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。     

磁性三维氮掺杂碳纳米材料对6种双酚类化合物的吸附性能及其在泡腾分散微萃取中的应用

采用简单高温煅烧法成功制备了磁性钴镍基氮掺杂三维碳纳米管与石墨烯复合材料(CoNi@NGC),将其作为吸附剂用于水体中6种双酚类化合物(BPs)的吸附性能和机理研究。将CoNi@NGC复合纳米材料用作萃取介质,运用酸碱泡腾片的CO₂强力分散作用,开发了泡腾反应强化的分散固相微萃取前处理方法,结合高效液相色谱-荧光检测(HPLC-FLD)快速定量饮料中痕量BPs。采用扫描电镜、透射电镜、傅里叶红外光谱、氮气吸脱附、X射线光电子能谱和磁滞回线等技术手段对材料形貌结构进行表征,结果显示:该吸附剂成功实现氮元素的掺杂,且具有较大的比表面积(109.42 m²/g)、丰富的孔径及较强的磁性(17.98 emu/g)。吸附剂投加量、pH、温度、时间等因子优化试验表明:当pH=7,在初始质量浓度为5 mg/L的BPs混合溶液中投加5 mg CoNi@NGC, 298 K反应5 min,对双酚M(BPM)、双酚A(BPA)的吸附率分别高达99.01%和98.21%。作用90 min时对双酚Z(BPZ)、BPA、BPM的吸附率近100%。在吸附过程中,BPs与CoNi@NGC之间的整个吸附过程主要受氢键、静电作用和π-π共轭作用共同控制。整个吸附过程符合Freundlich吸附等温线模型和准二级动力学方程,吸附自发进行。进一步将CoNi@NGC作为萃取介质制备成磁性泡腾片,利用泡腾分散微萃取技术高效富集和提取6种盒装饮料中的BPs,优化了影响富集效果的泡腾片的存在与否、洗脱剂种类、洗脱时间、洗脱体积等关键因子,在最佳萃取条件下(pH=7,投加5 mg CoNi@NGC, 2 mL丙酮洗脱6 min),结合HPLC-FLD,新开发的泡腾分散微萃取方法提供的检出限为0.06~0.20 μg/L,定量限为0.20~0.66 μg/L,日内和日间精密度分别为1.44%~4.76%和1.69%~5.36%,在实际样品中不同水平下的加标回收率为82.4%~103.7%,在桃汁中检测到BPA和双酚B(BPB)分别为2.09 μg/L和1.37 μg/L。再生试验表明该吸附材料至少可以重复使用5次以上,显著降低了分析的试验成本。与其他方法相比,该方法具有灵敏度高、萃取速度快、环境友好等优点,在常规食品污染监测中具有较强的应用价值。     

分散固相萃取-超高效液相色谱-串联质谱法测定水产品中5种硝基咪唑类和6种苯二氮卓类药物北大核心CSCD

建立了分散固相萃取-超高效液相色谱-串联质谱法同时测定水产品中5种硝基咪唑类和6种苯二氮卓类药物残留的方法。样品用1%(v/v)氨水乙腈提取,提取液经十八烷基键合硅胶(C18)和N-丙基乙二胺(PSA)吸附剂净化,在45℃下用氮气吹至近干,用1 mL甲醇-水(1∶9,v/v)溶液复溶,过0.22μm尼龙-66滤膜后用超高效液相色谱-串联质谱测定。目标化合物采用Kinetex F5色谱柱(100 mm×3.0 mm,2.6μm)分离,以0.1%(v/v)甲酸水溶液和甲醇作为流动相进行梯度洗脱,在电喷雾离子源(ESI)、正离子扫描和多反应监测(MRM)模式下进行测定,基质匹配外标法定量。结果表明,5种硝基咪唑类和6种苯二氮卓类药物在8.5 min内完成色谱分离分析,目标物在0.5~20μg/L范围内线性关系良好,相关系数均大于0.995,检出限和定量限分别为0.2~0.5μg/kg和0.5~1.0μg/kg。以草鱼、对虾和大黄鱼为样品基质,在3个不同的添加水平下,5种硝基咪唑类和6种苯二氮卓类药物的平均回收率为73.2%~110.6%,相对标准偏差(RSD)小于15%。本研究建立的方法具有简单、快速、灵敏度高和成本低等优势,可用于水产品中5种硝基咪唑类和6种苯二氮卓类药物的快速检测。该方法的建立为我国水产品质量安全相关监管部门同时监控水产品中硝基咪唑类和苯二氮卓类药物残留提供了技术支持。     

混合型固相萃取-高效液相色谱-串联质谱法测定稻米中3种谷维素北大核心CSCD

建立了利用高效液相色谱-串联质谱结合混合型阴离子交换固相萃取柱测定稻米中3种谷维素(环木菠萝烯醇阿魏酸酯(CA-FA)、24-亚甲基环木菠萝烯醇阿魏酸酯(24MCA-FA)和菜油甾醇阿魏酸酯(Camp-FA))含量的分析方法。实验通过优化3种谷维素的多反应监测(MRM)质谱参数,比较了在不同流动相中的分离度以及响应强度,同时考察了不同提取条件、净化条件对3种谷维素提取率和净化效果的影响,再结合外标法定量,实现了对稻米中3种谷维素的定量分析。实验结果表明,采用5 mmol/L乙酸铵水溶液为流动相A,甲醇∶乙腈=1∶1(v/v)为流动相B,梯度洗脱,3种谷维素在Agilent Eclipse XDB-C8色谱柱(150 mm×2.1 mm,3.5μm)上基本分离且响应强度和峰形最佳;提取条件经正交实验优化后可得:料液比为1∶20(g/mL)、提取溶剂为甲醇、浸泡时间为12 h、超声温度为40℃以及超声时间为20 min时,3种谷维素提取率最高;对混合型阴离子交换固相萃取柱的上样溶剂以及洗脱溶剂优化后,样品基质效应为1.6%~10.8%。在各优化条件下,3种谷维素在各自的线性范围内线性良好,相关系数(r2)均≥0.9983,检出限(LOD)为0.5~1.0μg/L,定量限(LOQ)为2.0~3.5μg/L。在稻米样品本底浓度2、5和10倍的加标水平下3种谷维素的平均回收率为86.1%~110.6%,相对标准偏差(RSD)为0.9%~3.2%。该方法可快速准确测定稻米中3种谷维素的含量,为后续稻米中谷维素类化合物测定及鉴定奠定基础。     

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.     

Extraction of parabens by melamine sponge with determination by high-performance liquid chromatography

In the present study, we propose a novel method for the extraction of parabens in personal care products. A new, simple adsorptive material was obtained by combining metal-organic frameworks and melamine sponges using the adhesive property of polyvinylidene fluoride. This new material, metal-organic frameworks/melamine sponges, was found to be particularly suitable for solid-phase extraction. The structural characteristics of metal-organic frameworks/melamine sponges were first analyzed by scanning electron microscopy. Subsequently, solid-phase extraction was performed on sample solutions, and the extracted substances were then analyzed by high-performance liquid chromatography. Following optimization of important experimental conditions, excellent recovery rates were obtained. Our novel method was then applied to the extraction of four parabens (methylparahydroxybenzoates, ethylparahydroxybenzoates, propylparahydroxybenzoates, and butylparahydroxybenzoates) from real samples. The results yielded limits of detection of 0.26–0.41 ng/mL. The inter- and intra-day recoveries were 104.0–109.7% and 91.2–98.1%, respectively (relative standard deviation, <13.8%).     

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of solid-phase extraction techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects.     

Facile synthesis of a novel magnetic covalent organic frameworks for extraction and determination of five fungicides in Chinese herbal medicines

A novel magnetic covalent organic framework was synthesized via a one-step coating approach with solvothermal reaction employing 2,4,6-tris(4-aminophen-yl)-1,3,5-triazine and 2,4,6-triformylphloroglucinol as two building blocks by covalent bonding. The prepared magnetic covalent organic frameworks were properly characterized by different techniques and employed as adsorbents of magnetic solid-phase extraction. An analytical method was developed for the simultaneous determination of five fungicides in two Chinese herbal medicine samples via magnetic solid-phase extraction coupled to ultra high performance liquid chromatography with tandem mass spectrometry analysis. Under optimized magnetic solid-phase extraction conditions, the method exhibited satisfactory recoveries (74.0−109.6%) with relative standard deviations of 0.4−4.6%, low limits of detection (0.003−0.015 μg/kg), and good linearity (R² > 0.9960). Compared with the traditional extraction method, the proposed method required a lower amount of adsorbent (3 mg) and extraction time (5 min). The adsorbent also had favorable reusability (not less than eight times). Therefore, the magnetic covalent organic frameworks could be a promising adsorbent for the extraction and quantitation of fungicides in Chinese herbal medicines.     

Preparation of bamboo-derived magnetic biochar for solid-phase microextraction of fentanyls from urine

In this study, a biochar-based magnetic solid-phase microextraction method, coupled with liquid chromatography–mass spectrometry, was developed for analyzing fentanyl analogs from urine sample. Magnetic biochar was fabricated through a one-step pyrolysis carbonization and magnetization process, followed by an alkali treatment. In order to achieve desired extraction efficiency, feed stocks (wood and bamboo) and different pyrolysis temperatures (300–700°C) were optimized. The magnetic bamboo biochar pyrolyzed at 400°C was found to have the greatest potential for extraction of fentanyls, with enrichment factors ranging from 58.9 to 93.7, presumably due to H-bonding and π–π interactions between biochar and fentanyls. Various extraction parameters, such as type and volume of desorption solvent, pH, and extraction time, were optimized, respectively, to achieve the highest extraction efficiency for the target fentanyls. Under optimized conditions, the developed method was found to have detection limits of 3.0–9.4 ng/L, a linear range of 0.05–10 μg/L, good precisions (1.9–9.4% for intrabatch, 2.9–9.9% for interbatch), and satisfactory recoveries (82.0–111.3%). The developed method by using magnetic bamboo biochar as adsorbent exhibited to be an efficient and promising pretreatment procedure and could potentially be applied for drug analysis in biological samples.     

Determination of 38 antibiotics in raw and treated wastewater from swine farms using liquid chromatography-mass spectrometry

The present study firstly aimed at developing a multi-residue method to identify and quantify 38 veterinary antibiotics (belonging to five different classes) not only for raw swine wastewater but also for wastewater differently treated by different units. The proposed method is based on a solid-phase extraction procedure and ultra high performance liquid chromatography with mass spectrometry. For sample preparation, the optimal loading sample volume was selected as 50 mL, the pH of which was adjusted to approximately 3.0 using formic acid. Then 0.1 g/L ethylenediaminetetraacetic acid disodium salt was added. The recovery rates for different types of wastewaters were in the range of 35.94–124.51% and the relative standard deviations were in the range of 0.36–14.62%. All the matrix standard curves exhibited high linearity (0.9956–0.9999). The matrix effects for the target antibiotics ranged from –61.73 to +148.75%. To ensure the practicality of the method, we performed the detection of the actually added concentration to determine method detection limits and quantitation limits. The quantitation limits of most of the target antibiotics were 0.04 μg/L, except for spiramycin (0.1 μg/L) and roxithromycin (0.2 μg/L). This optimized and validated method was applied to analyze antibiotic residues in swine water samples from four swine farms.