国家标准方法中砷化氢发生装置的改进

GB/T 13079-2006《饲料中总砷的测定》银盐法(仲裁法)中的砷化氢发生装置,加锌口是直通发生器的磨砂塞子口(图1)。GB/T 5009.11-2003《食品中总砷及无机砷测定》银盐法中的砷化氢发生装置无加锌口,直接从导气口加锌粒(图2)。在测定饲料或食品中砷含量时,采取放进锌粒后马上塞上塞子,以防止气体逸出。图1 GB/T 13079-2006中砷化氢发生装置Fig.1 GB/T 13079-2006hydrogen arsenide generator     

化学气相发生气液分离装置

本实用新型涉及一种化学气相发生气液分离装置，包括混合反应器、气液分离装置和载气输送管。所述气液分离装置的气相输出管的管路中设置气体混合器，所述载气输送管与气体混合器连接。该装置可用于各类原子光谱仪器的化学气相发生系统，有效地消除化学气相发生过程中产生的大量气泡，并降低进入原子化器的待测气中的水份含量，从而提高了仪器的信噪比，有效地改善了仪器的检出下限。该装置采用抽力较强的混气装置，能将气液分离装置中的反应生成气迅速抽出并与载气均匀混合，这样可以显著降低送往原子化器中气体的湿度，其露点大大低于室温，显著提高了仪器的灵敏度和稳定性。     

快速碘量法测定微量砷

近年来国内许多单位采用二乙基二硫代氨基甲酸银(简称Ag-DDC)比色法测定微量砷。我厂也曾采用此法,但该法需要特殊的砷化氢发生装置,砷转化为有毒的砷化氢气体,分析一个液体样约需1.5小时,试剂费用高,满足不了生产的需要。本法根据AsO_3~3+I_2+H_2O(?)AsO_4~3+2I+2H~+这一反应,研究了严格控制pH值及消除钼、铁等元素的干扰,探索了含低价硫、钼及有机物高的液体试样中砷的测定方法,方法精密度优于6％,回收率92—106％。主要试剂 50％碘化钾溶液(配制时加2—3粒     

乙炔微型系列化实验装置

常量乙炔实验室制备中,由于电石中含有硫化钙、磷化钙及砷化钙杂质,与水作用放出的硫化氢、磷化氢、砷化氢气体,使制得的乙炔气体具有强烈的恶臭,严重地污染了实验室环境,在不同程度上危害着师生的身心健康。若采用下列微型实验装置,大大减少了对环境的污染。     

AgDDC光度法测定砷的探讨

砷是环保、卫生防疫等部门的一个重要分析项目。目前 ,Ag DDC光度法测定砷用得比较普遍。1　试验部分1 .1　仪器与试剂72 2分光光度计 ;1 0 0 ml测砷装置氯化亚锡溶液 :40 0 g·L-1碘化钾溶液 :1 50 g· L-1吸收液及以上试剂按文献 [1 ]配制砷标准溶液 (国家一级标准物质 GBW0 861 1 ) :1 mg· ml-1;砷中间液 :1 0 .0μg· ml-1;砷工作液 :1 .0 0μg· ml-1。无砷锌粒甲 :1 0～ 2 0目无砷锌粒乙 :颗粒较大 ,约绿豆大小。1 .2　试验方法在砷化氢发生瓶中加入砷工作液 (或水样适量 ) ,加水至 50 ml。分别加入浓硫酸 4ml,碘化钾溶液 4ml和…     

等效ISO与原国标砷化氢发生器对比试验

食品中砷的检测,国家卫生部与标准局规定用DDC-Ag比色法。本文着重介绍了ISO推荐的砷化氢发生器(见图1)与原国标砷化氢发生器的对比试验。结果表明,等效ISO砷化氢发生器平均回收率为92.16％(n=12),C.V.为1.83％;原国标砷化氢发生器平均回收率为82.82(n=12),C.V.为3.01％。因此,等效ISO砷化氢发生器具有优越性,并值得推广。     

砷钼杂多酸-灿烂绿光度法测定铜合金中微量砷

本文以砷化氢分离、碘液吸收,在酒石酸锑钾存在下,用砷钼杂多酸-灿烂绿光度法测定了铜合金中微量砷。方法简便,选择性好,灵敏度高。测定标样中的微量砷,结果与标准值吻合。     

大体积进样-浓缩柱在线富集-离子色谱法测定水中痕量及超痕量溴酸盐

建立了一种测定水中痕量及超痕量溴酸盐的在线富集大体积进样离子色谱法。采用实验室常备的柱容量较高的Dionex IonPac AG23保护柱作为浓缩柱,连接在定量环处富集溴酸盐。淋洗液自动发生装置在线生成高纯度氢氧化钾淋洗液进行梯度洗脱,抑制电导检测。实验结果表明:溴酸盐质量浓度范围在0.05~51.2 μg/L之间时线性关系良好,相关系数r≥0.9995,方法检出限为0.01 μg/L。与常规进样相比,进样量可高达5 mL,浓缩因子约为240倍。本方法成功应用于市售纯净水中溴酸盐的测定,2个加标水平的回收率在90%~100%之间,RSD(n=6)为2.1%~6.4%。该方法无需前处理,操作简单,准确度和精密度良好。通过大体积进样实现高倍富集,适用于痕量及超痕量溴酸盐的分析。     

氢化物预富集-ICP-AES法测定海水中砷的研究

要测定水中ppb数量级的砷,氢化物的发生可作为一种富集分离手段。通常海水中砷的平均浓度是3ppb左右,而且海水中存在有大量的常见元素,对微量元素的测定常发生干扰。若采用ICP-AES法测定时,这种干扰就会大大减小,截止目前,尚未见到采用ICP-AES法直接测定海水中砷的方法。我们设计了双管同时进样的封闭式反应装置,用NaBH_4还原可溶性的亚砷酸盐,生成砷化氢(AsH_3),作为ICP-AES法测定海水中超痕量砷的预先分离手段。本文对一些物理和化学条件进行了最佳化试验选择,获得砷的检出限为0.2ppb,定量测定下限为1ppb,回收率为82—106%,变异系数≤±15%。     

介绍一个富有创意的自制气体发生装置

该自制发生装置的器材全部采用废弃物组装而成,若算成本只不过0.3元左右,然而却能够极为方便的运用于反应物状态为固-液、液-液,并不需要加热制取气体的实验。该装置的组装及使用,对于增强师生变废为宝的意识,对于增强师生的创新理念,对于节省实验经费,对于经费短缺的我国西部农村中学实验室建设等,将起到很好的促进作用。     

Derivatization of organometal(loid) species by sodium borohydride problems and solutions.

Like other derivatization techniques, hydride generation is a chemical reaction that produces side-reactions leading to analytical problems. Demethylation of dimethylarsinic acid was observed to be dependent upon the pH level of the hydride generation reaction mixture. If the reaction mixture was acidic, then in addition to (CH3)2AsH, the monomethyl arsenic hydride [(CH3)AsH2] could be detected. Demethylation and also the formation of an unidentified arsenic species were noted when trimethyl arsonic oxide was used as derivatization educt. All of these effects depend on the pH level of the hydride generation mixture. We observed significant levels of organometal(loid) species of elements such as Ge, As, Sn, Sb, Hg and Bi in blank hydride generation mixtures. The organometal(loid) contamination was irreproducible even during I day using a single solution of sodium borohydride in deionized water. We concluded that the organometal(loid) contamination arises directly from the derivatization agent, sodium borohydride, itself. Use of helium purging and various adsorptive materials to decontaminate the sodium borohydride solution prior to analysis did not result in a significant decrease in organometal(loid) contamination levels. Use of a palladium-cluster stabilised with 1,10-phenanthrolin as alternative hydride generation derivatization agent was not found to be suitable, since reaction yields were poor and transmethylation reactions were noted.     

DFT study of arsine (AsH3) gas adsorption on pristine,Stone-Wales-defected,and Fe-doped single-walled carbon nanotubes

Structural Chemistry - To find the possible way of adsorption and detecting the toxic gas of AsH3, we have studied the interactions between AsH3 molecule and modified (5,5) single-walled carbon...     

A simple in situ visual and tristimulus colorimetric method for the determination of trace arsenic in environmental water after its collection on a mercury(II)-impregnated paper.

A simple in situ visual and tristimulus colorimetric method for the determination of trace arsenic in environmental water after collecting arsenic on a test paper impregnated with mercury(II) bromide and rosaniline chloride by its reduction aeration has been developed. The color development on the test paper is based on the formations of AsH(HgBr)2 (yellow) and/or As(HgBr)3 (brownish yellow) by a reaction between mercury(II) bromide and arsine (AsH3), which is produced through the reduction of As(III) (arsenite ion) and/or As(V) (arsenate ion) in a sample solution. To a sample solution, potassium iodide, tin(II) chloride, zinc sand and 4 ml of 6 M hydrochloric acid solution were added successively. The liberated arsine was collected on the test paper. The yellow or brownish-yellow color intensity on the test paper was measured by a tristimulus colorimeter and also by a visual method. The established method is applicable to the determination of arsenic in environmental water sample such as river, brackish, and seawater types.     

Thermodynamic properties of arsenic compounds and the heat of formation of the As atom from high level electronic structure calculations

Structures, vibrational frequencies, atomization energies at 0 K, and heats of formation at 0 and 298 K are predicted for the compounds As(2), AsH, AsH(2), AsH(3), AsF, AsF(2), and AsF(3) from frozen core coupled cluster theory calculations performed with large correlation consistent basis sets, up through augmented sextuple zeta quality. The coupled cluster calculations involved up through quadruple excitations. For As(2) and the hydrides, it was also possible to examine the impact of full configuration interaction on some of the properties. In addition, adjustments were incorporated to account for extrapolation to the frozen core complete basis set limit, core/valence correlation, scalar relativistic effects, the diagonal Born-Oppenheimer correction, and atomic spin orbit corrections. Based on our best theoretical D(0)(As(2)) and the experimental heat of formation of As(2), we propose a revised 0 K arsenic atomic heat of formation of 68.86 ± 0.8 kcal/mol. While generally good agreement was found between theory and experiment, the heat of formation of AsF(3) was an exception. Our best estimate is more than 7 kcal/mol more negative than the single available experimental value, which argues for a re-examination of that measurement.     

在线预还原-氢化物发生-原子荧光光谱法测定尿液中总无机砷

自行设计并制作了一种在线自动还原装置用于将尿样中可能存在的无机砷从砷(Ⅴ)还原砷(Ⅲ)。为使砷(Ⅴ)还原至砷(Ⅲ),将尿样4.8mL与1.2mL混合还原剂(每升溶液中含硫脲100g及抗坏血酸50g)混合后在反应器中于70℃加热2min。分取此溶液1.5mL与20g.L-1硼氢化钾溶液(溶于5g.L-1氢氧化钠溶液中)2.0mL,在氢化物发生器中反应生成AsH3,然后由载气(氩气)带至原子化器中,并进行原子荧光检测,所制的在线还原器及测定砷的方法已应用于儿童尿样中无机砷的测定,并在这些样品的基础上用标准加入法做回收试验,测得回收率在90.2%～102.6%之间。     

Automated micro stopped-flow/continuous-flow apparatus for serial measurement of enzyme reactions and its application as a real-time analyser for column chromatography

By functional combination of two modes of stopped-flow (SF) and flow-injection analysis (FIA), an automated micro apparatus is constructed for serial measurement of enzyme reactions. The complete operation of the apparatus, including kinetic data aquisition, is controlled by a personal computer. The apparatus has three specific features: (a) the volume required per measurement of a time course in an enzyme reaction is as small as 30 μl for each of enzyme and assay solution; (b) the time course can be traced by sampling ten observation points in a maximum of 1 s; and (c) the serial measurement of such a time course can be performed with automated cyclic operation (10 s per operating cycle as the lower limit). In addition to enzymatic activity, simultaneous monitoring of protein concentration, pH and conductivity in the enzyme solution can be sequentially conducted by the automated micro SF/FIA apparatus equipped with appropriate detectors. The successful application of such a four-channel apparatus to ion-exchange and affinity column chromatography of calf bone alkaline phosphatase proves that it is useful as a practical real-time analyser for enzyme activity together with other parameters to be monitored in liquid chromatography.     

Ab initio calculations of the electronic states of AsH2 including dissociation characteristics

Multireference configuration interaction calculations have been carried out for low-lying electronic states of AsH(2). Bending potentials for the ten lowest states of AsH(2) are obtained in C(2v) symmetry for As-H distances fixed at the the ground state equilibrium value of 2.845 a(0), as well as for the minimum energy path constrained to R(1) = R(2). The calculated equilibrium geometries for the X?(2)B(1) ground state and the A?(2)A(1) excited state agree very well with the previous experimental and theoretical results, whereas the data for the higher-lying states are obtained for the first time. Asymmetric potential energy surface (PES) cuts (at R(1) = 2.845 a(0), θ = 90.7°) and two-dimensional (2D) PESs for the lowest three states are also new. The calculated ab initio data are used for analysis of possible AsH(2) photodissociation channels and predissociation effects. It is shown that the A?(2)A(1)-X?(2)B(1) transition dipole moment decreases with increasing bending angle, which influences the intensity distribution in the A?(0,0,0)→X? emission spectrum (v(2)' bending series), shifting its maximum to smaller v(2)' quantum numbers.     

AsH3 ultraviolet photochemistry: an ab initio view

Multireference configuration interaction calculations have been carried out for low-lying electronic states of AsH(3). Bending potentials for the nine lowest states of AsH(3) are obtained in C(3v) symmetry for As-H distances fixed at the ground state equilibrium value of 2.850 a(0), as well as for the minimum energy path constrained to R(1) = R(2) = R(3). The calculated equilibrium geometry and bond energy for the X (1)A(1) ground state agree very well with the previous experimental and theoretical data. It is shown that the lowest excited singlet state belongs to the (1)A(1) symmetry (in C(3v)), in contradiction to the previous calculations. This state is characterized by a planar equilibrium geometry. Asymmetric stretch potential energy surface (PES) cuts along the H(2)As-H recoil coordinate (at R(1) = R(2) = 2.850 a(0), θ = 123.9° and 90°) for numerous excited states and two-dimensional PESs for the X and ? states up to the dissociation limits are obtained for the first time. The ? (1)A(1), B(1)E-X (1)A(1) transition moments are calculated as well and used together with the PES data for the analysis of possible photodecay channels of arsine in its first absorption band.     

Electrochemical Detection of Alloxan on Reduced Graphene Oxide Modified Glassy Carbon Electrode

Alloxan is a toxic reagent that strongly induces the diabetes by destroying insulin‐producing β‐cells in the pancreas of living organisms. The reduction product of alloxan is dialuric acid, which is responsible for the intracellular generation of ROS to enhance the stress in living cells to cause kidney disease or diabetic nephropathy. Herein, we studied for the first time the electrochemical properties of alloxan on reduced graphene oxide modified glassy carbon electrode (rGO/GCE) in 0.1 M phosphate buffer solution (PBS) at pH 7. The obtained results were compared with graphene oxide modified GCE (GO/GCE) and bare GCE surfaces. The modified rGO/GCE showed well defined redox couple with 10 fold increase in both reduction as well as oxidation peak current for alloxan than that of GO/GCE and bare GCE. Differential pulse voltammetry (DPV) technique shows the linear increase in both oxidation and reduction peak current of alloxan in the range of 30 μM to 3 mM with LOD of 1.2 μM. An amperometric signal of alloxan is also increases with respect to each addition of 50 μM of alloxan on rGO/GCE at constant potential of ?0.05 V. The linear range of alloxan is observed between 50 μM to 750 μM (S/N=3). This kind of rGO/GCE surface is more suitable platform or sensor matrix for estimating unknown concentration of alloxan molecule in the real biological systems.     

Pyrolytic carbon coating method for contoured graphite tubes and their use in furnace atomic absorption spectrometric determination of boron and uranium

Tubes are machined from rods of suitable graphite according to a modified design so that there is a recess of 20-μl capacity in the inner surface at the tube centre; this improves reproducibility and sensitivity. Pyrolytic carbon coating is accomplished independently of the atomic absorption instrument by using a simple apparatus (dimensions are given). Tube lifetimes are considerably longer than those of both coated and uncoated commercial tubes. The coated tubes described have lifetimes long anough at high atomizing temperatures to determine uranium and boron on a routine basis. The boron memory is eliminated and that of uranium successfully controlled. The addition of organic solvents to the analyte solution to enhance sensitivity for uranium is reported.