样品前处理介质的制备与应用研究进展

样品分析是环境污染物研究和控制的基础,到目前为止,环境样品前处理仍是环境样品分析的瓶颈问题,其中,针对复杂环境基质中的痕量污染物开发高效率和高选择性的吸附材料是样品前处理的关键和研究热点。微孔有机聚合物、有序介孔硅材料、金属有机骨架聚合物、分子印迹聚合物、碳纳米管和石墨烯等新材料具有骨架密度低、比表面积大、孔尺寸可调控、表面可修饰、化学和物理性质稳定等优点,在样品前处理领域展现出巨大的应用潜力。该文对近年来这些新型纳米材料在固相萃取、分散固相萃取、固相微萃取、磁固相萃取、搅拌棒吸附萃取和基质固相分散萃取等样品前处理领域的最新研究进展做了简要评述,为更好地开发新型纳米材料在复杂和痕量样品前处理中的应用提供了参考。     

Aminobenzohydrazide based colorimetric and ‘turn-on’ fluorescence chemosensor for selective recognition of fluoride

Chemosensors based on aminobenzohydrazide Schiff bases bearing pyrene/anthracene as fluorophores have been designed and synthesized for F⁻ ion recognition. The addition of fluoride ions to the receptors causes a dramatically observable colour change from pale yellow to brown/red. ¹H NMR studies confirm that the F⁻ ion facilitates its recognition by forming hydrogen bond with hydrogens of amide and amine groups. Moreover these sensors have also been successfully applied to detection of fluoride ion in commercial tooth paste solution.     

Trace-level determination of pyrethroid,neonicotinoid and carboxamide pesticides in beeswax using dispersive solid-phase extraction followed by ultra-high-performance liquid chromatography-tandem mass spectrometry

The aim of the work was to develop an analytical procedure able to quantify traces of 13 neonicotinoids and pyrethroids as well as carboxamide in beeswax at low levels (ng g^?1) to evaluate the contamination. For this purpose, an efficient sample preparation procedure was developed based on solid–liquid extraction using dispersive diatomaceous earth and acetonitrile. This step was followed by a selective and sensitive analysis based on ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (ESI-MS/MS). This analytical procedure was validated based on International Conference on Harmonization guidelines. The limits of quantification ranged from 1 ng g^?1 (thiamethoxam, clothianidin, imidacloprid, acetamiprid, thiacloprid and boscalid) to 40 ng g^?1 (lambda-cyhalothrin). The method was then successfully applied to 60 samples of beeswax collected in several areas of France. The presence of thiacloprid, boscalid, imidacloprid and deltamethrin in beeswax was confirmed. The most frequently quantified pesticide was boscalid.     

X射线荧光光谱法测定铁基合金中合金组分的通用工作曲线的制作——基本参数(FP)法虚拟合成标准样品的应用

应用基本参数(FP)法虚拟合成标准样品制作了X射线荧光光谱法测定不同类型的铁基合金中的26种元素的通用工作曲线。选择最佳的仪器工作条件和合理的待测元素的分析线系,测定了9种元素、受共存元素重叠干扰的校正系数,用瑞利散射线扣除背景及通道材料的影响。在设定虚拟合成标准样品中各元素的含量,并算得在此设定值下的理论荧光强度后,用FP法计算各元素在其定值下的最终强度,从而完成了FP法工作曲线。应用此虚拟合成单标工作曲线对多种标准样品进行测定,证明该工作曲线可用于各种类型的铁基合金的分析。     

超高效液相色谱-四极杆飞行时间质谱同时检测血样中4种卡西酮类新精神活性物质

建立了同时检测血样中3,4-亚甲二氧基甲卡西酮(Methylone)、3,4-亚甲二氧基乙卡西酮(Ethylone)、4-氯甲卡西酮(4-CMC)、4-氯乙卡西酮(4-CEC)4种卡西酮类新精神活性物质的超高效液相色谱-四极杆飞行时间质谱法(UHPLC-QTOF MS/MS)。取0.5 mL血液,按体积比5∶2∶13将血液、水和乙腈混合,涡旋振荡1 min,以12 000 r/min离心15 min将蛋白沉淀,取上清液待测。采用Acquity UPLC^?BEH C₁₈色谱柱(2.1 mm×100 mm,1.7μm)分离,0.1%甲酸-水(5 mmol/L乙酸铵)和乙腈作为流动相进行梯度洗脱,采用多反应监测(MRM)模式,正离子[M+H]⁺扫描检测。结果表明,4种目标药物在5～500 ng/mL质量浓度范围内线性关系良好,检出限为2 ng/mL,定量下限为5 ng/mL,回收率为87.3%～111%,日内和日间相对标准偏差分别不大于8.1%和8.6%。该方法可同时检测血样中4种卡西酮类新精神活性物质,满足实际检验需要。     

基于单颗粒电感耦合等离子体质谱法测定环境基质水样中纳米银颗粒

采用单颗粒电感耦合等离子体质谱法(SP-ICP-MS)同时测定环境水样中纳米银颗粒(AgNPs)的颗粒浓度、质量浓度和粒径分布,并考察了溶液的pH值、溶解性有机质(DOM)浓度以及离子强度等对AgNPs测定的影响。结果表明:SP-ICP-MS方法对60 nm AgNPs标准溶液的测定结果与标准值一致,准确性较好;pH值(5.0～7.0)、离子强度(≤1 mmol/L)和DOM浓度(≤30 mg/L)对测定结果影响较小;当溶液的pH值≤5.0或离子强度1 mmol/L时,AgNPs的颗粒浓度和粒径随pH值的下降或离子强度的增强而减小。采用SP-ICP-MS方法测定河水、染料废水、养殖废水3种水样中AgNPs的加标回收率分别为98.1%、83.3%和93.3%,表明该方法在合适的基质条件下可用于快速准确测定环境水样中AgNPs的颗粒浓度、质量浓度和粒径分布。     

Field-amplified on-line sample stacking for determination of carnosine-related peptides by capillary electrophoresis

An on-line sample stacking method, namely field-amplified sample injection, has been developed for the separation and determination of carnosine, anserine, and homocarnosine by capillary electrophoresis. Using electrokinetic injection, about 130- to 160-fold improvement of sensitivity was achieved without loss of separation efficiency when compared to conventional sample injection. For conventional injection, the samples were dissolved in running buffer and then hydrodynamically injected for 10 s (3.45 kPa). Various parameters affecting separation and sample stacking were optimized. Under optimum conditions, linear responses were obtained over two orders of magnitude and the detection limits (defined as S/N = 3) of carnosine, anserine, and homocarnosine were 1.5 x 10(-8) to 1.6 x 10(-8) mol/L.     

Ionized water clusters,n = 2 to 6: A high-accuracy study of structures and energetics

Ionized water clusters, , have been of remarkable interest owing to their crucial roles in many chemical and biological processes. Small cationic water clusters , n = 2 to 6 serve as reasonable models for understanding the nature of the ionized water. In this study, employing high-level ab initio quantum chemical methods, such as the density-fitted orbital-optimized linearized coupled-cluster doubles (DF-OLCCD), coupled-cluster singles and doubles (CCSD), and coupled-cluster singles and doubles with perturbative triples [CCSD(T)], a high-accuracy study of structures and energetics for cationic water clusters [, n = 2-6] is presented. In this study, 2 dimer, 8 trimer, 18 tetramer, 23 pentamer, and 25 hexamer clusters are reported. Most of the structures considered are reported for the first time. Relative, binding, and vertical attachment energies (VAEs), for the first time, are presented at the complete basis set (CBS) limit, extrapolating energies of the aug-cc-pVTZ and aug-cc-pVQZ basis sets, to provide the most accurate energetics to date. Our results demonstrate that as cluster size increases, the VAE value decreases, which indicates that large-size clusters better compensate for the electron deficiency compared with small-size clusters. The VAE values for pentamer and hexamer clusters are 118.5 to 165.5 and 121.9 to 153.7 kcal mol⁻¹, respectively. Further, our binding energy results, at the CCSD(T)/CBS level, indicate strong bindings in cationic clusters due to hydrogen bond interactions. The average binding energy per water molecule varies from −16.6 to −21.8 kcal mol⁻¹ for the clusters considered. Hence, we present the most extensive and accurate study on ionized water clusters to date. Further, our results indicate that the DF-OLCCD method is very promising for ionic molecular clusters, and its accuracy approaches the CCSD(T) quality. The inexpensive analytic gradients of DF-OLCCD, compared with CCSD(T), make it very helpful for high-accuracy studies of molecular geometries.     

Complete active space analysis of a reaction pathway: Investigation of the oxygen–oxygen bond formation

Water nucleophilic attack is an important step in water oxidation reactions, which have been widely studied using density functional theory (DFT). Nevertheless, a single-determinant DFT picture may be insufficient for a deeper insight into the process, in particular during the oxygen–oxygen bond formation. In this work, we use complete active space self-consistent field calculations and describe an approach for a complete active space analysis along a reaction pathway. This is applied to the water nucleophilic attack at a Ru-based catalyst, which has successfully been used for efficient water oxidation and in silico design of new water oxidation catalysts recently.     

On-tissue chemical derivatization of volatile metabolites for matrix-assisted laser desorption/ionization mass spectrometry imaging

Mass spectrometry imaging (MSI) of volatile metabolites is challenging, especially in matrix-assisted laser desorption/ionization (MALDI). Most MALDI ion sources operate in vacuum, which leads to the vaporization of volatile metabolites during analysis. In addition, tissue samples are often dried during sample preparation, leading to the loss of volatile metabolites even for other MSI techniques. On-tissue chemical derivatization can dramatically reduce the volatility of analytes. Herein, a derivatization method is proposed utilizing N,N,N-trimethyl-2-(piperazin-1-yl)ethan-1-aminium iodide to chemically modify short-chain fatty acids in chicken cecum, ileum, and jejunum tissue sections before sample preparation for MSI visualization.