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91.
María-Teresa Celis Luis H. Garcia-Rubio 《Journal of Dispersion Science and Technology》2013,34(1-3):293-299
In emulsion polymerization, the formation of particles has an important effect on the rate of reaction and on the final properties of the latex. To investigate particle nucleation mechanisms in emulsion polymerization it is necessary to establish the initial conditions of the emulsified system before the reaction takes place. This research reports on a technique to continuously monitor the droplet size distribution of liquid-liquid emulsions using spectroscopy. The on-line particle characterization methodology is based on an integrated sampling and dilution strategy combined with spectroscopy methods. It is shown that the sampling system integrated with a multiwavelength turbidity detector provides reliable estimates of droplet populations as function of the dispersed phase concentration in emulsions of saturated hydrocarbons. The results provide not only the groundwork necessary for the elucidation of particle nucleation during emulsion polymerization process but also suggests the potential of this combined technology to further our understanding of liquid-liquid emulsions. 相似文献
92.
C. Hernández-Jaimes B. Fouconnier C. Pérez-Alonso J. L. Munguía-Guillén 《Journal of Dispersion Science and Technology》2013,34(1):64-71
Equisetum arvense supercritical CO2 extracts (EAE) contained an initial antioxidant activity of 10.3 mM TEAC that suffered a sharp first order kinetics decay characterized by half-life time (t1/2) of 1.05 ± 0.03 and 0.86 ± 0.03 weeks at 25 and 4°C, respectively. The aim of the present work was to develop a nanoemulsion formulation for providing EAE protection against deleterious environmental factors and extending its shelf-life functionality. The nanoemulsion area was identified by constructing pseudoternary phase diagrams and response surface methodology was used to optimize the preparation conditions. The best formulation achieved an EAE encapsulation efficiency of 97.5 ± 0.5% and antioxidant activity half-life time (t1/2) was extended to 12.32 ± 0.40 and 14.56 ± 0.60 weeks at 25 and 4°C, respectively. 相似文献
93.
Electrospray ionization mass spectrometry (ESI‐MS) is a useful technique for solving organometallic and coordination chemistry characterization problems that are difficult to address using traditional methods. However, assigning the ESI mass spectra of such compounds can be challenging, and the considerations involved in doing so are quite different from assigning the mass spectra of purely organic samples. This is a tutorial article for organometallic/coordination chemists using ESI‐MS to analyze pure compounds or reaction mixtures. The fundamentals of assigning ESI mass spectra are discussed within the context of organometallic and coordination systems. The types of ions commonly observed by ESI‐MS are categorized and described. Finally, a step‐by‐step guide for the assignment of organometallic and coordination chemistry ESI mass spectra is provided along with two case studies. 相似文献
94.
95.
Anna Lucia C. H. Villavicencio Jorge Mancini-Filho Henry Delince 《Radiation Physics and Chemistry》2000,57(3-6):295-298
Based on the enormous potential for food irradiation in Brazil, and to ensure free consumer choice, there is a need to find a convenient and rapid method for detection of irradiated food. Since treatment with ionising radiation causes DNA fragmentation, the analysis of DNA damage might be promising. In this paper, the DNA Comet Assay was used to identify exotic meat (boar, jacaré and capybara), irradiated with 60Co gamma rays. The applied radiation doses were 0, 1.5, 3.0 and 4.5 kGy. Analysis of the DNA migration enabled a rapid identification of the radiation treatment. 相似文献
96.
David W. Holt 《Accreditation and quality assurance》2000,5(9):389-391
This report addresses the proposition: current proficiency testing (PT) schemes for therapeutics and toxicology can easily
engender complacency. The proposition was based on the premise that there are substantial between-laboratory differences and
objectives in the supply of services for the measurement of drugs, as a result of which it is difficult to design PT schemes
which adequately cover the requirements of all laboratories. Thus, acceptable performance in a PT scheme may lead participants
to consider that they have tested their procedures more rigorously than is the case. Four areas, validity of the PT scheme,
PT material, frequency of testing and acceptance criteria are examined.
Received: 15 April 2000 · Accepted: 15 April 2000 相似文献
97.
介绍用无动力采样技术采集样品、离子色谱法分析SO2污染物浓度的监测方法。国际实验室间分析结果的比对实验表明,离子色谱法具有快捷、准确及自动化程度较高等优点。该方法在城市和背景区域环境空气背景值研究,如SO2污染物迁移规律、空气质量预测预报模型验证及远距离传输等方面具有很大的实用价值。 相似文献
98.
建立了液相色谱-四极杆串联质谱法定量检测海参和海胆中单唾液酸神经节苷脂的分析方法。采用Svennerholm法从海胆或海参样品中提取神经节苷脂,经C8固相萃取柱净化,采用APS-2 NH2柱(150 mm×2.1 mm, 3 μm),以乙腈和50 mmol/L乙酸铵溶液(pH 5.6)为流动相,梯度洗脱。样品中每种成分的定量在多反应监测模式下进行。该方法具有极高的灵敏度,定量限可低至纳克级。非硫酸酯化单唾液酸神经节苷脂(NMG)和硫酸酯化单唾液酸神经节苷脂(SMG)在1~40 ng进样量范围内呈现良好的线性关系;定量结果显示所测海参样品中美国红参的NMG含量最高,海胆样品中紫海胆的SMG含量最高;海胆中总的单唾液酸神经节苷脂含量(4.30~6.40 mg/g)明显高于各海参样品(8~131 μg/g)。该方法稳定可靠,适合海胆和海参中微量单唾液酸神经节苷脂的定量分析。 相似文献
99.
蛋白质的还原-烷基化是蛋白质酶切中的重要步骤,常用的烷基化试剂是碘乙酰胺(IAA),但是IAA除了和半胱氨酸发生反应,也可能和其他多种氨基酸发生副反应。我们模拟常规的酶切条件,系统地研究了蛋白质真实酶切时所有酶切肽段发生烷基化的情况。结果表明,多种氨基酸可以发生烷基化,其趋势为:半胱氨酸>肽段N端氨基酸>天冬氨酸>谷氨酸>组氨酸>天冬酰胺>赖氨酸>酪氨酸,同时也发现同一肽段上的氨基酸烷基化具有排他性和聚集性。根据定性结果,采用质谱多反应监测(MRM)技术对多个肽段进行了定量分析,评估了过烷基化对蛋白质定量分析的影响。该研究结果表明,过量的烷基化修饰对蛋白质的定性与定量分析都可能产生较大影响。在蛋白质组学研究的样本处理流程中,应避免样本的过烷基化。 相似文献
100.
The principal objective of this work was to develop and demonstrate a new methodology for silver nanoparticle (AgNP) detection and characterization based on asymmetric-flow field flow fractionation (A4F) coupled on-line to multiple detectors and using stable isotopes of Ag. This analytical approach opens the door to address many relevant scientific challenges concerning the transport and fate of nanomaterials in natural systems. We show that A4F must be optimized in order to effectively fractionate AgNPs and larger colloidal Ag particles. With the optimized method one can accurately determine the size, stability and optical properties of AgNPs and their agglomerates under variable conditions. In this investigation, we couple A4F to optical absorbance (UV–vis spectrometer) and scattering detectors (static and dynamic) and to an inductively coupled plasma mass spectrometer. With this combination of detection modes it is possible to determine the mass isotopic signature of AgNPs as a function of their size and optical properties, providing specificity necessary for tracing and differentiating labeled AgNPs from their naturally occurring or anthropogenic analogs. The methodology was then applied to standard estuarine sediment by doping the suspension with a known quantity of isotopically enriched 109AgNPs stabilized by natural organic matter (standard humic and fulvic acids). The mass signature of the isotopically enriched AgNPs was recorded as a function of the measured particle size. We observed that AgNPs interact with different particulate components of the sediment, and also self-associate to form agglomerates in this model estuarine system. This work should have substantial ramifications for research concerning the environmental and biological fate of AgNPs. 相似文献