Determination of 3-nitroaniline in water samples by directly suspended droplet three-phase liquid-phase microextraction using 18-crown-6 ether and high-performance liquid chromatography

Liquid–liquid–liquid microextraction (LLLME) with directly suspended droplet in high-performance liquid chromatography (HPLC) has been applied as a new, rapid and easy method for the determination of 3-nitroaniline in environmental water samples. The target compound was extracted from the aqueous sample solution (donor phase, pH 13) into an organic phase and then was back-extracted into a directly suspended droplet of an acidic aqueous solution (acceptor phase, pH 0.3). In this method, without using a microsyringe as supporting device, an aqueous large droplet is freely suspended at the top-center position of an immiscible organic solvent, which is laid over the aqueous sample solution while being agitated. Then, the droplet was withdrawn into the microsyringe and directly was injected into the HPLC system with UV detection at 227 nm. Up to 148-fold enrichment of the analyte could be obtained under the optimal conditions [i.e. donor phase: 0.1 M sodium hydroxide solution (4.5 mL); organic phase: o-xylene/1-octanol (90:10, v/v; 250 μL); acceptor phase: 0.5 M hydrochloric acid and 500 mM 18-crown-6 ether (6 μL); extraction time: 60 s; back-extraction time: 6 min and stirring rate: 600 rpm]. The limit of detection was 1 μg/L (n = 7) and the relative standard deviation (RSD, n = 5) was 4.9 at S/N = 3. The calibration graph was linear in the range of 5–1500 μg/L with r = 0.9983. All experiments were carried out at room temperature (22 ± 0.5 °C).     

Study on the redox reactions for organic dyes and S‐nitrosylated peptide in electrospray droplet impact

Reduction of analytes in ionization processes often obscures the determination of molecular structure. The reduction of analytes is found to take place in various desorption/ionization methods such as fast atom bombardment (FAB), secondary ion mass spectrometry (SIMS), matrix‐assisted laser desorption/ionization (MALDI) and desorption ionization on porous silicon (DIOS). To examine the extent of the reduction reactions taking place in electrospray droplet impact (EDI) processes, reduction‐sensitive dyes and S‐nitrosylated peptide were analyzed by EDI. No reduction was observed for methylene blue. While methyl red has a lower reduction potential than methylene blue, the reduction product ions were detected. For S‐nitrosylated peptide, protonated molecule ion [M + H]⁺ and NO‐eliminated molecular ion [M − NO + H]^+• were observed but reduction reactions are largely suppressed in EDI compared with that in MALDI. As such, the analytes examined suffer from little reduction reactions in EDI. Copyright © 2008 John Wiley & Sons, Ltd.     

Particle adsorption in evaporating droplets of polymer latex dispersions on hydrophilic and hydrophobic surfaces

Stain patterns formed by drying up of droplets of polymer latex dispersion on hydrophilic and hydrophobic surfaces were examined in light of the mechanism of particle adsorption in evaporating droplets. On hydrophilic surfaces, the volume of droplets decreased with time, keeping the initial outline of contact area, and circular stain patterns were formed after the dry-up of droplets. By the microscopic observation of particles in the droplets, it was found that a large portion of the particles were forced to adsorb on the outline of the contact area where a microscopic thin water layer was formed because of hydrophilicity of the surface. On hydrophobic surfaces, on the other hand, the contact area of droplets decreased as evaporation proceeded, while no particle was adsorbed on the surface at the early stages. The particles in the droplets started to aggregate when the concentration of particles reached a critical value, and the aggregates adsorbed on the surface forming tiny spots after the dry-up. Time evolutions of contact angle, contact area and volume of the droplets were analyzed in light of differences in the adsorption mechanisms between hydrophilic and hydrophobic surfaces. Received: 14 January 1998 Accepted: 1 May 1998     

基于微流控双水相液滴流酶促反应的尿素检测

以简单、快速的微流控酶促反应方法实现了尿素浓度的可视化检测。 在微流控双水相液滴流动中,利用脲酶水解尿素生成碳酸铵使液滴内的中性红指示剂变色,并对液滴颜色强度进行分析来确定待测样品中尿素的浓度,检测范围可达到0~50 mg/mL。 双水相体系克服了传统油水分析检测平台生物相容性低的缺陷。 液滴流以较少的试剂消耗、极大的比表面积、微米级的扩散距离大大提高了反应速率,导致了较快的分析检测速度,将检测时间缩短为20 s左右。 为应用化学领域的尿素快速分析检测提供借鉴和参考。     

Comparison between the performance of an immobilized impinging jet stream reactor and a slurry impinging jet stream reactor for photocatalytic phenol degradation

A new immobilized photocatalytic impinging jet stream reactor was designed, and the influences of the effective parameters like jet flow rate, TiO₂ coating disc diameter, nozzle-to-disc distance, and initial concentration on phenol removal were investigated. The reactor was also used as a slurry reactor, and degradation efficiencies in both reactors were compared based on their catalyst loading. The results indicated that the slurry reactor has a higher degradation efficiency than the immobilized reactor at the same TiO₂ loading and other operational conditions. The slurry reactor needs to separate and recover the TiO₂ nanoparticles from the reaction medium which increases the overall process complexity and cost, while the immobilized reactor could be reused at least 4times without any significant decrease in removal efficiency. RTD result indicates that the tank in series model (N?=?5) could properly predict the reactors hydrodynamic behavior.     

Determination of Mercury(II) in Drinking Water by Total Reflection X-ray Fluorescence Spectrometry and Liquid–Liquid Microextraction

The total reflection X-ray fluorescence determination of mercury(II) in drinking water at concentrations of 7?×?10^?2 to 3.0?µg/L is reported. The mercury(II) preconcentration protocol includes directly suspended droplet microextraction with benzene as a molecular iodine complex. The proposed approach is highly selective. The elements Cr, Mn, Fe, Co, Ni, Zn, and Pb at concentrations up to 0.1?g/L did not interfere with the extraction of trace mercury(II). The method is characterized by high sensitivity (limit of detection of 21?ng/L) and suitable reproducibility (relative standard deviation of 0.12 for 100?ng/L). The accuracy of the results was confirmed by recovery and the method of standard addition.     

Droplet Precise Self‐Splitting on Patterned Adhesive Surfaces for Simultaneous Multidetection

Precise separation and localization of microdroplets are fundamental for various fields, such as high‐throughput screening, combinatorial chemistry, and the recognition of complex analytes. We have developed a droplet self‐splitting strategy to divide an impacting droplet into predictable microdroplets and deposit them at preset spots for simultaneous multidetection. No matter exchange was observed between these microdroplets, so they could be manipulated independently. Droplet self‐splitting was attributed to anisotropic liquid recoiling on the patterned adhesive surface, as influenced by the droplet Weber number and the width of the low‐adhesive stripe. A quantitative criterion was also developed to judge the droplet self‐splitting capability. The precise separation and distribution of microdroplets enabled simultaneous arrayed reactions and multiple analyte detection using one droplet of sample.     

X‐ray photoelectron spectroscopy depth analysis of metal oxides by electrospray droplet impact

The electrospray droplet impact (EDI) method is a newly developed etching method using extremely large charged water cluster ions with masses of several 10⁶ u. This work presents a comparative XPS study of chemical states of the transition metal oxides, TiO₂ and Ta₂O₅, etched by Ar⁺ and EDI. Selective sputtering of oxygen was observed by Ar⁺ etching for these samples, but no chemical modification took place by EDI. This finding provided further evidence that EDI has the capability of nonselective etching for both inorganic and organic materials. Copyright © 2011 John Wiley & Sons, Ltd.     

微流控液滴软模板制备二氧化钛中空微球

应用微流控液滴技术合成功能材料已发展成为一个新兴领域。本文以夹流结构微流控芯片产生的微液滴作为软模板,以液滴模板界面处发生的水解反应生成二氧化钛球壳,并经后续脱核处理,制备二氧化钛中空微球。采用激光诱导荧光成像、扫描电镜等手段对微球形貌结构进行了分析表征。结果表明,通过控制微流控芯片液滴合成条件,可以得到壁厚约2 μm的二氧化钛中空微球。这种以微流控液滴为模板的合成方法简单灵活,若与其他材料改性方法相结合,有望实现对更多元、更复杂功能微球材料的制备,并进一步拓宽其在光电和催化剂材料领域的应用。     

多相分散体系中气泡/液滴聚并和破碎的群平衡模拟

多相分散体系中气泡/液滴聚并和破碎过程的模拟对于过程工业中离散相粒径分布的调控具有极为重要的意义。群平衡模型（population balance model, PBM）是模拟离散相聚并和破碎的常用方法。然而由于多相分散体系的复杂性,PBM中现有的聚并和破碎模型通常基于现象模型、统计分析、经验关联式或半理论半经验方法,尚未有模型能够全面地考虑流场和物性对聚并或破碎过程的物理约束,从而使准确预测各类工况的聚并与破碎现象成为挑战性的课题。本文总结了目前针对气-液/液-液体系破碎和聚并过程的机理分析、主流模型、群平衡方程的求解方法以及PBM在气-液和液-液体系中的应用,并评述了各种模型的研究现状和未来发展方向。