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991.
Mycoestrogen determination in cow milk: Magnetic solid‐phase extraction followed by liquid chromatography and tandem mass spectrometry analysis 下载免费PDF全文
Anna Laura Capriotti Chiara Cavaliere Patrizia Foglia Giorgia La Barbera Roberto Samperi Salvatore Ventura Aldo Laganà 《Journal of separation science》2016,39(24):4794-4804
Recently, magnetic solid‐phase extraction has gained interest because it presents various operational advantages over classical solid‐phase extraction. Furthermore, magnetic nanoparticles are easy to prepare, and various materials can be used in their synthesis. In the literature, there are only few studies on the determination of mycoestrogens in milk, although their carryover in milk has occurred. In this work, we wanted to develop the first (to the best of our knowledge) magnetic solid‐phase extraction protocol for six mycoestrogens from milk, followed by liquid chromatography and tandem mass spectrometry analysis. Magnetic graphitized carbon black was chosen as the adsorbent, as this carbonaceous material, which is very different from the most diffuse graphene and carbon nanotubes, had already shown selectivity towards estrogenic compounds in milk. The graphitized carbon black was decorated with Fe3O4, which was confirmed by the characterization analyses. A milk deproteinization step was avoided, using only a suitable dilution in phosphate buffer as sample pretreatment. The overall process efficiency ranged between 52 and 102%, whereas the matrix effect considered as signal suppression was below 33% for all the analytes even at the lowest spiking level. The obtained method limits of quantification were below those of other published methods that employ classical solid‐phase extraction protocols. 相似文献
992.
Jianxun Li Jihao Shan Zhiqiang Kong Chunlin Fan Zijuan Zhang Bei Fan 《Journal of separation science》2020,43(2):486-495
In this study, an effective speed‐regulated directly suspended droplet microextraction method was developed to condense pesticide residues from teas through dispersive solid‐phase extraction prior to analysis by gas chromatography with tandem mass spectrometry. The extractant was intentionally dispersed into the sample solution in the form of globules through high‐speed agitation. This procedure increases the contact area between the binary phases and shortens the distribution equilibrium time. The fine globules reassembled by decelerating stirring speed, the extractant could be taken out for gas chromatography with tandem mass spectrometry. Recovery studies were performed under optimized extraction conditions by using matrix blanks fortified with pesticides at three concentrations (10, 50, and 100 µg/kg). Over 87% of the recoveries for the analytes in four tea matrices were acceptable given their recovery ranges of 70–120% and relative standard deviations of ≤20%. The limits of quantification of most pesticides were lower than 10 µg/kg and thus satisfied the requirements for maximum residue levels prescribed by the European Community. A total of 38 tea samples from local markets were analyzed by using the proposed method. Results showed that chlorpyrifos was the most frequently detected pesticide in teas. The method is a potential choice for the routine monitoring of pesticide residues in complex matrices. 相似文献
993.
Using the techniques of approximation and factorization of convolution operators we study the problem of irregular sampling of band-limited functions on a locally compact Abelian group G. The results of this paper relate to earlier work by Feichtinger and Gröchenig in a similar way as Kluvánek's work published in 1969 relates to the classical Shannon Sampling Theorem. Generally speaking we claim that reconstruction is possible as long as there is sufficient high sampling density. Moreover, the iterative reconstruction algorithms apply simultaneously to families of Banach spaces. 相似文献
994.
通过对成都市固体废弃物填埋场的实地考察,了解到垃圾在收集、填埋过程中所存在的一些问题以及填埋场对周边生态环境所造成的影响,并有针对性的对成都市固体废弃物填埋场产生的渗滤液和填埋气体等问题提出整改建议. 相似文献
995.
《科学通报(英文版)》1995,40(16):1342-1342
996.
HY型沸石经过400℃真空煅烧,150℃吸附吡啶,分别在150℃、200℃、250℃、300℃、350℃真空脱附,先由红外光谱测得吸附在Lewis酸(简称L酸)和Bronsted酸(简称B酸)中心的吡啶吸收峰消光度(频率分别为1453cm~(-1)和1543cm~(-1)),然后,由紫外光谱测定其吡啶含量。求得两个红外吸收峰的消光系数为:ε~L=0.095±0.005cm~2/μmol,εB=0.065±0.004cm~2/μmol,计算了两种酸的酸量。测定了HY沸石和超稳Y沸石表面酸的酸强度分布。HY沸石的总酸量比超稳Y高,超稳Y酸强度比HY强。稳定化过程使总酸量减小,酸强度增加。在HY沸石中,L酸酸量随煅烧温度升高而升高,B酸酸量在300℃左右煅烧时达到最大,总酸量在300—350℃煅烧时出现最大。这与HY沸石催化苯的烷基化反应转化率比较,催化活性和总酸量存在密切联系。 相似文献
997.
Anaïs Giustiniani Philippe Gugan Manon Marchand Christophe Poulard Wiebke Drenckhan 《Macromolecular rapid communications》2016,37(18):1527-1532
Macrocellular silicone polymers are obtained after solidification of the continuous phase of a poly(dimethylsiloxane) emulsion, which contains poly(ethylene glycol) drops of sub‐millimetric dimensions. Coalescence of the liquid template emulsion is prohibited by a reactive blending approach. The relationship is investigated in detail between the interfacial properties and the emulsion stability, and micro‐ and millifluidic techniques are used to generate macrocellular polymers with controlled structural properties over a wider range of cell sizes (0.2–2 mm) and volume fractions of the continuous phase (0.1%–40%). This approach could easily be transferred to a wide range of polymeric systems.
998.
Dr. Baoyan Xing Dr. Sai Ge Prof. Jianguo Zhao Dr. Hui Yang Dr. Jie Song Dr. Yu Geng Dr. Yuying Qiao Prof. Ling Gu Prof. Peide Han Prof. Guibin Ma 《ChemistryOpen》2020,9(10):1018-1026
Solid-state NMR analysis on wurtzite alloyed CdSe1−xSx crystalline nanoparticles and nanobelts provides evidence that the 113Cd NMR chemical shift is not affected by the varying sizes of nanoparticles, but is sensitive to the S/Se anion molar ratios. A linear correlation is observed between 113Cd NMR chemical shifts and the sulfur component for the alloyed CdSe1−xSx (0<x<1) system both in nanoparticles and nanobelts (δCd=169.71⋅XS+529.21). Based on this correlation, a rapid and applied approach has been developed to determine the composition of the alloyed nanoscalar materials utilizing 113Cd NMR spectroscopy. The observed results from this system confirm that one can use 113Cd NMR spectroscopy not only to determine the composition but also the phase separation of nanomaterial semiconductors without destruction of the sample structures. In addition, some observed correlations are discussed in detail. 相似文献
999.
在氧离子导体La2Mo1.7W0.3O9的基础上,采用固相法合成了La位掺杂的Ca系列新型氧化物La2-xCaxMo1.7W0.3O9-δ(0≤x≤0.2)。通过XRD、Raman和XPS等手段对化合物结构进行表征,交流阻抗谱测试其电性能。结果表明:掺杂离子Ca2+的半径小于基质离子La3+的半径导致晶格收缩;Ca的掺杂在La2Mo1.7W0.3O9自身内置氧空位的基础上增加了额外的氧空位,提高了氧离子导体的电导率,550 ℃电导率由0.79 × 10-4 S·cm-1 (x=0.0)增加到1.5 × 10-4 S·cm-1 (x=0.16,0.2),电导率增加89.9%。 相似文献
1000.
作者通过对国产与引进同类复合轴瓦材料的性能进行全面分析对比,找出国内产品质量低劣的根本原因在于固相复合时的复合压下率过大;提出改善国产复合轴瓦材料的措施:控制复合压下率——连杆瓦材料的钢背压下率为50—55%,曲轴瓦材料的钢背压下率为45—50%,并优化出热处理工艺——固相复合之前钢背840℃退火;固相复合之后350℃再结晶退火。 相似文献