ISSN:0148-3919    

DOI:10.1080/01483918908049186

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The use of multivariate computation techniques for the treatment of data from multi-wavelength photo diode-array detectors is an important step in computer-guided optimization strategies in HPLC. The treatment should provide the user with data on the identity and retention times of the individual solutes. These data are essential for those optimization strategies that can be classified as “interpretive”-methods, since peak recognition of both pure peaks and overlapping peak systems is a prerequisite for these methods. The peak recognition is based on comparison of spectra using their correlation coefficient.

ISSN:0148-3919    

DOI:10.1080/01483918908049187

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The optimisation of eluent composition in reversed-phase liquid chromatography is a complex process, which often requires the expenditure of a significant amount of effort on the part of the chromatographer. To assist in this task an expert system has been developed which used a gradient elution experiment to determine the appropriate initial solvent strength, followed by response-surface modelling using an iterative regression method to determine the mobile phase composition for optimum resolution. Spectral information from a multichannel diode array detector is used to provide retention information for this model. Peak homogeneity is assessed by a number of independent modules, the output from which is interpreted by the expert system and used to validate the response surface model constructed by the optimisation procedure.

ISSN:0148-3919    

DOI:10.1080/01483918908049188

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A method suitable for automated optimization of HPLC separations is developed. A sequential strategy based on a non-linear interpolation between measured retention data permits a stepwise approximation to a global optimum. This scheme provides a smooth representation of the elution behaviour from an unspecified number of regularly or irregularly spaced data points. The accuracy of the so defined curves can be gradually improved by successive addition of new experimental data as they become available. It is possible, therefore, to employ variables yielding multimodal response hypersurfaces in the optimization work. Further emphasis is given to an individual weighting of all detectable compounds with respect to their analhtical relevance. Examples including an isocratic separation of fat soluble vitamins as well as gradient separations of dansylated amino acids and steroid hormones demonstrate some applications of the proposed procedure.

ISSN:0148-3919    

DOI:10.1080/01483918908049189

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Utilizing experimentally estimated capacity factors and calculated activity coefficients of the solutes in the mobile phase, as well as octadecylsilica stationary phases of varying coverage, the selectivity of separation in a reversed-phase liquid chromatographic system is studied. The retention times were measured for n-alkanes (C5-C7), n-alcohols (C5-C7) and benzene derivatives in methanol - water mobile phases. A strictly linear relationship between the experimentally determined selectivity factor (α) and the calculated selectivity factor in the mobile phase (αm) is observed. The relative retention in the stationary phase (αs) is independent of the mobile phase strength and the silica surface coverage, i.e., αsis merely a function of the molecular structure of related solutes. Therefore, a change in surface coverage does not lead to a change in α.

ISSN:0148-3919    

DOI:10.1080/01483918908049190

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Comination of the Triangular Mixture Design Statistical Technique (TMDST) and Multi-Criteria Decision Making (MCDM) allows the evaluation of the performance of multi-solvent mobile phase systems for RP-HPLC with respect to two criteria simultaneously. If the minimal resolution of two adjacent peaks, Rsmin, and the retention time of the last peak of a chromatogram, kmax, are used as criteria for the optimization, then one can compare multi-solvent mobile phase systems by their MCDM plots. The solvent system that can give a charomatogram with an acceptable resolution in shortest possible analysis time for a given searation problem can be selected. Multi-solvent mobile phase systems that need a longer analysis time to obtain the same acceptable resolution for this separation, can be ruled out. This is demonstrated by the comparison of the performance of ternary and quaternary iso-eluotropic mobile phase systems in the separation of a mixture of benzene derivatives on a RP octyl column.

ISSN:0148-3919    

DOI:10.1080/01483918908049191

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The tripartite “PRISMA” optimization model is summarized, which includes all possible solvent combinations between 1–5 solvents. The solvent composition is characterized by the solvent strength (ST) and the selectivity points (PS).

ISSN:0148-3919    

DOI:10.1080/01483918908049192

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The methods for calculation of retention volumes and bandwidths in liquid chromatography with binary gradients, ternary “solvent-strength” gradients, ternary “selectivity” gradients and “combined selectivity - solvent strength” ternary gradients are surveyed. These calculation methods form the basis for the predictive optimization of profiles of binary and ternary gradients. Various strategies for predictive optimization are discussed and illustrated by practical optimization example of the gradient-elution separation of a mixture of mono- and di- aminoanthraquinones.

ISSN:0148-3919    

DOI:10.1080/01483918908049193

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Optimization of peptide separations in HPLC involves more than simply optimizaing the mobile phase in terms of flow-rate and gradient-rate. The first step in optimizing the separation of a complex peptide mixutre obtained from chemical and/or proteolytic digestion is the selection of the mode or combination of modes required for the separation. For example, should a single or multimodal approach be used, and which mode(s) (SEC, IEC, RPC) should be selected? The second step is to make an asssment of the performance characteristics of the HPLC columns (selectivity, efficiency and deviations from ideal behaviour) to be used. The most logical approach to assessing column performance is to employ HPLC peptide standards designed specifically for this purpose under a set of standard chromatographic run conditions. The third step involves utilizing the information obtained with the standars and any knowledge concerning the expected size, charge and polarity of the peptide fragments to select the initial mobile phase conditions for each mode of chromatography. In SEC, we are concerned with the pH, ionic strength and whether or not denaturing or benign conditions should be used in the mobile phase. In IEC, we must consider pH which can drastically affect the net charge on the peptide fragments and, thus, the overall separation. Denaturing conditions may be required to eliminate conformational effects of large peptides. In RPC, decisions such as the ion-pairing reagent to be used and the pH of the mobile phase are important issues. The fourth step involves the optimization of the gradient-rate and flow-rate to provide maximum resolution in the minimum time period. A detailed explanation of these steps are included.

ISSN:0148-3919    

DOI:10.1080/01483918908049194

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Some resolution based optimization criteria are adapted by using weighting factors to express the quality of separation of a limited subset of components in samples containing more solutes. Criteria are evaluated in detail with respect to the successive objectives of the analyst: satisfactory resolution for the peaks of interest, the peaks make the best use of the available separation space, and the analysis time is at minimum (while the resolution is maintained at the required level). A sequential use of the appropriate optimization criteria is suggested to achieve the separation of the peaks of interest with a satisfactory resolution in the shortest possible analysis time.

ISSN:0148-3919    

DOI:10.1080/01483918908049195

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor