Design of functional guanidinium ionic liquid aqueous two-phase systems for the efficient purification of protein

A series of novel cationic functional hexaalkylguanidinium ionic liquids and anionic functional tetraalkylguanidinium ionic liquids have been devised and synthesized based on 1,1,3,3-tetramethylguanidine. The structures of the ionic liquids (ILs) were confirmed by ¹H nuclear magnetic resonance (¹H NMR) and 13C nuclear magnetic resonance (13C NMR) and the production yields were all above 90%. Functional guanidinium ionic liquid aqueous two-phase systems (FGIL-ATPSs) have been first designed with these functional guanidinium ILs and phosphate solution for the purification of protein. After phase separation, proteins had transferred into the IL-rich phase and the concentrations of proteins were determined by measuring the absorbance at 278 nm using an ultra violet visible (UV–vis) spectrophotometer. The advantages of FGIL-ATPSs were compared with ordinary ionic liquid aqueous two-phase systems (IL-ATPSs). The proposed FGIL-ATPS has been applied to purify lysozyme, trypsin, ovalbumin and bovine serum albumin. Single factor experiments were used to research the effects of the process, such as the amount of ionic liquid (IL), the concentration of salt solution, temperature and the amount of protein. The purification efficiency reaches to 97.05%. The secondary structure of protein during the experimental process was observed upon investigation using UV–vis spectrophotometer, Fourier-transform infrared spectroscopy (FT-IR) and circular dichroism spectrum (CD spectrum). The precision, stability and repeatability of the process were investigated. The mechanisms of purification were researched by dynamic light scattering (DLS), determination of the conductivity and transmission electron microscopy (TEM). It was suggested that aggregation and embrace phenomenon play a significant role in the purification of proteins. All the results show that FGIL-ATPSs have huge potential to offer new possibility in the purification of proteins.     

Magnetic graphene oxide modified with choline chloride-based deep eutectic solvent for the solid-phase extraction of protein

Four kinds of green deep eutectic solvents (DESs) based on choline chloride (ChCl) have been synthesized and coated on the surface of magnetic graphene oxide (Fe₃O₄@GO) to form Fe₃O₄@GO-DES for the magnetic solid-phase extraction of protein. X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were employed to characterize Fe₃O₄@GO-DES, and the results indicated the successful preparation of Fe₃O₄@GO-DES. The UV–vis spectrophotometer was used to measure the concentration of protein after extraction. Single factor experiments proved that the extraction amount was influenced by the types of DESs, solution temperature, solution ionic strength, extraction time, protein concentration and the amount of Fe₃O₄@GO-DES. Comparison of Fe₃O₄@GO and Fe₃O₄@GO-DES was carried out by extracting bovine serum albumin, ovalbumin, bovine hemoglobin and lysozyme. The experimental results showed that the proposed Fe₃O₄@GO-DES performs better than Fe₃O₄@GO in the extraction of acidic protein. Desorption of protein was carried out by eluting the solid extractant with 0.005 mol L⁻¹ Na₂HPO₄ contained 1 mol L⁻¹ NaCl. The obtained elution efficiency was about 90.9%. Attributed to the convenient magnetic separation, the solid extractant could be easily recycled.     

A novel polymeric ionic liquid-coated magnetic multiwalled carbon nanotubes for the solid-phase extraction of Cu,Zn-superoxide dismutase

A novel magnetic adsorbent, benzyl groups functionalized imidazolium-based polymeric ionic liquid (PIL)-coated magnetic multiwalled carbon nanotubes (MWCNTs) (m-MWCNTs@PIL), has been successfully synthesized and applied for the extraction of Cu, Zn-superoxide dismutase (Cu, Zn-SOD). The m-MWCNTs@PIL were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and zeta-potential nanoparticles. In this method, the m-MWCNTs@PIL could interact with Cu, Zn-SOD through hydrogen bonding, π-π and electrostatic interactions. The extraction performance of the m-MWCNTs@PIL in the magnetic solid-phase extraction (MSPE) procedure was investigated, coupled with the determination by UV–vis spectrophotometer. Compared with m-MWCNTs@IL and m-MWCNTs, the m-MWCNTs@PIL exhibited the highest extraction capacity of 29.1 mg/g for Cu, Zn-SOD. The adsorbed Cu, Zn-SOD remained high specific activity after being eluted from m-MWCNTs@PIL by 1 moL/L NaCl solution. Besides, the m-MWCNTs@PIL could be easily recycled and successfully employed in the extraction of Cu, Zn-SOD from real samples. Under the optimal conditions, the precision, repeatability and stability of the proposed method were investigated and the RSDs were 0.29%, 1.68% and 0.54%, respectively. Recoveries were in the range of 82.7–102.3%, with the RSD between 3.47% and 5.35%. On the basis of these results, the developed method has great potential in the extraction of Cu, Zn-SOD or other analytes from biological samples.     

Phenylboronic acid-functionalized cross-linked chitosan magnetic adsorbents for the magnetic solid-phase extraction of benzoylurea pesticides

In this study, a 4-formylphenylboronic acid-modified cross-linked chitosan magnetic nanoparticle (FPBA@CCHS@Fe₃O₄) was fabricated. The synthesized material was utilized as the magnetic solid-phase extraction adsorbent for the enrichment of six benzoylurea pesticides. In addition to B-N coordination, FPBA@CCHS@Fe₃O₄ interacts with benzoylureas through hydrogen bonds and π-π stacking interaction on account of rich active groups (amino and hydroxyl) and aromatic rings in structure. Compared to traditional extraction methods, less adsorbent (20 mg) and reduced extraction time (3 min) were achieved. The adsorbent also exhibited good reusability (no less than 10 times). Coupled with a high-performance liquid chromatography–diode array detector, satisfactory recoveries (89.1–103.9%) and an acceptable limit of detection (0.2–0.7 μg/L) were obtained. Under optimized conditions, the established method was successfully applied to the tea infusion samples from six major tea categories with acceptable recoveries ranging from 76.8 to 110%, indicating its application potential for the quantitative detection of pesticides in complex matrices.     

Magnetic polyethyleneimine functionalized reduced graphene oxide as a novel magnetic solid-phase extraction adsorbent for the determination of polar acidic herbicides in rice

A novel magnetic polyethyleneimine modified reduced graphene oxide (Fe₃O₄@PEI-RGO) had been fabricated based on a self-assemble approach between positive charged magnetic polyethyleneimine (Fe₃O₄@PEI) and negative charged GO sheets via electrostatic interaction followed by chemical reduction of GO to RGO. The as-prepared Fe₃O₄@PEI-RGO was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), thermal gravimetric analyzer (TGA), vibrating sample magnetometer (VSM) and zeta potential analysis, and then was successfully applied to determine four phenoxy acid herbicides and dicamba in rice coupled with high performance liquid chromatography (HPLC). As a surface modifier of RGO, PEI not only effectually affected the surface property of RGO (e.g. zeta potential), but also changed the polarity of RGO and offered anion exchange groups to polar acidic herbicides, which would directly influence the type of adsorbed analytes. Compared with Fe₃O₄@PEI, Fe₃O₄/RGO and Fe₃O₄@PEI-GO, the as-prepared Fe₃O₄@PEI-RGO, integrating the superiority of PEI and RGO, showed higher extraction efficiency for polar acidic herbicides. Besides, the adsorption mechanism was investigated as well. It turned out that electrostatic interaction and π-π interaction were considered to be two major driving force for the adsorption process. Response surface methodology (RSM), a multivariate experimental design technique, was used to optimize experimental parameters affecting the extraction efficiency in detail. Under the optimal conditions, a satisfactory performance was obtained. The calibration curves were linear over the concentration ranging from 2 to 300 ng g⁻¹ with correlation coefficients (r) between 0.9985 and 0.9994. The limits of detection (LODs) were in the range of 0.67–2 ng g⁻¹. The recoveries ranged from 87.41% to 102.52% with relative standard deviations (RSDs) less than 8.94%. Taken together, the proposed method was an efficient pretreatment and enrichment procedure and could be successfully applied for selective extraction and determination of polar acidic herbicides in complex matrices.     

A cross-linker containing aldehyde functionalized ionic liquid for chitosan

The synthesis of conductive and eco-friendly new chitosan composite biopolymer with a novel aldehyde functionalized ionic liquids (AFILs) was investigated in this work. The AFILs, 1,1′-(pentane-1,5-diyl) bis(4-formylpyridin-1-ium) dibromide (C₅PyBr), 1,1′-(octane-1,8-diyl) bis(4-formylpyridin-1-ium) dibromide (C₈PyBr) and 1,1′-(decane-1,10-diyl) bis(4-formylpyridin-1-ium) dibromide (C₁₀PyBr) have been synthesized and they were characterized by FT-IR, UV–vis and ¹H-NMR and ¹³ C-NMR, TG, and DSC analyses. The synthesized AFILs, C₅PyBr C₈PyBr and C₁₀PyBr were used as cross-linker for chitosan biopolymers and the cross-linked chitosan composites, chitosan/1,1′-(pentane-1,5-diyl)bis(4-formylpyridin-1-ium)dibromide (Ch/C₅PyBr), chitosan/1,1′-(octane-1,8-diyl)bis(4-formylpyridin-1-ium)dibromide (Ch/C₈PyBr) and chitosan/1,1′-(decane-1,10-diyl)bis(4-formylpyridin-1-ium)dibromide (Ch/C₁₀PyBr) were prepared. Herein, the synthesized AFILs have not only cross-linked chitosan, but also provide them the desired novel, functional groups. The prepared chitosan composites were characterized by FT-IR for the analysis of structural, TG and DSC for the thermal behavior, and an electrometer for the electrical conductivity. The electrical conductivity of the prepared Ch/C₅PyBr composite was measured as 1.69?×?10^?5 ± 2.37?×?10^?5 S cm^?1 by the four-point probe at room temperature and this value is higher about 4500-fold than the electrical conductivity of the chitosan.     

Preparation and evaluation of molecularly imprinted ionic liquids polymer as sorbent for on-line solid-phase extraction of chlorsulfuron in environmental water samples

In this report, vinylimidazolium ionic liquid as a functional monomer for preparation of chlorsulfuron (CS) imprinted polymers were first studied. The imprinted materials showed high selectivity for CS, and fast kinetics so that adsorption equilibrium was achieved within 5 min. These materials have been further employed to detect trace CS from water samples by online preconcentration coupled with HPLC. The sorbent offered good linearity (0.005-30 μg L(-1), r(2)>0.99) for on-line solid-phase extraction of trace chlorsulfuron. Under the optimal experimental conditions, the recovery for chlorsulfuron was in the range of 81.0-110.1% for the water samples, with RSDs ranging from 1.2 to 7.6%.     

Molecularly imprinted polymer based on magnetic ionic liquid for solid-phase extraction of phenolic acids

In this study, 1-allyl-3-octylimidazolium tetrachloroferrate ionic liquid was first synthesized. Molecularly imprinted polymer was prepared by suspension polymerization using 1-allyl-3-octylimidazolium tetrachloroferrate as functional monomer and chlorogenic acid as template molecule. The polymer was characterized by Fourier transformed infrared spectroscopy and scanning electron microscopy. Thermal stability of the polymer was investigated. The solid-phase extraction method based on magnetic molecularly imprinted polymer was developed for gallic acid, protocatechuic acid, caffeic acid, chlorogenic acid, p-coumaric acid, and ferulic acid. The sample pH, the type and volume of stripping solution, sorbent amount, and extraction time were optimized for phenolic acids. The analysis of phenolic acids after extraction was carried out using high-performance liquid chromatography with UV detection. Limit of detection, limit of quantification, linear range, correlation coefficient, and reproducibilities of within-day and between-day for phenolic acids were determined. The residues of phenolic acids in apple samples were successfully detected by the developed method. Recovery of standard spiked apple samples was ≥81 for all the phenolic acids.     

磺酸功能化聚合离子液体基磁性吸附剂的制备及对敌草快的萃取

有效萃取复杂食品样品中的极性污染物是实现其准确测定的瓶颈,也是食品安全分析的难点。针对污染物的结构特点,设计和发展能与之产生特定作用的新型材料是高效萃取的关键。敌草快是一种广谱性除草剂,为碱性的阳离子有机化合物。该文以1-乙烯基咪唑和1,3-丙磺酸内酯为原料合成了磺酸功能化的离子液体,通过自由基聚合反应,将其固载至磁性纳米颗粒表面,得到磺酸功能化的聚(1-乙烯基-3-丙基磺酸基咪唑氯盐)修饰的磁性纳米颗粒(Poly([VPImi-SO₃H][Cl])-MP)。采用红外光谱、扫描电镜、振动样品磁强计和热重分析等对其结构、形貌和磁性进行了表征。将其作为磁性固相萃取的吸附剂,萃取青菜中的敌草快。磺酸基的功能化使Poly([VPImi-SO₃H][Cl])-MP的表面在一定pH下带有丰富的负电荷,与敌草快之间产生强的静电吸引作用,可实现对敌草快的有效萃取。对影响萃取效率的各种参数如溶液pH、吸附剂质量、吸附时间、解吸剂种类和体积等进行了优化。在优化条件下,结合磁性固相萃取和高效液相色谱技术,对方法的性能及适用性进行了考察。敌草快在0.2～20μg/g...     

A novel poly(deep eutectic solvent)-based magnetic silica composite for solid-phase extraction of trypsin

Novel poly(deep eutectic solvent) grafted silica-coated magnetic microspheres (Fe₃O₄@SiO₂-MPS@PDES) were prepared by polymerization of choline chloride-itaconic acid (ChCl-IA) and γ-MPS-modified magnetic silica composites, and were characterized by vibrating sample magnetometer (VSM), Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectra (XPS), thermal gravimetric analysis (TGA) and transmission electron microscope (TEM). Then the synthetic Fe₃O₄@SiO₂-MPS@PDES microspheres were applied for the magnetic solid-phase extraction (MSPE) of trypsin for the first time. After extraction, the concentration of trypsin in the supernatant was determined by a UV–vis spectrophotometer. Single factor experiments were carried out to investigate the effects of the extraction process, including the concentration of trypsin, the ionic strength, the pH value, the extraction time and the temperature. Experimental results showed the extraction capacity could reach up to 287.5 mg/g under optimized conditions. In comparison with Fe₃O₄@SiO₂-MPS, Fe₃O₄@SiO₂-MPS@PDES displayed higher extraction capacity and selectivity for trypsin. According to the regeneration studies, Fe₃O₄@SiO₂-MPS@PDES microspheres can be recycled six times without significant loss of its extraction capacity, and retained a high extraction capacity of 233 mg/g after eight cycles. Besides, the activity studies also demonstrated that the activity of the extracted trypsin was well retained. Furthermore, the analysis of real sample revealed that the prepared magnetic microspheres can be used to purify trypsin in crude bovine pancreas extract. These results highlight the potential of the proposed Fe₃O₄@SiO₂-MPS@PDES-MSPE method in separation of biomolecules.     

Supported imidazolium ionic liquid phases: A new material for solid-phase extraction

This study reports a material that is based on the concept of ionic liquid analogue: a slightly crosslinked polymer-supported imidazolium trifluoroacetate salt (IL-CF₃COO⁻) that favorably combines the properties of ionic liquids (ILs) and the advantages of a solid support.The ionic liquid-supported material was evaluated for the first time as a solid-phase extraction (SPE) sorbent for selectively and quantitatively extracting pharmaceuticals from aqueous samples.The novel IL-CF₃COO⁻ was evaluated under reversed-phase (RP), weak anion exchange (WAX), strong anion exchange (SAX) and strong cation exchange (SCX) SPE procedures, and we found that SAX conditions are the most suitable for investigating the behaviour of the IL-CF₃COO⁻ material. Under SAX conditions, the IL-CF₃COO⁻ material was capable of selectively and quantitatively extracting a group of acidic compounds from aqueous samples, while washing basic analytes that were also present in the sample.The SPE method using IL-CF₃COO⁻ material was used to analyse 1000 ml of different aqueous samples (ultrapure, tap and river) with complete recovery of the acidic compounds studied. Moreover, the method provided clean chromatogram and high recoveries when percolating complex real samples, such as 1000 ml of river water and 250 ml of effluent wastewater from a sewage treatment plant spiked at low levels with the analytes studied.     

A self-assembly pipette tip graphene solid-phase extraction coupled with liquid chromatography for the determination of three sulfonamides in environmental water

A sensitive, economical, and miniaturized self-assembly pipette tip graphene solid-phase extraction (PT-G-SPE) coupled with liquid chromatography fluorescence detection (LC-FD) was developed for rapid extraction and determination of three sulfonamide antibiotics (SAs) in environmental water samples. The PT-G-SPE cartridge, assembled by packing 1.0 mg of graphene as sorbent into a 100 μL pipette tip, showed high adsorption capacity for the SAs owing to the large surface area and unique structure of graphene. The factors that affected the extraction efficiency of PT-G-SPE, including sample volume, pH, sorbent amount, washing solvent and eluent solvent were optimized. Good linearity for SAs was obtained in a range of 2–4000 pg mL⁻¹ with correlation coefficients (r²) ≥ 0.9993. The recoveries of the SAs at three spiked levels ranged from 90.4% to 108.2% with relative standard deviations (RSD) ≤ 6.3%. In comparison with other sorbents such as C₁₈, HLB, SCX, PCX, and multiwalled carbon nanotubes, one advantage of using graphene as sorbent of pipette tip solid-phase extraction (PT-SPE) was that PT-G-SPE could adsorb larger sample volume (10 mL) at a small amount of sorbent (1 mg) and low solvent consumption with good extraction efficiency, which not only increased the fraction of analytes to LC and the sensitivity of SAs determination, but also reduced the cost and pollution.     

Carbon nanotube-based magnetic bucky gels in developing dispersive solid-phase extraction: application in rapid speciation analysis of Cr(VI) and Cr(III) in water samples

In this work, we developed dispersive solid-phase extraction method with the use of carbon nanotube based magnetic bucky gels. The hydrophilic carbon nanotube (CNT)-based magnetic bucky gels (M-BGs) were developed with the features of magnetic susceptibility to permit fast injection of sorbent, rapid retrieval of the sorbent and high dispersion of MWCNT in the aqueous sample. We combined magnetic multi-wall carbon nanotube nanocomposite (MMWCNTs) with hydrophilic ionic liquids in order to prepare highly stable carbon nanotube-based magnetic bucky gels. The hydrophilic ILs act simultaneously as modifier and disperser for MMWCNTs and reduce the agglomeration of sorbent in water .Consequently they enhance the extraction efficiency. We used the unique features of this responsive gel (fluidity, stability, magnetic properties, and strong sorbing ability) in developing a new, fast, sensitive, simple, and environmental-friendly magnetic bucky gel-based dispersive solid-phase extraction method (M-BG-dSPE) combined with fibre optic linear array detection spectrophotometer (FO-LADS) for preconcentration and speciation of Cr(VI) and Cr(III) in water samples. The properties of MMWCNT and magnetic bucky gels were characterised by scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and Fourier transform infrared spectrophotometer (FT-IR). Under the optimised conditions, the enrichment factor of the method was 318, the limit of detection was 0.1 ng mL^?1 and the repeatability of the method, expressed as the relative standard deviation (RSD, n = 5), varies between 3.2% and 2.5% in different concentrations. The proposed procedure has been applied for speciation of Cr(VI) and Cr(III) in water samples with good recoveries in the range from 90 to 105%. Validation of the method was carried out by comparison of the obtained results with results obtained by the ET-AAS and spiking-recovery method.     

Metal-organic framework derived magnetic nanoporous carbon as an adsorbent for the magnetic solid-phase extraction of chlorophenols from mushroom sample

In this work, a metal-organic framework derived nanoporous carbon(MOF-5-C) was fabricated and modified with Fe_3O_4 magnetic nanoparticles. The resulting magnetic MOF-5-derived porous carbon(Fe_3O_4@MOF-5-C) was then used for the magnetic solid-phase extraction of chlorophenols(CPs) from mushroom samples prior to high performance liquid chromatography–ultraviolet detection. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and N_2 adsorption were used to characterize the adsorbent. After experimental optimization, the amount of the adsorbent was chosen as 8.0 mg, extraction time as 10 min, sample volume as 50 m L, desorption solvent as 0.4 m L(0.2 mL×2)of alkaline methanol, and sample p H as 6. Under the above optimized conditions, good linearity for the analytes was obtained in the range of 0.8–100.0 ng g~(-1)with the correlation coefficients between0.9923 and 0.9963. The limits of detection(S/N = 3) were in the range of 0.25–0.30 ng g~(-1), and the relative standard deviations were below 6.8%. The result showed that the Fe3O4@MOF-5-C has an excellent adsorption capacity for the analytes.     

Polyimidazolyl acetate ionic liquid grafted on cellulose filter paper as thin-film extraction phase for extraction of non-steroidal anti-inflammatory drugs from water

Recently, pharmaceuticals and personal care products in the water environment exhibited potential risks to both human and aquatic organisms. In order to improve the sensitivity and accuracy of pharmaceutical detection, the polyimidazolyl acetate ionic liquid was synthesized by Radziszewski reaction and coated on cellulose filter papers as a thin-film extraction phase for extraction of non-steroidal anti-inflammatory drugs from water. The attenuated total reflection-infrared spectrometry, thermogravimetric analysis, and scanning electron microscope analyses demonstrated that the polyimidazolyl acetate ionic liquid was successfully prepared and attached to the surface of the cellulose filter paper through chemical bonding. The adsorption capacity of the homemade thin-film extraction material for the four non-steroidal anti-inflammatory drugs was greater than 8898 ng/cm² under the optimum conditions, and the desorption rate was over 90%. Then, a paper-based thin-film extraction phase-high-performance liquid chromatography-tandem mass spectrometry method was established for the extraction of non-steroidal anti-inflammatory drugs in water. This method provided limits of detection and limits of quantification were in the range of 0.02–0.15 and 0.17–0.50 μg/L, respectively. Hence, the obtained thin-film extraction phase showed excellent recovery and reproducibility for the target non-steroidal anti-inflammatory drugs with carboxyl groups from water.     

n-Octadecylphosphonic acid grafted mesoporous magnetic nanoparticle: Preparation, characterization, and application in magnetic solid-phase extraction

A new sorbent for magnetic solid-phase extraction, n-octadecylphosphonic acid modified mesoporous magnetic nano particles (OPA/MMNPs), was easily prepared via a two-step strategy. MMNPs were synthesized by a solvent-thermal process, and then OPA was grafted onto the surface of MMNPs via the strong Lewis acid/base interaction. The resultant material was characterized by transmission electron microscopy, tensionmeter, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, elemental analysis, and nitrogen adsorption analysis. The results demonstrated that the particles exhibited mesoporous structure, superparamagnetic (57emu/g) and extremely hydrophobic (water contact angle of 136°) properties. To evaluate the extraction performance of the resultant sorbent, polycyclic aromatic hydrocarbons (PAHs) were chosen as model analytes. The extraction conditions were optimized. Based on these, a rapid, convenient and efficient method for the determination of PAHs in water samples was established by combination of magnetic solid-phase extraction and gas chromatography-mass spectroscopy. The linearity range of proposed method was 0.2-100μg/L with correlation coefficients (R(2)) of 0.9726-0.9970. The intra- and inter-day relative standard deviations (RSDs) were less than 17.6%. Batch-to-batch reproducibility was acceptable with RSD values less than 12.1%.     

基于石墨烯海绵的固相萃取-液相色谱法测定化妆品中6种紫外吸收剂

以石墨烯海绵（GS）为固相萃取材料,建立了固相萃取-高效液相色谱（SPE-HPLC）同时测定化妆品中6种紫外吸收剂的分析方法。样品经甲醇超声提取,用自制的石墨烯海绵固相萃取小柱净化富集,丙酮洗脱。采用Agilent Zorbax SB-C18色谱柱（150 mm×4.6 mm,5 μm）进行分离,甲醇-水（95∶5,v/v）为流动相,紫外检测波长为340 nm。结果表明,6种紫外吸收剂均在各自的范围内线性关系良好,2-（2'-羟基-5'-甲基苯基）苯并三氮唑的相关系数（r） > 0.997,其他5种r > 0.999。方法的检出限（LOD,S/N=3）和定量限（LOQ,S/N=10）分别为0.08~1.82 μg/L和0.26~6.07 μg/L。在20、50和100 μg/L 3个加标水平下,6种目标物的加标回收率为61.1%~119.0%,相对标准偏差（RSD）小于1%（n=6）。该法简便、快速,灵敏度高,重复性好,适用于不同类型化妆品中紫外吸收剂的检测。     

Design of guanidinium ionic liquid based microwave‐assisted extraction for the efficient extraction of Praeruptorin A from Radix peucedani

A series of novel tetramethylguanidinium ionic liquids and hexaalkylguanidinium ionic liquids have been synthesized based on 1,1,3,3‐tetramethylguanidine. The structures of the ionic liquids were confirmed by ¹H NMR spectroscopy and mass spectrometry. A green guanidinium ionic liquid based microwave‐assisted extraction method has been developed with these guanidinium ionic liquids for the effective extraction of Praeruptorin A from Radix peucedani. After extraction, reversed‐phase high‐performance liquid chromatography with UV detection was employed for the analysis of Praeruptorin A. Several significant operating parameters were systematically optimized by single‐factor and L₉ (3⁴) orthogonal array experiments. The amount of Praeruptorin A extracted by [1,1,3,3‐tetramethylguanidine]CH₂CH(OH)COOH is the highest, reaching 11.05 ± 0.13 mg/g. Guanidinium ionic liquid based microwave‐assisted extraction presents unique advantages in Praeruptorin A extraction compared with guanidinium ionic liquid based maceration extraction, guanidinium ionic liquid based heat reflux extraction and guanidinium ionic liquid based ultrasound‐assisted extraction. The precision, stability, and repeatability of the process were investigated. The mechanisms of guanidinium ionic liquid based microwave‐assisted extraction were researched by scanning electron microscopy and IR spectroscopy. All the results show that guanidinium ionic liquid based microwave‐assisted extraction has a huge potential in the extraction of bioactive compounds from complex samples.     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Development of a new strategy for the synthesis of graphene oxide-alumina nanocomposite as an efficient adsorbent for dispersive solid-phase extraction of parabens

The present study investigates the synthesis and application of the graphene oxide-alumina nanocomposite as a new adsorbent for the dispersive solid-phase extraction of three parabens and their determination using high-performance liquid chromatography-ultraviolet detection. The characterization of the synthesized material was accomplished and its size, morphology, chemical composition, porosity, and thermal stability were studied. Application of the proposed strategy for the synthesis of the nanocomposite resulted in the incorporation of Al₂O₃ nanoparticles into graphene oxide nanosheets, further resulting in the exfoliation of graphene oxide nanosheets increasing their surface area. An orthogonal rotatable central composite design was used to optimize the extraction. Under the optimum conditions, the analytical performance of the method showed a suitable linear dynamic range (0.2–100.0 μg/L), reasonable limits of detection (0.03–0.05 μg/L), and preconcentration factors ranging from 128 to 173. Finally, the new validated method was applied for the determination of parabens in some real samples including wastewater, cream, toothpaste, and juice samples with satisfactory recoveries (88%–109%), and relative standard deviations less than 8.7% (n = 3). Results demonstrated that inserting alumina nanoparticles into graphene oxide nanosheets improved the extraction efficiency of parabens, as polar acidic compounds, by providing additional efficient interactions including hydrogen bonding, dipole-dipole, and Brønsted and Lewis acid-base interactions.