Retention relationships

The retention time of a chromatographic peak is defined by the first moment of the Gaussian distribution M, equation (2.14)) and is measured from the point of injection to the peak maximum. 

However, most analytical applications require a definition of retention that is independent of system variables such as column dimensions and flow rate. 

The retention volume of a peak is equal to the volume of liquid that passes through the column from the point of injection to the point at which the peak maximum exits the column. It is related to the flow rate and the retention time by the equation 

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Vol. 93. Quantitative Structure-Chromatographic Retention Relationships. By Roman Kaliszan... 

D., Balahan, A. T. Comparison of weighting schemes for molecular graph descriptors application in quantitative structure-retention relationship models for alkylphenols in gas-liquid chromatography. J. Chem. Inf. Comput. Sci. 2000, 40, ITl-lM,. 

Kaliszan, R. Quantitative-structure-retention relationships applied to reversed-phase high-performance liquid chromatography. J. Chromatogr. 1993,... 

R. Kaliszan, "Quantitative Structure Chromatographic Retention Relationships", Wiley, New York, NY, 1987. 

Kaliszan, "Quanti-tative Structure-Chronatographie Retention Relationships", Miley, Mew Yor)c, NY, 1987. 

Stadalius, M. A., Gold, H. S., and Snyder, L. R., Optimization model for the gradient elution separation of peptide mixtures by reversed-phase high-performance liquid chromatography. Verification of retention relationships, /. Chromatogr., 296, 31, 1984. 

Aguilar, M. I., Hodder, A. N., and Hearn, M. T. W., High-performance liquid chromatography of amino acids, peptides, and proteins. LXV. Studies on the optimisation of the reversed-phase gradient elution of polypeptides. Evaluation of retention relationships with (3-endorphin-related polypeptides, /. Chromatogr., 327, 115, 1985. 

Law, B. and Weir, S., Quantitative structure-retention relationships for secondary interactions in cation-exchange liquid chromatography, ]. Chromatogr. A, 657, 17, 1993. 

T. Baczek and R. Kaliszan, Combination of linear solvent strength model and quantitative structure-retention relationships as a comprehensive procedure of approximate prediction of retention in gradient liquid chromatography. J. Chromatogr.A 962 (2002) 41-55. 

T. Cserhati, A. Kosa and S. Balogh, Comparison of partial least-square method and canonical correlation analysis in a quantitative structure-retention relationship study. J. Biochem. Biophys. Meth., 36 (1998) 131-141. 

Woloszyn, T. F., Jurs, P. C. Anal. Chem. 64, 1992, 3059-3063. Quantitative structure-retention relationship studies of sulfur vesicants. 

At present, the selection of an organic modifier is estimated from the aliphatic or aromatic nature of analytes. However, the properties of analytes often cannot be easily obtained. Examples of quantitative structure-retention relationships based on the log-P and van der Waals volume of analytes are demonstrated in Chapter 6. 

Quantitative Structure-Retention Relationships in Reversed-phase Liquid Chromatography... 

A quantitative analysis of the structure-retention relationship can be derived by using the relative solubility of solutes in water. One parameter is the partition coefficient, log P, of the analyte measured as the octanol-water partition distribution. In early work, reversed-phase liquid chromatography was used to measure log P values for drug design. Log P values were later used to predict the retention times in reversed-phase liquid chromatography.The calculation of the molecular properties can be performed with the aid of computational chemical calculations. In this chapter, examples of these quantitative structure-retention relationships are described. 

Fornal et al. [75] determined selectivity differences for bases in RP-HPLC under high pH conditions. They used quantitative structure retention relationships (QSRR) to model retention behavior. They reported that the stability of the columns they used (Waters XTerra MS, Zorbax Extend, Thermo BetaBasic) was limited with... 

Kaliszan, R. (2007) QSRR quantitative structure-(chromatographic) retention relationships. Chemical Reviews, 107, 3212-3246. 

TJ Schmidt, I Merfort, G Willuhn. Gas chromatography-mass spectrometry of flavonoid aglycones. II. Structure-retention relationships and a possibility of differentiation between isomeric 6- and 8-methoxyflavones. J Chromatogr 669 236-240, 1994. 

In addition to the pore size-particle size retention relationship problems mentioned above, other factors can influence a filter medium s retention characteristics. Absorptive retention can be influenced by the organism size, organism population, pore size of the medium, pH of the filtrate, ionic strength, surface tension, and organic content. Operational parameters can also influence retention, such as flow rate, salt concentration, viscosity, temperature, filtration duration, filtration pressure, membrane thickness, organism type, and filter medium area [52,53]. 

The concentration of test chemicals applied directly or dissolved in culture media may be modified to test concentration-dependent alterations in epithelial barrier properties. Also different molecular weights of fluorescein may be substituted to alter permeability and retention relationships as a function of the test chemical used. 

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