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排序方式: 共有128条查询结果,搜索用时 156 毫秒
1.
X射线荧光光谱法快速测定稀土萃取生产的中控样品 总被引:3,自引:0,他引:3
本文介绍了一种新型样品杯,通过使用这种样品杯,实现了大型X射线荧光光谱仪在稀土萃取生产过程中的现场分析,同时还对基体效应,谱线干扰,背景扣除等进行了研究。实践证明本法准确可靠,简便快速。 相似文献
2.
蒙脱石修饰碳糊电极测定氨基酸的研究:Ⅱ.酪氨酸的测定 总被引:13,自引:1,他引:13
本文报道蒙脱石修饰碳糊电极测定酪氨酸,在0.001mol/L KCl-HCl(pH=2.0)溶液中开路富集,介质交换后微分脉冲阳极溶出伏安法测定,在0.5-2.5μg/ml范围内有线性,检测限为63ng/ml。可避免其他氨基酸,微量元素和常量金属元素的干扰,直接用于氨基酸药物样品的分析,获得了满意的结果,还对酪氨酸在电极上的反应机理进行了探讨。 相似文献
3.
金在碳糊电极上的静电吸附及溶出伏安测定 总被引:6,自引:0,他引:6
阳极溶出伏安法测定金具有灵敏度高,操作简便等优点,但共存金属往往干扰测定,影响该方法的应用。为减少干扰,已有阴极溶出伏安法的报道。 作者曾采用修饰了三烷基叔胺的碳糊电极,通过开路萃取富集和介质交换,测定矿样中的金,并且发现,碳糊电极本身能在正电位下直接富集微量金,在阴极溶出伏安法中显示了 相似文献
4.
High-level expression of soluble human β-defensin-2 fused with green fluorescent protein in Escherichia coli cell-free system 总被引:2,自引:0,他引:2
Human β-defensin-2 (hBD2), a small cationic peptide, exhibits a broad range of antimicrobial activity and does not acquire
any microbial resistance. To produce this uneasily detectable, degradable, and toxic polypeptide efficiently, an alternative
approach based on the Escherichia coli cell-free biosynthesis system was proposed. The approach implies that a polypeptide of interest is synthesized as a fusion
protein linked to a green fluorescent protein (GFP) through a cleavable spacer. With batch-mode operation, a significant amount
of hBD2 fused with GFP (0.25 mg/mL) can be expressed in this cell-free system. The productivity of the fusion protein can
be improved up to 1.2 mg/mL by employing a continuous-exchange cell-free system. Furthermore, the GFP moiety provides directly
visible and quantitative monitoring of the polypeptide synthesis, and the product is soluble and stable. This work will be
helpful in allowing the rapid and visible expression of other similar defensins using an in vitro cell-free system. 相似文献
5.
Peilin Z Jianzhong Z Shenzhong Y Xikang Z Guoxiong Z 《Analytical and bioanalytical chemistry》1995,353(2):171-173
The electrochemical characterization of boron-doped polycrystalline diamond thin-film (BDF) electrodes was studied using the anodic scan after concentrating lead in 0.1 mol/L KCl - 41 micromol/L Hg(NO(3))(2) and 0.1 mol/L KNO(3) - 0.01 mol/L HNO(3) - 41 micromol/L Hg(NO(3))(2); accumulation voltage was -0.90 V. The results obtained were compared with those given by glassy carbon (GC) electrodes and proved that the BDF electrodes offered high sensitivity, good precision and extreme stability over a 2-month period. These electrodes provided good resolving power for the determination of lead and cadmium and gave satisfactory results in the analysis of a pure water sample. 相似文献
6.
柠檬酸在D354树脂上的离子交换研究 总被引:5,自引:2,他引:5
研究了大孔型弱碱性阴离子交换树脂D354分离水中柠檬酸的相平衡和动力学。Langmuir方程能够良好地关联等温线。建立了离子交换过程的孔扩散模型,并以正交配置法与Gear法结合进行数据拟合。结果表明,液膜阻力对交换过程具有重大影响,简单线性推动力模型能够很好地描述液膜传质过程。 相似文献
7.
8.
9.
Peilin Deng Fan Yang Zhitong Wang Shenghua Chen Yinzheng Zhou Shahid Zaman Prof. Dr. Bao Yu Xia 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10899-10905
Carbon dioxide (CO2) conversion is promising in alleviating the excessive CO2 level and simultaneously producing valuables. This work reports the preparation of carbon nanorods encapsulated bismuth oxides for the efficient CO2 electroconversion toward formate production. This resultant catalyst exhibits a small onset potential of −0.28 V vs. RHE and partial current density of over 200 mA cm−2 with a stable and high Faradaic efficiency of 93 % for formate generation in a flow cell configuration. Electrochemical results demonstrate the synergistic effect in the Bi2O3@C promotes the rapid and selective CO2 reduction in which the Bi2O3 is beneficial for improving the reaction kinetics and formate selectivity, while the carbon matrix would be helpful for enhancing the activity and current density of formate production. This work provides effective bismuth-based MOF derivatives for efficient formate production and offers insights in promoting practical CO2 conversion technology. 相似文献
10.
Caiming Tang Jianhua Tan Peilin Zhang Yujuan Fan Zhiqiang Yu Xianzhi Peng 《Journal of mass spectrometry : JMS》2020,55(9)
Kinetic isotope effects (KIEs) occurring in mass spectrometry (MS) can provide in‐depth insights into the fragmentation behaviors of compounds of interest in MS. Yet, the fundamentals of KIEs in collision‐induced dissociation (CID) in tandem mass spectrometry (MS/MS) are unclear, and information about chlorine KIEs (Cl‐KIEs) of organochlorines in MS is particularly scarce. This study investigated the Cl‐KIEs of dichloromethane, trichloroethylene, and tetrachloroethylene during CID using gas chromatography‐electron ionization triple‐quadrupole MS/MS. Cl‐KIEs were evaluated with MS signal intensities. All the organochlorines presented large inverse Cl‐KIEs (<1, the departures of Cl‐KIEs from 1 denote the magnitudes of Cl‐KIEs), showing the largest magnitudes of 0.797, 0.910, and 0.892 at the highest collision energy (60 eV) for dichloromethane, trichloroethylene, and tetrachloroethylene, respectively. For dichloromethane, both intra‐ion and inter‐ion Cl‐KIEs were studied, within the ranges of 0.820–1.020 and 0.797–1.016, respectively, showing both normal and inverse Cl‐KIEs depending on collision energies. The observed Cl‐KIEs generally declined from large normal to extremely large inverse values with increasing collision energies from 0 to 60 eV but were inferred to be independent of MS signal intensities. The Cl‐KIEs are dominated by critical energies at low internal energies of precursor ions, resulting in normal Cl‐KIEs; while at high internal energies, the Cl‐KIEs are controlled by rotational barriers (or looseness/tightness of transition states), which lead to isotope‐competitive reactions in dechlorination and thereby inverse Cl‐KIEs. It is concluded that the Cl‐KIEs may depend on critical energies, bond strengths, available internal energies, and transition state looseness/tightness. The findings of this study yield new insights into the fundamentals of Cl‐KIEs of organochlorines during CID and may be conducive to elucidating the underlying mechanisms of KIEs in collision‐induced and photo‐induced reactions in the actual world. 相似文献