic nanoparticles as sorbent in dispersive solid-phase extraction for the rapid enrichment of mercury species from natural water samples

The sulfhydryl-functionalised core-shell Fe₃O₄@SiO₂ magnetic nanoparticles (Fe₃O₄@SiO₂–RSH MNPs)-based dispersive solid-phase extraction method was developed. The goal of this method is the extraction of mercury species from natural water samples. An interesting aspect of the method is that, thanks to the spontaneously aggregate, the MNPs with a sub-30-nm-size range could be fast and efficiently extracted by 0.45 μm pore size mixed cellulose esters membrane filter. Thus, the elution step can be conducted by passing small amounts eluent through the MNPs on the membrane. It is also found that addition of Ag⁺ to water sample could improve the elution efficiency, and furthermore, minimises the matrix effects during the extraction of mercury species from natural water samples. The feasibility of the method was studied, and extraction efficiency was evaluated. The results showed that, calculated at 5 ng/L spiked concentration levels, absolute recoveries were 89.4%, 91.9% and 64.2%, and enrichment factors (EFs) were 596, 613 and 428, for inorganic mercury, methylmercury and ethylmercury, respectively. The high EFs were achieved in 5 min of overall extraction time. The method was applied to groundwater and river water samples. The results showed that its suitability for use in fast extracting trace levels of mercury species from natural water samples.     

Paper-based device with on-chip reagent storage for rapid extraction of DNA from biological samples

Microchimica Acta - Conventional methods for extraction of DNA are expensive, time-consuming and tedious. To overcome these limitations, a paper-based DNA extraction device was developed that...     

Preparation of a chitosan-coated C18-functionalized magnetite nanoparticle sorbent for extraction of phthalate ester compounds from environmental water samples

Novel superparamagnetic chitosan-coated C₁₈-functionalized magnetite nanoparticles (MNPs) were successfully synthesized and applied as an effective sorbent for the preconcentration of several typical phthalate ester compounds from environmental water samples. The MNPs were 20 nm in diameter and had a high magnetic saturation value (52 emu g⁻¹), which endowed the sorbent with a large surface area and the convenience of isolation from water samples. Phthalate esters could be extracted by the interior octadecyl groups through hydrophobic interaction. The hydrophilic porous chitosan polymer coating promoted the dispersion of MNPs in water samples, and improved the anti-interference ability of the sorbent without influencing the adsorption of analytes. The main factors affecting the adsorption of phthalate esters, including the pH of the solution, humic acid, sample loading volume, adsorption time, and desorption conditions, were investigated and optimized. Under the conditions selected (pH 11, adsorption time 20 min, elution with 10 mL of acetonitrile, and concentration to 0.5 mL), concentration factors of 1,000 were achieved by extracting 500 mL of several environmental water samples with 0.1 g of MNP sorbent. The method detection limits obtained for di-n-propyl phthalate, di-n-butyl phthalate, dicyclohexyl phthalate, and di-n-octyl phthalate were 12.3, 18.7, 36.4, and 15.6 ng L⁻¹, respectively. The recoveries of spiked samples ranged from 60 to 100%, with a low relative standard deviation (1–8%), which indicated good method precision.