A New Equation for Solute Retention in Liquid Chromatography

In consideration of the adsorption of solvent,diluent and solute molecules on the surface of a stationary phase,a new equation for solute retention in liquid chromatography is presented. This equation includes three parameters: the displacement equilibrium constant( K _ sd ) between the solvent and diluent molecules on the surface of the stationary phase,the total number( N ) of the solvent and diluent molecules released from the stationary phase after one solute molecule being adsorbed,and the parameter( I ) related to the thermodynamic equilibrium constant for the solute adsorption on the stationary phase. Over the whole concentration range of the solvent in the mobile phase,the experimental retention data can be well described by this equation,parameters K _ sd ,N and I can be obtained by the regression analysis of the experimental retention data,and consequently the number of the solvent and the diluent molecules displaced by one solute molecule from the stationary phase can also be derived at different solvent concentrations in the mobile phase.

A UNIFIED RETENTION MODEL OF SOLUTE IN LIQUID CHROMATOGRAPHY

Based on six thermodynamic equilibria,a unified retention model of solute in liquid chromatography(LC)is first proposed.The unified model was tested and proved to be valid for a LC sys- tem with mobile phase consisting of a complete range of multiple,ternary or binary components and each kind of LC except size exclusion chromatography.In addition,so long as making some assumptions and mathematical conversions,the expressions of various popular models in LC can be derived by using the unified model.

INTERSECTION POINT RULE OF THE RETENTION VALUE AND NORMAL BOILING POINT OF THE HOMOLOGUES IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

In this paper, a linear relationship between the logarithm of capacity factor k and normal boiling point to of the homologues has been derived, based on the basic retention equation of liquid chromatography according to statistical thermodyoamics proposed by professor Ln Peizhang and others, This equation has been verified by a large number of experimental data, all the strsight lines of lnk- of bumologues for different mobile phass coaiposltion cross each other at the same point, So the intereection point equation van proposed, wbich was used to prodict the retention valu, the result was satisfactory.

INTERSECTION POINT RULE OF THE RETENTION VALUE AND MOBILE PHASE COMPOSITION OF THE HOMOLOGUES IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Based on the intersection point rule of the retention value and normal boiling point of homologues in reversed-phase high-performance liquid chromatography(RPLC), the intersection point rule of the retention value of homologues and mobile phase composition has been derived, and was testified by a lot of experimental data from the literature. With this newly proposed equation, we can use the retention value of the compound in one mobile phase composition to predict its retention value in any other mobile phase composition. For fourteen groups of homologues in five mobile phase compositions on five Kinds of columns, the overall average absolute error of 721 data sets is 2.8%.

Study on Retention in Liquid Chromatography

After joining the faculty at Toyohashi University of Technology (TUT) in 1978, the author has found two areas in separation sciences where microcolumn liquid chromatography (micro LC) can be beneficial One is the hyphenated techniques between many spectroscopic methods such as mass (MS), infrared (FT IR) and atomic emission (ICP), and micro LC The other one is rather difficult, but basic and theoretical approach which deals with retention mechanism in LC The latter project has especially been giving him a lot of scientific funs and honors in the last 20 years On the occasion of being awarded by The Society for Chromatographic Sciences the author would like to summarize his contributions to this topic which asks us "What Is Chromatographic Retention?

A Modification on the Retention Equation of Liquid-Solid Chromatography lnk' = A + BlnC_(B_1)+CC_(B_1)

1 Theory Let us consider a liquid-solid adsorbent system. There are two solvents B0 and B1 in the liquid phase. B0 is a weaker solvent and B1 is a stronger one. By means of statistical thermodynamics and the ideal localized trap model, the adsorption equation of solvent B0 on the surface of adsorbent phase can be expressed as follows.

Investigation of retention and chiral recognition mechanism using quantitative structure-enantioselectivity retention relationship in high performance liquid chromatography

The enantiomers of a series of fourteen O-ethyl O-(substituted) phenyl N-isopropyl-phosphoroamidothioates have been separated by high performance liquid chromatography (HPLC) on the Pirkle-type chiral stationary phase. Seven molecular descriptors were calculated and four significant descriptors were chosen to correlate against the experimental lnk' values in order to form the quantitative structure-enantioselectivity retention relationships (QSERRs). Through the QSERRs, the retention and enantioselectivity mechanism were examined.

A STOICHIOMETRIC DISPLACEMENT MODEL FOR RETENTION OF SOLUTE IN LIQUID CHROMATOGRAPHY WITH MULTI-COMPONENT SYSTEM

Considering all the kinds of interactions between solute and solvent, solute and stationary phase, solvent and stationary phase molecules as well as the competitional adsorption among various kinds of solvent molecules on the stationary phase, we present a stoichiometric displacement model of solute retention with four sets of parameters in liquid chromatography. This model was tested with data from both literature and experiments done by ourselves. These results show that this model may fit the experimental data for a liquid chromatography system with various kinds of mobile phases consisting of a complete range of multi-components and with different types of stationary phases.

RETENTION PREDICTION OF CONJUGATED BILE ACIDS AND BARBITUR ATES BY USING INTER ACTION INDEX IN REVERSED PHASE LIQUID CHROMATOGRAPHY

Ⅰ. INTRODUCTION Recently, reversed phase liquid chromatography (RPLC) has become a very efficient standard technique for the modern analyses and is widely used for the analysis of many types of compounds. Retention prediction plays an important part in the thermodynamic studies in RPLC. Many attempts have been made to establish Kováts-like retention

THE UNIFIED FORM OF RETENTION EQUATION OF CHROMATOGRAPHY

The unified form of retention equation of chromatography is suggested by adoptingstatistical thermodynamics and lattice theory. According to different conditions, the retentionformulas of GC, LC and SFC can be obtained from this unified equation. Those formulashave been confirmed by experimental data.

THE EFFECTS OF MOLECULAR STRUCTURE ON PARAMETERS a, b AND c IN RETENTION EQUATION AND PREDICTION OF CAPACITY FACTORS IN RP-HPLC

In this paper, the effects of molecular structure on the parameters a, b and c in retention equation are investigated theoretically and experimentally. Parameter b in RP-HPLC approaches a small constant, because there is very weak displacement adsorption. Parameter c in RP-HPLC is mainly determined by the difference between solute-strong solvent and solute-weak solvent interaction and can be quantitatively correlated with the structural parameters of solute such as van der Waals volume (Vw), dipole moment (μA) and hydrogen bond energy (XAH). Parameter a has similar rules to parameter c. The prediction of k’ value for non-polar, homologous compounds is studied. The linear relationship between k’ and coverage of amount of the bonded chain in RP-HPLC is confirmed.

Retention and chiral recognition mechanism of organo-phosphorus compounds in high-performance liquid chromatography

In normal phase condition, a series of chiral phosphorus organic compounds have been separated by high-performance liquid chromatography. In order to study the retention and chiral recognition mechanism, the method of quantitative structure-enantioselectivity retention relationships (QSERRs) has been investigated from the quantitative equations established between the chromatographic retention of enantiomers and their molecular descriptors of physicochemical properties. The results show that on the Pirkle-type chiral stationary phase (CSP) of Sumichiral OA4700, it is the parameter of LUMO that gives the most contribution to the chromatographic retention of O-ethyl O-(substituted) phenyl N-isopropyl phosphoroamidothioates resulting from the interaction of hydrogen bond and (or) π-π interaction. Meanwhile, the chiral recognition is formed from the contribution of logP and LUMO.

A Study on Relationship Between Gas Chromatographic Retention Value and Atomic Hydrophobic Parameters

A study on relationship between molecular structure and chromatographic retention values for realizing the identification and prediction of chromatographic retention values has been the major task of chromatographic thermodynamics. In 1964, Prof. Lu Peizhang established the relationship between molecular structural parameters and chromatographic retention values in gas-liquid chromatography by using statistical thermodynamical methods. Based on his work, some Chinese researchers have performed the prediction of chromatographic retention values.

Determination of Methanol Increment in Mobile Phase Consisting of Methanol and Water by On-line UV Spectrometry in Reversed Phase Liquid Chromatography

An on-line UV spectrometric method for the quantitative determination ofmethanol increment of methanol-water in the mobile phase (i.e., of greater concentration than thatof the mobile phase) by frontal analysis (FA) of insulin in reversed phase liquid chromatography(RPLC) was presented. When the methanol increment concentration ranged from 0.05% to 0.50%,V(CH_3OH)/V(H_2O), a set of elution curves could be obtained at 198 nm by a diode-array detector inthe presence of 47% methanol, V(CH_3OH)/V(H_2O) containing 0.03% hydrochloric acid,V(CH_3OH-H_2O)/V(HCl) in the mobile phase. The plateau height of the elution curves of the methanolincrement was found to be proportional to the methanol increment in the mobile phase. The methanolincrement could be determined on a quantitative basis. When the method was used to investigate theelution curve of insulin by FA in RPLC, a small plateau, being the methanol increment, was detectedbefore the usual insulin plateau of each elution curve. In this case the methanol increment wasfound to vary with insulin concentration in the mobile phase. When that concentration was between0.025 mg/mL and 0.30 mg/mL, the methanol increment could be determined in the range from 0.03% to0.19% with a deviation of ±10%. A nuclear magnetic resonance spectrometer (NMR) was also employedto confirm the obtained result. A methodology with a very rigorous experimental procedure forobtaining results of such accuracy is also included. The presented result may be used to prove thata displacement process definitely occurs as insulin is adsorbed by the RPLC stationary phase inFA.

A Direct Evidence of Stoichiometric Displacement between Insulin and Methanol in Reversed Phase Liquid Chromatography

With four kinds of mobile phases, methanol water, ethanol water, 2 propanol and acetonitrile water (all containing 0 1% triflu roacetic acid), the displacement between solute and solvent in RPLC was proved to be universal in frontal analysis (FA). Based on the measured Z value in usual RPLC to be a constant and the quantitative determination of methanol increment in mobile phase in FA, the stoichiometric displacement (SD) between insulin and methanol was directly proved by the experiment. The SD was also proved to occur only on about the one fourth of the maximum amount of adsorbed methanol in the bonded phase layer (BPL) without any dynamic problem of mass transfer, while in FA, the SD firstly occurs on the surface of the BPL and then gradually sinks into the deeper sites companied with a dynamic problem. Although the displaced solvent by the same solute is less in the former case, the SD is independent of how deep of the solute enters the BPL. In addition, the adsorbed amount of solute on an adsorbent not only depends on the numbers of the adsorbed layer on the adsorbent surface, but also on the extent of the complete removal of the displaceable solvent in the BPL. The physical fundamental of the SD and the methodology for investigation were also discussed.

Predicting a, c indices in reversed-phase high-performance liquid chromatography (RP-HPLC) from Kovats index in gas chromatography (GC)

KOVATS index is the most precise index system reflecting the interaction between the molecules of solutes and stationary phase in gas chromatography at present. Large quantity of Kovats in dex data have been published. It is a good way to use Kováts index in gas chromatography to predict the retention value in liquid chromatography, which is significant in theory and apphcation.

基于N-酰基甘氨酸保留指数系统的代谢物色谱峰对齐方法

色谱峰对齐(peak alignment)是非靶向代谢组学分析中常用的数据处理步骤。色谱峰对齐的目的是整合多批次液相色谱-质谱(LC-MS)分析得到的代谢物数据,从而确保数据的可比性与可靠性。然而,微小的色谱分离条件变化会导致连续分析之间的色谱保留时间(retention time,RT)漂移,进而影响色谱峰对齐的准确性。本文提出了一种基于保留指数系统的色谱峰漂移校正策略(retention index-based chromatographic peak-shift correction,RI-based CPSC),应用于代谢物的保留时间漂移校正和色谱峰对齐。为此,我们合成了一系列N-酰基甘氨酸(C2~C23)同系物作为校正物,建立了一套液相色谱保留指数系统。该保留指数系统能够有效修正由流速、洗脱梯度、仪器系统和色谱柱变化所引起的色谱保留时间漂移。利用保留指数系统,我们构建了基于Python的程序(https://github.com/WHU-Fenglab/RI-based-CPSC)来调整原始数据的保留时间,以修正系统的保留时间偏移,随后,应用Joint Aligner算法进行色谱峰对齐。以人粪便样作为测试样,评估了RI-based CPSC策略的色谱峰对齐准确性。以一份时间跨度为157天的长期数据为例,RI-based CPSC策略的应用可以将色谱峰对齐率从15.5%显著提高至80.9%,说明RI-based CPSC策略能够显著提高多批次LC-MS分析的色谱峰对齐准确性。

普瑞巴林胃滞留缓释片含量测定及高黏性辅料对测定结果的影响

建立普瑞巴林胃滞留缓释片含量测定的高效液相色谱法(HPLC),采用一种特殊的样品前处理方式成功解决了普瑞巴林回收率低的难题。通过比较盐析法和辅料分散法,建立了克服供试品溶液黏稠的前处理方法。两种前处理方法均可用于本品的含量测定,但盐析法简便易行。采用的HPLC条件为Inertsil ODS-3(4.6 mm×0.25 m,5μm)色谱柱,流动相3.4 g/L磷酸二氢钾(氨水调pH至6.3)-甲醇(85︰15),柱温30℃,流速1.0 mL/min,进样量50μL,检测波长210 nm。盐析法方法学验证结果显示,制剂中普瑞巴林平均回收率为99.74%,RSD为0.43%;精密度试验的RSD为0.77%;供试品溶液12 h内稳定,色谱系统耐用性良好,辅料不干扰含量检测。本研究建立的测定方法稳定、可靠,适用于普瑞巴林胃滞留缓释片的含量测定。

液液萃取/气相色谱-质谱法结合自动解卷积-Kováts保留指数法定性分析电子烟液中的挥发性成分

基于液液萃取/气相色谱-质谱法结合自动解卷积-Kováts保留指数法,建立了电子烟液中挥发性成分的检测方法。对提取溶剂种类进行了优化,并依据烟液中香气成分的香气特征,分析果味和烟草味烟液的香韵构成和差异,确定不同果味烟液的特征香气成分。结果表明:①以乙醚为提取溶剂能减弱丙三醇对其他组分识别的干扰。②自动解卷积法能准确识别共流出组分和低含量组分;Kováts保留指数法提升了化合物识别的准确度。③在10种烟草味烟液中检出15种成分,以豆香、焦香香韵化合物为主;在21种果味烟液中检出80种成分,以果香、花香香韵化合物为主,确定了16类果味烟液的特征香气成分。通过随机验证实验,该方法可有效分辨不同果味类型的果味烟液和烟草味烟液。该方法样品用量少、前处理过程简单、样品分析用时短,能满足烟液中香气成分的检测需要,可为果味电子烟液的检验识别和监管提供参考。

参葛颗粒HPLC特征图谱及含量测定研究

目的采用高效液相色谱(HPLC)法创建参葛颗粒特征图谱及含量测定方法。方法色谱柱Kromasil 100-5-C_(18)(4.6 mm×250.0 mm,5μm);流动相乙腈-水;柱温30℃;流速为1.0 ml/min;进样量10μl;检测波长为220 nm,采用对照品比对、超高压液相色谱串联四级杆飞行时间质谱联用技术对特征峰进行化学成分指认及药味归属,并检测10批参葛颗粒的特征图谱和含量。结果建立了参葛颗粒的HPLC图谱,标记8个特征峰并进行了指认,10批颗粒批间一致性良好,10批颗粒葛根素的含量范围为10.6611~11.9936 mg/g。结论建立的参葛颗粒特征图谱及含量测定方法操作简单,具有良好的稳定性、重现性,对参葛颗粒中所含的化学成分进行了较全面的展示,也可为其他相关中药复方制剂的质量控制研究提供参考。