Synthesis and characterization of isotopically enriched methylmercury (CH3201Hg+)

A simple procedure for the synthesis of an important standard, isotopically enriched methylmercury, which is not commercially available, has been established successfully. The isotopically enriched standard synthesized is utilized in conventional isotope dilution mass spectrometry (IDMS), as well as in speciated IDMS (SIDMS), for determination of the true concentration of methylmercury in environmental samples. The CH₃²⁰¹Hg⁺ standard has been synthesized from commercially available ²⁰¹HgO and tetramethyltin. The synthesis time required is 1 h at 60°C. The product is highly pure, yielding more than 90% as ²⁰¹Hg in CH₃²⁰¹Hg⁺. Hazardous dimethylmercury does not occur during this synthesis procedure. The product synthesized was analyzed using high‐performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP‐MS) and ICP‐MS alone in order to determine its concentration, isotopic composition and purity. The stability of the product was also evaluated for over 6 months and found to be stable at 4°C in the dark. The isotopically enriched methylmercury synthesized can be used in SIDMS and IDMS analyses as a standard. Copyright © 2003 John Wiley & Sons, Ltd.     

Working methods paper: Micro‐scale preparation and characterization of isotopically enriched monomethylmercury

A synthesis method for the micro‐scale laboratory preparation of isotopically enriched monomethylmercury (MMHg) has been successfully established. This compound is an important standard for species‐specific isotope dilution analysis. The isotopically enriched MMHg has been synthesized from commercially available mercury oxide (²⁰¹HgO) using methylcobalamin co‐enzyme as methylating agent. The time required is less than 2 h and the final yield is about 90%. The proposed method is faster than those previously reported in the literature. It allows work on a micro scale to control the use of expensive enriched isotope standard. It also allows control of unintentional formation of dimethylmercury. The enriched mercury‐containing reaction products were analyzed by capillary gas chromatography coupled to an inductively coupled plasma mass spectrometer after derivatization with sodium tetraethylborate. The isotopic composition, concentration, purity and stability of the synthesized, enriched MMHg have been investigated in order to establish standard protocols for MMHg isotope dilution analysis or isotope labeling incubation experiments. Copyright © 2002 John Wiley & Sons, Ltd.     

Reactivity of the Indenyl Radical (C9H7) with Acetylene (C2H2) and Vinylacetylene (C4H4)

The reactions of the indenyl radicals with acetylene (C₂H₂) and vinylacetylene (C₄H₄) is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined with theory to reveal that the resonantly stabilized and thermodynamically most stable 1-indenyl radical (C₉H₇^.) is always formed in the pyrolysis of 1-, 2-, 6-, and 7-bromoindenes at 1500 K. The 1-indenyl radical reacts with acetylene yielding 1-ethynylindene plus atomic hydrogen, rather than adding a second acetylene molecule and leading to ring closure and formation of fluorene as observed in other reaction mechanisms such as the hydrogen abstraction acetylene addition or hydrogen abstraction vinylacetylene addition pathways. While this reaction mechanism is analogous to the bimolecular reaction between the phenyl radical (C₆H₅^.) and acetylene forming phenylacetylene (C₆H₅CCH), the 1-indenyl+acetylene→1-ethynylindene+hydrogen reaction is highly endoergic (114 kJ mol⁻¹) and slow, contrary to the exoergic (−38 kJ mol⁻¹) and faster phenyl+acetylene→phenylacetylene+hydrogen reaction. In a similar manner, no ring closure leading to fluorene formation was observed in the reaction of 1-indenyl radical with vinylacetylene. These experimental results are explained through rate constant calculations based on theoretically derived potential energy surfaces.     

超高效液相色谱-四极杆/静电场轨道阱高分辨质谱快速精准测定粮食中多种真菌毒素

采用直接提取稀释的快速前处理方法,结合稳定同位素稀释技术,利用超高效液相色谱-四极杆/静电场轨道阱高分辨质谱,建立了粮食中16种真菌毒素的快速精准分析方法。样品采用乙腈-水-乙酸溶液(70∶29∶1,体积比)提取,以C18色谱柱进行色谱分离,通过全扫描模式进行定量检测,并采用稳定同位素稀释以减少基质效应对定量分析的影响。结果表明,16种真菌毒素在一定浓度范围内均具有良好的线性关系,相关系数(r2)均大于0.999,4种常见粮食基质(小麦、玉米、大米、大麦)的限量浓度水平的加标回收率(n=6)为75.3%~123.5%,相对标准偏差为0.41%~14.7%。该方法简单、准确,适用于粮食中真菌毒素的检测,可满足日常监测工作的需要。     

贻贝中有机氯农药和多氯联苯标准物质的研制及同位素稀释高分辨质谱法定值

建立了贻贝中有机氯农药(OCPs)和多氯联苯(PCBs)标准物质的研制和定值方法,该研究对我国开展环境生物标准物质的研制具有重要的方法学借鉴价值。该标准物质样品为采自大连湾海域的贻贝,其定值目标物包括18种OCPs和16种PCBs,采用的定值测量方法是目前世界上最权威、最准确的同位素稀释-高分辨气相色谱/高分辨质谱联用法(ID-HRGC/HRMS)。所研制的标准物质具有定值目标物种类多、不确定度较小(约10%)等特点。该标准物质是目前国际上唯一一种采用同位素稀释高分辨质谱法进行定值的底栖生物中OCPs标准物质,于2012年3月通过了国家一级标准物质的终审,并于2012年6月被国家质量监督检验检疫总局批准为国家一级标准物质(GBW10069)。该标准物质可用于食品安全控制、环境监测、质量检测等领域相关分析方法的评价、测量质量控制及技术仲裁检验等。     

CoCl2·6H2O催化合成3,4-二氢嘧啶-2-酮衍生物

3 ,4 二氢嘧啶 2 酮类化合物可用作钙拮抗剂、降压剂、α1ａ 拮抗物等而成为近年来生物活性有机杂环化合物研究的热点之一[1 ] 。通常该类化合物是用Ｂｉｇｉｎｅｌｉ[2 ,3] 反应得到的。为了提高其产率 ,人们作了大量的研究工作[4,1 1 ] 。本文利用Ｃｏ Ｃｌ2 6Ｈ2 Ｏ作催化剂 ,乙醇作溶剂 ,乙酰乙酸乙酯、芳香醛和脲一锅煮合成 3,4 二氢嘧啶 2 酮 ,同时考查了芳香醛的取代基及乙酰丙酮对产物收率的影响。反应方程式如下 :1　实验部分1 1　仪器与试剂熔点用毛细管法测定 ,温度计未校正。Ｅ ＱＵＩＮＯＸ5 5红外光谱仪 (ＫＢｒ压片 ) ;…     

Chemical and electrochemical grafting of polyaniline onto poly(vinyl chloride): synthesis,characterization, and materials properties

We have designed and developed a new strategy for the chemical and electrochemical graft copolymerization of aniline onto poly(vinyl chloride). For this purpose, first phenylamine groups were incorporated into poly(vinyl chloride) via a nucleophilic substitution reaction in the presence of a solvent composed of 4‐aminophenol, potassium carbonate, and dry N,N‐dimethylformamide at room temperature, in order to avoid cross‐linking. The macromonomer obtained was used in chemical and electrochemical oxidation copolymerization with aniline monomer to yield a poly(vinyl chloride)‐g‐polyaniline (PVC‐g‐PANI) graft copolymer. The chemical structures of samples as representatives were characterized by means of Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The electroactivity behaviors of the synthesized samples were verified under cyclic voltammetric conditions. The electrical conductivity and electroactivity measurements showed that the PVC‐g‐PANI graft copolymer has lower electrical conductivity as well as electroactivity than those of the pure PANI. However, the lower electrical conductivity and electroactivity levels in this material can be improved at the price of solubility and processability. Moreover, the thermal behavior and chemical composition of the synthesized graft copolymer were investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Hydrothermal synthesis, crystal structure and photoluminescence of [HgCl2(C6NO2H5)]nn[HgCl2]n(C6NO2H5)

The first example of isonicotinic acid compounds with infinite mercury halide chains, [HgCl₂(C₆NO₂H₅)]_n n[HgCl2]n(C₆NO₂H₅) (1), was synthesized through hydrothermal reactions and structurally characterized by X-ray single crystal diffraction. Compound 1 features a one-dimensional (1-D) motif, based on infinite 1-D [HgCl₂(C₆NO₂H₅)]_n chains, neutral HgCl₂ moieties and isolated isonicotinic acid molecules. The [HgCl₂(C₆NO₂H₅)]_n chains, HgCl₂ moieties and isonicotinic acid molecules are interlinked by hydrogen bonds and π-π interactions to give a two-dimensional supramolecular layer. Photoluminescent investigation reveals that the title compound exhibits a strong emission in blue region. The emission band is identified as the π -π* transitions of the isonicotinic acid moieties.     

Development of human serum certified reference material for quantification of polychlorinated biphenyls

Human serum certified reference material (CRM), NMIJ CRM 7407-a, for the analysis of polychlorinated biphenyls (PCBs) was developed by the National Metrology Institute of Japan. A pool of commercially available human serum was used as a raw material of the CRM. This sample is in the form of a liquid comprising approximately 4 g stored in a cryogenic polypropylene vial. Homogeneity assessment was performed, and the material was homogeneous enough for PCB 118, PCB 138, PCB 153, and PCB 194: the relative uncertainties due to inhomogeneity were 2.5–10.5%. The results obtained from the stability assessment indicated that the target PCBs were stable: the relative uncertainties due to instability were 0–14.7%. The certification was carried out using two different types of GC columns for each target PCB to avoid interferences on GC separation; the certified values of the target PCBs (PCB 118, PCB 138, PCB 153, and PCB 194) were 9.7–129.8 ng/kg. This is the first frozen human serum CRM in which PCBs were determined by isotope dilution mass spectrometry.     

Thermokinetics on the reaction of formation of Dy[(C_5H_8NS_2)_3(C_(12)H_8N_2)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H2O) in absolute ethanol at 298.15 K has been determined as (-16.12±0.05) kJ·mol-1 by a microcalor-meter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59±0.29) kJ·mol-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.     

Thermochemistry of europium and dithiocarbamate complex Eu(C5H8NS2)3(C12H8N2)

A solid complex Eu(C₅H₈NS₂)₃(C₁₂H₈N₂) has been obtained from reaction of hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen⋅H₂O) in absolute ethanol. IR spectrum of the complex indicated that Eu³⁺ in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms from the o-phen. TG-DTG investigation provided the evidence that the title complex was decomposed into EuS. The enthalpy change of the reaction of formation of the complex in ethanol, Δ_r H _m ^θ(l), as –22.214±0.081 kJ mol^–1, and the molar heat capacity of the complex, c _m, as 61.676±0.651 J mol^–1 K^–1, at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy change of the reaction of formation of the complex in solid, Δ_r H _m ^θ(s), was calculated as 54.527±0.314 kJ mol^–1 through a thermochemistry cycle. Based on the thermodynamics and kinetics on the reaction of formation of the complex in ethanol at different temperatures, fundamental parameters, including the activation enthalpy (ΔH _≠ ^θ), the activation entropy (ΔS _≠ ^θ), the activation free energy (ΔG _≠ ^θ), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained. The constant-volume combustion energy of the complex, Δ_c U, was determined as –16937.88±9.79 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_c H _m ^θ, and standard enthalpy of formation, Δ_f H _m ^θ, were calculated to be –16953.37±9.79 and –1708.23±10.69 kJ mol^–1, respectively.     

Gas-Phase Synthesis of Triphenylene (C18H12)

For the last decades, the hydrogen-abstraction−acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C₁₄H₉]^.) with vinylacetylene (C₄H₄), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH – triphenylene (C₁₈H₁₂) – via an unconventional hydrogen abstraction–vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level.     

Aminotelechelics: A convenient synthesis and characterization of primary amino-terminated telechelic poly(propylene glycol) and polyisobutylene

The synthesis of amino-terminated telechelic poly(propylene glycol) and polyisobutylene from their corresponding dihydroxy-terminated derivatives was studied. The synthesis of these aminotelechelics was achieved by the coupling of imidazolylformates with ethylenediamine. The structure of the resulting amino-functionalized polymers was determined by ¹H NMR, ¹³C NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. On the basis of the spectroscopic and spectrometric results, a complete conversion of dihydroxy termini into diamino end groups was observed; that is, the number-average functionality was found to be 2. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 587–596, 2004     

Continuous flow isotope ratio mass spectrometry for the measurement of nanomole amounts of (13)CO(2) by a reverse isotope dilution method

A simple method for the determination of nanomole amounts of (13)CO(2) generated from an in vitro reaction is reported. The incubation medium contains a known amount of unlabeled sodium bicarbonate and the gaseous (13)CO(2) enriches the atmosphere upon which a measurement of the isotopic enrichment ((13)CO(2)/(12)CO(2)) is made corresponding to a reverse isotope dilution. The quantification of the (13)CO(2) was performed by gas chromatography/isotope ratio mass spectrometry. This assay was validated in terms of linearity, accuracy and precision using three different substrates which produce (13)CO(2) either by enzymatic reaction [(13)C]urea, sodium [(13)C]formate) or by chemical reaction (sodium [(13)C]bicarbonate). Four calibration curves were tested for each (13)C-labeled substrate, allowing the quantification of (13)CO(2) from 25 pmol to 150 nmol. The dynamics of the assay were obtained as a function of the quantity of unlabeled sodium bicarbonate added to each sample.     

同位素稀释高效液相色谱-串联质谱法测定水果及其制品中的展青霉素

建立了同位素稀释高效液相色谱-串联质谱法对水果及其制品中的展青霉素进行测定。澄清果汁(浊汁、固液体及固体样品需用果胶酶酶解处理,乙酸乙酯提取浓缩后复溶)经混合型阴离子交换柱净化、富集后,采用Waters HSS T3柱(2.1 mm×100 mm,1.8μm)以乙腈-水为流动相梯度洗脱,电喷雾离子源离子化,负离子多反应离子监测(MRM)模式检测,同位素稀释内标法定量。展青霉素在5~250 ng/m L浓度范围内线性关系良好,相关系数(r~2)大于0.999,该方法在不同基质不同加标浓度下,回收率为90.6%~110.1%,相对标准偏差(RSD)为1.4%~3.9%,定量下限为5.0μg/kg(苹果汁中定量下限为2.0μg/kg)。该方法准确可靠、灵敏度高,适合于水果及其制品中展青霉素的测定,可满足我国GB 2761-2011对于水果制品、果蔬汁和酒类(仅限苹果和山楂)中展青霉素残留的检测要求。     

An inverse gas chromatographic characterization of polypyrrole-coated poly(vinyl chloride) powder particles

Polypyrrole-coated poly(vinyl chloride) powder particles (PPy-PVC) were prepared by the in-situ chemical polymerization of pyrrole in aqueous solutions in the presence of PVC powder particles using the method of Ouyang and Chan [Polymer 39 (1998) 1857] and characterized by inverse gas chromatography (IGC). By employing n-alkane, 1-heptene, chloroform and tetrahydrofuran molecular probes, the dispersive and acid–base components of the surface energy of the composite materials were estimated at infinite dilution. The values of the dispersive contribution to the surface energy (γ_S^d), at 50 °C, range from 30.3 to 43.5 mJ/m² for the composites, which is much lower than the value of 83.2 mJ/m² obtained for para-toluene sulfonate-doped polypyrrole (PPyTS) bulk powder. This indicates that the injected molecules probe both polypyrrole and the underlying PVC, thus indicating that the conducting polymer is rather patchy at the surface of the insulating polymer substrate. This conclusion supports the previous results obtained by X-ray photoelectron spectroscopy (XPS) [19], indicating that both the coating PPyTS and the substrate PVC are detected by their elemental markers nitrogen and sulfur, and chlorine, respectively.     

Synthesis of bis(2-cyanoacrylates) from 2-cyanoacryloyl chloride and 2-butene- and 2-butyne-1,4-diols

The interaction of 2-cyanoacryloyl chloride with unsaturated 1,4-diols leads to bis(2-cyanoacrylates) with a double or triple C-C bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 779–780, April, 1995.     

用FTIR研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用溶液法得到线形多嵌段聚氨酯（PU）与聚氯乙烯（PV）、氯化聚氯乙烯（CPVC）的共混物。用FTIR研究PU/PVC、PU／CPVC共混物的相容性，发现PVC、CPVC的加入破坏了PU中原来的氢键，并且PU中的炭基（C=0）与PVC、CPVC中的α－H形成了新的氢键，因而说明了PU／PVC、PU／CPVC共混物具有良好的相容性。     

用DSC研究线形多嵌段聚氨酯与聚氯乙烯、氯化聚氯乙烯共混相容性

用示差扫描量热法（DSC）研究了线形多嵌段聚氨酯（PU）与聚氯乙烯（PVC）、氯化聚氯乙烯（CPVC）共混相容性，说明了PU／VC、PU／CPVC的相容是由于共混物中形成了新的氢键的缘故．聚酯型聚氨酯与PVC、CPVC的相容性要好子聚酸型聚氨酯，CPVC与PU的相容性又要好于PVC．聚氨酯中硬段的引入不利于PU／PVC、PU／CPVC的相容性．     

氯化镉催化三组分“一锅法”合成4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮的研究

在氯化镉催化作用下,以环己烷为溶剂,芳香醛、芳香酮和脲三组分"一锅法"合成了一系列4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮化合物。考察了溶剂和催化剂用量对产率的影响。通过IR、1H NMR、13C NMR和元素分析对产品结构进行了表征。该合成方法具有操作简单、反应时间短、反应条件温和,产率高等优点。