4种激光粒度仪对下蜀土湿法粒度测试的对比研究

使用4种应用较为广泛的激光粒度仪(Mastersizer2000、Bettersize2000、Horiba LA950和LS13320)对粒度差异较小的下蜀土(土塘剖面)进行了测试,从而对比分析不同激光粒度仪对于下蜀土的粒度组成测试差异及其这种差异对研究结果可能产生的影响.结果表明:对粉砂颗粒组分的分析,4种激光粒度分析仪分析结果的差异最小,而对砂和粘土颗粒组分分析的差异最大.就粒度频数曲线、概率累积曲线、粒度组分、C-M图、粒度参数散点图及粒度参数剖面垂向变化等统计参数与统计方式而言,4种仪器的测试结果均有一定的差异,其中,概率累积曲线、粒度参数散点图差异较大.粒度参数的剖面变化差异也较大,影响了对剖面的阶段性划分,这在一定程度上影响了研究结果,造成使用不同仪器,可能会得出不同的结果.     

超细稀土氧化物粉体粒度测定

采用美国布鲁克海文仪器公司制造的90 Plus粒度仪测定超细稀土氧化物粉体粒度. 以氧化钇为研究对象, 研究了分散剂、悬浮介质、待测样品浓度、分散时间等因素对亚微米级氧化钇粉体粒度测量精度的影响. 由此确定了能准确测定亚微米级氧化钇粉体粒度的测量条件.     

氧化钇粒度控制与测定

用氨水或碳酸氢铵与氯化钇溶液反应生成沉淀，煅烧沉淀制备了D50为0．45μmt 2-10μm的各种粒径的氧化钇粉末。分别采用Coulter MultisizerⅡ和90Plus粒度仪测定微米和亚微米级氧化钇粉体粒度，研究了分散剂，待测样品量，分散时间等因素对亚微米级氧化钇粉体粒度测量精度的影响。     

毛细管电泳无胶筛分介质分离DNA的机理

快速、高效而灵敏的分离技术对于DNA的分析是至关重要的。使用无胶筛分介质的毛细管电泳是最重要的DNA分离技术之一，通常使用无交联的高分子溶液作为无胶筛分介质。本文在介绍高分子溶液理论的基础上，综述了DNA在毛细管电泳无胶筛分介质（缠结溶液和稀溶液）中的分离机理，主要包括Ogston筛分模型、各种修正的爬行模型、瞬态缠结偶合机理及其改进机理等。     

基于纤维素衍生物的毛细管无胶筛分电泳及其应用

毛细管无胶筛分电泳近年来取得了很大进展。本文综述了以纤维素衍生物作为筛分介质的毛细管无胶筛分电泳的研究进展,包括筛分理论,筛分体系模式,以及它在DNA、蛋白质分离方面的应用。     

豚草聚合酶链反应产物的高效毛细管电泳检测

利用PE270A－HT型高效毛细管电泳仪,采用无胶筛分电泳,以羟丙基甲基纤维素（HPMC）为筛分介质,对三裂叶豚草（Ambrosia trifida L.)的聚合酶链反应（PCR）产物进行了分离分析,显示了高效、快速、无污染的毛细管电泳技术在植物DNA片段多态性分析方面的巨大的潜力。     

无胶筛分毛细管电泳分离盐生盐杆菌DNA片段

 由羟乙基纤维素和聚吡咯烷酮混合组成筛分介质 ,在涂敷聚硅氧烷的毛细管柱上 ,研究了LambdaDNA/EcoRⅠ +HindⅢ片段分离的最佳条件。实验表明 ,混合筛分介质与单一的羟乙基纤维素筛分介质相比 ,改变了筛分介质的孔径大小 ,抑制了毛细管壁对DNA的吸附 ,从而改善了分离 ,并首次在同一条件下将所含的 13个片段完全分离。方法简便、快速 ,曾应用于两组盐生盐杆菌DNA片段的分离及其碱基对数目的推测。     

激光粒度分析技术在药物研究和质量控制中的应用进展

近年来,激光粒度分析技术广泛应用于药物的质量研究和质量控制领域.从激光散射测定粒度的原理、仪器的一般要求和影响测试结果的因素、方法验证的要求以及该技术在药物领域中最新应用等方面进行综述,为激光粒度分析技术在药物中的应用开发提供有益的参考.     

含有金纳米粒子的筛分介质对不同长度DNA片段的毛细管电泳分离

探讨了含有金纳米粒子(GNPs)的筛分介质在毛细管电泳(CE)中对不同长度DNA片段的分离.以聚环氧乙烷(PEO)-金纳米粒子(GNPs)-TBE为CE筛分介质,用涂层的毛细管柱(37 cm×75 μm,有效长度27 cm)分离DNA Marker D和1 kbp DNA Ladder Marker标准DNA片段,考察了CE过程中各参数(如筛分介质质量浓度、分离电压、温度和筛分介质pH值)对不同长度DNA片段分离的影响.对比了新型筛分介质与不含GNPs的PEO-TBE筛分介质的分离效果,并将新型筛分介质用于实际样品的检测.结果表明,在筛分介质中添加GNPs后能够改进CE的分离效果,且分离时间短.方法较适于分离较宽范围的DNA片段.     

江西龙南乡标稀土矿石干筛法和水洗筛分法颗粒粒度分析

颗粒粒度分布是土壤最重要的物理性质之一,对土壤水分运动和溶质迁移,以及水土流失有重要影响,同样对离子型稀土矿石的渗透性能和水力学特性有着重要影响。通过江西龙南乡标稀土矿石干筛法和水洗筛分法颗粒粒度分析结果比较研究发现,干筛法粒度分析结果反映的是团粒的颗粒粒度分布特征,而水洗筛分法粒度分析结果可基本反映单颗粒粒度分布特征。因此,在研究离子型稀土矿石或原地浸矿边坡土体颗粒粒度分布时,应考虑不同水动力条件下团聚体的稳定性,合理选择粒度分析方法。     

Steam-stable zeolitic imidazolate framework ZIF-90 membrane with hydrogen selectivity through covalent functionalization

A novel covalent functionalization strategy was developed to prepare reproducible ZIF-90 molecular sieve membranes by using 3-aminopropyltriethoxysilane as a covalent linker between the ZIF-90 layer and Al(2)O(3) support via imines condensation. The ZIF-90 membranes show high thermal and hydrothermal stabilities, and they allow the separation of hydrogen from larger gases by molecular sieving.     

Evaluation of sample preparation (grinding and sieving) of bivalves, coffee and cowpea beans for multi-element analysis

Elemental analyses of food samples require several pre-treatment steps that constitute a great potential source of errors. In this study, the influence of cryogenic, ball and knife mill devices and also sieving using different sizes of sieve (100, 300 and 500 μm) was evaluated for samples of bivalves, coffee and cowpea beans. A two-factor ANOVA was performed in each sample to test for differences between macro, micro and trace element concentrations determined by ICP OES. Results showed that the efficiency of the particle size reduction and sample homogeneity depends on the milling device and the nature of samples. Food samples may present segregation after comminution, and sieving might become a necessary step. Nevertheless, the sieve aperture has to be chosen cautiously, once it might influence the final element concentration. Overall, the expected results by employing cryogenic grinding, such as rapid sample homogenization and small particle size generated were also observed for ball mill. Contamination can be a critical issue for some elements and need to be evaluated individually.     

Low viscosity DNA sieving matrices for capillary electrophoresis

The rapid development of DNA capillary electrophoresis (CE) technology has increased the demand of new low viscosity sieving matrices with high separation capacity. The high throughput, resolution and automatic operation of CE systems have stimulated the application of the technique to different kinds of DNA analysis, including DNA sequencing, separation of restriction fragments, PCR products and synthetic oligonucleotides. In addition specific methods for PCR-based mutation assays for the study of known and unknown point mutations have been developed for use in CE. The key component for a large scale application of CE to DNA analysis is the availability of appropriate sieving matrices. This article gives an overview of the linear polymers used as DNA separation matrices with particular emphasis on the polymers that combine high sieving capacity, low viscosity and chemical resistance.     

Separation of DNA fragments in hydroxylated poly(dimethylacrylamide) copolymers

The novel polymer matrices reported here are low-viscosity sieving media for DNA capillary electrophoresis. This new family of matrices comprises copolymers of N,N-dimethylacrylamide with different monomers which increase polymer hydrophilicity. All these new copolymers self-coat on fused-silica capillaries. Resolution, peak spacing and peak width were the parameters taken into account to assess the influence of polymer structure on separation selectivity and efficiency. This work demonstrates that the performance of polydimethylacrylamide (PDMA) can be improved through copolymerization with hydrophilic monomers. The improvement is related to the efficiency parameter. The new copolymers, due to their low viscosity high sieving capacity and ability to suppress EOF, represent a better alternative to PDMA and are suitable replaceable matrices for capillary and microchip electrophoresis.     

Probing the mechanism of water adsorption in carbon micropores with multitemperature isotherms and water preadsorption experiments

The phenomenon of water adsorption in carbon micropores is examined through the study of water adsorption equilibrium in molecular sieving carbon. Adsorption and desorption isotherms are obtained over a wide range of concentrations from less than 0.1% to beyond 80% of the vapor pressure. Evidence is provided in support of a proposed bimodal water adsorption mechanism that involves the interaction of water molecules with functional groups at low relative pressures and the adsorption of water molecules between graphene layers at higher pressures. Decomposition of the equilibrium isotherm data through application of the extended cooperative multimolecular sorption theory, together with favorable quantitative comparison, provides support for the proposed adsorption mechanism. Additional support is obtained from a multitemperature study of water equilibrium. Temperatures of 20, 50, and 60 degrees C were probed in this investigation in order to provide isosteric heat of adsorption data for water interaction with the carbon molecular sieve. At low loading, the derived isosteric heat of adsorption is estimated to be 69 kJ/mol. This value is indicative of the adsorption of water to functional groups. At higher loading, the isosteric heat of adsorption decreases with increasing loading and approaches the heat of condensation, indicative of adsorption between graphene layers. Further support for the proposed adsorption mechanism is derived from carbon dioxide adsorption experiments on carbon molecular sieve that is preadsorbed with various amounts of water. Significant exclusion of carbon dioxide occurs, and a quantitative analysis that is based on the proposed bimodal water adsorption mechanism is employed in this investigation.     

毛细管电泳在核酸适配体研究及核酸适配体筛选中的应用

核酸适配体是指通过指数富集配体系统进化(SELEX)技术从随机寡核苷酸文库中筛选得到的高亲和性与特异性的寡核苷酸序列配体。毛细管电泳是高效、快速、低成本的微量分离分析技术。应用毛细管电泳高效、快速筛选核酸适配体是近几年出现的新方法。本文介绍了核酸适配体筛选过程中的主要分离方法如亲和色谱、醋酸纤维素膜、凝胶电泳和磁性分离等方法,并对近年来毛细管电泳在核酸适配体中的亲和作用研究以及用于核酸适配体筛选(CE-SELEX)的主要方法(ECEEM,NECEEM,Non-SELEX和三者比较)和研究进展进行了综述。     

Continuous-flow separation of nanoparticles by electrostatic sieving at a micro-nanofluidic interface

Continuous-flow separation of nanoparticles (NPs) (15 and 39 nm) is demonstrated based on electrostatic sieving at a micro-nanofluidic interface. The interface is realized in a poly(dimethylsiloxane) device with a nanoslit of 525 nm laterally spanning the microfluidic channel (aspect ratio of 540:1). Within this nanoslit, the Debye layers overlap and generate an electrostatic sieve. This was exploited to selectively deflect and sort NPs with a sorting purity of up to 97%. Because of the continuous-flow operation, the sample is continuously fed into the device, immediately separated, and the parameters can be adapted in real time. For bioanalytical purposes, we also demonstrate the deflection of proteins (longest axis 6.8 nm). The continuous operation mode and the general applicability of this separation concept make this method a valuable addition to the current Lab-on-a-Chip devices for continuous sorting of NPs and macromolecules.     

A liquid porosimetry technique for correlating intrinsic protein sieving: Applications in ultrafiltration processes

The understanding of variation in sieving properties of membranes is of great importance for the successful development of ultrafiltration applications. A liquid porosimetry technique is presented to quantify the sieving variation among several polyethersulfone ultrafiltration membranes. Observed sieving coefficients were measured with proper precautions taken to control and minimize fouling. These data were translated to intrinsic sieving coefficients using a stagnant film model. The intrinsic membrane sieving coefficient correlated well with the liquid porosimetry data. This liquid porosimetry technique can distinguish between membranes of different molecular weight cut-off and is sensitive enough to capture slight changes in the sieving coefficient of variants of the same cut-off membrane. This technique has several attractive features: it is non-destructive, independent of the module configuration and relatively simple to perform. Two potential applications of this technique are also examined: (1) quantification of the effect of membrane variation on high performance tangential flow filtration (HPTFF) for protein separations and (2) development of a membrane integrity test to ensure batch-to-batch consistency. This technique has the potential for use in membrane quality control, membrane selection, and validation of industrial ultrafiltration processes.     

Evaluation of sieving matrices used to separate alleles by cycling temperature capillary electrophoresis

Denaturing CE (DCE) is a powerful tool for analysis of DNA variation. The development of commercial multi-CE instruments allows large-scale studies of DNA variation (many samples and many fragments). However, the cost of consumables like capillary arrays and sieving matrix might limit the use of DCE in such studies. Thus, we have tested 72 different in-house formulated sieving matrices' ability to suppress EOF and separate PCR-amplified alleles with the DCE variant, cycling temperature CE (CTCE). The data herein demonstrate that alleles can be baseline-separated by use of PVP and poly(N,N-dimethyl acrylamide) polymers at various percentages and pH. Allele separation by CTCE is matrix-independent and consequently applicable to any capillary instrument used for DNA separation. Formulation of sieving matrix for CTCE was done by dissolving appropriate amount of polymer powder into the running buffers. Allele separation was observed at different pH (7.5-8.5), concentrations and molecular size of the polymer, without compromising the separation and reproducibility. Finally, the cost reduction of homemade matrices is more than 1000-fold as compared to commercial sieving matrices.     

High‐Flux Carbon Molecular Sieve Membranes for Gas Separation

Carbon membranes have great potential for highly selective and cost‐efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp² hybridized carbon sheets as well as sp³ hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m³(STP)/(m²hbar). Furthermore, by a post‐synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide.