Trace mercury (II) detection and separation in serum and water samples using a reusable bifunctional fluorescent sensor

In this work, a reusable bifunctional fluorescent sensor for simultaneous detection and separation of trace Hg²⁺ in water and serum, which contains a naphthalimide derivative of 2,6-bis(aminomethyl)pyridine covalently grafted to the surface of silica particles, was developed. Meanwhile, the fluorescence characteristics and the adsorbent properties of the sensor were investigated in detail. This sensor showed a very good linearity (correlation coefficient of R² = 0.9991) in the range 0.1-1 μM of Hg²⁺ with detection limits lower than 6.8 × 10⁻⁹ M. It can also be used as an adsorbent for the removal of mercuric ions from the contaminated aqueous solution. The regeneration of this sensor is very simple, only by modulating the pH value of the aqueous solution. It can be reused at least four cycles. In addition, the present approach has the advantages of rapidity, simplicity, and low cost. We believe that this approach may serve as a foundation for the preparation of practical fluorescent sensor for the rapid detection of Hg²⁺ in aqueous biological and environmental samples.     

强阴离子交换柱分离-氢化物发生-原子荧光光谱法测定水中As(Ⅲ)和As(Ⅴ)

本文报道水中As(Ⅲ)和As(Ⅴ)的Supelco强阴离子交换(SAX)柱分离-氢化物发生-原子荧光光谱(HG-AFS)法检测的新方法.方法的检出限为0.0466 μg/L,相对标准偏差为0.89%～1.01%,加标回收率为95.10%～105.30%.该方法具有操作简单,分离效果好,测定精确度、准确度高等优点.将其应用于水样分析,可测定水中砷的不同价态.     

Adsorption of benzene from benzene/n-C6 and n-C7 mixture by nano Beta zeolite with different Si/Al ratios

The adsorption of benzene from benzene/n-alkane mixtures was studied by two types of nano Beta zeolite with Si/Al ratios of 11.5 and 24.5. Benzene was adsorbed into benzene/n-hexane and n-heptane mixtures which had 0.5% up to 10% mole fraction of benzene using batch technique in the ambient temperature. The nano Beta zeolite has active sites on its surface, which have interaction with π electron in benzene, and this can increase the heat of adsorption. The Si/Al ratio defines the number of active sites in the zeolite surface and the heat of adsorption. However, an increase in the active sites of Beta zeolite declines the entropy of adsorption. Therefore, free energy of mixing specifies the potential of adsorption in Beta zeolite.As the results indicated in all mixtures, benzene is adsorbed more than n-hexane and n-heptane into the Beta zeolite surface, which suggests that this type of zeolite has a high separation factor (∼50) for benzene in Beta zeolite (Si/Al = 24.5). Also, Beta zeolite with Si/Al = 24.5 had a greater separation factor than Beta zeolite with Si/Al = 11.5 in similar mixtures.     

Determination of Occurrence Characteristics of Heavy Metals in Soil and Water Environments in Tianshan Mountains,Central Asia

China has one of the fastest-growing economies in the world, but this economic development has important implications for environmental changes in this country. Our research was to quantify the presence of heavy metals in soil and water environments in the Tianshan Mountains region of China, associated with the economic development of this region. We used anomaly analysis, correlation analysis, and principal component analysis to assess the occurrence characteristics of heavy metals in this area. Results showed that Co, Cr, As, and Ni are more prevalent in water environments than in soil environments; in contrast, Cd, Zn, Pb, Hg, and Mn are more prevalent in soil samples than in water samples. This analysis grouped 10 heavy metals in soil and water environments into three principal components. In soil environments, the prevalence order was Co, Ni, Cr, As > Mn, Zn, Pb > Hg, Cd, Cu. In water environments, the order was Cu, Co, Ni, Cr, As > Hg, Mn, Zn > Cd, Pb. It is possible to distinguish between the natural and the anthropogenic sources of heavy metals in the Tianshan Mountains. With the current rapid economic development in the Tianshan Mountains, anthropogenic sources are playing principal roles in serious heavy metal accumulations in this region. This problem warrants immediate and widespread attention to prevent further deterioration of the soil and water environments.     

嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法分析痕量铬的形态

研究了嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法对尿中痕量铬的形态分析方法,探讨了嵌段分子筛聚合材料P123-SH吸附铬的原理和最佳条件。在pH 7.0、常温下,Cr3+和Cr(Ⅵ)被很好的分离,且Cr3+可被该材料定量吸附,其吸附容量为6.15 mg/g。吸附的Cr3+可用2 mol/L的HCl洗脱,用石墨炉原子吸收法测定洗脱下来的Cr3+,往溶液中加入0.1%抗坏血酸将Cr(Ⅵ)还原为Cr3+测总铬,Cr(Ⅵ)含量为总铬减去Cr3+,方法测定Cr3+的检出限为0.011μg/L(3σ,n=11),线性范围为0.1～10μg/L,加标回收率在94%～106%之间,对0.50μg/L的Cr3+溶液平行测定7次,RSD为3.6%。方法可应用于生物样品和环境样品中痕量铬的形态分析。     

发酵液中谷氨酰胺提取新工艺

本文根据谷氨酸和谷氨酰胺的电离常数的差异,采用一种新型的离子交换工艺,通过单根阴离子交换柱,从谷氨酰胺发酵液中提取谷氨酰胺。粗晶溶解液通过阴离子交换柱后,谷氨酰胺最高收率达到83％,谷氨酸去除率90％。该法在显著提高产品收率的同时,还大大减少了酸碱用量。     

TiO_2/Ag_2NCN复合光催化剂的制备与可见光催化性能

利用银盐与单氰胺水溶液的沉淀反应,通过共混不同质量分数的纳米TiO2粒子制备了TiO2/Ag2NCN复合光催化剂.使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外(FTIR)光谱仪和紫外-可见(UV-Vis)吸收光谱仪对复合光催化剂的结构进行了表征.结果表明,锐钛矿相TiO2纳米颗粒沉积在Ag2NCN表面形成异质结构,二者间以弱的物理作用力相结合.TiO2的掺杂使得复合颗粒的UV-Vis吸收光谱发生红移,带隙变窄.以亚甲基蓝(MB)为光催化降解对象,研究了TiO2/Ag2NCN复合颗粒的可见光催化活性.结果表明,与单一Ag2NCN相比,复合颗粒表现出增强的光催化性能.对TiO2/Ag2NCN复合颗粒的光催化反应动力学过程及光催化机理进行了探讨.     

Role of the shape of various bacteria in their separation by Microthermal Field-Flow Fractionation

The steady-state movement of the spherical and non-spherical particles, such as prolate or oblate rotational ellipsoids, cylinders, or parallelepipeds, suspended in a liquid and exposed to a unidirectional temperature gradient, is analyzed theoretically. The differences in the ratios of the rotational to translational diffusion coefficients of the non-spherical to spherical particles, the heterogeneity of thermal conductivity of the particle body, and the heterogeneity in surface chemical nature make possible to separate the particles according to differences in shape. Preliminary experimental separations of Gram-positive and Gram-negative, nearly spherical and rod-shaped bacteria performed by Microthermal Field-Flow Fractionation confirmed that the fractionation of the cells according to differences in shape is possible.     

A critical look at the definition of multidimensional separations

Multidimensional (MD) separations, especially comprehensive two-dimensional (2D) separations such as comprehensive 2D LC (LC × LC), and comprehensive 2D GC (GC × GC), are potentially powerful separation techniques. It is important to have a clear definition of MD techniques to better understand the scope and boundaries of the subject. Widely accepted definitions of MD Separations have their roots in the definition proposed by Giddings. Giddings also added several comments that clarified the scope of his definition. However, some researchers extend Giddings’ definitions beyond their intended scope. Doing so disqualifies such comprehensive 2D techniques as LC × LC, GC × GC and 2D TLC from being considered as 2D techniques. In other instances, extended treatment of Giddings’ definition is used as a basis to justify design-parameters of comprehensive 2D separations despite the fact that these parameters lead to sub-optimal implementations. We believe that the shortcomings in the definition and its popular interpretations are serious enough to warrant attention, especially by those interested in designing optimal instrumentation for MD separations like comprehensive 2D GC. After discussion of the weaknesses in the currently used definitions, we propose to define n-dimensional analysis as one that generates n-dimensional displacement information. We believe that this definition captures the spirit of Giddings’ definition while avoiding the problems associated with its popular interpretations.     

New separation methodologies for the distinction of the growth phases of Saccharomyces cerevisiae cell cycle

In the present work two separation techniques, namely the gravitational field-flow fractionation (GrFFF) and the reversed-flow gas chromatography (RFGC), are proposed for the distinction of the growth phases of Saccharomyces cerevisiae (AXAZ-1) yeast cycle at different temperatures (30 °C, 25 °C, 20 °C, and 15 °C) and pH (2.0, 3.0, 4.0 and 5.0) values. During the fermentation processes, differences observed in the peak profiles, obtained by GrFFF, can be related with the unlike cell growth. The distinction of the phases of AXAZ-1 cell cycle with the GrFFF, was also confirmed with the RFGC technique, which presented similar fermentation time periods for the alcoholic fermentation phases. Simultaneously, the reaction rate constant for each phase of the fermentation process and the activation energies were determined with the aid of the RFGC technique. Finally, the application of both the GrFFF and the RFGC techniques, in combination with high-performance liquid chromatography, allowed us to find the ideal experimental conditions (temperature and pH) for the alcoholic fermentation by AXAZ-1. The results indicate that S. cerevisiae cells performed better at 30 °C, whereas at lower temperatures decreases in the fermentation rate and in the number of viable cells were observed. Moreover, the pH of the medium (pH 5.0) resulted in higher fermentation rates and ethanol productivities.