迎头色谱法测定人参皂苷Rg1和Re的吸附量

制备色谱分离条件优化的基础是吸附等温线的测定及保留时间的预测。本文以人参皂甙Rg₁、Re为研究对象，用色谱单柱制备了人参粗粉中的人参皂甙Rg₁、Re,以迎头法测定了人参皂甙Rg₁、Re在C₁₈球形固定相中的吸附等温线，在竞争Langmuir模型基础上确定了吸附参数G和b，并应用非线性色谱理论的结果预测了人参皂甙Re的保留时间，上述结果与实验值进行了比较，平均相对误差为3.68%。在实验中发现了运用竞争Langmuir模型进行拟合的一些问题并进行了讨论。     

前沿分析法测定葡萄糖在制备色谱柱上的吸附等温线

吸附等温线对模拟移动床色谱操作参数的模拟和优化具有重要的指导意义。以前沿分析法测定65℃下葡萄糖在离子树脂色谱柱上的吸附等温线,实验结果表明该行为符合anti-langmuir吸附模型。用所求模型参数预测脉冲实验,模拟结果较好,验证了测定的模型参数准确可靠。     

逆向法确定色氨酸对映体竞争型吸附等温线

引言 吸附等温线测定是研究色谱分离过程的关键,其准确性直接影响到色谱分离过程的准确程度,因此,选择适当的实验方法和数学模型来模拟吸附等温线是模拟色谱分离过程的一个重要环节.常用的几种方法包括:前沿分析法、特征点洗脱法、特征点前沿分析法以及扰动法[1-2].其中前沿分析法是最常用的方法,该方法简单,准确性高,可用于多组分竞争型吸附等温数据的测定,但其数据采集过程非常耗时,对原料的需求量大,且需要考察单组分吸附等温模型与吸附数据的拟合程度.     

活性炭对电镀废水中Cr~(6+)的吸附——活性炭选择吸附的热力学和动力学方法

通过活性炭对电镀废水中Cr~(6+)的间歇法和流动法吸附实验研究,获得了吸附平衡时间、最佳pH 值,测得了吸附等温线和穿透曲线,并以吸附动力学角度测定了吸附速度和扩散系数。采用吸附初期的吸附速度和扩散系数等动力学参数来判断和比较活性炭吸附性能优劣是一种好方法。它既与测量吸附等温线所得结果一致,并且又和孔结构分布相联系。     

吸附热预测吸附等温线

实验测定了N2 在沸石分子筛、C2 H6 在活性炭、CO2 在硅胶上的吸附等温线 ,研究用Clausius Clapeyron方程求得等量吸附热、再利用所得的吸附热预测其它温度的吸附等温线数据的方法。将吸附热预测的等温线与实验值及插值法内插得到的吸附等温线数据进行了比较 ,结果表明吸附热预测值与实验值吻合较好。此外还对文献数据利用等量吸附热预测较高压力 ( 65 0kPa)下的等温线 ,均与文献中的实验值一致。为吸附工业操作需要不同温度下的等温线数据和吸附过程的模拟与设计提供了简便、准确的计算方法     

新型超高交联树脂对2-甲基-4-氯苯氧乙酸的吸附机理研究

在静态条件下,研究了水溶液中超高交联树脂ZZ和大孔吸附树脂Am berlite XAD-4吸附2-甲基-4-氯苯氧乙酸的热力学特性,测定了283K和323K温度下的吸附等温线。对两个温度下的吸附等温线的比较和热力学数据的计算,结果表明,在稀溶液中两种吸附剂对2-甲基-4-氯苯氧乙酸的吸附同时符合Langm u ir和F reund lich模型,并且两种吸附剂对2-甲基-4-氯苯氧乙酸的吸附都是放热过程。     

活性炭纤维吸附邻硝基苯胺水溶液的研究

采用活性炭纤维(ACF)处理邻硝基苯胺模拟废水,通过静态和动态吸附实验,研究了pH、盐含量、吸附时间对吸附效果的影响,测定了吸附等温线和动态穿透曲线,并进行了ACF再生实验。结果表明,在实验条件下,ACF对邻硝基苯胺的吸附速率很快,5 min去除率达96%,在pH4.4~10.4条件下吸附效果较好,盐的含量对吸附效果影响较小,吸附等温线能用Langmuir和Freundlich方程较好地拟合。溶液流速增大,穿透时间提前,吸附饱和的ACF用无水乙醇再生,重复5次,邻硝基苯胺的回收率均在95%以上,ACF的吸附效率无明显变化。     

模拟移动床色谱分离吴茱萸碱和吴茱萸次碱

以C18为固定相、甲醇/水=70/30（体积比）为流动相,利用三区带模拟移动床分离了两种生物碱,吴茱萸碱和吴茱萸次碱。通过前沿分析法测定了两种生物碱的吸附等温线,在实验浓度范围内符合线性吸附等温线,吴茱萸碱和吴茱萸次碱的亨利系数分别为3.11和5.25。利用经验公式估算了轴向扩散系数和有效传质系数。分别利用三角形理论和基于模型的优化方法对三区带模拟移动床的操作条件进行设计,在优化的条件下,最大进料流量为0.55 ml?min^-1,两种产品纯度均大于99%。通过异步切换策略,在不增加设备投资及保证产品纯度大于99%的前提下,将进料流量提高至0.62 ml?min^-1。     

D-核糖发酵液活性炭吸附脱色工艺和表征

以枯草芽胞杆菌发酵生产D-核糖的发酵液为脱色体系，用简易和准确测定发酵液中的吸光度表征发酵液中的色素浓度，阐述发酵液吸附脱色工艺参数的计算。根据实验确定340nm为最合适吸光度测定波长，建立了吸光度与发酵液中的色素浓度之间的函数关系。用活性炭脱色在间歇操作条件下最佳吸附时间为30min，操作温度为50℃，pH为3．5。建立色素吸附等温线和计算式，其等温线类型为L型。     

正戊烷和正己烷在5A分子筛上的液相吸附性能研究

测定了373~453K温度条件下正戊烷和正己烷在5A分子筛上的液相吸附平衡数据,用Langmuir方程和Freundlich方程对实验吸附等温线数据进行了拟合计算。结果表明,在453K温度下,正戊烷和正己烷在5A分子筛上仍可以达到7%左右的吸附容量,其吸附等温线符合Langmuir吸附等温类型,Langmuir吸附方程能够很好的拟合实验结果。Clapeyron-Clausius方程计算得到的正戊烷和正己烷在5A分子筛上吸附热、吸附熵等热力学数据表明,正戊烷、正己烷均易吸附于5A分子筛上,其吸附热为-24kJ/mol左右。     

Kinetic modeling for chromatographic separation of cytosine monophosphate and uracil monophosphate

Kinetic modeling for preparative chromatography is a topic of present interest in the fine chemicals and pharmaceutical industries. In this study, chromatographic separation of the two nucleotides CMP and UMP was simulated by the equilibrium-dispersive (ED) model, and the adsorption isotherms in the ED model were determined by the inverse method. Prediction performance of the model was validated under three different kinds of conditions and the importance of selecting isotherms was discussed in detail. Excellent agreement was achieved with the experimental band profiles and the prediction of the ED model. The ED model with bi-Langmuir isotherm was especially suitable for simulating chromatographic separation of CMP and UMP. The error of prediction by the ED model with bi-Langmuir isotherm was about 9.4 times smaller than that with Langmuir isotherm.     

Separation of Amino-Acids by Reversed Phase Chromatography: Development of a Model Mixture Dedicated to the Study of Solvent Gradient Chromatography Processes

Solvent gradient is currently used in analytical chromatography and presents an increasing interest in preparative chromatography. The applications relate to complex separations of mixtures where the target species has an intermediate affinity for the solid support compared to that of the other species, which is often the case during the purification of biomolecules extracted from natural raw materials or resulting from biotechnologies. In this case, separation leads to three fractions, impurities weakly retained, an intermediate fraction, and impurities strongly retained. An inexpensive and non-toxic mixture, containing five amino-acids, was identified as a good model mixture for such studies. These amino-acids were selected by taking into account their non-polar and hydrophobic nature. They were selected because of their aptitude for being easily detected in UV-visible spectroscopy without derivation. Separations were carried out by reversed phase chromatography. An experimental study first enabled determining the adsorption isotherm parameters of each amino-acid on an analytical column then on a preparative column for various organic solvent fractions. An empirical law was chosen to express the retention factor k as a function of the mobile phase composition (k=f (x_M)). An approach based on the column modeling by mixed cells in series enabled to simulate the separations obtained on the two types of columns. The use of the laws giving retention factor k as a function of the organic solvent fraction x_M then made it possible to carry out simulations for various solvent gradients. A simple methodology was developed to calculate the optimal solvent gradient. The gradient was optimized by minimizing the separation time and by respecting a constraint on the peaks resolution of the two species which are the most difficult to separate. A really good adequacy was observed between the experimental simulations and results for the weakly retained fraction as well as for the intermediate fraction which comprises components difficult to separate. Adequacy is not as good for strongly retained fraction but it is worth using these two species in the model mixture. This model mixture proves to be interesting to study solvent gradient preparative chromatography processes. The retention of these compounds is sensitive to the organic solvent fraction. It is easy to get these products which are inexpensive, non-toxic, and detectable without any derivation.     

逆向法测定酮洛芬对映体在Chiralpak AD柱上的吸附等温线

模拟移动床（SMB）色谱分离与纯化的操作过程复杂,对其进行设计与优化需要使用数值模拟方法,准确测定竞争型吸附等温线具有重要意义。采用逆向法确定了25℃下酮洛芬对映体在直链淀粉手性固定相（Chiralpak AD）上的竞争吸附等温线,先用高效液相色谱测得酮洛芬对映体在Chiralpak AD 柱上的过载流出曲线,再通过拟合实验测得的流出曲线确定吸附等温线模型及其参数。研究中采用平衡扩散模型描述酮洛芬对映体在色谱柱上流出的瞬态过程。参数拟合过程中,首先用非支配基因算法（NSGA-Ⅱ）在较广的参数空间内搜索吸附等温线模型参数,再以所得结果作为初值,使用Levenberg-Marquardt 算法（LMA）对参数进一步优化。比较了4种不同竞争吸附等温线模型对实验测得的流出曲线的拟合结果,其中五参数的Bi-Langmuir 模型拟合程度最好。测量了不同进料浓度和进料量条件下的流出曲线,并通过与模型预测结果的对照验证了所确定吸附等温线模型和参数。     

Single and competitive isotherms of phenol ando-cresol by pulsed-input method

There is a considerable industrial interest in both the scale-up and optimization of chromatographic operations used in the purification of fine chemicals and biomolecules. One of the major factors affecting the adsorption operation is the adsorption isotherm. Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to measure the adsorption isotherm of phenol ando-cresol. From the experimental results, the retention times were decreased with increasing sample sizes, and the front of the peak was very stiff, so Langmuir adsorption isotherm was applied. Also Early-eluting component, phenol, in a mixture of the two components elutes faster than that in a pure component. Pulsed-injection method (PIM) was used to determine the two parameters of the Langmuir isotherm. The resulting parameters, a and b, were used to calculate the elution profiles of phenol ando-cresol in pure and mixed state. The agreement between the experimental data and calculated elution profiles was fairly good in a mixture as well as a pure component.     

Extraction of 2-hydroxyphenol by surfactant coated nanosized magnetic particles

A colloidal suspension of magnetic particles coated with double layer surfactant molecules was prepared, characterized and used for separation of some chemicals. The aqueous magnetic fluid was prepared by chemical precipitation method and characterized by total organic carbon analyzer (TOC), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The TOC and TGA measurements indicate that the prepared magnetic particles are coated with surfactant molecules in double layers. The outer surfactant layer has free polar heads. TEM measurement results show that magnetic particles are nanosized. A mixture of 2-hydroxyphenol (strong polar) and 2-nitrophenol (weak polar) was chosen as the target system. Results show that the magnetic fluid can selectively adsorb 2-hydroxyphenol from the mixture, whereas the adsorption of 2-nitrophenol is insignificant. For 2-hydroxyphenol, the adsorption equilibrium can be described well by Langmuir isotherm, and the adsorption kinetic can be fitted well by a linear driving force mass transfer model.     

对二甲苯/间二甲苯在KX和CaX上的吸附平衡和动态吸附性能

通过静态吸附实验,测定了对二甲苯、间二甲苯在分子筛KX和CaX上的吸附速率曲线及吸附等温线;动态吸附穿透实验测定了对二甲苯/间二甲苯混合液在固定床中的连续流出曲线。结果表明,对二甲苯、间二甲苯在CaX上的静态饱和吸附量和动态穿透吸附量均高于KX,但CaX对对二甲苯的吸附选择性不及KX;Langmuir吸附等温线方程可以很好地拟合对二甲苯、间二甲苯在CaX上的等温线;二级吸附速率方程可以较好地描述对二甲苯、间二甲苯的吸附动力学行为。     

PREDICTION OF THE ASYMMETRIC PEAK PROFILE USING A MATHEMATICAL METHOD WITH A COMPETITIVE LANGMUIR ISOTHERM

The adsorption characteristics of a single component and a binary component in the stationary phase using preparative chromatography were investigated with a six-adsorption isotherm model. These analyses were based on the Langmuir model. Each parameter of the adsorption isotherm was obtained with the adsorption raw data that was calculated by frontal analysis (FA). The experimental data and the values calculated using the adsorption isotherm model were compared. The bi-Langmuir model showed good agreement for phenol while the tri-Langmuir model showed good agreement for caffeine. Each characteristic of adsorption was obtained from these results. The effect of competitive adsorption was investigated using the parameters of the adsorption isotherm model with a single component. There was good agreement between the experimental data and the calculated values.     

PREDICTION OF THE ASYMMETRIC PEAK PROFILE USING A MATHEMATICAL METHOD WITH A COMPETITIVE LANGMUIR ISOTHERM

The adsorption characteristics of a single component and a binary component in the stationary phase using preparative chromatography were investigated with a six-adsorption isotherm model. These analyses were based on the Langmuir model. Each parameter of the adsorption isotherm was obtained with the adsorption raw data that was calculated by frontal analysis (FA). The experimental data and the values calculated using the adsorption isotherm model were compared. The bi-Langmuir model showed good agreement for phenol while the tri-Langmuir model showed good agreement for caffeine. Each characteristic of adsorption was obtained from these results. The effect of competitive adsorption was investigated using the parameters of the adsorption isotherm model with a single component. There was good agreement between the experimental data and the calculated values.