ISEC法在评价色谱介质孔径结构方面的应用

层析是生物大分子分离纯化的一种重要手段,层析介质作为层析过程的关键的一部分受到了广泛的关注。层析介质的孔径结构对其分离纯化的效果有着显著的影响,因此探究层析介质的孔径结构至关重要。介绍了测定色谱介质孔径结构常用的方法,如：压汞法、氮气吸附法、小角X射线散射法、电镜扫描法（SEM和TEM）和逆体积排阻色谱法(ISEC)。重点阐述了ISEC法的基本原理和常用的探针类型,总结了ISEC法应用中的优点及不足,介绍了ISEC法的发展历史及其在国内外的研究现状。     

逆体积排阻色谱法在评价色谱介质孔径结构方面的应用

介绍了影响层析介质分离纯化效果的结构参数。总结了测定色谱介质孔径结构常用的方法,如压汞法、氮气吸附法、小角X射线散射法、电镜观察法(SEM和TEM)和逆体积排阻色谱法(ISEC)。介绍了ISEC的基本原理及其涉及到的探针类型。对ISEC相关理论,尤其是溶质半径、色谱理论和体积排阻色谱法(SEC)随机理论进行了重点阐述。比较了ISEC的优缺点。介绍了ISEC在评价介质孔径结构中的应用,对ISEC的应用前景进行了展望。     

纤维素醚改性硫铝酸盐水泥浆体中可蒸发水的1H低场核磁弛豫特征

采用低场核磁共振仪测定了不同种类及掺量的纤维素醚改性硫铝酸盐水泥浆体在各龄期的横向弛豫时间,并结合维卡仪测定水泥浆体的凝结时间,研究了纤维素醚对硫铝酸盐水泥早期水化的影响机制。结果表明:纤维素醚在水泥浆体中的吸水作用会影响浆体的早期水化。纤维素醚的掺入使得低场核磁共振的横向弛豫时间信号出现了一个代表纤维素醚吸附水的弛豫峰,峰的面积大小与纤维素醚对硫铝酸盐水泥早期水化的影响程度有关。纤维素醚的取代度越大,峰面积越大,吸水和缓凝作用相对越强。     

不同粒径纳米氧化硅改性白水泥水化过程的^(1)H低场核磁弛豫特征EI北大核心CSCD

采用^(1)H低场核磁共振仪连续监测不同粒径(15,50 nm和100 nm)纳米氧化硅对白水泥从加水到水化72 h横向弛豫时间的变化,研究不同粒径氧化硅对水泥水化过程的影响程度,最后结合维卡仪测定水泥浆的凝结时间。结果表明:纳米氧化硅的晶核作用会影响水泥的早期水化过程,还可以通过物理吸附和火山灰反应打破早期水泥浆体的絮凝结构,减少大孔隙的数量,提高水泥浆体的均质性。此外,纳米氧化硅粒径越小,水化过程中自由水含量消耗越快,表现出的凝结时间越短。     

低场核磁共振法测定电子浆料的分散性

采用低场核磁共振法快速测定了不同分散工艺、研磨时间、分散剂及含量所制备的导电浆料的横向弛豫时间,结果表明：当以BYK为分散剂,其含量为0.6%时,采用纳米均质分散工艺,研磨时间为30分钟时可制备出稳定分散的导电浆料。相比于其他检测浆料分散性的方法,对于浆料不需进行任何前处理,可直接于浓稠状态下测试,且设备操作简单,能快速得到结果,可有效提高研发和生产效率。     

基于逾渗理论的多孔过滤介质孔径分布估计方法

结合逾渗理论和网格模型,建立了过滤系数与过滤介质孔径分布的联系方程。利用此方程结合过滤实验数据获得过滤介质孔径分布的统计参数,同时与其他方法获得孔径分布参数以及其他文献中的数据进行比较,并利用计算机模拟过滤过程验证了获得的孔径分布参数,结果表明基于逾渗理论的过滤模型用于孔径分布参数的估计是比较准确和有效的。     

过滤高黏度物料的多层复合过滤介质

介绍了可压缩、高黏度及胶状物等难过滤物料的性质、过滤难题和强化过滤分离的方法,针对实例设计了六层复合结构滤布并测试了其过滤效果。     

非织造过滤介质孔径及截留性能的研究

对应用于液固分离和气固分离的非织造过滤介质的孔径和截留性能测试方法做了研究,指出采用气体流量法进行孔径性能测试,可同时得到非织造过滤介质的最大孔径、平均孔径及孔径分布,全面表征了其孔径性能;并对用于液固和气固分离2个不同领域的非织造过滤介质采用不同的方法做了截留性能测试。同时,对比非织造过滤介质的孔径和截留性能,对二者之间的关联做了探索,为实际工业过程中非织造过滤介质的选用和评价提供了指导。     

低场核磁表征交联橡胶性能的研究

研究低场核磁法测定的天然橡胶(NR)硫化胶的交联密度、核磁参数T2随测试温度的变化趋势,确定测试的温度区间;改变硫黄用量,测定NR硫化胶的交联密度并与平衡溶胀法的测定值进行比较。结果表明:低场核磁法与平衡溶胀法测定结果有很强的相关性;将核磁参数与力学性能进行比较,指出了交联密度增大时力学性能的变化趋势。     

两种凝胶过滤介质纯化Sabin株脊髓灰质炎病毒效果的比较

目的比较两种不同的凝胶过滤介质对Sabin株脊髓灰质炎病毒的分离纯化效果。方法将Ⅰ、Ⅱ、Ⅲ型Sabin株脊髓灰质炎病毒收获液各3批经超滤浓缩后,分别采用Sepharose CL-6B和Sepharose 6FF填料进行凝胶过滤纯化,分段收集各纯化峰,检测D抗原及蛋白含量,计算比活性、蛋白去除率及抗原回收率,确定病毒峰收集范围。取抗原含量最高的病毒收获液,利用DEAE Sepharose FF离子交换填料进行纯化后,检测Vero细胞DNA残留量、Vero细胞蛋白残留量、牛血清白蛋白残留量、抗生素残留量。结果 Sepharose 6FF填料按6%柱体积上样进行凝胶纯化,纯化的Ⅰ、Ⅱ、Ⅲ型病毒收获液抗原回收率均值分别为78.69%、78.03%和78.37%,与Sepharose CL-6B填料按3%柱体积上样(77.29%、78.60%和77.36%)相比,差异无统计学意义(P0.05)。两种填料纯化的各型收获液再经离子交换纯化后,蛋白去除率、比活性、Vero细胞DNA残留量、Vero细胞蛋白残留量、牛血清白蛋白残留量、抗生素残留量检测结果均符合《中国药典》三部(2015版)相关要求,两种填料纯化的各型收获液比活性差异无统计学意义(P0.05)。结论使用Sepharose 6FF纯化的各型病毒纯化液抗原回收率和比活性与Sepharose CL-6B无明显差异,但可以减少纯化的上样次数,大幅提高纯化效率,可用Sepharose 6FF替换Sepharose CL-6B。     

Experimental study on drying characteristics of wheat by low-field nuclear magnetic resonance

The characteristics of transverse relaxation time (T₂) of water in wheat were studied by measuring the relaxation time of low-field nuclear magnetic resonance. Analysis of the exponential distribution of T₂ revealed that wheat contains five water components. The T₂ relaxation time and distribution significantly changed during drying. The dynamic characteristics of five water components during wheat drying were determined using the signal quantity of their characteristic peaks, which showed different features. Weakly chemically bound water (T₂₂) and water ascribed to cell wall (T₂₃) were the main source of water loss. Moreover, most T₂₃ and extracellular water (T₂₄) were removed during drying. Water migration between strongly chemically bound water (T₂₁) and the other water components was bidirectional. This process was not only affected by temperature but also by wheat moisture content and proportion of the five water components. The start time of water migration advanced and growth rate of T₂₁ at the end of drying to that before drying increased at 60, 70, and 80°C. Drying at varied temperatures should be applied according to the characteristics of five water components during the drying process. In addition, high initial temperature was found to be necessary to achieve high drying rate of T₂₃, T₂₄, and free water (T₂₅). The use of drying temperature of 80°C at the early stage and then changing to 70°C reduced the heat consumption by 4.81% and increased the drying time by 9.61%.     

逆体积排阻层析法测定层析介质的孔径分布

针对层析介质的孔径分析,基于刚性球状分子进入柱状孔的假设,分别采用高斯正态分布和对数正态分布描述孔径分布,利用简化的单孔分配因子模型,建立了孔径分布函数和分配因子Kd的关联,通过体积排阻层析实验测定系列标准物的Kd,从而拟合得到孔径分布信息,建立了逆体积排阻层析法。以葡聚糖作为分子大小的标准物,测定了5种典型层析介质(SP Sepharose FAST FLOW、Q Sepharose FAST FLOW、ToyopearlDEAE-650M、Streamline DEAE和Sephadex G-150)的Kd,计算和比较了不同介质的孔径分布,分析了介质的可吸附孔表面积等结构参数,证实了逆体积排阻层析法分析层析介质孔径分布的可行性和实用性。     

Relationship between pore fluid velocity distribution and pore size distribution

This study investigated the normalized velocity magnitude distribution and normalized pore volume distribution in different porous media with porosity between 13.5% and 85%, including sandstones, carbonates, synthetic silica, sphere packings and fiber scaffolds. It was found that both velocity magnitude and pore size follow the same distribution. These results allow the prediction of the velocity distribution in a porous medium when its pore structure is known or tuning the velocity by controlling the pore structure.     

Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)

Nuclear magnetic resonance (NMR) has been widely used in petrophysical characterization of sandstones and carbonates, but little attention has been paid in the use of this technique to study petrophysical properties of coals, which is essential for evaluating coalbed methane reservoir. In this study, two sets of NMR experiments were designed to study the pore types, pore structures, porosity and permeability of coals. Results show that NMR transverse relaxation (T₂) distributions strongly relate to the coal pore structure and coal rank. Three T₂ spectrum peaks identified by the relaxation time at 0.5-2.5 ms, 20-50 ms and >100 ms correspond to pores of <0.1 μm, >0.1 μm and cleats, respectively, which is consistent with results from computed tomography scan and mercury intrusion porosimetry. Based on calculated producible and irreducible porosities through a T₂ cutoff time method, we propose a new NMR-based permeability model that better estimates the permeability of coals. In combination with mercury intrusion porosimetry, we also propose a NMR-based pore structure model that efficiently estimates the pore size distribution of coals. The new experiments and modeling prove the applicability of NMR in petrophysical characterization of intact coal samples, which has potential applications for NMR well logging in coalbed methane exploration.     

孔径梯度分布对亲油型滤材气液过滤性能的影响

在天然气净化、大型旋转机械曲轴箱通风和压缩空气过滤等领域,气液聚结过滤器具有广泛的应用。利用滤材过滤性能实验装置,分析了气液过滤过程中不同孔径梯度分布的亲油型滤材的压降、穿透率和饱和度变化,比较了其过滤性能、内部液体分布特性以及对液滴二次夹带现象的影响。结果表明：在气液过滤过程“通道压降”阶段,孔径递增滤材压降和0.8 μm以上液滴穿透率的变化曲线具有明显的分层特征。不同孔径梯度分布滤材的稳态过滤性能存在明显差异,主要原因是滤材内部存在液体运移通道的传递现象。通过与孔径递减和孔径均匀分布滤材的稳态过滤性能对比,发现孔径递增滤材在保证较低压降的同时具有最高的品质因子,有利于减少液滴二次夹带现象的发生,且对0.8 μm以上不同粒径液滴均具有最高的过滤效率,即孔径递增滤材在气液聚结过滤器设计中更具优势。     

A comparison of nitrogen adsorption and thermogravimetric methods in the assessment of the pore size distribution of mesoporous silica gels

The pore dimensions are determined by using adsorption and thermogravimetry methods for unmodified silica gel Si-100 and silanized silica gel Lichrosorb RP-18. Thermal desorption measurements for various liquids were performed under quasi-isothermal conditions. Methanol, acetone, benzene and n-hexane were used as a wetting liquids. Pore size distributions and total pore volumes derived from thermal desorption compare reasonably well with results obtained from the analysis of adsorption isotherms of nitrogen. For different types of adsorbates the effects connected with the presence of the surface liquid film are discussed. The presence of long alkyl chains on the silica surface strongly influences the pore diameter calculated from thermogravimetric data.     

采用超高分子量聚乙烯过滤介质强化过滤过程的研究

采用颗粒烧结法制备的超高分子量聚乙烯过滤介质,对用途广泛、难过滤的一种无机盐醋酸钙物料做了动态强化过滤过程研究。在对3种超高分子量聚乙烯过滤介质表征的基础上,考察了不同操作压力、旋转速度、固含量、操作温度等对过滤过程的影响。研究表明,过滤通量随着过滤介质孔径增大、压力增大、温度升高、固含量降低均有所增加,截留效果较好,滤液浊度都在30.0 NTU以下,实现了有效的过滤分离,可供技术工程化应用研究参考。     

人工伴侣与凝胶过滤色谱耦合作用促进高浓度溶菌酶复性研究

研究了人工伴侣系统,即十六烷基三甲基溴化铵(CTAB)和β 环糊精(β CD)促进高浓度变性 还原溶菌酶的氧化复性。确定CTAB与β CD的浓度比为1∶4,CTAB与变性溶菌酶的结合时间在10—50min内复性收率较高。同时发现,利用人工伴侣和凝胶过滤色谱的耦合作用可有效提高溶菌酶的复性收率,在连续复性操作条件下可使进料质量浓度为1mg/mL的变性酶获得87%的总复性收率。