Ion chromatography for rapid and sensitive determination of fluoride in milk after headspace single-drop microextraction with in situ generation of volatile hydrogen fluoride

In this article, we report a new method that involves headspace single-drop microextraction and ion chromatography for the preconcentration and determination of fluoride. The method lies in the in situ hydrogen fluoride generation and subsequent sequestration into an alkaline microdrop (15 μL) exposed to the headspace above the stirred aqueous sample. The NaF formed in the drop was then determined by ion chromatography. The influences of some crucial single-drop microextraction parameters such as the extraction temperature, extraction time, sample stirring speed, sulphuric acid concentration and ionic strength of the sample, on extraction efficiency were investigated. In the optimal condition, an enrichment factor of 97 was achieved in 15 min. The calibration working range was from 10 μg L⁻¹ to 2000 μg L⁻¹ (R² = 0.998), and the limit of detection (signal to noise ratio of 3) was 3.8 μg L⁻¹ of fluoride. Finally, the proposed method was successfully applied to the determination of fluoride in different milk samples. The recoveries of fluoride (at spiked concentrations of 200 μg L⁻¹ and 600 μg L⁻¹ into milk) in real samples ranged from 96.9% to 107.7%. Intra-day precision (N = 3) in terms of peak area, expressed as relative standard deviation, was found to be within the range of 0.24-1.02%.     

Mechanoluminescence and thermoluminescence of Mn doped ZnS nanocrystals

This paper reports the synthesis of ZnS:Mn nanocrystals by the chemical route in which mercaptoethanol was used as the capping agent. The particle size of such nanocrystals was measured using XRD and TEM patterns and was found to be in between 3and 5 nm. It was found that the peak position of TL glow curve and the TL intensity of ZnS:Mn nanoparticles increases as the particle size is decreased. The isothermal decay technique is used to determine the trap-depth. The stability of the charge carriers in the traps increase with the decrease in size of the nanoparticles. The higher stability may be attributed to the higher surface/volume ratio and also to the increase in the trap-depth with decreasing particle size. When a ZnS:Mn nanocrystal is deformed the peak intensity I_m increases linearly with the increasing height of the load. After I_m, initially the ML intensity decreases at a fast rate, and later on it decreases at a slow rate. The ML in ZnS:Mn nanocrystals can be understood on the basis of the piezoelectrically induced electron detrapping model.     

Mid-infrared radiation transmission through fluoride glass multimode optical fibers

Measurement of the transmission laser radiation from Q-switched and free-running Er:YAG lasers operating at 2.94 μm through fluoride glass multimode optical fibers of 448, 465 and 620 μm core diameter were performed. Attenuation measurements were obtained as a function of the laser energy input, of the bending angle and of the radius of curvature. The fibers exhibited low attenuation under straight and bent conditions. The output beam quality was also studied using the appropriate beam profiler. The output beam profiles showed a central multi-spiked energy distribution.     

Crystal growth and luminescent properties of Pr-doped K(Y,Lu)3F10 single crystal for scintillator application

Pr1%:K(Y_1−xLu_x)₃F₁₀ (x=0, 0.2, 0.4) single crystals were grown by the μ-PD method. All the grown crystals were greenish and perfectly transparent without any inclusions or cracks. Radioluminescence spectra and decay kinetics of the Pr1%:K(Y,Lu)₃F₁₀ crystals were measured. Emission from the Pr³⁺ 5d–4f transition, peaking around 260 nm and of the decay time of around 22 ns were observed. The 5d–4f emission intensities of the Pr1%:K(Y,Lu)₃F₁₀ crystals were higher than that of the standard BGO scintillator.     

Electrochemical Cycled Structure of MnV_2O_6 Nanoribbons Synthesized via Hydrothermal Route

1 Introduction Low-dimensional nanostructures, such as nanorods, nanowires, and nanotubes, have received much attention for their superior optical, electrical, catalytic and magnetic properties.     

六西格玛管理中的网络计划技术及其应用

利用网络计划技术,对节点(事项)和箭条(作业活动)分别规定了六个时间值,讨论了他们之间的关系;结合实例应用,分析了资源的合理配置,得到了有一定参考意义的结果.     

氟电极测定铝的新方法——Apple Ⅱ-ISE智能离子计的应用

本文提出一种氟电极测铝的新方法,即二次回归校正曲线法及分段抛物插值法。由于汇集了1.该法依据的数学模型与实验数据相符;2.AppleⅡ-ISE智能离子计具有较强的数据处理功能;3.氟电极性能良好等三个特点,故本法准确可靠,快速方便,具有一定理论意义和较大实用价值。     

氮掺杂有序介孔碳-Ni纳米复合材料的制备及电化学性能

以F127为模板剂,Ni Cl2为镍源,尿素为氮源,间苯二酚甲醛原位聚合树脂为碳源,分别采用均相法和两相法制备Ni-NOMC-1,Ni-N-OMC-2纳米复合材料。X射线衍射(XRD)、激光拉曼以及透射电子显微镜(TEM)等测试结果表明,复合材料具有有序介孔结构,Ni以金属微粒形式嵌于碳骨架中,提高了有序介孔碳的石墨化程度。X射线光电子能谱测试(XPS)表明尿素热解后以4种形式存在:sp3杂化与C结合的N原子,吡啶N原子,sp2杂化与C结合的N原子以及quaternary-N原子。Ni-N的共改性改变了碳载体的理化性质,有利于Pt纳米粒子的负载与分散。均相法制备的Ni-N-OMC-1复合材料微波负载Pt后,氧还原极限电流密度为5.32 m A·cm-2,氢氧化电化学活性面积高达138.53 m2·g-1,电化学催化活性优于商业20%Pt/C材料(4.49 m A·cm-2,96.98 m2·g-1)。     

An improved and practical route for the synthesis of enzalutamide and potential impurities study

An improved and practical synthesis of enzalutamide was accomplished in five steps. Starting from 4-bromo-2-fluoro-benzonic acid, a methyl esterification, Ullmann ligation, methyl esterification, ring closing reaction and final methyl amidation provided the target in 35% total yield with 99.8% purity. Five identified impurities were also synthesized. This efficient and economical procedure avoids the use of highly toxic reagents and multiple recrystallization operations, which is suitable for further industrialization.