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991.
992.
993.
超高效液相色谱-串联质谱快速检测精米、玉米与土豆样品中噻呋酰胺残留 总被引:3,自引:0,他引:3
采用分散固相萃取(QuEChERS)为样品前处理方法,建立了超高效液相色谱-串联质谱(UPLCMS/MS)快速检测精米、玉米和土豆中噻呋酰胺残留的分析方法。样品经乙腈提取,PSA净化,超高效液相色谱分离,电喷雾电离、负离子扫描,三重四极杆串联质谱以多反应监测扫描方式进行检测,基质匹配标准品外标法进行定量分析。结果显示,噻呋酰胺在1.0~1 000μg·L-1范围内呈良好线性(r2=0.999 0)。在0.01~1.0 mg·kg-1加标水平范围内,噻呋酰胺在精米、玉米和土豆中的平均回收率为89.1%~109.3%,相对标准偏差为3.5%~8.7%,检出限(LOD)为0.009~0.015μg·kg-1,定量下限(LOQ)为0.032~0.049μg·kg-1。该方法简便、快速、准确,可用于精米、玉米和土豆中噻呋酰胺农药残留的确证检测。 相似文献
994.
采用直接浸渍法、过氧化氢均相氧化沉积法和氨水催化水解法制备了石墨烯负载的铁、钴、镍金属氧化物纳米颗粒.研究了三种沉积方法对颗粒尺寸分布的影响;采用透射电子显微镜、傅里叶变换红外光谱、X射线衍射和X射线光电子能谱表征了催化剂的形貌与结构.用过氧化氢均相氧化沉淀法可制得粒径分布最均匀的纳米颗粒.过氧化氢的氧化作用可使石墨烯表面的氧化基团含量最大化,为纳米颗粒提供了足够的吸附与成核点.氨水加速了金属离子的水解与成核,导致纳米颗粒的粒径增大与不均.以苯甲醇氧化为探针反应考察了催化剂的性能.催化剂的活性按以下顺序逐渐下降:过氧化氢辅助沉积法>直接浸渍法>氨水催化水解法,与纳米颗粒尺寸增长趋势一致.纳米催化剂颗粒尺寸与其活性的良好关联性显示,发展石墨烯负载尺寸可控的纳米催化剂的方法具有重要意义. 相似文献
995.
A variety of linear and 3-arm star polyethylene (PE) model polymers covering a wide range of molecular weight are synthesized by the living polymerization of butadiene and the subsequent hydrogenation. Several rheological parameters of these model linear and 3-arm star PE samples are analyzed for detecting the long chain branching (LCB) structure. It is found that the analyses based on zero shear viscosity, vGP plot and flow activation energy are very sensitive to the 3-arm star PEs. The information on the presence of LCB can be obtained with these methods even for low molecular weight samples, which can not be determined by GPC-MALLS. However the information about the LCB structure can not be obtained by the rheological methods alone. 相似文献
996.
In this study, four hydroxyl-terminated polydimethylsiloxanes(PDMSOH) with different viscosities and hydroxyl contents were used to improve the toughness of polycarbonate(PC) through reactive melt blending. A largely improved toughness of PC has been achieved, and the low temperature toughness of PC/PDMSOH blends could overtake that of PC homopolymer in much higher temperatures(e.g.-10 °C versus 23 °C). Moreover, it was found that the more the hydroxyl content, the less the PDMSOH was needed to reach the highest toughness, suggesting that equivalent molar ratio between the carbonyl group content of PC and the hydroxyl group content of PDMSOH was required for the toughening of PC. Ultraviolet spectrophotometry was used to analyze the possible reaction between PC and PDMSOH. Contact angle was measured to assess the change of interfacial interaction between PC and PDMSOH as change of viscosity and hydroxyl content. The formation of PC-co-PDMSOH copolymer was believed to be the key for the toughening effect. This work gives a profound recommendation of the optimum kind and dosage of PDMSOH which should be used to improve the toughness of PC and will find immediate industrial applications. 相似文献
997.
Poly(butylene succinate) (PBS) with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties (crystallinity as well as crystal morphology). Our work is important for the design and preparation of PBS with proper molecular weight for its practical application. 相似文献
998.
Wang Qiang Feng Ling-ran Wei Luo Li Han-guang Wang Lin Zhou Ya Yu Xiao-bin 《Applied biochemistry and biotechnology》2014,174(1):452-460
To improve the fermentation efficiency of lycopene, a plasma jet, driven by an active helium atom supplied with atmospheric and room temperature plasma (ARTP) biological breeding system, was used as a new method to generate mutations in Blakeslea trispora (?). After several rounds of screening, a mutant A5 with high concentration of lycopene and dry biomass was isolated, which showed a maximum lycopene concentration (26.4?±?0.2 mg/g dry biomass) which was 55 % higher than the parent strain (16.9?±?0.3 mg/g dry biomass) in the production of lycopene. Compared with parent strain, B. trispora A5 required less dissolved oxygen (10 % less than that of parent strain) to reach maximum concentration in a 5-L stirred tank reactor batch fermentation. 相似文献
999.
Three-arm and four-arm star-like polybutadienes(PBds) were synthesized via the combination of living anionic polymerization and the click coupling method. Kinetic study showed that the click reaction between the azido group terminated PBd-t-N3 and the alkyne-containing multifunctional linking reagent was fast and highly efficient. All coupling reactions were fully accomplished within 40 min at 50 °C in toluene in the presence of the reducing agent Cu(0), proven by 1H-NMR, FTIR and GPC measurements. For the coupling reactions between the PBd-t-N3 polymer and dialkyne-containing compound, the final conversion of the coupled PBd-PBd polymer was ca. 97.0%. When a PBd-t-N3 polymer was reacted with trialkyne-containing or tetraalkyne-containing compound, the conversion of three-arm or four-arm PBd was around 95.5% or 87.0%, respectively. Several factors influencing the coupling efficiency were studied, including the molecular weight of the initial PBd-t-N3, arm numbers and the molar ratio of the azido group to the alkynyl group. The results indicated that the conversion of the target products would be promoted when the molecular weight of the PBd-t-N3 was low and the molar ratio of the azido to alkynyl groups was close to 1. 相似文献
1000.
Hong Zhu Feng Wen Peng Li Xiang Liu Jianmei Cao Min Jiang Feng Ming Zhaoqing Chu 《Applied biochemistry and biotechnology》2014,172(6):3163-3175
Brachypodium distachyon has been proposed as a new model system for gramineous plants with a sequenced genome and an efficient transformation system. Many transgenic B. distachyon plants have been generated in recent years. To develop a reliable fast method for detecting transgenic B. distachyon and quantifying its transgene copy numbers, a species-specific reference gene is of great priority to be validated both in qualitative PCR and quantitative real-time PCR detection. In this study, we first proved that the BdFIM (B. distachyon fimbrin-like protein) gene is a suitable reference gene in qualitative PCR and quantitative real-time PCR for B. distachyon. Fourteen different B. distachyon varieties were tested by both qualitative and quantitative PCRs, and identical amplification products of BdFIM were obtained with all of them, while no amplification products were observed with samples from 14 other plant species, suggesting that BdFIM gene was specific to B. distachyon. The results of Southern blot analysis revealed that the BdFIM gene was low copy number in seven tested B. distachyon varieties. In conclusion, the BdFIM gene can be used as a reference gene, since it had species specificity, low heterogeneity, and low copy number among the tested B. distachyon varieties. Furthermore, the copy number of inserted sequences from transgenic B. distachyon obtained by real-time PCR methods and Southern blot confirmed that the BdFIM gene was an applicable reference gene in B. distachyon. 相似文献