Host-Guest Interactions of Cyclopentanocucurbit[6]uril with Alkyl Imidazolium Hydrochlorides

The host-guest interactions between cyclopentanocucurbit-[6]uril(CyP₆Q[6]) as host and six alkyl imidazolium hydrochloride as guests(g1, g2, g3, g4, g5, and g6) have been studied by various techniques, such as ¹H NMR spectroscopy, isothermal titration calorimetry, mass spectrometry, and single-crystal X-ray diffraction analysis. The experimental results showed that CyP₆Q[6] formed 1:1 inclusion complexes with each of guests g1-g6. The part of the guest entered the cavity of CyP₆Q[6] changes as the alkyl chain increases in length. It can be seen that the length of the alkyl chain plays a key role in determining the mode of host-guest interactions.     

Simple and Equipment-Free Paper-Based Device for Determination of Mercury in Contaminated Soil

This work presents a simple and innovative protocol employing a microfluidic paper-based analytical device (µPAD) for equipment-free determination of mercury. In this method, mercury (II) forms an ionic-association complex of tetraiodomercurate (II) ion (HgI₄²⁻_(aq)) using a known excess amount of iodide. The residual iodide flows by capillary action into a second region of the paper where it is converted to iodine by pre-deposited iodate to liberate I_2(g) under acidic condition. Iodine vapor diffuses across the spacer region of the µPAD to form a purple colored of tri-iodide starch complex in a detection zone located in a separate layer of the µPAD. The digital image of the complex is analyzed using ImageJ software. The method has a linear calibration range of 50–350 mg L⁻¹ Hg with the detection limit of 20 mg L⁻¹. The method was successfully applied to the determination of mercury in contaminated soil and water samples which the results agreed well with the ICP-MS method. Three soil samples were highly contaminated with mercury above the acceptable WHO limits (0.05 mg kg⁻¹). To the best of our knowledge, this is the first colorimetric µPAD method that is applicable for soil samples including mercury contaminated soils from gold mining areas.     

超高效液相色谱-串联质谱法同时测定土壤中30种抗生素

土壤基质复杂,土壤中残留的抗生素种类繁多,浓度多为痕量水平,高灵敏度的仪器方法、有效的净化和富集方法、多种类抗生素的同时检测是土壤中抗生素检测的重点和难点。该研究建立了固相萃取-超高效液相色谱-串联质谱法同时测定土壤中7类(磺胺类、氟喹诺酮类、四环素类、大环内酯类、β-内酰胺类、酰胺醇类和林可酰胺类)30种抗生素的方法。首先,通过参数优化确定最佳质谱条件,选择BEH-C18色谱柱,以0.1%(v/v)甲酸甲醇溶液-0.1%(v/v)甲酸水溶液为流动相,10%(v/v)甲醇水溶液为进样溶剂。然后,通过提取条件(萃取剂种类及体积)和固相萃取条件(上样液pH、淋洗液有机溶剂比例、洗脱液种类及体积)的优化,确定使用10 mL乙腈和Na₂EDTA-McIlvaine缓冲液的混合溶液(1∶1, v/v)为萃取剂,萃取液pH调节至8.0后,采用HLB小柱进行固相萃取,并以10 mL超纯水淋洗净化,最后用10 mL甲醇-乙腈(1∶1, v/v)洗脱目标分析物。在优化的分析条件下,该方法的定量限为0.043~4.04 μg/kg,目标化合物的标准曲线线性关系良好,相关系数在0.992~1.00的范围内,在20、100、200 μg/kg的添加浓度下,大多数目标化合物的加标回收率范围为44.8%~164%,相对标准偏差为0.700%~14.8%。将该方法用于6个实际土壤样品的分析,结果显示在30种抗生素中,17种抗生素有检出,其中12种抗生素的检出率为100%。环丙沙星和诺氟沙星是土壤样品中含量最高的两种抗生素,它们的含量范围分别是13.7~32.1和15.6~43.6 μg/kg。本研究建立的方法简单、快速、溶剂使用量少,能用于土壤样品中痕量水平的7类30种抗生素的同时测定。     

Cu/MoS2的熔盐电解法制备及其在碱性条件下析氢反应性能的提高

通过熔盐电解法并掺杂过渡金属Cu制备2种不同纳米结构的Cu/MoS_2。采用涂敷法制备工作电极,通过X射线衍射(XRD)、透射电子显微镜(TEM)、能量散射X射线谱(EDS)、扫描电子显微镜(SEM)、选区电子衍射(SAED)以及各种电化学手段验证了其结构和性能。结果表明,纳米片状Cu/MoS_2在碱性溶液(1 mol·L~(-1)KOH)中表现出优异的析氢催化性能:在电流密度为10 mA·cm~(-2)时过电位为199.6 mV,Tafel斜率为59 mV·dec~(-1),双电层电容为26.1 mF·cm~(-2),等效电荷转移电阻为12.4Ω,具有较为良好的电化学耐久性和稳定性。     

石墨消解-原子荧光光谱法测定土壤中的总硒

为准确定量土壤硒总量,提出以逆王水(1+1)-石墨消解法消解土壤,氢化物原子荧光光谱法(HG-AFS)测定土壤总硒含量的方法。其中,对消解方式、消解时间和仪器条件进行了探讨,确定最优检测条件。称取0.2g土壤样品加入5mL逆王水(1+1),于石墨消解仪120℃消解1.5h,冷却至室温后用超纯水定容至25mL,原子荧光光度计测定总硒含量。结果显示,9种土壤标准物质测定值都在理论值范围内,其相对标准偏差为2.6%,加标回收率为92.3%～110%,检出限为0.68ng/L。方法测定结果准确,操作简单、实验周期短、成本低、安全。     

碱消解-火焰原子吸收光谱法测定土壤中六价铬

建立了碱消解-火焰原子吸收光谱法测定土壤中六价铬的方法。讨论了pH值对六价铬测定的影响。干扰实验的结果表明同等含量的三价铬对六价铬测定无干扰。实验对比了无背景校正、氘灯背景校正、塞曼背景校正三种工作方式,分别对低、中、高三个水平土壤六价铬标准物质进行了测定,结果表明,低含量的土壤样品用塞曼背景校正方式测定的结果更准确,最终选择了塞曼背景校正的工作方式。方法的线性范围0.1～2.0mg/L,线性相关系数R为0.999 8,相对标准偏差(RSD)为1.1%;当取样量5g,定容体积100mL时,方法检出限为0.20mg/kg,加标回收率为84.8%～86.9%,能满足日常测定需求。     

超级微波消解电感耦合等离子体质谱法 测定土壤中13种元素

建立了超级微波消解-电感耦合等离子体质谱（ICP-MS）测定多类型土壤基质中钒、铬、锰、钴、镍、铜、锌、砷、钼、锑、铊、铅和铀等13种元素含量的方法。采用超级微波消解法对样品进行前处理,比较了超级微波前处理与常规微波前处理消解效果,并优化了消解酸体系。在最优条件下,13种元素的的方法检出限（LOD）为0.0002~0.2 mg/kg,方法定量限（LOQ）范围为0.001~0.6mg/kg。在0~500 μg/L范围内线性回归系数（R2）在0.9996~1.0000,各元素加标回收率在76.3%~126%,此方法准确度可以满足复杂基体样品多元素同时测定的需求,一次样品前处理可实现18个样品的同时测定,相较于常规前处理方法大幅减少酸使用的同时更加安全、高效、不易污染样品,可为土壤重金属污染监测工作提供可靠的分析方法支撑。     

水载流-原子荧光光谱法同时测定土壤中痕量砷、汞

改变原子荧光光谱法以稀酸为载流的进样方式,以水为载流在新型双道原子荧光光谱仪上同时测定了土壤中的痕量砷(As)、汞(Hg)。采用王水水浴加热溶解样品,用50 g/L硫脲-抗坏血酸混合溶液预先将砷还原为As(Ⅲ),保持10%(体积分数)以上盐酸浓度,不转移直接定容静置后测定。优化了仪器工作条件,详细考察了以水为载流测定的可行性,选择了同时测定As、Hg所需的硼氢化钾浓度和盐酸浓度。节省了酸试剂用量,操作快速,单个样品测定仅需20 s左右。方法检出限As为0.005 mg/kg,Hg为0.0008 mg/kg,相对标准偏差(RSD,n=7)在1.0%~7.4%,经土壤国家标准物质和实际样品验证,适合土壤中痕量As、Hg的同时快速测定。     

Aggregation Mode,Host-Guest Chemistry in Water,and Extraction Capability of an Uncharged,Water-Soluble,Liquid Pillar[5]arene Derivative

An uncharged, water-soluble per-ethylene-glycol pillar[5]arene derivative ( 1 ) was synthesized and its aggregation mode, host-guest chemistry in water and extraction ability was explored. Compound 1 is a liquid at room temperature; in water, limited self-aggregation occurred at high concentrations as deduced from diffusion NMR and dynamic light scattering. Compound 1 forms pseudo-rotaxane-like 1 : 1 host-guest complexes with 1,ω-di-substituted alkanes with association constants on the order of 10³–10⁴ m ⁻¹. Interestingly, NMR experiments showed that the guest location relative to the host ring system differs among the different complexes. In proof-of-concept experiments, compound 1 was shown to extract structurally related organic compounds from benzene into water with significant selectivity. Compound 1 , which is a liquid at room temperature and has only limited interactions with its side arms, can, in principle, be regarded as a complement to or as a kind of type I porous liquid.     

Enantioselective Synthesis of Acyclic Orthogonally Functionalized Compounds Bearing a Quaternary Stereocenter Using Chiral Ammonium Salt Catalysis

We herein report an asymmetric protocol to access a series of orthogonally functionalized acyclic chiral target molecules containing a quaternary stereogenic center by carrying out the enantioselective α-alkylation of novel orthogonally functionalized dioxolane-containing cyanoacetates under chiral ammonium salt catalysis. By using just 1 mol % of Maruoka's spirocyclic ammonium salt catalysts enantioselectivities up to e.r.=97.5 : 2.5 could be achieved and further functional group manipulations of the products were carried out as well.