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1.
Shu-ying Han Xin Ming Zheng-chun Qi Dong Sheng Hong-zhen Lian 《Analytical and bioanalytical chemistry》2010,398(6):2731-2743
Simple acids are usually applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography.
The purpose of this study is to investigate the retention behavior of various weak acidic compounds (monoprotic, diprotic,
triprotic, and tetraprotic acids) using acetic or perchloric acid as ion suppressor in a binary hydroorganic mobile phase.
The apparent n-octanol–water partition coefficient (K
ow
″) was proposed to calibrate the n-octanol–water partition coefficient (K
ow) of weak acidic compound. LogK
ow
″ was found to have a better linear correlation with logk
w, the logarithm of the retention factor obtained by extrapolating to neat aqueous fraction of the mobile phase, for all weakly
ionizable acidic compounds. This straightforward relationship offers a potential medium for direct measurement of K
ow data of weak acidic analytes and can be used to predict retention behavior of these compounds in the ion suppression reversed-phase
liquid chromatographic mode. 相似文献
2.
Costas Giaginis Stamatios Theocharis Anna Tsantili‐Kakoulidou 《Journal of separation science》2013,36(24):3830-3836
The advantageous effect of n‐octanol as a mobile phase additive for lipophilicity assessment of structurally diverse acidic drugs both in the neutral and ionized form was explored. Two RP C18 columns, ABZ+ and Aquasil, were used for the determination of logkw indices, and the results were compared with those previously reported on a base‐deactivated silica column. At pH 2.5, the use of n‐octanol‐saturated buffer as the mobile phase aqueous component led to high‐quality 1:1 correlation between logkw and logP for the ABZ+ column, while inferior statistics were obtained for Aquasil. At physiological pH, the correlations were significantly improved if strongly ionized acidic drugs were treated separately from weakly ionized ones. In the latter case, 1:1 correlations between logD7.4 and logkwoct indices were obtained in the presence of 0.25% n‐octanol. Concerning strongly ionized compounds, adequate correlations were established under the same conditions; however, slopes were significantly lower than unity, while large negative intercepts were obtained. According to the absolute difference (diff = logD7.4–logkw) pattern, base‐deactivated silica showed a better performance than ABZ+, however, the latter seems more efficient for the lipophilicity assessment of highly lipophilic acidic compounds. Aquasil may be the column of choice if logD7.4<3 with the limitation, however, that very hydrophilic compounds cannot be measured. 相似文献
3.
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 logkw indices suitable to substitute for octanol–water logP or logD 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+. Logkw/logD7.4 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
4.
Shu-ying Han Chao Liang Jun-qin Qiao Hong-zhen Lian Xin Ge Hong-yuan Chen 《Analytica chimica acta》2012
The retention factor corresponding to pure water in reversed-phase high performance liquid chromatography (RP-HPLC), kw, was commonly obtained by extrapolation of retention factor (k) in a mixture of organic modifier and water as mobile phase in tedious experiments. In this paper, a relationship between log kw and log k for directly determining kw has been proposed for the first time. With a satisfactory validation, the approach was confirmed to enable easy and accurate evaluation of kw for compounds in question with similar structure to model compounds. Eight PCB congeners with different degree of chlorination were selected as a training set for modeling the log kw ? log k correlation on both silica-based C8 and C18 stationary phases to evaluate log kw of sample compounds including seven PCB, six PBB and eight PBDE congeners. These eight model PCBs were subsequently combined with seven structure-similar benzene derivatives possessing reliable experimental Kow values as a whole training set for log Kow ? log kw regressions on the two stationary phases. Consequently, the evaluated log kw values of sample compounds were used to determine their log Kow by the derived log Kow ? log kw models. The log Kow values obtained by these evaluated log kw were well comparable with those obtained by experimental-extrapolated log kw, demonstrating that the proposed method for log kw evaluation in this present study could be an effective means in lipophilicity study of environmental contaminants with numerous congeners. As a result, log Kow data of many PCBs, PBBs and PBDEs could be offered. These contaminants are considered to widely exist in the environment, but there have been no reliable experimental Kow data available yet. 相似文献
5.
Separation behavior of basic compounds on unbonded silicon oxynitride and silica high‐performance liquid chromatography stationary phases with reversed‐phase eluents
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Huihui Wan Hongmin Zhong Xingya Xue Xinmiao Liang 《Journal of separation science》2016,39(20):3860-3867
Unbonded silicon oxynitride and silica high‐performance liquid chromatography stationary phases have been evaluated and compared for the separation of basic compounds of differing molecular weight, pKa, and log D using aqueous/organic mobile phases. The influences of percentage of organic modifier, buffer pH, and concentration in the mobile phase on base retention were investigated on unbonded silicon oxynitride and silica phases. The results confirmed that unbonded silicon oxynitride and silica phases demonstrated excellent separation performance for model basic compounds and both the unbonded phases examined possessed a hydrophobic/adsorption and ion‐exchange character. The silicon oxynitride stationary phase exhibited high hydrophilicity compared with silica with a reversed‐phase mobile phase. An ion‐exclusion‐type mechanism becomes predominant for the separation of three aimed bases on the silicon oxynitride column at pH 2.8. Different from silicon oxynitride stationary phase, no obvious change for the retention time of three model bases on silica stationary phase at pH 2.8 can be observed. 相似文献
6.
Javier Gotta Sonia Keunchkarian Cecilia Castells Mario Reta 《Journal of separation science》2012,35(20):2699-2709
The prediction capability of the solvation parameter model in reverse‐phase liquid chromatography at different methanol‐water mobile phase compositions and temperatures was investigated. By using a carefully selected set of solutes, the training set, linear relationships were established through regression equations between the logarithm of the solute retention factor, logk, and different solute parameters. The coefficients obtained in the regressions were used to create a general retention model able to predict retention in an octadecylsilica stationary phase at any temperature and methanol‐water composition. The validity of the model was evaluated by using a different set (the test set) of 30 solutes of very diverse chemical nature. Predictions of logk values were obtained at two different combinations of temperature and mobile phase composition by using two different procedures: (i) by calculating the coefficients through a mathematical linear relationship in which the mobile phase composition and temperature are involved; (ii) by using a general equation, obtained by considering the previous results, in which only the experimental values of temperature and mobile phase composition are required. Predicted logk values were critically compared with the experimental values. Excellent results were obtained considering the diversity of the test set. 相似文献
7.
Jacek Achrem‐Achremowicz Elżbieta Kępczyńska Marek Żylewski Zbigniew Janeczko 《Biomedical chromatography : BMC》2010,24(3):261-267
A series of superlipophilic or highly lipophilic semisynthetic betulin derivatives was prepared and their relative lipophilicity was measured by reversed‐phase thin‐layer chromatography (RP‐TLC) at different pH values using 1,4‐dioxane–acetate buffer mixtures as mobile phases. Cholesterol, 17β‐estradiol and pure betulin were used as the reference compounds. Linear relationships were found between RM values and 1,4‐dioxane concentrations in the mobile phases. LogP values were also calculated with computer programs ACD/LogP (ChemSketch 11.0, Advanced Chemistry Development Inc.) and ClogP (Daylight Chemical Information Systems Inc.). The empirical and theoretical data were compared, and the RM0 values correlated well with logP. Two of the synthesized betulin derivatives are reported for the first time. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
8.
Xiangli Liu Ping Fan Ming Chen Hossam Hefesha GerhardK.E. Scriba Detlef Gabel Alfred Fahr 《Helvetica chimica acta》2010,93(2):203-211
The objective of this study was to investigate drug–membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log Ks) and the comparison with lipophilicity indices obtained by liposome/H2O, octan‐1‐ol/H2O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti‐inflammatory drugs and β‐blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH 7.4. No correlation was found between log Ks from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log Ks from ILC and lipophilicity indices from IAM chromatography and octan‐1‐ol/H2O. However, ILC and liposome/H2O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems. 相似文献
9.
The retention behavior of neutral, positively charged, and negatively charged solutes on the IAM.PC.DD2 stationary phase was investigated and compared. A set of monofunctional compounds and complex drugs (steroids, nonsteroidal anti‐inflammatory drugs, and β‐blockers) were selected for this study, i.e., neutral solutes and solutes with acidic or basic functionalities which are positively charged or negatively charged at pH 7.0. The correlation between the retention factor log kw at pH 7.0 on the IAM.PC.DD2 stationary phase and the partition coefficient log Poct or the distribution coefficient log D7.0 showed that the retention mechanism depends on the charge state and structural characteristics of the compounds. The neutrals were least retained on the IAM.PC.DD2 stationary phase, and positively charged solutes were more retained than negatively charged ones. This implies that the retention of the charged solutes is controlled not only by lipophilicity but also by the electrostatic interaction with the phospholipid, with which positively charged solutes interact more strongly than negatively charged ones. 相似文献
10.
11.
Summary The linear relationship between logk
w andS derived from molecular interactions and statistical thermodynamics was investigated by four series of different polar probe
solutes. For each series of similar polar solutes, structurally related compounds with similar dipolarity/polarizability and
hydrogen bonding energy, a linear relationship between logk
w andS was obtained. The more similar the solutes, the greater were the regression coefficients obtained. For two series of solutes
with different strong polar groups resulting in different dipolarity/polarizability and hydrogen bonding energy, two parallel
lines were observed in the logk
w-S plots. Each line represented one series of compounds and the distance between them indicated the difference in the dipolarity/polarizability
and hydrogen bonding energy. Based on the parallel lines implying information on structurally related compounds in the logk
w-S plot, a method of classification of structurally related compounds was put forward and the linear logk
w-S correlation for unknown components in nonaqueous RP-HPLC analysis ofAstragalus extract with isopropanol-methanol mobile phase was studied. Two nearly parallel lines were obtained in the logk
w-S plot and two series of structurally related compounds were classified in this way. 相似文献
12.
13.
采用改进的反相高效液相色谱法(RP-HPLC)测定了持久性有机污染物(POPs)包括多环芳烃(PAHs)、多氯二苯并二恶英(PCDDs)、多氯二苯并呋喃(PCDFs)和十溴二苯乙烷(DBDPE)等的正辛醇-水分配系数(logKow)。采用保留时间双点校正法(DP-RTC)校正因色谱柱老化等引起的保留时间漂移。以37种有可靠logKow实验值的苯系物、PAHs、PCDD/Fs类似物为模型化合物,建立了logKow和外推至纯水相的保留因子logkw的定量结构-色谱保留关系(QSRR)模型,回归方程为logKow=(1.18±0.02)logkw+(0.36±0.11),其相关系数(R2)为0.985,交叉验证相关系数(R2cv)为0.983,标准偏差(SD)为0.16。进而,用4个已有可靠logKow实验值的验证化合物(联苯、芴、PCDD 1和PCDF 114)对模型进行了外部验证,表明RP-HPLC测得的logKow值与摇瓶法/慢搅法结果有很好的一致性,尤其是对疏水性强的化合物。采用该模型测定了29种特别受关注的POPs的logKow值,这些化合物的logKow实验值均未见报道。所建立的DP-RTC-HPLC是测定强疏水性POPs的logKow值的一种值得推荐的方法。 相似文献
14.
15.
Kerli Martin Sandip A. Kadam Ulriika Mattinen Johan Bobacka Ivo Leito 《Electroanalysis》2019,31(6):1061-1066
The construction and study of solid‐contact acetate‐selective electrodes is described using a 1,3‐bis(carbazolyl)urea derivative as a neutral hydrogen‐bonding ionophore and poly(3,4‐ethylenedioxythiophene) as the solid contact. It was shown recently that this ionophore binds acetate (logKass=4.98) that is used as primary ion in this study. The electrodes show linearity over the activity range of 10?4.50–10?1.10 with a sub‐Nernstian slope of ?51.3 mV per decade and a detection limit of 10?5.00. The anion‐selectivity pattern of these electrodes deviates markedly from the Hofmeister pattern. When adding ionophore to the membrane the logarithm of the selectivity coefficient (logK) for SCN? decreased from 6.5 to 1.2, logK for I? decreased from 5.7 to 0.9, logK for NO3? decreased from 4.3 to 0.6 and logK for Br? decreased from 3.3 to 0.1. The selectivity coefficients of hydrophilic anions such as Cl?, F?, HPO42?, and SO42? are significantly lower than in case of the ionophore‐free membrane. It was discovered that the constructed electrodes are also relatively selective to bicarbonate. This work is an important step towards the further development of solid‐contact anion‐selective electrodes. 相似文献
16.
Vronique Gobry Graldine Bouchard Pierre‐Alain Carrupt Bernard Testa HubertH. Girault 《Helvetica chimica acta》2000,83(7):1465-1474
Sildenafil (ViagraTM) was examined for its ionization and lipophilicity by two‐phase titration and electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) in the 1,2‐dichloroethane/H2O system. The dissociation constants (basic pKa=6.78, acidic pKa=9.12) and partition coefficients of the various species, together with the effects of electrical potential, were used to construct an ionic partition diagram (pH‐potential representation). This allowed to interpret the transfer mechanisms of sildenafil at liquid/liquid interfaces, suggesting in particular that an intramolecular H‐bond influences the lipophilicity of the neutral and cationic species. Conformational calculations confirmed this hypothesis. 相似文献
17.
Although simple acids, replacing buffers, have been widely applied to suppress the ionization of weakly ionizable acidic analytes in reversed-phase liquid chromatography (RPLC), none of the previously reported works focused on the systematic studies about the retention behavior of the acidic solutes in this ion-suppression RPLC mode. The subject of this paper was therefore to investigate the retention behavior of monobasic weak acidic compounds using acetic, perchloric and phosphoric acids as the ion-suppressors. The apparent octanol-water partition coefficient (K″ow) was proposed to calibrate the octanol-water partition coefficient (Kow) of these weak acidic compounds, which resulted in a better linear correlation with log kw, the logarithm of the hypothetical retention factor corresponding to neat aqueous fraction of hydroorganic mobile phase. This log K″ow−log kw linear correlation was successfully validated by the results of monocarboxylic acids and monohydrating phenols, and moreover by the results under diverse experimental conditions for the same solutes. This straightforward relationship not only can be used to effectively predict the retention values of weak acidic solutes combined with Snyder-Soczewinski equation, but also can offer a promising medium for directly measuring Kow data of these compounds via Collander equation. In addition, the influence of the different ion-suppressors on the retention of weak acidic compounds was also compared in this RPLC mode. 相似文献
18.
Tatjana Djaković‐Sekulić Nada Perišić‐Janjić Evgenija Djurendi 《Biomedical chromatography : BMC》2009,23(8):881-887
The chromatographic behaviour of salicylic acid derivatives was investigated using reversed‐phase high performance thin‐layer chromatography (RP HPTLC) with methanol–water and dioxane–water binary mixtures as mobile phase in order to establish relationships between chromatographic data and selected physico‐chemical parameters that are related to ADME (absorption, distribution, metabolism and elimination). Some of the investigated compounds were screened for antioxidant activity. Examination of chromatographic behaviour revealed a linear correlation between RM values and the volume fraction of mobile phase modifier. Obtained RM0 values were correlated with lipophilicity, solubility, human intestinal absorption, plasma‐protein binding, and blood–brain barrier data. The comparison among chromatographic data obtained by two mobile phase was performed with a statistical technique, principle component analysis. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
19.
Stella C Galland A Liu X Testa B Rudaz S Veuthey JL Carrupt PA 《Journal of separation science》2005,28(17):2350-2362
An RPLC was developed to rapidly determine lipophilicity of neutral and basic compounds using three base deactivated RPLC stationary phases particularly designed for the analysis of basic compounds, namely, Supelcosil ABZ(+)Plus, Discovery RP Amide C16, and Zorbax Extend C18. The work consisted of three sets of experiments. In the first log kw values of neutral compounds were extrapolated using hydroorganic mobile phases at different compositions. Good correlation between log kw and log Poct indicated that the method was appropriate for these supports, without adding a silanol masking agent. In the second set of experiments, isocratic log k values of neutral and basic compounds were measured with three different mobile phases. The best estimation of lipophilicity was obtained for neutral and basic compounds when the secondary interactions were strongly reduced (i. e., when basic compounds were under their neutral form). In the third set of experiments, isocratic retention factors of basic compounds (in their neutral form) were measured with a high-pH mobile phase, on a chemically stable support (Zorbax Extend C18). Under these chromatographic conditions, correlation between the isocratic retention factors and log Poct (log D10.5) for basic compounds was similar to that for neutral compounds. 相似文献
20.
New synthesized 1,4‐disubstituted thiosemicarbazide derivatives were analyzed in the RP system, modified with the addition of salts; chaotropic (sodium hexafluorophosphate – Na PF6), cosmotropic (sodium phosphate – NaH2PO4), and neutral (NaCl) on Zorbax XDB C18 column. The effect of the eluent composition on the analytes retention (k), system efficiency (N), peak symmetry (As), and LOD values were all examined and compared to unmodified organic‐aqueous mobile phase system. It was established that eluent modified with chaotropic salts addition was also the most advantageous according to other peak parameters such as the theoretical plates numbers and asymmetry factors. The lower LOD values were achieved in comparison to unmodified organic‐aqueous eluent system. Compatibility of lipophilicity parameters calculated by the use of computer software with experimental ones measured by RP‐HPLC was also the best for chaotropic modified mobile phase. To explain the observed phenomena, molecular modeling was performed for chosen representative compound in different environment representing examined mobile phase composition. 相似文献