磁固相萃取/气相色谱一质谱法分析水样中的16种邻苯二甲酸酯类化合物

合成了一种由Fe3 O4磁性纳米粒子(MNPs)和多壁碳纳米管(MWCNTs)组成的复合纳米材料,用于水样中16种邻苯二甲酸酯类化合物(PAEs)的磁固相萃取(MSPE),并结合气相色谱-质谱(GC - MS)法进行定量分析.合成的纳米材料用傅立叶变换红外光谱表征.为提高萃取效率,优化了解析溶剂的种类和用量、解析时间、...     

Electrochemistry and Adsorptive Stripping Voltammetric Determination of Amoxicillin on a Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode

The study of electrochemical behavior of amoxicillin (AMX), a β‐lactam antibiotic, is described on a multiwalled carbon nanotubes (MWCNTs) modified electrode by electrochemical impedance spectroscopy (EIS) and adsorptive stripping voltammetry for sensitive determination of AMX in pharmaceutical and human urine samples within a wide pH range from 2.0 to 10.0. Also, studies by Fe₂O₃ nanoparticles modified carbon paste electrode show that iron oxide impurities in the MWCNTs are not active sites for sensing of amoxicillin. Under optimized conditions, the oxidation peak has two linear dynamic ranges of 0.6–8.0 and 10.0–80.0 μM with a detection limit of 0.2 μM and a precision of <4%.     

基于碳基磁性材料的磁固相萃取技术在食品分析应用中的研究进展

食品中残留的痕量有毒物质严重威胁人体健康,对其进行分析十分必要。然而,食品中有毒物质种类多、量少、基质复杂,需选择适当的样品预处理技术进行提取和净化。磁固相萃取(MSPE)因具有操作简单、省时快速、无需离心过滤、环境友好等优点,被认为是一种高效的样品预处理技术并应用于食品分析中。MSPE中使用的磁性吸附剂的吸附容量和选择性是影响MSPE萃取效率和选择性高低的关键,对所建立分析方法的准确度起着关键作用。碳基磁性材料是具有价格低廉、来源丰富、比表面积大、化学稳定性好、吸附容量高、绿色环保等优点的一类新型功能性磁性材料,可以富集不同性质的有机、无机分析物,在环境分析、生物检测、污染治理等多个领域取得了较大进展。近年来,基于碳基磁性材料的MSPE技术在食品分析预处理领域逐渐得到应用,但尚处于起步阶段,存在巨大的应用潜力。该文以碳基类别(碳纳米管、石墨烯、金属有机骨架衍生碳、活性炭等)为主线,综述了采用MSPE技术,以碳基磁性材料为吸附剂,对食品样品中酯类、真菌毒素、多环芳烃、抗生素、生物碱、酚类、维生素、抗菌药等物质进行萃取,进而采用液相色谱法等进行分析的应用实例,同时阐述了该技术存在的问题,并对其发展方向做出了展望。该综述将为基于碳基磁性材料的MSPE技术在食品分析中的广泛应用提供理论依据和技术支撑。     

Development of an Aluminium Doped TiO2 Nanoparticles‐modified Screen Printed Carbon Electrode for Electrochemical Sensing of Vanillin in Food Samples

A new chemically modified electrode based on titanium dioxide nanoparticles (TiO₂‐NPs) has been developed. Aluminium was incorporated into the TiO₂‐NPs to prepare aluminium doped TiO₂ nanoparticles (Al‐TiO₂‐NPs). Aluminium doped TiO₂ nanoparticles‐modified screen printed carbon electrode (Al‐TiO₂‐NPs/SPCE) was employed as easy, efficient and rapid sensor for electrochemical detection of vanillin in various types of food samples. Al‐TiO₂‐NPs were characterized by energy‐dispersive X‐ray (EDX), transmission electron microscopy (TEM), and X‐ray diffraction (XRD) and analyses showing that the average particle sizes varied for the Al‐NPs (7.63 nm) and Al‐TiO₂‐NPs (7.47 nm) with spherical crystal. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to optimize the analytical procedure. A detection limit of vanillin was 0.02 μM, and the relative standard deviation (RSD) was 3.50 %, obtained for a 5.0 μM concentration of vanillin. The electrochemical behaviour of several compounds, such as vanillic acid, vanillic alcohol, p‐hydroxybenzaldehyde and p‐hydroxybenzoic, etc., generally present in natural vanilla samples, were also studied to check the interferences with respect to vanillin voltammetric signal. The applicability was demonstrated by analysing food samples. The obtained results were compared with those provided by a previous method based on liquid chromatography for determination of vanillin.     

Rapid and sensitive detection of the phenoxy acid herbicides in environmental water samples by magnetic solid‐phase extraction combined with liquid chromatography–tandem mass spectrometry

Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid‐phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino‐functionalized multiwalled carbon nanotubes were prepared by mixing bare magnetic Fe₃O₄ nanoparticles with commercial amino‐functionalized multiwalled carbon nanotubes in water. Then the amino‐functionalized multiwalled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 μg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter‐ and intraday relative standard deviations less than 12.6%.     

Magnetic solid-phase extraction based on magnetic carbon nanotube for the determination of estrogens in milk

In this work, a novel method for the fabrication of magnetic carbon nanotubes based on 'aggregation wrap' was proposed. When carbon nanotubes and magnetic nanoparticles were vortically mixed in a solvent, the magnetic nanoparticles were wrapped into the carbon nanotube bundles that formed during the aggregation process, leading to the formation of magnetic carbon nanotubes. Thus, the resultant material can be separated from the solvent rapidly and conveniently by a magnet. Our investigation demonstrated that the 'aggregation wrap' mechanism for the preparation of magnetic composite is also applicable to other self-aggregated micro/nanomaterials, including graphene, graphite, C(60), etc. To testify the feasibility of the magnetic composites in sample preparation, the resultant magnetic carbon nanotubes were applied as sorbents for magnetic solid-phase extraction (MSPE) of estrogens in milk samples. Under optimized conditions, a rapid, convenient and efficient method for the determination of estrogens in milk samples was established by the combination of MSPE with high-performance liquid chromatography with fluorescence detector. The linearity range of the proposed method was 5-2000 μg/L with correlation coefficients (R) of 0.9983-0.9994. The limit of detection (LOD) for three estrogens ranged from 1.21 to 2.35 μg/L. The intra- and inter-day relative standard deviations (RSDs) were <9.3%. The reproducibility of the MSPE with different batches of magnetic carbon nanotubes was acceptable with RSD values <3.6%.     

Extraction of methocarbamol from human plasma with a polypyrrole/multiwalled carbon nanotubes composite decorated with magnetic nanoparticles as an adsorbent followed by electrospray ionization ion mobility spectrometry detection†

In this work, a polypyrrole/multiwalled carbon nanotubes composite decorated with Fe₃O₄ nanoparticles was chemically synthesized and applied as a novel adsorbent for the extraction of methocarbamol from human plasma. Electrospray ionization ion mobility spectrometry was used for the determination of the analyte. The properties of the magnetic‐modified adsorbent were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform IR spectroscopy, and X‐ray diffraction. The effects of experimental parameters on the extraction efficiency of the sorbent were investigated. Under the optimized conditions, the linear dynamic range was found to be 2–150 ng/mL with the detection limit of 0.9 ng/mL. The relative standard deviation was 5.3% for three replicate measurements of methocarbamol in plasma sample. The extraction efficiency of the sorbent for the determination of different drugs with various polarities was also compared to that of Fe₃O₄‐polypyrrole and Fe₃O₄‐multiwalled carbon nanotubes sorbents. Finally, the method was used for the determination of methocarbamol in blood samples.     

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.     

Sensitive and Selective Electrochemical Sensor Based on Molecularly Imprinted Polypyrrole Hybrid Nanocomposites for Tetrabromobisphenol A Detection

Abstract

A sensitive and selective electrochemical sensor based on electropolymerized molecularly imprinted polypyrrole and gold nanoparticles–multiwalled carbon nanotubes (AuNPs–MWCNTs) hybrid nanocomposites was developed for the determination of tetrabromobisphenol A (TBBPA). A glassy carbon electrode (GCE) was modified with MWCNTs, and the AuNPs–MWCNTs/GCE was prepared by an electrodeposition method in HAuCl₄ solution. The AuNPs–MWCNTs nanocomposite showed high electrocatalytic activity, good conductivity, and sufficient reactive sites for the direct electro-oxidation of TBBPA. The molecularly imprinted polymers (MIPs) as recognition elements were synthesized through in situ electro-polymerization of pyrrole as functional monomers in the presence of the TBBPA template molecules. Under the optimal conditions, the developed sensor exhibited good selectivity towards TBBPA compared with structural analogs, high sensitivity, and excellent producibility. The electrochemical responses of the sensor toward TBBPA were obtained in the linear range from 0.5?nM to 1?μM with a limit of detection equal to 0.24?nM at a signal-to-noise ratio of 3.     

Magnetic solid‐phase extraction based on carbon nanotubes for the determination of polyether antibiotic and s‐triazine drug residues in animal food with LC–MS/MS

Carbon nanotubes‐magnetic nanoparticles, comprising ferroferric oxide nanoparticles and carbon nanotubes, were prepared through a simple one‐step synthesis method and subsequently applied to magnetic solid‐phase extraction for the determination of polyether antibiotic and s‐triazine drug residues in animal food coupled with liquid chromatography with tandem mass spectrometry. The nanocomposites were characterized by transmission electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The components within the nanocomposites endowed the material with high extraction performance and manipulative convenience. Compared with carbon nanotubes, the as‐prepared carbon nanotubes‐magnetic nanoparticles showed better extraction and separation efficiencies for polyether antibiotics and s‐triazine drugs thanks to the contribution of the iron‐containing magnetic nanoparticles. Various experimental parameters affecting the extraction efficiency had been investigated in detail. Under the optimal conditions, the good linearity ranging from 1 to 200 μg/kg for diclazuril, toltrazuril, toltrazuril sulfone, lasalocid, monensin, salinomycin, narasin, nanchangmycin, and maduramicin, low limits of detection ranging from 1 to 5 μg/kg, and satisfactory spiked recoveries (77.1–91.2%, with the inter relative standard deviation values from 4.0 to 12.2%) were shown. It was confirmed that this novel method was an efficient pretreatment and enrichment procedure and could be successfully applied for extraction and determination of polyether and s‐triazine drug residues in complex matrices.     

碳纳米管@SiO_2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO2为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO2@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhanced Raman scattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO2@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

碳纳米管@SiO2@Ag纳米复合材料的制备及其表面增强拉曼效应

本文以SiO₂为中间层,在多壁碳纳米管(MWCNTs)表面负载Ag纳米粒子,制备出CNTs@SiO₂@Ag纳米复合材料,并采用TEM、XRD、UV-Vis、XPS等对纳米复合材料的结构、形貌和成分进行了表征,同时对该纳米复合材料的表面增强拉曼散射(Surface-enhancedRamanscattering,SERS)效应进行了研究。结果显示,Ag纳米颗粒有效提高了CNTs的SERS活性,纳米复合材料的拉曼峰强度是单纯CNTs拉曼峰强的近5倍。进一步研究了吸附罗丹明6G生物染料分子的SERS光谱,结果表明R6G分子的拉曼信号的质量与强度得到显著提高。因此,所制备的CNTs@SiO₂@Ag纳米复合材料有望作为SERS的活性基底,应用于生物无损检测领域。     

Development of magnetic multiwalled carbon nanotubes as solid-phase extraction technique for the determination of p-hydroxybenzoates in beverage

In this work, magnetic multiwalled carbon nanotubes were synthesized through a facile hydrothermal process, and then successfully used as magnetic solid-phase extraction sorbents for the determination of p-hydroxybenzoates in beverage. The prepared magnetic multiwalled carbon nanotubes presented both satisfactory superparamagnetism and strong capacity of absorption, with magnetic Fe(3)O(4) beads of 200 nm average diameters decorated at either ends of the tubes. The hybrid nanocomposites showed a high efficiency in the extraction and enrichment of p-hydroxybenzoates via π-π stacking of targeted molecules onto the polyaromatic composed surface of multiwalled carbon nanotubes, which entitled them promising magnetic solid-phase extraction sorbents for p-hydroxybenzoates at trace level from complex drink samples. By using an external magnetic field, p-hydroxybenzoates adsorbed on magnetic multiwalled carbon nanotubes could be rapidly isolated in only 30 s, and subsequently analyzed by liquid chromatography-diode array detector after elution with organic solvents. Extraction conditions such as eluting solvent, the amounts of magnetic sorbents added, pH values, adsorption and desorption time were investigated and optimized to achieve the best effect. Method validations including linearity, detection limit, and precision were also studied. The linearities were in the wide range of 0.05-500 μg/mL with correlation coefficients higher than 0.9983 for all p-hydroxybenzoates. The limits of detection were less than 20 ng/mL. Acceptable RSDs were achieved within 5-8% for all analytes. The results indicated that the proposed method based on magnetic multiwalled carbon nanotubes as magnetic solid-phase extraction absorbents was rapid, efficient, and convenient for the analysis of the targeted compounds of p-hydroxybenzoates in beverage sample.     

磁性多壁碳纳米管固相萃取-气相色谱-质谱法检测水样中的13种邻苯二甲酸酯类化合物

建立了磁性多壁碳纳米管(MWCNTs)固相萃取结合气相色谱-质谱检测水样中13种邻苯二甲酸酯类化合物(PAEs)的方法。优化了萃取时间、水样pH值、解吸溶剂的种类和用量、解吸时间等影响萃取效率的主要条件。最终确定萃取时间为10 min,水样pH 5～7,解吸溶剂为2 mL丙酮,解吸时间为5 min。在优化的条件下,各组分的萃取回收率为89.7%～100.5%。方法具有较高的灵敏度,检出限(信噪比(S/N)为3)为0.08～0.47 μg/L。3种实际样品的加标回收率为84.5%～107.5%,相对标准偏差为1.9%～12.8%。该方法操作简便、省时,准确、灵敏、环保,可用于水样中PAEs的检测,并成功地应用于自来水、瓶装饮用水和湖水样品的分析,13种PAEs均未检出。     

Highly Active Nickel Nanoparticles Supported on TiO2 Nanotube Electrodes for Methanol Electrooxidation

Nickel nanoparticles/TiO₂ nanotubes/Ti electrodes were prepared by galvanic deposition of nickel nanoparticles on the TiO₂ nanotubes layer on titanium substrates. Titanium oxide nanotubes were fabricated by anodizing titanium foil in a DMSO fluoride‐containing electrolyte. The morphology and surface characteristics of titanium dioxide nanotubes and Ni/TiO₂/Ti electrodes were investigated using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy, respectively. The results indicated that nickel nanoparticles were homogeneously deposited on the surface of TiO₂ nanotubes. The electrocatalytic behaviour of nickel nanoparticles/TiO₂/Ti electrodes for the methanol electrooxidation was studied by electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetry and chronoamperometry methods. The results showed that Ni/TiO₂/Ti electrodes exhibit a considerably higher electrocatalytic activity toward the oxidation of methanol.     

Pt–Ni alloy nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation in alkaline media

The Pt–Ni alloy nanoparticles with different Pt/Ni atomic ratios supported on functionalized multiwalled carbon nanotubes surface were synthesized via an impregnation-reduction method. The nanocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. XRD demonstrated that Pt was alloyed with Ni. TEM showed that the Pt–Ni alloy nanoparticles were uniformly dispersed on the multiwalled carbon nanotubes (MWCNTs) surface, indicating appropriate amount of Ni in Pt–Ni alloy which facilitates the dispersion of nanoparticles on the MWCNT surface. XPS revealed that the Pt 4f peak in Pt–Ni/MWCNT (4:1) catalyst shifted to a lower binding energy compared with Pt/MWCNT catalyst, and nickel oxides/hydroxides such as NiO, Ni(OH)₂, and NiOOH were on the surface of Pt–Ni nanoparticles. Electrochemical data based on cyclic voltammetry and chronoamperometric curves indicated that Pt–Ni (4:1) alloy nanoparticles exhibited distinctly higher activity and better stability than those of Pt/MWCNTs toward methanol oxidation in alkaline media.     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

A Label‐Free Amperometric Immunosensor Based on Redox‐Active Ferrocene‐Branched Chitosan/Multiwalled Carbon Nanotubes Conductive Composite and Gold Nanoparticles

A novel immunosensor has been developed by self‐assembling Au NPs onto a ferrocene‐branched chitosan/multiwalled carbon nanotubes (CS‐Fc/MWCNTs) modified electrode for the sensitive determination of hepatitis B surface antigen (HBsAg). The formation of CS‐Fc effectively avoids the leakage of Fc and retains its electrochemical activity. Incorporation of MWCNTs and Au NPs into CS‐Fc further increases the electrochemical active Fc in the CS films and provides interactive sites for the immobilization of HBsAb. The morphologies and electrochemistry of the formed biofilm were investigated by using scanning electron microscopy and electrochemical techniques. The immunosensor exhibits a specific response to HBsAg in the range of 1.0–420 ng mL^?1. Excellent analytical performance, fabrication reproducibility and operational stability of the proposed immunosensor indicated its promising application in clinical diagnostics.     

聚多巴胺/多壁碳纳米管/玻璃碳电极上多巴胺的电分析

基于多巴胺（DA）在多壁碳纳米管（MWCNTs）修饰玻璃碳（GC）电极上的电聚合,制得聚多巴胺(PDA)/MWCNTs/GC电极,并对该修饰电极进行了电化学阻抗谱 (EIS)和循环伏安法(CV)表征。 在该修饰电极上,DA呈现良好的电化学行为。在pH=7.4磷酸缓冲溶液中其氧化电流显著高于在裸电极上的响应,且能有效地抑制2.0 mmol/L抗坏血酸(AA)或K4Fe(CN)6的直接电化学响应,表明MWCNTs可增敏信号,且阳离子选择透过性PDA膜可抑制阴离子的电化学干扰。 采用CV实验检测DA,DA氧化的半微分伏安峰高(ipa-sd)与多巴胺浓度在0.08～1.76 μmol/L范围内呈线性关系,在无抗坏血酸和有0.5 mmol/L抗坏血酸共存时的线性回归方程分别为ipa-sd(μA/s1/2)=0.107+0.405c(μmol/L)（r2=0.986）和ipa-sd(μA/s1/2)=0.628+0.649c(μmol/L)(r2=0.992),检测限均为8.0×10-8 mol/L(S/N=3)。 该法用于盐酸多巴胺注射液中多巴胺的快速测定,结果满意。     

A Sensitive Simultaneous Determination of Epinephrine and Piroxicam Using a Glassy Carbon Electrode Modified with a Nickel Hydroxide Nanoparticles/Multiwalled Carbon Nanotubes Composite

The electrooxidation of epinephrine (EPI) and piroxicam (PRX) has been investigated by application of nickel hydroxide nanoparticles/multiwalled carbon nanotubes composite electrode (MWCNTs‐NHNPs/GCE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. The modified electrode showed suitable electrochemical responses for EPI and PRX determination. Under the optimum conditions the electrode provides a linear response versus EPI and PRX concentrations in the range of 1–220 µM and 0.7–75 µM, respectively using the DPV method. Linear responses versus EPI and PRX concentrations in the range of 1–1000 µM and 1–800 µM, respectively, were obtained using the CA method. The modified electrode was used for determination of EPI and PRX in human urine with satisfactory results.