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在Polanyi吸附势理论基础上,结合程序升温脱附曲线的测定,建立了一个快速测定吸附热的新方法,详细讨论了该方法的原理,通过微机采样和数据处理,测定一条吸附热与覆盖度的曲线仅需1h左右。 相似文献
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建立了热脱附-气相色谱质谱法测定印刷业废气排放中9种特征污染物的分析方法,使用不锈钢吸附管(填料ScalphaC100)采样,热脱附解析富集,经DB-624UI(30 m×0.25 mm×1.4μm)色谱柱分离,结合电子轰击电离源(EI)全扫描模式(SCAN)定性定量检测。考察了吸附管热脱附温度、时间等参数对特征污染物脱附效果的影响。结果表明:9种特征污染物在5.0~100 ng范围内线性良好,相关系数r均大于0.997,当采样体积为300 mL时,方法检出限为0.005~0.008 mg·m-3,定量限为0.020~0.032 mg·m-3。按照标准加入法在5、20、100 ng 3个浓度水平的加标回收实验下,9种特征污染物加标回收率为87.7%~107%;RSD(n=6)为0.5%~6.8%。该方法高效、简洁、快速、准确,可满足印刷业废气排放中9种特征污染物检测分析。 相似文献
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应用搅拌棒吸附萃取富集及热解吸进样与气相色谱-质谱相结合测定了水样中3种烷基酚(即正辛基酚、叔辛基酚和正壬基酚)的含量。将水样预先用盐酸调节其酸度至pH 3,分取10.00mL置于顶空瓶中,放入搅拌棒进行吸附萃取。取出搅拌棒,置于热脱附管上解吸并通过程序升温进样系统进样,用DB-5MS柱进行色谱分离。质谱分析条件:电子轰击正离子源,全扫描模式(定性分析)和选择离子扫描模式(定量分析)。3种烷基酚的质量浓度均在5~200ng·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在1.2~2.5ng·L-1之间。以实际水样为基体进行加标回收试验,测得回收率在95.0%~118%之间,测定值的相对标准偏差(n=5)在0.90%~10%之间。 相似文献
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大体积搅拌棒吸附萃取技术与热脱附-气相色谱-质谱法测定地表水中多环芳烃 总被引:1,自引:0,他引:1
基于搅拌棒吸附萃取(SBSE)技术建立了气相色谱-质谱测定地表水中16种多环芳烃(PAHs)的分析方法。该法采用多搅拌吸附棒同时富集,依次热脱附冷聚焦后进样的方式有效解决了搅拌棒吸附时间长、富集水样体积小等问题。优化后的结果表明,在0.2~10 ng/L范围内(萘为0.5~10 ng/L范围),16种PAHs的线性关系良好,相关系数(r)均0.99,方法检出限(MDL)为0.03~0.20 ng/L(萘为0.50 ng/L)。用该方法对钱塘江流域地表水进行测定,共检测出11种PAHs,含量为0.13~1.57 ng/L,不同添加水平下的加标回收率为75.6%~108.9%。该法可应用于地表水样品中该类物质的超痕量检测。 相似文献
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应用搅拌棒吸附萃取-热脱附-气相色谱-质谱分析烟用香料的化学成分 总被引:4,自引:0,他引:4
应用搅拌棒吸附萃取法(SBSE)提取烟用香料的化学成分,并利用热脱附(TD)和色谱-质谱联用(GC-MS)进行分析。对影响萃取效果的因素(萃取时间和氯化钠的加入量)进行了考察,并采用正交试验法对影响热脱附的3个主要因素(脱附温度、脱附时间和冷阱温度)进行了优化,得到了较优的实验条件。对方法的重现性进行了考察,同一样品6次测定所得30个组分的峰面积的相对标准偏差(RSD)平均值小于10%,说明所建立方法的重现性较好。在样品中鉴别出酯类、酮类和醛类等30种不同化学组分,这些物质反映了该香料的香气特点。实验证明SBSE和TD适用于烟用香料的快速分析测定。 相似文献
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采用热脱附-气相色谱-质谱法,建立了同时分析环境空气中67种挥发性有机物的分析方法。对比了5种不同填充材料不锈钢吸附管对78种挥发性有机物的吸附能力。填充材料为Tenax TA和Carbograph 1TD的混合填料吸附管对分析物的捕集效果最好,在30 mL/min高纯He气持续吹脱45 min的情况下,未发生穿透(即穿透率小于10%)的化合物达67种,分析物的种类包括芳香烃、脂肪烃、卤代烃和含氧挥发性有机物等。优化了使用该吸附管测定67种目标物时的热脱附条件。在5~100 ng范围内,目标化合物的色谱响应值与其量间具有良好的线性关系,其相关系数(r)均在1.0000~0.9977之间。方法检出限为0.3~2.4 ng,以采样体积1 L计算,检出限为0.3~2.4 μg/m3。加标量为20 ng时,7次重复实验目标化合物回收率均在81.6%~114.9%之间,目标化合物的相对标准偏差为1.2%~10.1%。采用该方法对某车厢内空气进行了检测,检出了包括酯类、卤代烷烃、卤代烯烃以及芳香族化合物在内的19种目标化合物,其范围为1.1~84.1 μg/m3。该方法准确、可靠、灵敏度高,实现了对环境空气中67种目标污染物的准确定量。 相似文献
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Summary The effect of the acidity of the media on the adsorption of phenol and creasols was investigated using TLC and using the RF-values as a measure of the adsorption ability of active carbon. Three types of chromatographic layers were employed: silica
gel, silica gel containing 3% of active carbon and silica gel containing 6% of active carbon. Standard solutions of phenol,
m-cresol and o-cresol were used as the samples. The acetic acid content of the solvent mixture significantly influences the
adsorption of phenol and cresols on the active carbon layer. An increase in the acetic acid content results in a decrease
of the adsorption of phenols. However, under specific conditions [81∶5∶7 hexane-diethyl ether-acetic acid, and 48∶2∶8 benzene-acetone-acetic
acid developers] the competitive adsorption of phenols and acetic acid may take place, which has been observed by a steep
increase in the adsorption of phenol and cresols. 相似文献
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Ph. Ponteins B. Medda Ph. Demont C. Lacabanne 《Journal of Thermal Analysis and Calorimetry》1997,48(3):623-634
The correlation between structure/microstructure and thermomechanical properties has been investigated by the Thermally Stimulated Creep (TSC) technique in a high performance thermostable thermoset matrix composite. The high resolving power of this technique allows us to analyse the retardation mode. The kinetics of molecular movements liberated at the glass transition has been investigated by the technique of fractional loading: the analysis of each elementary process gives the real compliance and the retardation time as a function of temperature. The values of the activation parameters show the existence of a compensation phenomenon which characterizes the microstructure. It also gives access to the loss compliance of the composite material as a function of temperature and frequency. The predictive calculation of loss compliance has been validated by the results obtained by dynamic mechanical analysis (DMA). 相似文献
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Enthalpies of wetting of several pure liquids onto active carbon were measured at 298.15 K with a quasi-isothermal microcalorimeter Setaram MS 80 II. New measuring cells with three independent cavities of about 15 cm3 were created. The advantage of this new method is the high weight-in of active carbon and a reduced time per measurement for reaching a constant baseline. Experiments were carried out with n-alkanes, 1-alkanols, cyclohexane, 2,2,4-trimethyl-pentane (isooctane) and water. The experimental results for the enthalpy of wetting show a dependence of the geometric heterogeneity of the active carbon and the polarity of liquids. 相似文献
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Piotr Kutrowski Piotr Michorczyk Lucjan Chmielarz Zofia Piwowarska Barbara Dudek Jan Ogonowski Roman Dziembaj 《Thermochimica Acta》2008,471(1-2):26-32
Active carbon was used as a support for chromium(III) oxide phase. The synthesized materials appeared to be very active catalysts of the propane dehydrogenation in the presence of CO2. An influence of the Cr content on the catalytic activity and selectivity was observed. The best results were achieved over the sample containing about 5 wt.% of Cr. A negative effect of activity decay with time-on-stream was found. The reasons of the observed deactivation were explained using the thermal analysis method. A behavior of the fresh and used samples was tested in a temperature range of 25–1000 °C in different atmospheres (inert gas, air or CO2). It was found that the catalytic runs resulted in a partial decomposition of surface O-containing groups, which together with CrOx species play a role of active centers. Moreover, a formation of inactive carbonaceous deposit on the catalyst surface was observed. 相似文献
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V. V. Abalyaeva G. V. Nikolaeva O. N. Efimov 《Russian Journal of Electrochemistry》2008,44(7):828-834
Polyaniline (PANI)-based composite materials containing 5 to 65 wt % of multi-wall carbon nanotubes (MCNT) are prepared. Their electrochemical characteristics are studied, in particular, the effect of the MCNT content in the composite on the composite and PANI specific capacitance. The increase in the composite capacitance, as well as the capacitance of the PANI being part of the composite, varies over the range from 5 to 25 wt %. This MCNT content is optimal for the preparing of a new MCNT-and PANI-based composite material. Over the above-given range, the increase in capacitance and the improving of conductivity are compromised at best. For a set of samples with varying MCNT content, the conductivity curve practically replicates the capacitance curve. The critical conductivity changes fall practically into the same range (5–30 wt %). 相似文献
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Anton V. Tokarev Elena V. Murzina Kari Eränen Heidi Markus Arie J. Plomp Johannes H. Bitter Päivi Mäki-Arvela Dmitry Yu. Murzin 《Research on Chemical Intermediates》2009,35(2):155-174
Liquid-phase lactose oxidation was investigated over supported Pd/C and Pd-carbon nanofibre catalysts, which were characterized
by several methods. A complex relationship between catalyst activity and catalyst acidity was established, i.e. optimum catalyst
acidity resulted in the highest activity in lactose oxidation. In-situ catalyst potential measurements during lactose oxidation
gave information about the extent of accumulation of oxygen on the metal surface. These results could be correlated with catalyst
deactivation, which was extensive over the most acidic catalysts at low reaction temperatures. Selectivity for the desired
product, lactobionic acid, was a maximum of approximately 83% at 93% conversion. The main side-product was lactulose formed
via isomerisation of lactose. Lower selectivity toward lactobionic acid was obtained when the rate of oxidation of lactose
was low. 相似文献
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The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using a novel type of porous carbon composite membrane/glassy carbon electrode based on the low-cost common filter paper by a simple method. The resulting device exhibited excellent electrocatalytic activities toward the oxygen reduction reaction. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements demonstrated that the porous morphology and uniformly dispersed Fe3C nanoparticles of the PCCM play an important role in the oxygen reduction reaction. A linear response range from 2μmol/L up to 110 μmol/L and a detection limit of 1.4 μmol/L was obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation, was 3.0%. The successful fabrication of PCCM/GC electrode may promote the development of new porous carbon oxygen reduction reaction material for the oxygen reduction sensor. 相似文献
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Jianwei Li Guangcheng Zhang Jiantong Li Lisheng Zhou Zhanxin Jing Zhonglei Ma 《先进技术聚合物》2017,28(1):28-34
In this study, a series of reinforced polyimide (PI)/carbon fiber (CF) composite foams were fabricated through thermal foaming of polyester ammonium salt (PEAS) precursor powders. The PEAS precursor powders containing different contents of chopped CF were synthesized from benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and 4,4′‐diaminodiphenyl ether (ODA). The effects of different CF loadings on foaming behavior of PEAS/CF composite precursor powders, final cellular morphology, and physical properties of PI composite foams were investigated. The results revealed that the chopped CF acted as nucleation agent in the foaming process. The dispersion of CF can be evaluated using digital microscope. It is interesting to find that the chopped CF were highly oriented along the direction of cell arrises. As a result, the mechanical properties of PI foams were significantly enhanced owing to the incorporation of chopped CF. Furthermore, the thermal stability of PI composite foams were also slightly improved owing to fine dispersion of CF. In addition, the PI/CF composite foam shows uniform cell size distribution and the best comprehensive physical properties as chopped CF loading at around 6 wt%. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Viscoelastic characteristics of cured phenolic resin–carbon fiber composite materials were investigated through glass transition and degradation reaction processes in the high‐temperature region up to 400°C. A typical glass transition of the crosslinked thermoset polymer was followed by irreversible degradation reactions, which were exhibited by the increasing storage modulus and loss modulus peak. A degradation master curve was constructed by using the vertical and horizontal shift factors, both of which complied well with the Arrhenius equation in light of the kinetic expression of degradation rate constants. Using an analogy to the Havriliak–Negami equation in dielectric relaxation phenomena, a viscoelastic modeling methodology was developed to characterize the frequency‐ and temperature‐dependent complex moduli of the degrading thermoset polymer composite systems. The temperature‐dependent relaxation time of the degrading composites was determined in a continuous fashion and showed a minimum relaxation time between the glass transition and degradation reaction regions. The capability of the developed modeling methodology was demonstrated by describing the complex behavior of the viscoelastic complex moduli of reacting phenolic resin composite systems. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 907–918, 1999 相似文献