A dynamic wicking technique for determining the effective pore radius of pregelatinized starch sheets

A dynamic wicking technique is employed for the first time for the determination of the effective mean pore radius of a thin-layer porous food: drum dried pregelatinized starch sheets. The technique consists of measuring the penetration rate of various n-alkanes in the porous matrix of the starch sheets and using this data to calculate the effective pore radius via the Washburn equation. Pore sizes in the order of a few nanometers have been determined in the starch sheets depending on the drum dryer’s operating variables (drum rotation speed, steam pressure and starch feed concentration). The conditions for the application of the technique in porous foods are discussed as compared to the conditions for single capillaries and inorganic porous material measured in other studies.     

Portable remote Raman system for monitoring hydrocarbon, gas hydrates and explosives in the environment

We report our initial efforts to use a small portable Raman system for stand-off detection and identification of various types of organic chemicals including benzene, toluene, ethyl benzene and xylenes (BTEX). Both fiber-optic (FO) coupled and a directly coupled f/2.2 spectrograph with the telescope have been developed and tested. A frequency-doubled Nd:YAG pulsed laser (20 Hz, 532 nm, 35 mJ/pulse) is used as the excitation source. The operational range of the FO coupled Raman system was tested to 66 m, and the directly coupled system was tested to a distance of 120 m. We have also measured remote Raman spectra of compressed methane gas and methane gas hydrate. The usefulness of the remote Raman system for identifying unknown compounds is demonstrated by measuring stand-off spectra of two plastic explosives, e.g. tri-amino tri-nitrobenzene (TATB) and beta-HMX at 10 m stand-off distance. The remote Raman system will be useful for terrestrial applications such as monitoring environmental pollution, in identifying unknown materials in public places in 10s or less, and for detecting hydrocarbon plumes and gas hydrates on planetary surfaces such as Mars.     

Miniature liquid flow sensor and feedback control of electroosmotic and pneumatic flows for a micro gas analysis system.

Accurate liquid flow control is important in most chemical analyses. In this work, the measurement of liquid flow in microliters per minute was performed, and feedback control of the flow rate was examined. The flow sensor was arranged on a channel made in a polydimethylsiloxane (PDMS) block. The center of the channel was cooled by a miniature Peltier device, and the change in temperature balance along the channel formed by the flow was measured by two temperature sensors. Using this flow sensor, feedback flow control was examined with two pumping methods. One was the electroosmotic flow method, made by applying a high voltage (HV) between the reagent and waste reservoirs; the other was the piezo valve method, in which a micro-valve-seat was fabricated in a PDMS cavity with a silicone diaphragm. The latter was adopted for a micro gas analysis system (microGAS) for measuring atmospheric H2S and SO2. The obtained baselines were stable, and better limits of detection were obtained.     

The MEDINA facility for the assay of the chemotoxic inventory of radioactive waste packages

A new analytical facility called MEDINA (Multi Element Determination based on Instrumental Neutron Activation) and based on Prompt- and Delayed-Gamma-Neutron-Activation-Analysis (P&DGNAA) using a 14 MeV neutron generator is developed for the determination of non-radioactive elements and substances in 200-l radioactive waste drums. The qualitative performance of MEDINA is studied by measuring (1) the gamma-ray spectra for the empty chamber, (2) for an empty 200-l steel drum in presence or not of ⁶⁰Co and ¹³⁷Cs sources and (3) for a 200-l steel drum filled with concrete in order to determine the level of interferences induced by activation products of the facility components and to investigate further optimization steps to improve the measurements sensitivity. The measurement carried out for the empty drum with the radioactive sources show the possibility to characterize radioactive waste packages containing both ⁶⁰Co and ¹³⁷Cs with activities ranging between 20 and 80 MBq at least.     

An electroelution apparatus for sequential transfer of sodium dodecyl sulfate-proteins into agarose and mass spectrometric identification of Li-Na-dodecyl sulfate-proteins from solubilized agarose

Separated protein bands are sequentially electrophoresed into low melting agarose plugs distributed in an apparatus of original design along the surface of a plastic drum. The rotation of the drum is synchronized to migration of electrophoretic bands to receive each band individually. Agarose plugs are dissolved enzymatically for transfer into the mass spectrometer. One microL of the agarose solution containing 1 pmol of each of three lithium and natrium salts of dodecyl sulfate (Li-Na-DS)-proteins were applied to matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) without any prepurification. It yields a signal indistinguishable from that obtained in the absence of agarose.     

氢气在混合溶剂丙酮-水中的溶解度

本文报导一种能准确测定气体在混合溶剂中溶解度并能同时测定溶剂的饱和蒸气压的实验装置, 在20～40 ℃的温度范围内, 分别测定了氢气在丙酮、水和混合溶剂丙酮-水中的溶解度, 及其相应的蒸气压。     

Thermal degradation of polyethylene and polystyrene from the packaging industry over different catalysts into fuel-like feed stocks

Thermal degradation of waste polymers was carried out as a suitable technique for converting plastic polymers into liquid hydrocarbons, which could be used as feed stock materials. The catalytic degradation of waste plastics (polyethylene and polystyrene) was investigated in a batch reactor over different catalysts (FCC, ZSM-5 and clinoptillolite). The effects of catalysts and their average grain size on the properties of main degradation products (gases, gasoline, diesel oil) are discussed. The temperature range of 410-450 °C was used in the process. Both equilibrium FCC catalyst and natural clinoptilolite zeolite catalyst had good catalytic activity to produce light hydrocarbon liquids, and ZSM-5 catalyst produced the highest amount of gaseous products. Gases and liquids formed in cracking reactions were analyzed by gas chromatography. The liquid products consisted of a wide spectrum of hydrocarbons distributed within the C₅-C₂₈ carbon number range depending on the cracking parameters. The composition of hydrocarbons had linear non-branched structure in case of polyethylene, while from polystyrene more aromatics (ethyl-benzene, styrene, toluene, and benzene) were produced. The yields of volatile products increased with increasing degradation temperature. The olefin content of liquids was measured with an infrared technique and an olefin concentration of 50-60% was observed. The concentration of unsaturated compounds increased with decreasing temperature, and in the presence of catalysts. The activation energies were calculated on the basis of the composition of volatile products. The apparent activation energies were decreased by catalysts and catalyst caused both carbon-chain and double bond isomerisation.     

Novel Fabrication of Conductive Polymers Contained Micro‐Array Gas Sensitive Films Using A Micromanipulation Method

A novel method for fabricating a micro gas sensor film on an indium tin oxide (ITO) electrode patterned using micro‐machining technology was developed. A micromanipulation system equipped with a counter electrode (Au; Ø10 μm) and a microsyringe, which was connected to a microinjection system, was first constructed. With this system, micro gas sensor arrays could be successfully prepared on ITO electrodes. Two kinds of micro gas sensor films were prepared, based on polythiophene (PTh) and poly(3‐n‐dodecylthiophene) (PD). The response behavior of conventional PTh and micro‐PTh films against NH₃ at three different operating temperatures (25, 40 and 60 °C) was investigated by measuring the resistance of the film. With the micro‐PTh film, a reversible response was observed against NH₃ when measured at 40 and 60 °C. In addition, the responsive characteristics of the microsensor films against different testing gases were examined at the three operating temperatures. The resistance of the microsensor films of PTh and PD changed considerably, depending on the type of testing gas, allowing these sensor films to be used for the detection of various gases. Furthermore, the microsensor films had a high stability compared with conventional films prepared from the same polymer.     

Continuous dynamic-gravimetric preparation of calibration gas mixtures for air pollution measurements

 The preparation of calibration gas mixtures for air pollution measurements by the dynamic-gravimetric method was investigated using sulphur dioxide in nitrogen as a model. The target mole fraction was 200×10^–9 mol/mol, with the option of also getting smaller mole fractions. Thermal mass flow meters calibrated with reference mass flows were used to measure the dilution gas flow (nitrogen). The relative standard uncertainty of the dilution gas flows between 10 mg/s (approx. 500 ml/min) and 40 mg/s (approx. 2000 ml/min) was 0.15%. The mass flow of the target component measured as the permeation rate was determined via the quasi-continuous observation of the loss in the permeation tube mass during the measuring time. A magnetic coupling system and an adapted microbalance were used for this purpose. The results presented show permeation rates measured over the lifetime of a tubular permeation source. The measurement cycles took between 3 days and 7 h at least. The relative standard uncertainty of the mixture composition did not exceed 2%. First comparisons with gas mixtures prepared by the static-gravimetric method show compatibility. The applicability of the system is not restricted to the SO₂/N₂ mixture. It can also be used for preparing other gas mixtures in this field of application. Received: 26 April 2000 / Accepted: 12 September 2000     

气体传感器阵列信号的盲分离研究

本文在使用一个四单元微热板式集成气体传感器阵列测试煤矿中的两种主要易燃易爆气体一氧化碳和甲烷的基础上, 将气体传感器阵列与盲信号分离技术相结合, 讨论了混合气体分析的盲可辨识性, 并使用盲信号分离中的一种主要方法独立分量分析法(ICA)进行了分析和验证.     

Selective olefin permeation through Ag(I) contained silicone rubber-graft-poly(acrylic acid) membranes

The silicone rubber (SR) based graft copolymer, SR-graft-poly(acrylic acid) (SR-g-AA), was modified by incorporating silver ion (SR-g-AA-Ag⁺) for C₄ olefin/paraffin gases separation. Olefin could be transported across the complex membrane by the silver ion facilitated transport. The permeation properties, as measured by gas chromatography equipped with a gas permeability analyzer, implied a facilitating effect for olefin. Typical trans-2-butene/n-butane selectivity in the 95.6% grafted complex membrane at 25°C is 4.0. Also, the influences of AA% grafting, measuring temperature and pressure to the permeation properties of C₄ gases were studied. In addition, the sorption behaviors of C₄ gases in SR based membranes are presented and discussed by the Flory-Huggins equation. Finally, the selectivity of solubility and diffusivity in these SR based membranes are also discussed.     

Rapid <Superscript>224</Superscript>Ra measurements in water via multiple radon detectors

We introduce an improved on-site rapid analysis system for measuring ²²⁴Ra in natural waters. Radium isotopes are pre-concentrated on “Mn-fibers” before measurement of ²²⁰Rn. A Nafion drying system is used to lower the humidity in the detectors while maintaining a relatively constant moisture level in the Mn fiber in order to maintain a high and reproducible radon emanation. River water samples measured by this method agreed well with an analysis via RaDeCC, a very sensitive technique for measuring ²²⁴Ra. This method is recommended for fieldwork in remote areas when electricity and helium gas, required by traditional techniques, are not available.     

Measurement of EMI shielding of plastic composites using a dual chamber facility

The use of plastic materials as housings for electronic equipment depends on the ability to change the plastic composition from an insulator into an electrical conductor. Because there is a wide latitude in the level of conductivity that is achievable in such a composition, it is important to be able to relate the level of electromagnetic interference (EMI) shielding attained to the bulk resistivity of the conductive plastic composition. This report describes the use of a dual chamber method for measuring the EMI shielding effectiveness of polymer-based compositions. The system described is capable of measuring the shielding effectiveness of filled composites, coated samples, flat and molded structures and gaskets, and the effect of void spaces and joints. The dynamic range of this system is 80 dB, which is sufficient for most plastic compositions. Finally, a correlation between shielding effectiveness and bulk resistivity for filled compositions is presented, based on plane wave analysis. Theoretical predictions and experimental results are shown to be in excellent agreement.     

Phosphine Production Potential of Various Wastewater and Sewage Sludge Sources

ABSTRACT

A laboratory incubation procedure followed by gas chromatographic detection was used to measure phosphine production potential in representative wastewater and sewage sludge sources. Phosphine production potential was determined by measuring the rate of phosphine formation in samples incubated under laboratory conditions over a seven day period when both electron donors and the targeted electron acceptor were not limiting factors. Results of our experiments showed that except the primary effluent and secondary effluent wastewater samples all other samples studied (influent wastewater, various type of sludge and sediment sources) produced phosphine. The minimum phosphine production potential value (0.39 pg/ml wastewater/day) was measured in composite influent wastewater samples while the maximum (268 pg/g wet sludge/day) was measured in sediment samples collected from an open-air sewage treatment plant.     

超临界水中煤与聚苯乙烯的共液化研究

在间歇式高压反应装置中,研究了兖州烟煤与塑料聚苯乙烯(PS)在超临界水中的共液化,考察了水/物料比(质量比10～30)、反应温度(360℃～430℃)和塑料添加量(10%～40%)对煤液化转化率及产物收率的影响.结果表明,随着水/物料比的增加,煤液化转化率先升高,之后变化不大;油气产率则呈上升的趋势.反应温度高于420...     

Evaluation of nuclear effects in the analysis of plastics by neutron activation analysis

Validation of a method for the determination of trace elements in plastic using neutron activation analysis (NAA) required evaluation of nuclear effects. Since plastic is a moderator of neutrons, it is possible that the neutron flux may be affected in such a way as to effectively increase or decrease the measured activity of radionuclides within the plastic. Such effects are likely to depend on the thickness of the sample and so thicknesses of plastic ranging from 1 to 20 mm were used to quantify the effects. A standard containing vanaldium (a thermal neutron absorber) and silver (with epithermal neutron resonances) was used in a sandwich of the plastic. The sandwich was then irradiated and the standard counted. The activity of each radionuclide for each thickness was evaluated. The results showed that a variation of only 10% maximum was observed for thicknesses up to 20 mm. An increase in measured activity was observed for both the thermal and epithermal absorbers.     

Measurement of the composition of gas desorbed from coal by gas chromatography

Summary Direct methods for the determination of the gas content of a coal seam are based upon extracting a coal sample, enclosing it in a sealed container and measuring the volume of the gas evolved. In our work we measured evolved gas as a function of time, type and quantity of low rank coal (lignite) at normal (atmospheric pressure and temperature) conditions. The evolved gas was, collected in gas sampling bags and analyzed by GC for its main components (carbon dioxide, methane and dimethyl sulfide). From the parameters obtained (gas volume, CH₄:CO₂ ratio, rate of gas desorption, time concentration profile and different lithotypes of lignite) a more detailed identification of hazardous areas in underground coal extraction could be ensured. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

GC–MS法测定塑料及其制品中三(2-氯乙基)磷酸酯

采用气相色谱–质谱联用法检测塑料及其制品中阻燃剂三(2-氯乙基)磷酸酯的含量。样品采用微波萃取,萃取温度为100℃,时间为10 min,浓缩样品溶液至近干后定容至1 m L,用0.45μm滤膜过滤,采用气相色谱–质谱联用仪进行定性定量分析。三(2-氯乙基)磷酸酯的质量浓度在0.1~10.0μg/mL范围内与色谱峰面积呈良好的线性,线性相关系数为0.999 8,检出限为0.02 mg/kg。空白样品加标回收率为85.1%~94.6%,测定结果的相对标准偏差在1.60%~4.15%(n=7)之间。该方法准确度高,重现性好,可作为塑料及其制品中三(2-氯乙基)磷酸酯的检测方法。     

Simulation of experimentally observed dilation phenomena during integral gas sorption in glassy polymers

A molecular modeling investigation of dilation effects induced by sorbed gas molecules in two glassy polymers is presented. As experimental reference, integral sorption of CO₂ and CH₄ was measured for polysulfone (PSU) and a polyimide (6FDA‐TrMPD, PI4) at 308 K and a pressure of 10 bar. Simultaneously, the gas induced swelling effect was measured with a dilatometer based on a capacitive distance sensor recorded. The experimental evidence of the (on the observed time scale and concentration levels) elastic nature of the gas induced dilation is supported by the dilation and contraction behavior observed in molecular dynamics (MD) simulations of respective detailed atomistic packing models. These models were constructed in accordance with gas concentration levels obtained from the experimental sorption results. Quantitative deviations between simulated and measured dilations are discussed as a consequence of an anelastic response of the polymer matrix which is too fast to be resolved in the experiments whose kinetics is dominated by diffusional processes. In the simulation, the initial insertion of penetrant molecules into equilibrated packing models “circumvents” the slow diffusional process of the experiment and allows a reasonable representation of the dilation process as well as a closer investigation. Our simulation approach reveals a different behavior for PSU and PI4 on the corresponding time scale. Most likely, the different chain mobility of the two polymers is responsible for the respective response to the inserted amount of gas molecules which is discussed in terms of the different chain mobilities of the two polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 59–71, 2008     

Methane Decomposition on the Surface of Molybdenum Nanoparticles at Room Temperature

The decomposition of methane on molybdenum nanoparticles was studied experimentally at room temperature. The molybdenum nanoparticles were synthesized in the gas phase using UV laser photolysis of Mo(CO)6 vapor in a flow reactor. The working part of the flow reactor was equipped with quartz windows for introducing the radiation from a pulsed Nd:YaG laser operating at the fourth harmonic (266 nm) at a frequency of 10 Hz. Methane was used as a carrier gas. As a result of irradiation of a mixture of methane with Mo(CO)6 vapors in the gas phase at room temperature, nanoparticles with sizes of 2–50 nm were synthesized. The phase composition of the nanoparticles included pure molybdenum, molybdenum carbide Mo2C, and molybdenum oxide MoO3. During the reaction, the hydrogen yield was measured with a VG-7 highly sensitive hydrogen analyzer based on a semiconductor metal–dielectric sensor. The measured H2 concentration varied from 5 to 25 ppm depending on the concentration of Mo(CO)6. The possibility of methane decomposition on molybdenum nanoparticles at room temperature was discussed based on the obtained data.