Characterization of various reversed-phase columns using the linear free energy relationship

Sándi, Ákos; Szepesy, L.

doi:10.1016/s0021-9673(98)00535-4

Cited by 80 publications

(31 citation statements)

References 52 publications

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“…Good relationship between log k w and log P oct was established for the compounds examined. Linear solvation free-energy relationships (LSERs) based on the solvatochromic parameters [25][26][27][28][29] was used to unravel the retention mechanism of the solutes on this novel stationary phase and to compare the mechanism with the partitioning mechanism in 1-octanol/water. In addition, the log k w /log P oct relationship was validated using a test set of 13 neutral, acidic and basic drugs.…”

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confidence: 99%

Lipophilicity Measurement of Drugs by Reversed Phase HPLC over Wide pH Range Using an Alkaline-Resistant Silica-Based Stationary Phase, XBridgeTM Shield RP18

et al. 2008

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The lipophilicity of solutes, conventionally expressed by their partition coefficient in the 1-octanol/water system (log P oct ), is of high significance from both physicochemical and pharmacological viewpoints.1,2) A number of intermolecular forces between a solute and its environment (i.e., solvents) determine the partitioning process and its equilibration. In pharmacology, the forces are particularly important because they control the migration of solutes (drugs) to biomembranes. Not a few studies have been reported on the relationship between log P oct and adsorption/permeation of drugs in cell cultures and/or tissue preparations. 3-7)The reference procedure to measure log P oct is shake-flask method. The method is, however, time-consuming and narrow in applicable range (ca. Ϫ3Ͻlog PϽ4). The reversedphase HPLC (RP-HPLC) came to be a promising alternative to the shake-flask method, because it has advantages such as high throughput rate (which is of key importance to pharmaceutical industry with a vast number of potential drug candidates), insensitivity to impurities and/or degradation products, broad applicable range, low sample consumption, good accuracy and automation possibilities. In RP-HPLC, lipophilicity indices are derived from the capacity factor log k, which is calculated from Eq. 1,where t r and t 0 are the retention times of the solute and of an unretained compound, respectively. Some workers have used isocratic log k values, measured in an appropriate mobile phase, as a lipophilicity parameter. 8-10) However, the majority of investigators use the capacity factors extrapolated to the 100% water (log k w ) condition in order to eliminate the effects of organic solvent.11-15) Indeed, the log k W has been proved to be useful for the investigation of a series of solutes covering broad lipophilicity range. Generally, the extrapolation is based on a quadratic relationship between the isocratic capacity factor log k and the volume fraction of organic solvent in the mobile phase, j.16) When methanol is used as an organic modifier, a linear relationship (Eq. 2) is often obtained for neutral solutes, 17,18) log kϭϪSjϩlog k wwhere S and log k w are the slope and the intercept of the regression curve, respectively. Until recently, most lipophilicity studies based on RP-HPLC had employed octadecyl silica (ODS) stationary phases 19,20) and silanol deactivated stationary phases. 15,21,22) As for ODS stationary phases, the correlations between log P oct and log k w (or log k) are generally good for structurally related solutes. 19,20) The decrease in correlation between them with increasing structural diversity of solutes is attributed to the specific interactions between the compounds and the residual silanol groups in such stationary phases. 23)Some studies have been done on silanol deactivated stationary phases, Supelcosil LC-ABZ and Discovery RP Amide C18, where their alkyl chains contain amide groups that electrostatically shield silanols from highly polar analytes. High correlations were found between log P ...

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Lipophilicity Measurement of Drugs by Reversed Phase HPLC over Wide pH Range Using an Alkaline-Resistant Silica-Based Stationary Phase, XBridgeTM Shield RP18

et al. 2008

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“…The LiCh-C18e and LiPur-C18 columns (1, 2) are well covered, endcapped quasi-neutral C18 columns [73]. The Symmetry phases (3,11) were prepared of high purity silica with ultrapure reagents.…”

Section: Resultsmentioning

confidence: 99%

“…We have calculated the coefficient ratios for a column set [73] but very small column-to-column deviations were found for unambiguous interpretation. We have found, however, that the ratio of the a and b coefficient is a good indication of the relative basicity/acidity of the column [80].…”

Section: Retention Characteristicsmentioning

confidence: 99%

“…All of the polarity indicators are much lower than for the other (even the C18) columns indicating that the polymer coating effectively shields the silica surface and no or very small polar interactions are possible with the stationary phase. For this reason retention factors of polar solutes are very small, even smaller than on the less hydrophobic cyano columns, while the retention factors for hydrophobic solutes are similar to the NP columns [73,82].…”

Section: Polar Selectivitymentioning

confidence: 99%

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Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs)

Szepesy¹

2003

J of Separation Science

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Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs)An overview is given of our studies on the use of linear solvation energy relationships (LSERs) for evaluation and comparison of RP-HPLC columns. From among the columns investigated, 19 columns of different types, viz. 12 narrow-pore, 7 wide-pore silicas containing various ligands (C18, C8, C4, CN) and obtained from 7 manufacturers, were compared and evaluated. Retention factors of 32 solutes of widely differing chemical properties were measured and evaluated to determine the effect of stationary phase properties on the retention of various types of solutes. When the same mobile phase is used with the different columns, the regression coefficients determined by multivariate regression characterize the various stationary phases. The columns investigated were evaluated on the basis of the relative importance of the various types of interactions reflecting the various surface properties of the stationary phases. Since the selectivity of separation is more important than is absolute selectivity, we have investigated and compared the various selectivity terms, hydrophobic, polar, and specific selectivity, displayed by the various columns, for the separation of different types of compounds. As the selectivity of separation depends also on the type and composition of the mobile phase, the effect of mobile phase on the various selectivity terms was evaluated.

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“…(22) using multiple correlations between the retention and the so-called solvatochromic parameters, which take into account solubility and solvation of the solute and the stationary phase [73,[74][75][76][77][78][79][80][81][82][83][84][85][86]:…”

Section: Qsrr Selectivity Characterizationmentioning

confidence: 99%

Column selectivity for two‐dimensional liquid chromatography

Jandera¹

2006

J of Separation Science

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Selectivity of phase system is of primary concern when designing a 2-D separation, as it affects the 2-D system orthogonality and consequently the peak capacity controlling the number of peaks that can be separated in the available 2-D retention space limited by the time of analysis. Possibilities for characterization of LC phase system selectivity with respect to different polar and nonpolar structural units are compared, with special attention to multidimensional samples with various types of repeat groups, such as homopolymers, (co)polymers, fatty acid esters with various acyl lengths and number and position of double bonds, etc. Possibilities of the 2-D LC separations of these and other sample types, including pharmaceuticals, natural phenolic compounds, biopolymers, etc., using various combinations of separation modes are reviewed. Rules for design of comprehensive 2-D LC x LC systems are discussed, with respect to mobile phase compatibility in the two systems and modulation techniques suppressing band broadening connected with the sample fraction transfer from the first to the second dimension. Pitfalls connected with online connection of normal-phase and RP LC systems and their possible practical solutions are addressed and illustrated by practical examples.

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Characterization of various reversed-phase columns using the linear free energy relationship

Cited by 80 publications

References 52 publications

Lipophilicity Measurement of Drugs by Reversed Phase HPLC over Wide pH Range Using an Alkaline-Resistant Silica-Based Stationary Phase, XBridgeTM Shield RP18

Lipophilicity Measurement of Drugs by Reversed Phase HPLC over Wide pH Range Using an Alkaline-Resistant Silica-Based Stationary Phase, XBridgeTM Shield RP18

Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs)

Column selectivity for two‐dimensional liquid chromatography

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