样品分析中分子印迹固相萃取的新技术进展

正样品前处理是通过提取、除杂、浓缩等步骤,将目标物与复杂样品基质分离开来,以提高检测灵敏度的一种样品处理方法。作为整个样品检测中最耗时的一个环节,样品前处理关系着整个分析方法的优劣,直接影响分析结果的准确度和精密度。固相萃取(solid-phase extraction,SPE)由于其形式多样、操作简单、对环境友好、易实现自动化、有机溶剂用量少、回收率和富集倍数高等优点,目前已被公认为使用大型仪器分析检测前对样品进行预处理的首选方法。固相萃取利用固体吸附剂来吸附液体样品中的目标物,使其与样品基质分离,然后再对吸附剂进行洗脱或加热解吸附,避免了很多传统萃取中两相不相容的缺点,实现了分离与富集目标物的目的。     

磁性纳米材料的功能化及其在农药残留检测中的应用

磁固相萃取技术是近年来不断发展的一种基于磁性纳米吸附材料的新型样品前处理技术。与传统吸附剂相比,磁性纳米材料凭借其粒径小、比表面积大、表面易功能化、独特的磁学性质、易于操控和再生、环境友好度高等诸多优点,在有效分离富集复杂基质中的痕量目标物方面展示了诱人的应用前景。近年来,磁固相萃取技术在农药残留检测领域取得了迅速发展。介绍了磁固相萃取技术,综述了近5年来碳材料、有机小分子、离子液体、高分子、无机氧化物、金属有机框架材料、多孔有机材料等功能化的磁性纳米材料的合成策略、在农药残留检测中的应用以及其与分析物之间吸附机理,并展望了其发展方向。     

亚胺类共价有机骨架材料在样品前处理中的应用

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料。I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点。近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、存储、催化、传感、光电材料等方面。I-COFs材料优异的物理化学性能使其非常适于用作复杂样品中痕量目标物的分离富集介质,其高比表面积、高孔隙率性能赋予了它极高的吸附负载量,这些性能使得目标分析物可被高效富集;通过控制有机单体的链段长度、几何结构、掺杂元素、取代基团等方面精确调控I-COFs的孔洞结构和功能化基团,从而实现目标痕量物质的选择性富集。目前,I-COFs材料在样品前处理领域作为新型萃取介质已引起了极大关注。该文综述了近年来I-COFs材料的主要类型、合成方法及其在固相萃取、磁性固相萃取、分散固相萃取和固相微萃取方面的研究进展,同时展望了I-COFs在样品前处理领域的发展前景。     

石墨烯应用于样品前处理的研究进展

样品前处理技术在样品分析中发挥着越来越重要的作用,而对分析物的富集能力和对样品基体的净化程度主要取决于高效的样品前处理材料,所以发展高性能的样品前处理材料一直是该领域的前沿研究方向。近年来,各类先进材料已经被引入样品前处理领域,发展了多种高性能的萃取材料。由于独特的物理化学性质,石墨烯已在各个研究领域获得广泛关注,在样品前处理领域也发挥着重要作用。基于高的比表面积、大的π电子结构、优异的吸附性能、丰富的官能团和易于化学改性等优点,石墨烯和氧化石墨烯基萃取材料被成功应用于各种样品的前处理,对不同领域中多种类型分析物表现出优异的萃取性能。该论文总结和讨论了近3年来石墨烯材料(石墨烯、氧化石墨烯及其功能化材料)在柱固相萃取、分散固相萃取、磁性固相萃取、搅拌棒萃取、纤维固相微萃取和管内固相微萃取等方面的研究进展。基于多种萃取机理如π-π、静电、疏水、亲水、氢键等相互作用,石墨烯萃取材料能够高效萃取和选择性富集不同类别的目标分析物,如重金属离子、多环芳烃、塑化剂、雌激素、药物分子、农药残留、兽药残留等。基于新型石墨烯萃取材料的各种样品前处理技术与多种检测技术如色谱、质谱、原子吸收光谱等联用,广泛应用于环境监测、食品安全和生化分析等领域。最后,总结了石墨烯在样品前处理领域中存在的问题,并展望了未来的发展趋势。     

磺化聚苯乙烯纳米纤维作为金刚烷胺固相萃取介质的研究

以电纺聚苯乙烯纳米纤维(PS NFs)为基底,通过磺化反应制得具有亲水性的磺化聚苯乙烯纳米纤维(SPS NFs),并通过静态和动态吸附实验考察其对金刚烷胺的吸附性能。据此建立了基于SPS NFs的固相萃取(SPE)法,并应用于动物源食品中痕量金刚烷胺的快速检测。结果表明,pH 4时,SPS NFs对金刚烷胺达到最优吸附,吸附动力学符合准二级动力学模型;优化SPS NFs的SPE条件(样液流速、洗脱条件等),结合超高效液相色谱-串联质谱(UPLC-MS/MS)检测鸡肉、鸡蛋、牛奶等样品中的金刚烷胺,2.0～20.0μg/kg加标水平的加标回收率为71.6%～87.5%,检测限为0.2μg/kg。与传统固相萃取法相比,本方法集分离、净化、浓缩功能于一体。     

尼龙6纳米纤维膜固相膜萃取-高效液相色谱法测定塑料瓶装矿泉水中双酚A

采用静电纺丝法制备尼龙6纳米纤维膜,结合固相膜萃取-高效液相色谱法测定了矿泉水中的双酚A。对洗脱溶剂及其体积、进样速度、样品体积、样品pH值、尼龙6纳米纤维膜的用量、及其活化方式和使用次数等影响因素进行了研究。结果表明:10mL样品调至pH8.0后,以3mL/min流速通过1.5mg尼龙6纳米纤维膜,300μL甲醇即可将膜上吸附的双酚A完全洗脱,每张膜至少可重复使用6次。在此最优化条件下,方法的线性范围为0.20～20.0μg/L;检出限为0.15μg/L,膜内和膜间的相对标准偏差均小于4.5%(n=6)。本方法应用于6种不同品牌的矿泉水中双酚A的分析测定,在1.0μg/L加标水平下,测得回收率为95.0%,双酚A测得浓度低于0.30μg/L。与固相萃取方法相比,本方法高效、环保,表明尼龙6纳米纤维膜是极具潜力的萃取介质     

替代模板分子印迹技术在样品前处理中的应用

分子印迹聚合物具有抗恶劣环境、选择性高、稳定性好等特点,广泛应用于复杂样品的前处理。采用结构类似物作为替代模板分子,可以解决分子印迹聚合物制备时目标物溶解性差的问题,替代模板分子印迹聚合物不仅对目标分析物具有选择性识别能力,还可以避免模板泄露对痕量分析造成的影响。本文综述了替代模板分子印迹技术在样品前处理中的应用进展,包括替代模板分子印迹技术在固相萃取、固相微萃取、色谱固定相、基质固相分散萃取中的应用,最后对替代模板分子印迹技术在未来的样品前处理中的研究进行了展望。     

电纺纳米纤维固相萃取拟除虫菊酯的研究

将电纺纳米纤维用于萃取分离拟除虫菊酯农药.实验发现电纺纳米纤维对甲氰菊酯、高效氯氟氰菊酯、溴氰菊酯、氰戊菊酯、氯菊酯和联苯菊酯农药有较好的吸附能力,对6种拟除虫菊酯农药的最大吸附容量分别为5.4、5.8、6.0、6.5、6.5和8.0μg/mg.应用电纺纳米纤维固相萃取一高败液相同时测定蔬菜样品中6种拟除虫菊酯农药.在优化实验条件下,6种拟除虫菊酯类农药分离效果较好,并在(0.01～0.04)～10mg/L浓度范围内与峰面积呈良好的线性关系(r2=0.9995～0.9999);方法的最小检测限为5～12μg/L,其加标回收率在85.8%～96.6%之间.     

聚多巴胺纳米纤维膜固相萃取-超高效液相色谱-串联质谱检测淡水鱼中四环素类和氟喹诺酮类药物残留

制备聚多巴胺(PDA)修饰的聚苯乙烯纳米纤维膜(PS NFsM)作为固相萃取吸附介质,可快速提取淡水鱼中3种四环素类(四环素、金霉素、土霉素)和3种氟喹诺酮类(恩诺沙星、环丙沙星、诺氟沙星)药物残留,结合超高效液相色谱-串联质谱(UPLC-MS/MS),建立了药物残留检测的新方法。利用静电纺丝法制备了聚苯乙烯纳米纤维膜,将其作为模板,通过自聚合作用,进行聚多巴胺功能化修饰,得到PDA-PS NFsM材料。对制得的PS NFsM和PDA-PS NFsM材料进行傅里叶红外光谱和场发射扫描电镜表征,证明PDA的成功修饰,修饰后的纳米纤维表面粗糙,呈现核-壳形貌,纤维内部为蜂窝状多孔结构。以空白加标样品的回收率为指标,对PDA-PS NFsM材料的用量、离子强度、样品溶液的流速、洗脱液和突破体积等影响SPE的因素进行考察及条件优化,确定了最佳的SPE条件。该方法对6种目标物的检出限为0.3~1.5 μg/kg,定量限为1.0~5.0 μg/kg,低于国家标准和行业标准;在各目标物的线性范围内均有良好的线性关系,决定系数(R²)大于0.999,方法的回收率为94.37%~102.82%,日间和日内的相对标准偏差(RSD)均小于10%,与国家标准和行业标准相当。通过固相萃取前后的基质效应对比,表明PDA-PS NFsM具有优秀的净化能力。最后,通过实际样品分析验证了方法的实际应用可行性。该文建立的基于PDA-PS NFsM材料的SPE方法是一种高效环保的方法,可为淡水鱼中药物残留的常规监测提供技术支持。     

分子印迹固相萃取技术在动物源食品中药物残留检测应用进展

以分子印迹材料作为特效吸附剂的分子印迹固相萃取技术具有从复杂样品中选择性吸附目标分子及其结构类似物的能力,较好地克服了由于样品复杂所带来的内源性干扰问题,因此非常适用于复杂样品的预处理与富集。本文介绍了分子印迹固相萃取技术的原理、最新进展以及相关萃取参数的优化过程,对近几年国内外分子印迹固相萃取技术在动物源食品中药物残留检测方面的应用进行了总结;阐明了分子印迹固相萃取技术在实际应用中存在的不足,并对其未来的发展进行了展望。     

Detection of Phthalate Esters in Environmental Water Samples-Comparison of Nylon6 Nanofibers Mat-based Solid Phase Extraction and Other Conventional Extraction Methods

In this article, a new method for simultaneous determination of six phthalate esters was developed by a combination of electrospun nylon6 nanofibers mat‐based solid phase extraction with high performance liquid chromatography‐ultraviolet detector (HPLC‐UV). The six phthalate esters were dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP), di‐n‐butyl phthalate (DBP), di‐(2‐ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP). Under optimized conditions, all target analytes in 50 mL environmental water samples could be completely extracted by 2.5 mg nylon6 nanofibers mat and eluted by 100 µL solvent. Compared with C18 cartridges solid phase extraction, C18 disks solid phase extraction and national standard method (China), nylon6 nanofibers mat‐based solid phase extraction was advantageous in aspects of simple and fast operation, low consumption of extraction materials and organic solvents. The four methods were applied to analysis of environment water samples. All the results indicated that the determination values of target compounds with the proposed method were consistent with C18 cartridges and C18 disks solid phase extraction method, and the new method was better than the national standard method in aspects of recovery, LOD and precision. Therefore, nylon6 nanofibers mat has great potential as a novel material for solid phase extraction.     

Automated analysis of polar pesticides in water by on-line solid phase extraction and gas chromatography using the co-solvent effect

In order to meet the requirements of analyzing very low concentrations of pesticides in water (typically at 0.1 μg/l or less), samples have to be concentrated prior to GC-analysis. Samplie pre-concentration by off-line methods based on solid phase extraction (SPE) or liquid-liquid extraction are very time consuming and cumbersome. Moreover, the quantitative performance of the analytical method as a whole in terms of accuracy and reliability is seriously hindered by elaborate, manually performed sample pre-treatment steps. This paper describes an automated method based on solid phase extraction and capillary gas chromatography. The technique was applied for the analysis of 31 polar organophosphorus and organonitrogen pesticides. A commercially available HPLC/GC instrument is modified, using the LC-part for solid phase extraction. The sample, of which only a few ml's is required to obtain sufficiently low detection limits, is delivered by a robotic large volume autosampler. After solid phase extraction and elution, the eluate is transferred into the GC via a so called “loop type interface”. In this paper the instrumentation and analytical methodology is described, as well as the main validation results. The quantitative performance (i.e. recovery and repeatability) of the most polar solutes like metamitron and dimethoate appears to be better than obtained with off-line SPE as a result of the more beneficial ratio between the amount of sorbent and the sample volume. As the loop-type interface causes losses of the most volatile compounds, a co-solvent is added. This co-solvent provides sufficient trapping capacity in the capillary pre-columns to allow quantitative analysis of even the most volatile pesticides. Moreover a better separation of early eluting compounds is also established.     

Photocrosslinked methacrylated chitosan-based nanofibrous scaffolds as potential skin substitute

Nanofibers based on natural polymers have recently been attracting research interest as promising materials for use as skin substitutes. Here, we prepared photocrosslinked nanofibrous scaffolds based on methacrylated chitosan (MACS) by photocrosslinking electrospun methacrylated chitosan/poly (vinyl alcohol) (PVA) mats and subsequently removing PVA from the nanofibers. We comprehensively investigated the solution properties of MACS/PVA precursors, the intermolecular action between MACS and PVA components, and the morphology of MACS/PVA nanofibers. Results indicated that the fiber diameter and morphology of the photocrosslinked methacrylated chitosan-based nanofibrous scaffolds were controlled by the MACS/PVA mass ratio and showed highly micro-porous structures with many fibrils. In vitro cytotoxicity evaluation and cell culture experiments confirmed that MACS-based mats with micro-pore structure were biocompatible with L929 cells and facilitated cellular migration into the 3D matrix, demonstrating their potential application as skin replacements for wound repair.     

Miniaturized pipette‐tip‐based electrospun polyacrylonitrile nanofibers for the micro‐solid‐phase extraction of nitro‐based explosive compounds

In this study, a self‐assembly of miniaturized pipette‐tip‐based solid‐phase extraction for the simultaneous extraction of nitroaromatic compounds was developed, with electrospun polyacrylonitrile nanofibers used as sorbents. The electrospun polyacrylonitrile nanofibers were characterized by scanning electron microscopy, FTIR analysis and surface area analysis. Good linearities for the four nitroaromatic compounds (2,6‐dinitrotoluene, 2‐nitrotoluene, 3‐nitrotoluene, and 4‐nitrotoluene) were obtained in a range of 250–1000 μg/L with coefficients of determination > 0.99. The limits of detection of these analytes were between 21 and 38 μg/L. The results showed that the pipette‐tip‐based solid‐phase extraction was effective in extracting nitrotoluenes in the pH regime of environmental interest (≈ 6). The investigation also revealed that the optimum mass of electrospun polyacrylonitrile nanofibers sorbent was 15 mg and 20 aspirating/dispensing cycles gave the maximum recovery of nitrotoluenes with 200 μL acetonitrile as the best eluting solvent. Moreover, the performance of the present method was studied for the extraction and determination of nitroaromatic compounds in real environmental water samples and good recoveries ranging from 70 to 115% were found, and respective relative standard deviations of <12% were obtained.     

Electrospun Nanofibers from a Tricyanofuran‐Based Molecular Switch for Colorimetric Recognition of Ammonia Gas

A chromophore based on tricyanofuran (TCF) with a hydrazone (H) recognition moiety was developed. Its molecular‐switching performance is reversible and has differential sensitivity towards aqueous ammonia at comparable concentrations. Nanofibers were fabricated from the TCF–H chromophore by electrospinning. The film fabricated from these nanofibers functions as a solid‐state optical chemosensor for probing ammonia vapor. Recognition of ammonia vapor occurs by proton transfer from the hydrazone fragment of the chromophore to the ammonia nitrogen atom and is facilitated by the strongly electron withdrawing TCF fragment. The TCF–H chromophore was added to a solution of poly(acrylic acid), which was electrospun to obtain a nanofibrous sensor device. The morphology of the nanofibrous sensor was determined by SEM, which showed that nanofibers with a diameter range of 200–450 nm formed a nonwoven mat. The resultant nanofibrous sensor showed very good sensitivity in ammonia‐vapor detection. Furthermore, very good reversibility and short response time were also observed.     

Case Study: Doping Substances in Equestrian Food Supplements

In the course of investigations on equestrian supplemental products for the presence of doping substances, two products were found to contain forbidden substances. As reported earlier a plant extract (Mexican cactus extract) named “Energy 5” contained the anabolic androgenic steroids (AAS) stanozolol, 17β-hydroxy-17α-methyl-5α-androstane-3β-ol (3β,5α-THMT) as well as mestanolone not declared on the label. In the present study, a product called “Super Kalm Paste” was tested. Analysis by gas chromatography - mass spectrometry (GC-MS) revealed that the preparation contained the class I anti-arrhythmics quinine (trade names Kinidin^TM, Durules) and cinchonine. The samples were prepared according to a sample preparation procedure established for anabolic steroids in nutritional supplements for humans. The sample treatment comprised the extraction and purification of the analytes as well as the chemical conversion with N-methyl-N-trimethylsilyl-trifluoracetamide (MSTFA) to yield the trimethylsilyl (TMS)-derivatives. To verify whether the administration of such products could lead to positive doping tests, a pilot excretion study on “Energy 5” was conducted with two geldings, and urine samples were collected. Gas chromatography - high resolution mass spectrometry (GC-HRMS) after solid phase extraction and mixed derivatisation has demonstrated the presence of the stanozolol metabolite 16β-hydroxy-stanozolol in urine samples after “Energy 5” application.     

Recent applications of metal–organic frameworks in sample pretreatment

Metal–organic frameworks are promising materials in diverse analytical applications especially in sample pretreatment by virtue of their diverse structure topology, tunable pore size, permanent nanoscale porosity, high surface area, and good thermostability. According to hydrostability, metal–organic frameworks are divided into moisture‐sensitive and water‐stable types. In the actual applications, both kinds of metal–organic frameworks are usually engineered into hybrid composites containing magnetite, silicon dioxide, graphene, or directly carbonized to metal–organic frameworks derived carbon. These metal–organic frameworks based materials show good extraction performance to environmental pollutants. This review provides a critical overview of the applications of metal–organic frameworks and their composites in sample pretreatment modes, that is, solid‐phase extraction, magnetic solid‐phase extraction, micro‐solid‐phase extraction, solid‐phase microextraction, and stir bar solid extraction.     

Biomedical application of responsive ‘smart’ electrospun nanofibers in drug delivery system: A minireview

Electrospinning is a versatile method for producing continuous nanofibers. It has since become an easy and cost-effective technique in the manufacturing process and drawn keen interests in most biomedical field applications. Nanofibers have garnered great attention in nanomedicine due to their resemblance with the extracellular matrix (ECM). Like nanoparticles, its unique characteristics of higher surface-to-volume ratio and the tunability of the polymers utilizing nanofiber have increased the efficiency in encapsulation and drug-loading capabilities. Smart or “stimuli-responsive” polymers have shown particular fascination in controlled release, where their ability to react to minor changes in the environment, such as temperature, pH, electric field, light, or magnetic field, distinguishes them as intelligent. Polymers are a popular material for the design of drug delivery carriers; consequently, various types of drugs, including antiviral, proteins, antibiotics, DNA and RNA, are successfully encapsulated in the pH-dependent nanofibers with smart polymers which is a polymer that can respond to change such as pH change, temperature. In this minireview, we discuss applications of smart electrospun pH-responsive nanofibers in the emerging biomedical developments which includes cancer drug targeting, oral controlled release, wound healing and vaginal drug delivery.     

Sol-gel based synthesis of complex oxide nanofibers

Electrospinning is a versatile and straight forward process for synthesizing one-dimensional (1D) nanostructures of diverse materials. Recently, a large variety of oxide ceramics have been synthesized in combination with conventional sol-gel processing. Here, the synthesis of BaTiO₃ nanofibers via electrospinning is reported. The structural evolution from amorphous to crystalline is presented under various heat treatment conditions. Nanofibers with well-defined perovskite tetragonal phase were achieved with an average crystallite size of about 20 nm. Furthermore, single crystalline BaTiO₃ nanofibers with 50 nm in diameter and lengths up to 1 μm were found, which is a novelty in electrospinning of ferroelectrics. XRD peak splitting confirmed the tetragonal perovskite structure, and this was fully supported by further evidence from selected area electron diffraction and Raman spectroscopy.