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2.
Reversed-phase high-performance liquid chromatography analyses were used for the determination of the retention factor (log k) of a set of quinolinesulfonamides. The analyses utilized a mixture of acetonitrile/water as the mobile phase. The log k values were linearly dependent on the concentration of acetonitrile and extrapolated to 100% water and gave the lipophilicity parameter log kw. The parameter log PHPLC was determined from log kw values using the calibration curve obtained for five standards. The log PHPLC parameters are discussed in terms of structure–lipophilicity relationships. Furthermore, the theoretical lipophilic parameters (log Pcalc) for all compounds were calculated using chemical programs (e.g., Advanced Chemistry Development (ACD/ logP), miLogP, AlogP, ClogP, and Pallas). The determined log PHPLC and calculated log Pcalc values were compared by linear regression analysis. 相似文献
3.
In the present work, the chromatographic behavior of eight selenium species, namely selenites (Se(IV)), selenates (Se(VI)), seleno‐DL ‐methionine (Se‐Met), selenocystine (Se‐Cyst), selenocystamine (Se‐CM), selenourea (Se‐U), dimethylselenide ((CH 3) 2Se) and dimethyldiselenide ((CH 3) 2Se 2), was investigated under different stationary and mobile phase conditions, in an effort to unravel secondary interferences in their underlying elution mechanism. For this purpose, two end‐capped and a polar‐embedded reversed‐phase stationary phases were employed using different mobile phase conditions. Retention factors (log kw) were compared with octanol–water distribution coefficients (log D) as well as with log kw values on two immobilized artificial membrane (IAM) columns and two immobilized artificial plasma proteins stationary phases, obtained in our previous work. The role of electrostatic interactions was confirmed by introducing the net charge of the investigated Se species as an additional term in the log kw/log D interrelation, which in most cases proved to be statistically significant. Principal component analysis of retention factors on all stationary phases and octanol–water log D values, however, showed that the elution of the investigated selenium species is mainly governed by partitioning mechanism under all different chromatographic conditions, while the pH of the mobile phase and the special column characteristics have only a minor effect. 相似文献
4.
The lipophilicity values of selected acridinone (imidazoacridinone and triazoloacridinone) derivatives were measured by gradient
reversed-phase high-performance liquid chromatography (RP-HPLC) using a C18 stationary phase with a water/acetonitrile mixture
as a mobile phase. The retention times obtained served as input data and appropriate log k w values ( i.e., the retention factor log k w extrapolated to 0% organic modifier) as an alternative to log P were calculated using the DryLab program. The relationships
between the lipophilicity (log k w) and the chemical structure of the studied compounds, as well as correlation between experimentally determined lipophilicities
(log k w) and log P data calculated using some commonly available software, are discussed. 相似文献
5.
The retention factors in pure water for a homologous series of s-triazines were calculated by a numerical method basing on Ościk's equation and were correlated with log k
w
values obtained by linear and parabolic extrapolation. Chromatographic data (log k
w
) were compared with the software-calculated partition coefficients in the n-octanol/water system (Alog P, IAlog P, clog P, log P
Kowin
, xlog P, log P
ACD
and log P
Chem.Off.) as alternative hydrophobicity indices. The effect of organic modifier (methanol and acetonitrile) and its concentration in the mobile phase used for log k
w
evaluation were investigated. Very good linear correlations were found between log k
w
values calculated by the numerical method and log P
ACD
, log P
Chem.Off
. and clog P values, independent of organic modifier type. 相似文献
6.
The potential of enhanced‐fluidity liquid chromatography, a subcritical chromatography technique, in mixed‐mode hydrophilic interaction/strong cation‐exchange separations is explored, using amino acids as analytes. The enhanced‐fluidity liquid mobile phases were prepared by adding liquefied CO 2 to methanol/water mixtures, which increases the diffusivity and decreases the viscosity of the mixture. The addition of CO 2 to methanol/water mixtures resulted in increased retention of the more polar amino acids. The “optimized” chromatographic performance (achieving baseline resolution of all amino acids in the shortest amount of time) of these methanol/water/CO 2 mixtures was compared to traditional acetonitrile/water and methanol/water liquid chromatography mobile phases. Methanol/water/CO 2 mixtures offered higher efficiencies and resolution of the ten amino acids relative to the methanol/water mobile phase, and decreased the required isocratic separation time by a factor of two relative to the acetonitrile/water mobile phase. Large differences in selectivity were also observed between the enhanced‐fluidity and traditional liquid mobile phases. A retention mechanism study was completed, that revealed the enhanced‐fluidity mobile phase separation was governed by a mixed‐mode retention mechanism of hydrophilic interaction/strong cation‐exchange. On the other hand, separations with acetonitrile/water and methanol/water mobile phases were strongly governed by only one retention mechanism, either hydrophilic interaction or strong cation exchange, respectively. 相似文献
7.
Similarities and differences between the retention characteristics of octadecylsilica wettable with water used in TLC and RP-18 used in HPLC have been elucidated by use of the linear relationships between log k and RM. The stationary phases compared were investigated with the same mobile phases—binary mixtures of methanol and water, acetonitrile and water, and tetrahydrofuran and water. For these adsorbents of the same type but differing in specific surface area the correlation line was shifted by log ( systemI/ systemII). High values of the correlation coefficients obtained over the whole range of mobile phase organic modifier concentration examined indicated that the TLC systems could be used to predict HPLC conditions for flavonoid separation. 相似文献
8.
A series of newly synthesized 1,3‐purinodiones with potential anticonvulsant activity, exhibiting affinity to adenosine A 1 and/or A 2A receptors, were subjected to micellar LC (MLC) with SDS as micelle‐forming agent and n‐propanol as organic modifier. Two C18 silica‐based columns were employed in MLC: a particle one and a monolithic. In parallel, those derivatives were also analyzed in RP‐LC on four silica‐based columns and on an immobilized artificial membrane column. The correlations between the relevant logarithms of the retention factors of analytes obtained in MLC, immobilized artificial membrane and RP‐LC systems on the one hand, and the calculated log P (clog P) and log D values (clog D) on the other, were examined. The level of the correlations of retention data from MLC and RP‐LC systems with clog P and clog D obtained is similar but it could be stressed that MLC allows increasing the speed of analysis and using only one mobile phase. Moreover, there is no need of applying an extrapolation procedure in lipophilicity determination. Therefore, the MLC systems, providing chromatographic data in a fast and efficient manner, were demonstrated as promising alternatives to the classical RP‐LC systems to estimate the lipophilicity of drugs and drug candidates. 相似文献
9.
Seven sartans have been chromatographed with acetonitrile-buffer and methanol–buffer in different proportions as mobile phases. The retention values, log k or R
M
were extrapolated to zero organic modifier content to obtain the log k
w
or R
MW
values. Calibration equations were obtained for standards of known lipophilicity. A simple method employing a gradient procedure of 10–100% acetonitrile or methanol in 60 min and standards of the extreme lipophilicity was also elaborated. Chromatographic log P values were compared to those calculated by use of different software products. Finally, principal component analysis was performed to explore and visualize similarities and differences among the drugs and among the methods. 相似文献
10.
Ionic liquids have been widely used as green alternative mobile phase additives to shield the residuals silanols groups and modify the stationary/mobile phase HPLC systems. The present study aimed to evaluate the performance of the ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]) in producing extrapolated log kw indices suitable to substitute for octanol–water log P or log D values. The effect of [EMIM][BF4] was investigated for a set of basic and neutral drugs using two different columns, BDS and ABZ +. [EMIM][BF4] was added simply alone or in combination with n‐octanol and was compared with the conventional masking agent n‐decylamine. [EMIM][BF4] reduced the retention by suppressing silanophilic interactions, althoug to a lower extent than n‐decylamine. Addition of n‐octanol further decreased the retention by shielding silanol sites on BDS and/or interacting with polar groups through hydrogen bonding on ABZ +. Log kw/log D7.4 relationships proved moderate compared with those derived upon addition of n‐decylamine. They were considerably improved upon the introduction of protonated fraction F+ in the correlation, reflecting ion pair formation between the chaotropic anion [BF4] ‐ and the protonated basic compounds. In this aspect, the ionic liquid [EMIM][BF4], although efficient as a masking agent, cannot be recommended as mobile phase additive to reproduce octanol–water partitioning. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
11.
AbstractHigh-performance liquid chromatography (HPLC) plays an important role in testing the pharmaceutically active compounds. In despite of the advantages of HPLC, thin-layer chromatography (TLC) retains its applicability to the different experimental tasks. The experimental conditions which allow hydrophilic interactions in the chromatographic system were tested in the HPLC and TLC systems for ivabradine, its related compounds, diltiazem and verapamil. Under the TLC conditions, retention behavior of the investigated compounds was tested on silica gel modified with cyanopropyl ligands as stationary phase and acetonitrile?+?methanol containing 25% v/ v formic acid. Under the HPLC conditions, we used silica gel modified with cyanopropyl ligands as a column packing and the acetonitrile + 0.25% aqueous solution of formic acid as mobile phase. Retention behavior of the investigated analytes depending on the changing volume fractions of the mobile phase modifier was characterized both for TLC and HPLC data sets by the Soczewiński–Wachtmeister equation. Linear relationships were established between the retention coefficients characterizing the retention mechanism ( RM0/ m, log k0/ m) and molecular properties of the investigated compounds. The Quantitative Structure Retention Relationship (QSRR) modeling was performed with the use of the stepwise multiple linear regression, in order to select molecular properties which influence retention. 相似文献
12.
A retention study on perfluorophenyl silica-based stationary phase was undertaken for some organic compounds containing different polar functionalities. The dependence of the retention factor on the content of organic modifier (acetonitrile, or methanol) in mobile phase was fitted by polynomial equations. The only exception was observed for adenine, which showed a sigmoidal dependence for the retention factor versus organic modifier content. The extrapolated values of retention factor for water as mobile phase (log k w) from these dependences were well correlated with octanol–water partition constants (log K ow), excepting the values for hexachlorocyclohexane isomers and adenine. Temperature dependences of the retention factor obeyed the van’t Hoff equation with thermodynamic parameters similar to those obtained in reversed phase on C8 or C18 stationary phases, excepting two statines whose dependences of ln k on the reciprocal value of absolute column temperature were nonlinear. Again, adenine had an atypical behavior with decrease in the retention factor with the increase in column temperature, due to possible tautomeric equilibria of this compound in presence of water, in accordance with theoretical models reported by literature. Charge modeling with MarvinSketch package program revealed charged centers from analyte molecule that could interact differently with charge centers from stationary phase. 相似文献
13.
2,4-Dihydroxyphenylthioamide derivatives modified on the N-aryl ring have substantial fungicidal activity. To determine their quantitative structure–activity relationships their lipophilicity was determined by use of the chromatographic methods column liquid chromatography and thin-layer chromatography. Methanol–water systems were used as mobile phases and the linear dependences of retention ( RM and log k) on volume fraction of organic modifier, φ, were determined. This enabled precise determination of lipophilicity ( RMw and log kw) by extrapolation. Correlations were found between quantities characterizing the lipophilicity of the compounds. Deviations enabled discovery of compound structural features which increase or reduce lipophilicity. When these data were correlated with biological activity against the phytopathogenic fungi Alternaria alternata and Botrytis cinerea parabolic dependences were obtained. 相似文献
15.
The lipophilicity of the novel 12 products of the reaction of N3-substituted amidrazones with cis-1,2-cyclohexanedicarboxylic anhydride (4 linear, 4 triazole-like and 4 isoindole ones) with potential pharmacologic activity was evaluated by thin layer and liquid chromatography. Using organic-aqueous eluent systems (with methanol or acetonitrile) on RP18 plates and C18 column, a linear relationship between the volume fraction of modifiers and the retention indices was obtained. The retention values, log k or R
M
were extrapolated to zero organic modifier content to obtain the log k
w or R
MW
values. 12 compounds with known literature lipophilicity were used as a calibration dataset. The results were compared in a multivariate way with in silico methods (ALOGPs, AC_logP, AB/LogP, COSMOFrag, miLogP, ALOGP, MLOGP, KOWWIN, XLOGP3). 相似文献
16.
Seven sartans have been chromatographed with acetonitrile-buffer and methanol–buffer in different proportions as mobile phases. The retention values, log k or R M were extrapolated to zero organic modifier content to obtain the log k w or R MW values. Calibration equations were obtained for standards of known lipophilicity. A simple method employing a gradient procedure of 10–100% acetonitrile or methanol in 60 min and standards of the extreme lipophilicity was also elaborated. Chromatographic log P values were compared to those calculated by use of different software products. Finally, principal component analysis was performed to explore and visualize similarities and differences among the drugs and among the methods. 相似文献
17.
A surface-confined ionic liquid (SCIL) and a commercial quaternary amine silica-based stationary phase were characterized
employing the linear solvation energy relationship (LSER) method in binary methanol/water mobile phases. The retention properties
of the stationary phases were evaluated in terms of intermolecular interactions between 28 test solutes and the stationary
phases. The comparison reveals a difference in the hydrophobic and hydrogen bond acceptance interaction properties between
the two phases. The anion exchange retention mechanism of the SCIL phase was demonstrated using nucleotides. The utility of
the SCIL phase in predicting log k
IL/water values by chromatographic methods is also discussed. 相似文献
18.
Theoretical and experimental quantitative structure–retention relationships (QSRR) models are useful for characterizing solvent properties and column selectivity in reversed phase liquid chromatography (RPLC). The chromatographic behavior of a model analyte, the herbicide atrazine, in a system derived from nine organic solvents and three chromatographic columns was used for developing QSRR models. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used as statistical approaches. The similarities and differences between linear solvation energy relationships (LSER), and semi-empirical and theoretical molecular models were demonstrated. QSRR models show high predictive power, and can successfully predict retention factor (log k) for new solvents. The models are useful for solvent optimization and reducing time for method development in RPLC. The herbicide atrazine can be readily analyzed at a low level, and all three columns provided good resolution, high-performance and symmetrical peaks. The method is suitable for analysis of atrazine in water samples. 相似文献
20.
The use of subcritical water as an eluent for reversed-phase liquid chromatography is further explored. Shape selectivity as well as thermodynamic values for solute transfer were measured and compared to those seen with traditional ambient methanol/water and acetonitrile/water mobile phases. Linear solvation energy analysis was also used to analyze extrapolated values of the retention factor in pure water at ambient temperatures (k ′w) for subcritical water and ambient hydroorganic mobile phases. Results indicate that it is likely that a large disruption in the hydrogen-bonding network of water at high temperatures causes unique chromatographic selectivity, as well as prohibits accurate extrapolation from high temperature to ambient conditions using pure water. Additionally, subcritical water was not found to be a suitable mobile phase for determining k ′w for use in estimating octanol/water partition coefficients. 相似文献
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