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

Sándi, Ákos; Szepesy, L.

doi:10.1016/s0021-9673(98)00536-6

Cited by 50 publications

(30 citation statements)

References 33 publications

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“…This parameter depends on the hydrophobic interaction between the stationary phase and the test compounds [37]. According to the Martin equation, a homologous series with increasing number of carbon atoms shows a linear relationship between the log retention factor and the number of carbon atoms [52].…”

Section: Methylene Selectivitymentioning

confidence: 99%

Micellar proportion: A parameter to compare the hydrophobicity of the pseudostationary phases or that of the analytes in micellar electrokinetic chromatography

et al. 2005

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Micellar proportion, t(prop,mic) = t(mic)/t(m), a quantity expressing how much time is spent by the analyte in the micellar phase related to its whole migration time (t(m)) has been introduced by utilizing the micellar phase residence time (t(mic)). The t(prop,mic) values have been determined for analytes of different chemical structures (alkyl benzene and alkyl phenone homologous series, alcohols, strongly hydrophobic peptides) studied by micellar elektrokinetic chromatography (MEKC) using various cationic and anionic pseudostationary phases. A good linear correlation was obtained between t(prop,mic) and the calculated hydrophobicity (CLOGP) of the analytes for all pseudostationary phases (CLOGP = A.logt(prop,mic) + B). Considering a given pseudostationary phase, t(prop,mic) as a relative quantity is a suitable parameter to characterize and compare experimentally the behavior of the various analytes in MEKC. Applying a set of probe molecules with known hydrophobicity, the CLOGP(50) value (showing the value of hydrophobicity of a virtual molecule spending exactly 50% of its migration time in the pseudostationary phase) has been calculated for each pseudostationary phase applied here. This experimentally determinable numerical value (characterizing the pseudostationary phase) can be utilized to compare the hydrophobicity and hence retention ability of the pseudostationary phases. The t(prop,mic) value was found to be applicable to compare the methylene selectivity of the different pseudostationary phases as well: logt(prop,mic) = A.Z + B, where Z is the number of carbon atoms of the alkyl chain in the alkyl benzene homologous series.

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Section: Methylene Selectivitymentioning

confidence: 99%

Micellar proportion: A parameter to compare the hydrophobicity of the pseudostationary phases or that of the analytes in micellar electrokinetic chromatography

et al. 2005

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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.…”

mentioning

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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“…2. As it is known from earlier results [28,35,45] methylene selectivity of the LiPFOS single phase is greater than that of the LDS single phase. The methylene selectivity (A value in Eq.…”

Section: Methylene Selectivitymentioning

confidence: 74%

Characterisation of mixed lithium dodecyl sulphate/lithium perfluorooctanesulphonate pseudo‐stationary phases in MEKC

et al. 2009

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Lipophilicity and methylene selectivity of mixed pseudo-stationary phases (PSPs) (containing lithium dodecyl sulphate (LDS) and lithium perfluorooctanesulphonate (LiPFOS) in different molar ratios) applied in MEKC have been investigated. Micellar proportion (t(prop,mic), a quantity expressing that how much time is spent by the analyte in the micellar phase related to its whole migration time), CLOGP(50) value (showing the value of hydrophobicity of a molecule spending exactly 50% of its migration time in the PSP) and methylene selectivity have been determined for different LDS/LiPFOS mixed phases. Values of the above-mentioned parameters have been determined for analytes with different chemical structures (alkylbenzene and alkylphenone homologous series, alcohols). Good linear correlation was obtained between either the micellar proportion, CLOGP(50), or methylene selectivity and the phase composition for the mixed phases. Lipophilicity and methylene selectivity of the mixed LDS/LiPFOS PSPs can be calculated and can continuously be changed by mixing the two single phases (LDS and LiPFOS) in the appropriate (and calculable) portion.

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

Cited by 50 publications

References 33 publications

Micellar proportion: A parameter to compare the hydrophobicity of the pseudostationary phases or that of the analytes in micellar electrokinetic chromatography

Micellar proportion: A parameter to compare the hydrophobicity of the pseudostationary phases or that of the analytes in micellar electrokinetic chromatography

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

Characterisation of mixed lithium dodecyl sulphate/lithium perfluorooctanesulphonate pseudo‐stationary phases in MEKC

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