离子液体均相液液微萃取-高效液相色谱法测定婴儿奶粉中5种三嗪类除草剂

建立了婴儿配方奶粉中三嗪类除草剂的均相液液微萃取-高效液相色谱分析方法。以离子液体为液液微萃取溶剂,Eclipse XDB-C18为色谱柱,乙腈和水为流动相梯度洗脱分离。详细研究了液液微萃取条件对实验结果的影响。在最优实验条件下,三嗪类除草剂的标准曲线呈良好的线性(r≥0.9992),草净津、敌草净、特丁通、特丁津和异戊乙净的检出限分别是12.1、13.8、11.8、14.6和13.7 μg/kg;婴儿配方奶粉中的加标回收率为92.2%~103.2%,相对标准偏差低于6%。该方法灵敏度高、操作简单,适用于奶粉样品中三嗪类除草剂残留的检测。     

Extraction of acetanilide herbicides in naked oat (Avena nuda L.) by using ionic‐liquid‐based matrix solid‐phase dispersion‐foam flotation solid‐phase extraction

The herbicides in naked oat (Avena nuda L.) samples were extracted, separated, and determined by using ionic‐liquid‐based matrix solid‐phase dispersion‐solvent flotation coupled with high‐performance liquid chromatography. The experimental parameters were optimized and evaluated by a univariate method and orthogonal experiment. A good linear relationship was obtained in the range of 5–5000 µg/kg, and the linear correlation coefficient are between 0.9989～0.9993. The quantification limits for alachlor, metazachlor, propanil, acetochlor, pretilachlor, metolachlor, and butachlor are 5.03, 2.62, 2.73, 4.58, 7.28, 5.05, 5.78 µg/kg, respectively. The average recoveries of the acetanilide herbicides at spiked concentrations of 10, 100, and 500 µg/kg ranged from 92.1 to 104.7%, and relative standard deviations were equal to or lower than 2.9%.     

基于均匀和正交试验设计的胶束电动毛细管色谱法同时测定消毒剂和抗抑菌产品中3种核苷类抗病毒药物

为防止消毒剂与抗抑菌产品中违规添加核苷类抗病毒药物,建立了胶束电动毛细管色谱（MEKC）同时分离测定消毒剂与抗抑菌产品中3种核苷类抗病毒药物（更昔洛韦、阿昔洛韦和喷昔洛韦）的新方法。通过3因素7水平均匀试验设计和4因素4水平的正交试验设计优化了十二烷基硫酸钠（SDS）、磷酸二氢钠（NaH₂PO₄）及硼砂（Na₂B₄O₇）在分离缓冲液中的浓度,最大限度地实现了3种核苷类抗病毒药物在短时间内的有效分离。以30.2 cm×50 μ m（有效长度为20 cm）未涂层熔融石英毛细管为分离柱,以25 mmol/L NaH₂PO₄+10 mmol/L Na₂B₄O₇（pH 7.41）+140 mmol/L（SDS）为分离缓冲溶液,分离电压为10 kV;进样压力为0.003 Pa,进样时间为4 s;检测波长为250 nm。3种抗病毒药物在一定的浓度范围内线性关系良好,相关系数r均不小于0.9995。3种抗病毒药物的检出限均为2.0 mg/kg,定量限均为7.0 mg/kg。低、中、高浓度加标回收率为85.4%~104.1%,相对标准偏差（RSD）均小于8.0%。该方法简便,快速,适于检测消毒剂与抗抑菌产品中更昔洛韦、阿昔洛韦和喷昔洛韦。     

一步法制备糖蜜基活性炭及其界面吸附行为

以糖厂废弃的糖蜜为原料,Na_2CO_3为活化剂,采用一步直接化学活化法制备了糖蜜基活性炭(AC).采用X射线衍射(XRD)、扫描电子显微镜(SEM)、N_2吸附-脱附及元素分析手段对产物进行了表征,证实其为多孔的石墨化碳材料,比表面积高达1023 m~2/g.研究了糖蜜基活性炭对溶液中的重金属离子Pb(Ⅱ)的脱除性能,结果表明:糖蜜基活性炭的吸附容量高于市售活性炭(CC),且所需吸附时间和投炭量均低于市售活性炭;其吸附动力学符合准二级动力学的Langmuir吸附,为单分子层的化学吸附;吸附Pb(Ⅱ)的糖蜜基活性炭可循环再生和重复使用.     

Au/Ti-SBA-15的制备及其催化CO氧化性能

采用气相键合法制备了表面经二氧化钛单层分布修饰的SBA-15材料,并以该材料为载体,用改进的原位沉积沉淀法制备了Au负载量为1%的系列催化剂(Au/Ti-SBA15),考察了它们在CO氧化反应中的催化性能.采用透射电镜、X射线衍射、N2吸附-脱附、紫外-可见漫反射吸收光谱、X射线荧光分析和电感耦合等离子体发射光谱等方法对修饰的载体及其负载金催化剂进行了表征.结果表明,SBA-15孔道对Au颗粒的生长起到很好的限制作用.制得的催化剂在广谱温度范围内均有良好的催化CO氧化活性,不仅在低温具有氧化活性,而且在高达500oC时CO转化率还能达到100%,催化剂的存储稳定性和重现性都较好.     

An Implantable Fiber Biosupercapacitor with High Power Density by Multi-Strand Twisting Functionalized Fibers

Biosupercapacitors (BSCs) that can harvest and store chemical energy show great promise for power delivery of biological applications. However, low power density still limits their applications, especially as miniaturized implants. Here, we report an implantable fiber BSC with maximal power density of 22.6 mW cm⁻², superior to the previous reports. The fiber BSC was fabricated by integrating anode and cathode fibers of biofuel cell with supercapacitor fibers through multi-strand twisting. This twisting structure endowed many channels inside and high electrochemical active area for efficient mass diffusion and charge transfer among different fibers, benefiting high power output. The obtained thin and flexible fiber BSC operated stably under deformations and performed high biocompatibility after implantation. Eventually, the fiber BSC was implanted subcutaneously in rats and successfully realized electrical stimulation of sciatic nerve, showing promise as a power source in vivo.     

Effect of Metal Foam on Natural Convective Heat Transfer of Nanofluids in a Photothermal Conversion System

Transport in Porous Media - In recent years, photothermal conversion and enhanced heat transfer have received increasing attention. In order to enhance the heat transfer efficiency of photothermal...     

A Theoretical and Empirical Comparison of Gradient Approximations in Derivative-Free Optimization

Foundations of Computational Mathematics - In this paper, we analyze several methods for approximating gradients of noisy functions using only function values. These methods include finite...     

Graphene and MXene Nanomaterials: Toward High‐Performance Electromagnetic Wave Absorption in Gigahertz Band Range

Searching for advanced microwave absorption (MA) nanomaterials is one of the most feasible ways to address the increasing electromagnetic pollution in both military and civil fields. To this end, graphene and MXene have won the widespread attention as the main representatives due to their remarkable structures and properties. The common features such as the large aspect ratio, active chemical surface, and varieties of synthesis processes endow graphene and MXene with unique superiorities for developing high‐efficiency MA structures, in particular lightweight assemblies and various hybrids. Meanwhile, the structural and performance differences (such as different conductivities) between them result in distinctive techniques in the design, fabrication, and application of their MA materials. Herein, the research progress in graphene‐ and MXene‐based MA materials is reviewed, with a special focus on advances in general strategies. Moreover, through the comparison between graphene‐ and MXene‐based MA materials, their respective advantages in achieving high‐performance MA are presented. Furthermore, the future challenge, research orientation, and prospect for these MA materials are also highlighted and discussed.     

Fiber-shaped organic electrochemical transistors for biochemical detections with high sensitivity and stability

Precise and continuous monitoring of biochemicals by biosensors assists to understand physiological functions for various diagnostics and therapeutic applications. For implanted biosensors, small size and flexibility are essential for minimizing tissue damage and achieving accurate detection. However, the active surface area of sensor decreases as the sensor becomes smaller,which will increase the impedance and decrease the signal to noise ratio, resulting in a poor detection limit. Taking advantages of local amplification effect, organic electrochemical transistors(OECTs) constitute promising candidates for high-sensitive monitoring. However, their detections in deep tissues are rarely reported. Herein, we report a family of implantable, fiber-shaped all-in-one OECTs based on carbon nanotube fibers for versatile biochemical detection including H_2O_2, glucose, dopamine and glutamate. These fiber-shaped OECTs demonstrated high sensitivity, dynamical stability in physiological environment and antiinterference capability. After implantation in mouse brain, 7-day dopamine monitoring in vivo was realized for the first time.These fiber-shaped OECTs could be great additions to the life science tool box and represent promising avenue for biomedical monitoring.