Automatic isotope gas analysis of tritium labelled organic materials

An analytical procedure and an automatic apparatus are described for the determination of tritium in organic compounds by gas counting. The sample is pyrolysed in hydrogen atmosphere at 1000°C, then, with hydrogen, the decomposition products are rinsed through a column of molecular sieve-5A heated to 550°C. Tritium in water, hydrogen sulphide, ammonia and hydrogen cyanide is transferred into the hydrogen stream by isotope exchange completed on the column. The inactive water vapor, hydrogen sulphide, ammonia and hydrogen cyanide as well as carbon dioxide are removed from the gas stream by appropriate absorbents, and the radioactive hydrogen together with tritiated methane, carbon monoxide and nitrogen included in the pyrolytic products is led into an internal proportional counter tube for radioactivity measurement. The method provides quantitative recovery, it is free of memory effect and suitable for the rapid assay of a wide variety of organic compounds containing C, H, N, O, S in addition to tritium.     

双柱气相色谱法测定明胶空心胶囊中环氧乙烷的残留量

采用弱极性、中极性的毛细管柱互补分离技术对明胶空心胶囊中的环氧乙烷进行定性、定量分析。样品用水提取,顶空进样,经DB–624或PLOT/Q色谱柱分离,氢火焰离子化检测器检测,外标法定量。结果表明,在0.1~1.6 mg/L内线性关系良好(r≥0.998),检出限为0.15 mg/kg,加标回收率为98.2%~105.1%,测定结果的相对标准偏差为3.6%~6.2%(n=6)。该方法操作简便、灵敏度高,能满足明胶空心胶囊中环氧乙烷的检测要求。     

The behavior of titanium,stainless steel,and copper-nickel alloys as plasma torch cathodes

Cathode erosion continues to be a problem hindering the widespread application of plasma technology. In this work, cathode erosion was studied on titanium, stainless steel 314, copper-nickel 10% and 30%, and copper 122 for magnetically rotated arcs operating in argon, nitrogen, and argon/hydrogen mixtures at a constant magnetic flux density of 0.1 T Titanium and stainless steel gave very low erosion rates in argon (0.2 and 0.3, g/C respectively). Cupronickels were shown to be suitable for nitrogen and hydrogen plasmas. The slope of hydrogen solubility versus temperature in the cathode material was found to be important in determining hydrogen plasma erosion characteristics. When the plasma gas has a high solubility in the cathode material, or can react with the cathode, a negative erosion rate may result. When gas solubility in the cathode is low, oxide stability and mode of electron emission may govern the erosion rate. A high gas solubility in the cathode material, as with hydrogen, can result in mechanical erosion due to micro-explosions near the cathode surface.     

Automatic isotope gas analysis of tritium labelled organic materials

An isotope analytical procedure and an automatic instrument developed for the determination of tritium in organic compounds and biological materials by internal gas counting are described. The sample is burnt in a stream of oxygen and the combustion products including water vapour carrying the tritium are led onto a column of molecular sieve-5A heated to 550 °C. Tritium is retained temporarily on the column, then transferred into a stream of hydrogen by isotope exchange. After addition of butane, the tritiated hydrogen is led into an internal detector and enclosed there for radioactivity measurement. The procedure, providing quantitative recovery, is completed in five minutes. It is free of memory effect and suitable for the determination of tritium in a wide range of organic compounds and samples of biological origin.     

Analytical method for atmospheric tritium with a portable tritium sampling system

A portable tritium sampler was developed for the stepwise collections of water vapour (HTO), hydrogen (HT) and hydrocarbons (CH₃T) in the atmosphere. First, water vapour was collected in an electronic cooler and an HTO collection column containing 400 g of molecular sieve. Next, dried air was introduced into an HT collection column containing 150 g of palladium catalyst. Hydrogen was then converted to water by catalytic oxidation at room temperature and the resultant water was immediately adsorbed on the molecular sieve bed supporting the catalyst. The remaining gas was finally introduced into a CH₃T collection column containing 100 g of molecular sieve through a platinum catalyst column, in which hydrocarbons were burnt at 400°C. The resultant water was adsorbed in the CH₃T collection column. The collection efficiencies of water in the HTO, HT and CH₃T collection columns were all estimated to be nearly 100%. This newly developed method was found to be useful for the routine tritium monitoring by applying it to actual air samples.     

Coulometric determination of microamounts of hydrogen in metal

Hydrogen in metal was extracted into a carrier gas (argon) by heating at about 1100 degrees , and oxidized to water with copper(II) oxide. The water was converted into ammonia with sodium amide at 80 degrees . The ammonia was then titrated with electrolytically generated hypobromite ion. The blank value of single determination could be reduced to less than 1 mug of water. Hydrogen in stainless steels, tantalum metal and pure tin metal could be determined satisfactorily, and some results were compared with those obtained by the ordinary vacuum extraction method.     

Regeneration of copper(II) oxide with hydrogen gas in the reduction column of an elemental analyzer

Nitrogen in organic samples may be determined on a routine basis after combustion in elemental analyzer instruments. If elementary copper is used in the reduction column, it will be oxidized to copper(II) oxide by passing oxygen and nitrogen oxides. Instead of changing the reduction column it is possible to regenerate the copper(II) oxide to elemental copper with hydrogen gas without removing the column from the oven. A modification of the original instrument and procedure is described. In this method, the capacity of the column will decrease after regeneration, but time and chemical costs will be saved.     

Mechanism of HTO formation in gaseous tritium mixtures

The mechanisms for the conversion of molecular tritium gas to tritiated water are examined for tritium mixtures with (1) oxygen and nitrogen, (2) oxygen and argon, and (3) water and helium, for which previous experimental data exist. By analyzing results of these experiments in light of the radiation chemistry involved in a mixture of tritium and other gases, an understanding of the conversion mechanisms is reached. The formation of H and/or OH free radicals as intermediate species is of particular significance in the formation of HTO in that these radicals initiate a number of reactions which lead to the formation of water. These reactions are analyzed in terms of steady-state kinetics to obtain predictive models which can be judged against the experimental observations. For the three experimentally observed mixtures, model agreement is found to be within a factor of 2–3.     

甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO₂-ZrO₂/SiC整体催化剂，并将其用于甲醇水蒸气重整制氢反应中。结果表明，与CuO/CeO₂-ZrO₂颗粒催化剂相比，CuO/CeO₂-ZrO₂/SiC整体催化剂催化活性较好，产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响，结果表明，当CeO₂-ZrO₂复合氧化物涂层涂覆量在15%±1%，CuO负载量为5%±1%时，催化性能较好；当反应温度为340℃，水醇物质的量比为1.2，甲醇水蒸气气体空速为4840 h^-1时，甲醇转化率为86.0%，产氢速率为1490.0 L/（m³·s），重整气中CO体积分数为1.55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明，随着气体空速变大，甲醇转化率下降，产氢速率上升，重整气中CO体积分数下降。随着水醇物质的量比增加，甲醇转化率先上升后下降，产氢速率先上升后下降，重整气中CO体积分数下降。随着反应温度的升高，甲醇转化率、产氢速率和重整气中CO体积分数均上升。     

介质阻挡放电等离子体甲烷/水蒸气重整制氢

采用自制的介质阻挡放电实验系统,进行了甲烷/水蒸气大气压下重整制氢实验研究。考察了水碳比（水蒸气/甲烷物质的量比）、气体总流量、放电电压和放电频率对甲烷转化率及氢气等主要产物产率的影响。结果表明,甲烷转化率和氢气产率随着水碳比和放电电压的增加而增大,随着气体总流量和放电频率的增加呈现先增大后减小的变化规律。在放电电压18.6 kV、放电频率9.8 kHz、水碳比3.4、反应气体总流量79 mL/min时,获最大氢气产率（14.38%）。此外,利用发射光谱对放电过程中的活性基团进行了原位诊断,得到了CH·、OH·、H₂及H_α活性粒子的光谱信号强度随实验参数的变化规律,并结合放电机理推测了氢气的生成路径。     

Stability test and improvement of hydrogen analyzer with trace reduction detector

We previously developed an analyzer able to detect hydrogen concentrations of less than 50 cm3/1000 m3. The analyzer uses a carrier gas purifier and a low temperature separation column to remove impurities preventing measurement of low concentrations from the carrier and sample gases. It uses a trace reduction detector with a mercuric oxide bed to detect the concentration of hydrogen based on the reduction reaction of mercuric oxide with hydrogen. We have now evaluated the performance of the analyzer by carrying out a series of tests that measured the spectrum peak and the retention time. We used three sample gases with hydrogen concentrations of 5, 20, and 50 cm3/1000 m3 in nitrogen dilution gas. The measured peak was stable (it was within a relative standard deviation of less than 10%), and there was a linear relationship between the peak and hydrogen concentration. However, the retention time gradually shortened as the measurements were repeated. The shortening was reduced by warming the low temperature separation column used in the analyzer; it was not observed when we used a hydrogen sample gas diluted by helium instead of nitrogen. Using nitrogen as a dilution gas apparently shortens the retention time. We thus added an MS-5A separation column and a thermal conductivity detector. The nitrogen and hydrogen in the sample/carrier gas are separated, and the nitrogen is efficiently removed by switching the pass line to a release line after the hydrogen has been sent to the low temperature separation column. An analyzer using this "after-cut method" was able to stably measure infinitesimal hydrogen concentrations and was not affected by nitrogen in the sample gas.     

Gas chromatography flow rates for determining deuterium/hydrogen ratios of natural gas by gas chromatography/high-temperature conversion/isotope ratio mass spectrometry

The effects of the gas chromatography flow rate on the determination of the deuterium/hydrogen (D/H) ratios of natural gas utilising gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/TC/IRMS) have been evaluated. In general, the measured deltaD values of methane, ethane and propane decrease with increase in column flow rate. When the column flow rate is 1 mL/min or higher, which is commonly used for the determination of D/H ratios of natural gas, the organic H in gas compounds may not be completely converted into hydrogen gas. Based on the results of experiments conducted on a GC column with an i.d. of 0.32 mm, a GC flow rate of 0.6 mL/min is proposed for determining the D/H ratios of natural gas by GC/TC/IRMS. Although this value may be dependent on the instrument conditions used in this work, we believe that correct deltaD values of organic compounds with a few carbon atoms are obtained only when relatively low GC flow rates are used for D/H analysis by GC/TC/IRMS. Moreover, as the presence of trace water could significantly affect the determination of D/H ratios, a newly designed inlet liner was used to remove trace water contained in some gas samples.     

Lignin conversion to hydrogen-containing gas under the action of microwave radiation

The paper describes the carbon dioxide reforming of lignin in the presence of Ni-, Fe, and Ni/Fe-containing active components formed directly on the surface under microwave irradiation. The deposition of 0.1 wt % iron acetylacetonate on the lignin surface results in a sharp increase in the microwave absorption capacity at a 0.5 kW power and induces lignin conversion to hydrogen-containing gas with a degree of hydrogen recovery reaching 90 %. The maximum lignin conversion (65%) is attained in 10 min under microwave irradiation. It was shown for the first time that deposition of metals (Fe and Ni) on lignin can provide for targeted change of the selectivity of reforming to synthesis gas and the process can thus be classified as a plasma catalytic one. Using the obtained results, it is possible to minimize the amount of catalyst and to propose an efficient route for hydrogen and synthesis gas production from lignin waste.     

薄层流动时安法测定电镀废水中的铜

应用薄层流动时安法测定电镀废水中铜的含量 .试样溶液由流动状态转换为静止状态时的时库仑电量与铜离子浓度 (2～ 16mg/L)呈良好的线性关系 .对样品溶液进行 8次平行测定的相对标准偏差小于 0 .1% ,标准加入法测定的回收率为 99%～ 10 3% .该方法克服了电容电流及电极表面性质改变等噪声干扰 ,具有快速灵敏、准确、再现性好的优点     

Determination of non-metallic elements by capacitively coupled helium microwave plasma atomic emission spectrometry with capillary gas chromatography

A capacitively coupled microwave helium plasma with a tubular tantalum electrode was evaluated as an element selective detector for gas chromatography (GC). The end of a 10-m bonded fused capillary column was directly inserted into the tubular electrode without any switching system. A heated copper tube was used to house the part of the GC column that protruded from the oven. The optimisation of operating parameters, line selection, background emission and horizontal and vertical observation position is described. Analytical figures of merit including sensitivity, reproducibility, signal to background ratio, selectivity, dynamic range and limit of detection (LOD), were evaluated for carbon, hydrogen, chlorine and bromine emission. Limits of detection in the low ng range (20 pmol) were obtained for halogenated compounds using carbon emission, whereas LODs in the 0.1 micrograms range (2 nmol) were obtained using chlorine or bromine emission lines.     

Specific features of the gas-chromatographic determination of the reaction products in the catalytic decomposition of hydrogen sulfide

Specific features of the determination of hydrogen sulfide in the presence of hydrogen were studied by gas chromatography with the use of a thermal conductivity detector and argon as the carrier gas. A chromatographic column with HayeSep A modified with 10 wt % H₃PO₄ was proposed for the simultaneous determination of both components. It was demonstrated that the elution curve of hydrogen sulfide in an argon atmosphere has a non-Gaussian shape because of the interaction of hydrogen sulfide with the tungsten filament of the sensing element of the catarometer. To eliminate this interaction, it was recommended that a gold-plated tungsten filament be used in the detector.     

Fe2O3/CNT催化湿法H2O2氧化苯酚

通过化学沉积法和热处理得到多壁碳纳米管负载Fe2O3催化剂 Fe2O3/CNT, Fe2O3的负载质量分数约为15.1%,XRD表征显示,负载的Fe2O3存在α和γ这2种晶型。考察了Fe2O3/CNT催化湿式H2O2氧化去除废水中苯酚催化性能,通过苯酚的去除率及反应过程中催化剂活性组分的溶出总量,研究了催化剂制备过程中添加聚乙烯醇对催化剂性能的影响。在苯酚和H2O2初始浓度分别为350和1 500 mg/L、催化剂投加量为1.0 g/L、温度80 ℃条件下,经过240 min的反应,苯酚去除率达100％,COD去除率为86.1％。     

Determination of cadmium in river water by sequential metal vapor elution analysis

Determination of cadmium in river water by sequential metal vapour elution analysis (column temperature; > 1500 K) with argon and hydrogen carrier gas and with atomic absorption spectrometric detection is described. The column is made of a molybdenum capillary tube (i.d. 1.22 mm) and the temperature is 1760 K. The cadmium vapor was separated from those of calcium, iron and sodium. The calibration graph was linear up to 15 μ/ml. Relative standard deviations of 0.8–4.3% were obtained in the range 1 to 15 μ/ml. Cadmium in spiked samples (river water) was determined. The results were in good agreement with the amount spiked.     

Abnormally high heat generation by transition metals interacting with hydrogen and oxygen molecules

Abnormally high heats, exceeding 2000 kJ/mol (20 eV) per molecule of O₂, are generated by interaction of the oxygen with the hydrogen absorbed on palladium, gold and nickel particles at 25 °C to 220 °C. The highest heats were observed when the metals were treated with micromole quantities of argon, prior to absorption of hydrogen, as well as its interactions with metal particles reaching nanometer size. In the latter case the heat evolutions due to the interactions with hydrogen were approaching 5000 kJ/mol. The interactions with oxygen in inert gas environments, such as that of argon, yielded higher heat evolutions than those given by pure O₂ pulses injected into nitrogen carrier gas. The results revealed an important role of argon in increasing the intensity of atomic hydrogen-oxygen reactions to a level several times higher than the heat of water formation from molecular hydrogen and oxygen.     

新型气体扩散电极体系高效产H2O2的研究

以自制新型石墨/聚四氟乙烯(PTFE)气体扩散电极在无隔膜体系中进行双氧水发生工艺的优化研究, 主要探讨了不同石墨和PTFE质量比、阴极电位、pH值和氧气流速对H2O2产率的影响. 结果表明, 以石墨和PTFE质量比为2:1的气体扩散电极为阴极, 在pH=3, Na2SO4浓度为0.1 mol•L−1, 氧气流速为0.4 L•min−1, 阴极电位为−0.55 V (vs SCE)时, 2 h后H2O2可以达到60 mg•L−1. 该新型体系有较高的H2O2产率和电流效率(可达60%以上), 且pH值适用范围较广, 可望应用于水中污染物的处理.