Numerical Approximation of the General Rate Model for Gradient Elution Chromatography Utilizing Core-Shell Particles.

An extended method of semidiscrete high-resolution finite volume is used in this paper to obtain numerical solutions for a formulated nonlinear lumped kinetic model of liquid chromatographic process to examine the effect of chromatographic column overloading gradient elution considering core-shell particles. The model constitutes linear solvent strength (LSS), Henry’s constant, coefficient of nonlinearity, and coefficient of axial dispersion. The effects of modulator concentration changes for the elution of single and two components are analyzed. The advantages of introducing gradient elution against isocratic elution in terms of core radius fraction are investigated intensively. Numerical temporal moments are generated from the solutions obtained for a more in-depth examination of the considered model. Moreover, multiple forms of a single- and two-component mixture are generated to analyze the influences of core radius fractions on gradient elution. For example, the obtained results are utilized to investigate the effects of the slope of gradient, concentration of modulator, solvent strength parameter, coefficient of nonlinearity, coefficient of mass transfer, and coefficient of axial dispersion on the profiles of concentration in order to improve the process performance using optimal core radius fraction parameter values.

A nonlinear lumped kinetic model of liquid chromatography is formulated and solved numerically to theoretically investigate the effect of column overloading on gradient elution. Linear solvent strength (LSS) model is utilized for Henry’s constant, non linearity coefficient and axial dispersion coefficient. A semi-discrete high-resolution finite volume scheme is extended and applied to obtain the approximate solutions of the governing model equations. The effects of changing modulator concentration are examined on the single and two-component elution. The benefits of gradient elution over isocratic elution are thoroughly discussed. The influences of optimizing free-parameters available in gradient chromatography are analyzed on the efficiency of the column and on the production of targeted components. For instance, the results obtained are used to study the effects of gradient slope, modulator concentration, solvent strength, nonlinearity coefficient, mass transfer coefficient, and axial dispersion coefficient on the concentration profiles.

Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method: III. Separation mechanism and gradient optimization

Linear general rate model of chromatography for core–shell particles: Analytical solutions and moment analysis

Numerical simulation of nonlinear chromatography with core–shell particles applying the general rate model

Retention prediction of low molecular weight anions in ion chromatography based on quantitative structure-retention relationships applied to the linear solvent strength model

The behavior of bovine whey proteins in Reversed‐Phase High Performance Liquid Chromatography (RP‐HPLC) systems has been investigated. The Linear Solvent Strength (LSS) model has been applied to the separation of these proteins studying how their retention time and band broadening change when different gradient parameters are modified. From our results it is deduced that the LSS model describes the behaviour of the whey proteins in RP‐HPLC. Also, it seems that ts (the retention time for non‐retained solutes) depends on the size of these proteins. The good fit observed between experimental data and the equations deduced from the LSS model allows the prediction of a gradient shape that permits a rapid analysis of the above mentioned proteins.

反相液相色谱(RPLC)是测定正辛醇/水分配系数(log P)的有效方法,但由于缺少同类型模型化合物,RPLC在测定强离解化合物的log P时遇到挑战。该文在硅胶基质C18色谱柱上,采用离子抑制反相液相色谱(IS-RPLC)和离子对反相液相色谱(IP-RPLC)分别对中性化合物、酚酸、羧酸、磺酸及部分两性化合物的保留行为进行了系统研究。在IS-RPLC模式下,利用中性化合物、弱离解的酚酸和苯羧酸作为模型化合物,建立了表观正辛醇/水分配系数(log D)与纯水相保留因子对数值(log kw)的定量结构-保留行为关系(QSRR)模型,测定了19种离解化合物的log D值,作为后续IP-RPLC的模型化合物及验证化合物。在IP-RPLC模式下,将中性、弱离解和强离解化合物作为混合模型组,以溶质静电荷ne、氢键酸碱性参数A和B为桥梁,建立了线性良好的log D-log kw-IP模型,采用3种不同类型的离解化合物进行了外部验证实验,预测值误差低于10%,证实了模型的可靠性。在此基础上,预测了8种强离解化合物的log D7.0值(pH 7.0条件下的log D值)。研究表明,利用结构相关参数沟通不同类型的模型化合物,是实现IP-RPLC测定强离解化合物log D值的一种行之有效的方法。与聚乙烯醇基质色谱柱相比,通用型的硅胶基质色谱柱上尽管存在着更多的次级作用,但可以为强离解化合物log D的测定提供更灵活的选择。

A novel strategy for retention prediction of nucleic acids with their sequence information in ion-pair reversed phase liquid chromatography

High-resolution separations of tryptic digest mixtures using core–shell particulate columns operated at 1200 bar

The linear solvent strength (LSS) model combined with quantitative structure‐retention relationships (QSRR) and artificial neural network (ANN) analysis has been shown to permit approximate prediction of the gradient high‐performance liquid chromatography (HPLC) retention time for any analyte on a once‐characterized column. The approach applies well to the reversed‐phase HPLC mode with a methanol‐water (buffer) eluent of linearly changing composition. Its suitability was tested for a representative series of structurally diverse analytes. In this approach the determination of retention times, t R, in two gradient runs for a predesigned model series of 15 analytes is first needed. Next, model QSRR equations describing t R in terms of analyte structure are derived to characterize the HPLC systems of interest. To quantitatively characterize the structure of the analytes the following three structural descriptors from molecular modeling are employed: total dipole moment; electron excess charge of the most negatively charged atom; and water‐accessible molecular surface area. Using these data a general QSRR equation is derived which is valid for a given column/eluent system. Next, having the structural descriptors for any analyte to be chromatographed in such a characterized HPLC system, one employs the previously derived general QSRR equation to calculate the analyte's retention time. The expected gradient retention time for any gradient conditions can be calculated by means of appropriate LSS equations. Independent of the standard QSRR calculation procedure based on multiple regression analysis (MRA), predictions of gradient retention times were performed by means of artificial neural networks (ANN). It has been found that the predictive power of ANN is similar to that of MRA. The combined LSS/QSRR approach has been demonstrated to provide approximate, yet otherwise unattainable, a priori predictions of gradient retention of analytes based solely on their chemical formulae. That way a rational chemometric basis for a systematic optimization of chromatographic separations has been elaborated as an alternative to the trial‐and‐error method normally applied at present.

Combination of linear solvent strength model and quantitative structure–retention relationships as a comprehensive procedure of approximate prediction of retention in gradient liquid chromatography

A carbon as mask is considered in this paper for the elimination of CNCl by adsorption in the activated carbon support and simultaneously second order chemical reaction with the impregnant metal. A model, taking into account nonlinear adsorption, chemical reaction, film and intraparticle mass transfer resistances, and axial dispersion is written and solved by the moving finite elements method. In the very short beds used in carbon gas masks, axial dispersion is probably important. Simulations are carried out for different values of the parameters in order to assess the influence of the intraparticle and film mass transfer resistances and of the rate of reaction on the system behavior in the presence of axial dispersion. It is shown that, although axial dispersion does not alter the general behavior of the system, its presence can reduce dramatically the usefulness of these respirators. On the other hand, two different correlations give more than 1 order of magnitude differences in the value of axial dispersion to be expected in the bed.

As of yet the commercial options of analytical scale silica monoliths are still limited to: silica, C8 and C18. Hence this study highlights the advantages of a novel phenyl first generation analytical scale silica monolith to overcome the limited selectivity, and provide a column capable of Π–Π interactions and high-throughput/low backpressure (<400 bar) separations.The retention characteristics of both non-endcapped and endcapped surfaces were chromatographically studied via: the height equivalent to a theoretical plate (HETP) curves to compare the efficiency as a function of linear velocity; the Tanaka test to compare six surface properties (hydrophobicity, steric selectivity, hydrogen bonding capacity, amount of alkyl chains, and ion exchange sites under acidic and basic conditions); the linear solvent strength (LSS) model to illustrate the methylene and phenyl selectivity. Additionally, the stability testing of both surfaces, throughout the chromatographic testing, demonstrates no degradation of the surface or column bed.HETP curves improved after endcapping, further more, the Tanaka test's hydrogen bonding value also reduced by 35%, indicating the minimization of the residual silanol groups. The LSS model showed excellent linearity for both surfaces (R2 > 0.991), and the phenyl endcapped monolith had comparable aromatic selectivity to a phenyl particle packed column.

In preparative chromatography, the adsorption of substances onto solid surfaces is influenced by temperature variations, leading to changes in the migration velocities of solutes within the chromatographic column. This research provides a detailed analysis of thermal fluctuations in porous media with dual adsorption sites, utilizing a non-isothermal General Rate Model (GRM) specifically tailored to the bi-Langmuir adsorption isotherm. Solute transport within heterogeneous porous media is governed by a system of nonlinear partial differential equations, characterized by convective flow dominance. This system is further coupled with a nonlinear algebraic equation describing the bi-Langmuir adsorption isotherm. To effectively address the challenges posed by this system, it is essential to develop robust and accurate numerical techniques capable of reliable simulations. This study extends and applies a second-order, semidiscrete, high-resolution finite volume method to simulate the governing equations. Numerical experiments, involving multicomponent mixture flows, are conducted to theoretically evaluate the influence of intraparticle diffusion, film mass transfer resistance, axial dispersion, enthalpy of adsorption, adsorption energy coefficients, and Henry constants on the velocity of simulated elution profiles.