Biomedical subjects

Yichu Shan

Publications and source records attributed to Yichu Shan.

5 recordsLinked to original sources

PubMed2006

Breakthrough curves and elution profiles of single solutes in case of adsorption isotherms with two inflection points.

The shape of breakthrough curves and elution profiles depends strongly on the course of the specific equilibrium functions characterizing the chromatographic system. For a highly efficient system the equilibrium theory provides a methodology how to predict the band profiles. The concept is frequently applied to analyze single component systems characterized by isotherms possessing simple shapes (Langmuir or anti-Langmuir behaviour). However, adsorption isotherms often possess more complicated shapes and have inflection points in their courses. This leads to the development of composite concentration waves and results in complex shapes of breakthrough curves and elution profiles. In this paper, the equilibrium theory is used to predict breakthrough curves for a chromatographic system characterized by an adsorption isotherm with two inflection points. The results obtained are validated by comparing with numerical solutions of the equilibrium dispersive model.

Adsorption↗

PubMed2006

[Application of adjustable moving overlapping separation range map in multisegment stepwise gradient elution condition optimization of high performance liquid chromatography].

Computer-assisted optimization of high performance liquid chromatographic separation conditions can be used to obtain optimized experimental conditions in relatively short time and low cost, and has been widely applied to the separation of complex samples. Based on "moving overlapping separation range map" method, a novel method of optimizing multi-segment stepwise gradient elution conditions, "adjustable moving overlapping separation range map" method, was developed. By predicting the retention time, peak width and resolution of each solute under different mobile phase conditions, the overlapping separation range map of the solutes in the sample is plotted. When the mobile phase composition on the current step is optimized, the overlapping separation range map for solutes eluted in next one or two steps is replotted simultaneously by considering the influence of elution conditions for current step on the retention of uneluted solutes. It is helpful to consider the separation of each solute in the sample simultaneously and find optimized separation conditions close to the global optimum by investigating the effect of mobile phase conditions for current step on the separation of solutes eluted in the current and next one or two steps. By slightly adjusting the optimized separation conditions using grid search method, the separation performance can be further improved. The application of "adjustable moving overlapping separation range map" method was illustrated by using experimental data from literature. The advantage of this method in high performance liquid chromatography was verified in binary mobile phase system.

English Abstract↗

PubMed2005

Optimization of gradient elution conditions in multicomponent preparative liquid chromatography.

Gradient elution is widely applied in analytical chromatography to reduce the separation time and/or to improve the selectivity. Increasingly the potential of modulating the solvent strength during gradient operation is exploited in preparative liquid chromatography. The purpose of this paper is to investigate theoretically the effect of optimizing free parameters available in gradient chromatography (extents and shapes of gradients) on the productivity of isolating a target component in a multicomponent mixture. An equilibrium stage model was used to quantify and compare different modes of operation (isocratic and various variants of gradient elution). By combining experimental design and artificial neural network concepts, optimal conditions were identified for the production of the second eluting component in a ternary mixture. The strong impact of the shape of gradients on process performance is elucidated.

Chromatography, Liquid↗

PubMed2004

Analysis of the isolation of a target component using multicomponent isocratic preparative elution chromatography.

The separation of a certain target component from a multicomponent mixture using isocratic preparative elution chromatography was studied theoretically. In particular, the important and most complicated case was considered that the target component does not elute in the first or last position. To specify the productivity of collecting this component different options are suggested to identify suitable times for fractionation. Using a conventional Craig model, capable to quantify chromatographic processes, the impact of several essential parameters (e.g. threshold concentration, desired purity, injection volume, separation factor between neighboring components, composition of the mixture) is evaluated for a ternary system based on parametric calculations. The paper provides simple tools to evaluate and optimize the productivity and other objective functions relevant in multicomponent preparative chromatography.

Chromatography, Liquid↗

PubMed2003

Determination of peptides and amino acids from wool and beer with sensitive fluorescent reagent 2-(9-carbazole)-ethyl chloroformate by reverse phase high-performance liquid chromotography and liquid chromotography mass spectrometry.

A new method for the sensitive determination of amino acids and peptides using the tagging reagent 2-(9-carbazole)-ethyl chloroformate (CEOC) with fluorescence (FL) detection has been developed. Identification of derivatives was carried out by liquid chromotography mass spectrometry. The chromophore in the 2-(9-fluorenyl)-ethyl chloroformate (FMOC) reagent was replaced by carbazole, which resulted in a sensitive fluorescence lerivatizing agent CEOC. CEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. Studies on derivatization demonstrate excellent derivative yields over the pH range 8.8-10.0. Maximal yields close to 100% are observed with three- to fourfold molar reagent excess. Derivatives exhibit strong fluorescence and allow direct injection of the reaction mixture with no significant disturbance from the major fluorescent reagent degradation by-products, such as 2-(9-carbazole)-ethanol and bis-(2-(9-carbazole)-ethyl) carbonate. In addition, the detection responses for CEOC derivatives are compared to those obtained with FMOC. The ratios AC(CEOC)/AC(FMOC) = 1.00-1.82 for fluorescence (FL) response and AC'(CEOC)/AC'(FMOC) = 1.00-1.21 for ultraviolet (UV) response are observed (here, AC and AC' are, respectively, FL and UV response). Separation of the derivatized peptides and amino acids has been optimized on a Hypersil BDS C18 column. Excellent linear responses are observed. This method was used successfully to analyze protein hydrolysates from wool and from direct-derivatized beer.

Amino Acids↗