Imitation of artificial membrane system via mobile phases with Tween-80 and cholic acid in biopartitioning micellar chromatography

The chromatographic behaviour of compounds of biomedical significance was studied using micellar mobile phases modified with polyoxyethylene (20) sorbitan monooleate (Tween-80). The influence of the surfactant within the 0.75-4% concentration range on the retention factor of model compounds was investigated. The biological surfactant cholic acid was introduced into the mobile phases in order to approach to the structure of natural membranes, viz. erythrocyte and cytoplasmatic membranes. It was found that curves of dependence of retention factor vs concentration of Tween-80 in the absence and presence of cholic acid in the mobile phase considerably diverge with one another, especially in the 2-3% concentration range of Tween-80 using C18-type support. Increasing the concentration of Tween-80 resulted in the increase of retention factors using phenyl-coated stationary phase.     

Study of chromatographic characteristics of inorganic analytes in biopartitioning micellar chromatography with ion‐pair additives

The chromatographic behavior of model ions of biomedical and environmental significance was investigated by using nonionic micellar mobile phases modified with ion‐pair additives. The influence of concentrations of polyoxyethylene (23) lauryl ether and ornithine hydrochloride in the mobile phase on the retention factors of chromium (III), chromium (VI), iodide and bromide ions was studied. The possible mechanisms of retention of the mentioned ions in biopartitioning micellar chromatography with zwitter ion‐pair additives were proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Permeability and toxicological profile estimation of organochlorine compounds by biopartitioning micellar chromatography

This paper points out the usefulness of biopartitioning micellar chromatography (BMC) as a high-throughput primary screening tool providing key information about the oral absorption, skin permeability (K(p)), brain-blood distribution coefficient (BB) and ecotoxicological parameters such as median lethal concentration (LC(50)) and bioconcentration factors of 15 organochloride compounds. The retention data of compounds in BMC conditions were interpolated in previously developed quantitative-retention activity relationships by our research group. Results show that the compounds studied readily cross the intestinal barrier (oral absorption > 90%) and the blood-brain barrier (log BB > 0.4). In addition, the organochlorines DDE, chlorobenzene, 1,3-dichlorobenzene and 1,2-dichlorobenzene are the compounds which can more quickly cross the skin barrier (log K(p ) > -0.74 cm/h). From a ecotoxicological point of view, it can be concluded that the most retained compounds, DDE, DDD, hexachlorobenzene and dicofol, are the most toxic and bioacumulative.     

Quantitative structure-retention relationships for ionic and non-ionic compounds in biopartitioning micellar chromatography

Quantitative structure-retention relationships, QSRRs, represent a powerful tool in chromatography. The objectives of QSRR studies are to predict the chromatographic retention behaviour of solutes based on their structural properties, to elucidate retention mechanisms, to optimize the separation of complex mixtures or to prepare experimental designs. In this paper, using the retention factors of 151 structurally unrelated solutes that cover a wide range of hydrophobicity, molecular size, hydrogen bonding properties and ionization degrees obtained in biopartitioning micellar chromatography (BMC) at different Brij35 micellar concentrations, several multivariate QSRR models are tested. It is demonstrated that the chromatographic retention of any molecule in BMC, independently of its family, can be adequately described by its hydrophobicity (expressed as log P) and its anionic and cationic total molar charge (expressed as alpha(A) and alpha(B)).     

Investigation of artificial biomembrane systems in biopartitioning micellar chromatography by method of mathematical design

An attempt to create and study an artificial membrane system was realized via biopartitioning micellar liquid chromatography. Towards this end the known formula of membrane permeability (on the basis of Fick's diffusion equation) was modified so that membrane permeability may be estimated in terms of chromatographic characteristics. The two-factoral experiments on the basis of mathematical design of second order were carried out. The regression equations are derived which describe the dependence of membrane permeability on the concentration of polyoxyethylene (23) lauryl ether in the mobile phase and its flow-rate for compounds with biomedical significance. Some regularities were revealed, which characterize the permeability of compounds of the different nature through membranes. The extremal dependence (with passing through minimum) of permeability on the concentration of non-ionic surfactant was observed for anionic compounds. The increasing character of permeability in relation with flow-rate of mobile phase was recognized for cationic samples. Both dependences were basically fulfilled for zwitterionic compounds.     

Development of predictive quantitative retention–activity relationship models of alkaloids by mixed micellar liquid chromatography

The mixed micellar liquid chromatography is a mode that uses mixed micellar system of Brij35/SDS (85 : 15) as a mobile phase under adequate experimental conditions, can simulate the resting membrane potential and the conformation of the long hydrophilic polyoxyethylene chains remains unchanged. In this article, the applications of biopartitioning micellar chromatography, using mixed micellar system to describe and estimate bioactivities of alkaloids, has been focused. The BMC_Brij35/SDS‐QRAR models of half‐life time, volume of distribution, plasma clearance and area under concentration–time curve were obtained using Brij35‐SDS retention data. The aim is to take a look at the capability of the mixed micellar liquid chromatography model to describe and/or estimate the bioactivity of alkaloids. Copyright © 2009 John Wiley & Sons, Ltd.     

Mixed micellar liquid chromatography methods: modelling quantitative retention-activity relationships of angiotensin converting enzyme inhibitors

The capability of biopartitioning micellar chromatography (BMC), using pure Brij35 solution and mixed micellar system of Brij35-SDS (85:15) as mobile phase, to describe and estimate bioactivities of angiotensin converting enzyme inhibitors at different pH has been studied. Quantitative retention-activity relationships (QRAR) in BMC were investigated for these compounds. The obtained BMC(Brij35-SDS)-QRAR models were compared with the traditional BMC(Brij35)-QRAR, and better statistically models were obtained using Brij35-SDS retention data. The superiority of BMC(Brij35-SDS)-QRAR is due to the fact that the mixed micellar mobile phase can simulate the resting membrane potential and the conformation of the long hydrophilic polyoxyethylene chains remains unchanged.     

胶束电动毛细管色谱法测定植物中的水杨酸

建立了以胶束电动色谱为分离模式测定植物中水杨酸的新方法。在一定范围内，随着硼酸和甲醇浓度的升高，苯甲酸内标和水杨酸的分离度以近似线性关系升高；随缓冲液pH的升高分离度呈非线性升高；随十六烷基三甲基溴化铵浓度的升高分离度呈非线性下降。在优化的条件下，两可在12min内分离。测定了苹果和梨样品，并做了回收率试验，回收率在97.1%-102%之间。     

Isocratic and gradient elution in micellar liquid chromatography with Brij‐35

Polyoxyethylene(23)lauryl ether (known as Brij‐35) is a nonionic surfactant, which has been considered as an alternative to the extensively used in micellar liquid chromatography anionic surfactant sodium lauryl (dodecyl) sulfate, for the analysis of drugs and other types of compounds. Brij‐35 is the most suitable nonionic surfactant for micellar liquid chromatography, owing to its commercial availability, low cost, low toxicity, high cloud temperature, and low background absorbance. However, it has had minor use. In this work, we gather and discuss some results obtained in our laboratory with several β‐blockers, sulfonamides, and flavonoids, concerning the use of Brij‐35 as mobile phase modifier in the isocratic and gradient modes. The chromatographic performance for purely micellar eluents (with only surfactant) and hybrid eluents (with surfactant and acetonitrile) is compared. Brij‐35 increases the polarity of the alkyl‐bonded stationary phase and its polyoxyethylene chain with the hydroxyl end group allows hydrogen‐bond interactions, especially for phenolic compounds. This offers the possibility of using aqueous solutions of Brij‐35 as mobile phases with sufficiently short retention times. The use of gradients of acetonitrile to keep the concentration of Brij‐35 constant is another interesting strategy that yields a significant reduction in the peak widths, which guarantee high resolution.     

Fast profiling ecotoxicity and skin permeability of benzophenone ultraviolet filters using biopartitioning micellar chromatography based on penetrable silica spheres

Penetrable silica possesses hierarchical pores, mesopores and penetrable macropores, offering fast mass transfer, satisfactory mechanical strength as well as low column pressure. In the present study, penetrable octadecyl-bonded silica (ODS) was for the first time used as biopartitioning micellar chromatography (BMC) stationary phase to profile ecotoxicity and skin permeability of benzophenone UV-filters. Mobile phase (MP) pH and concentration of polyoxyethylene(23)lauryl ether in the MP were systematically studied. Quantitative retention–activity relationships (QRARs) model was established to correlate retention factors (k) on BMC with bioconcentration factor (BCF) and transdermal rate (TR) of UV-filters. Coefficient of determination (r²) of the QRARs model between log BCF and log k were 0.9398–0.9753, while r² between TR and log k were 0.7569–0.8434, which demonstrated satisfactory predictive ability of the methodology. It was a powerful tool for fast screening by combining penetrable ODS with BMC, and avoiding column blockage often occurring in BMC.     

Structures of 1∶1 inclusion complexes of cholic acid with fluoroethanols; Conformational analysis of fluoroethanols in the host cavity

The crystal structures of the inclusion complexes of cholic acid (CA) with 2-fluoroethanol (MFEtOH), 2,2-difluoroethanol (DFEtOH) and 2,2,2-trifluoroethanol (TFEtOH) have been determined by X-ray crystallography, which demonstrates that the guest alcohols are accommodated inside the cavity provided by CA molecules in a similar manner to that for the ethanol molecule in the CA-ethanol inclusion complex. As distinct from the ethanol molecule, the methylene C atoms of the fluoroethanols are not disordered; instead, the substituted F atoms are statistically disordered. All the alcohols are hydrogen-bonded to the OH groups of CA. The X-ray study showed that 46% of MFEtOH adopt thetrans-trans conformer, which is different from the exclusively predominant conformer in the gas and liquid phases, i.e.,thegauche-trans conformer. The study also showed that the F atoms of DFEtOH are statistically disordered, suggesting the possibility that three conformers exist inside the cavity. Such disorder presumably occurs in order to fill the vacant space around the CH₂F and CHF₂ groups inside the cavity. By contrast, we could not observe any disorder of the F atoms of TFEtOH. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82176 (31 pages).     

离子液体对胶束电动色谱胶束微结构以及分离效果的影响

考察了离子液体对胶束电动色谱胶柬微结构以及分离效果的影响.研究结果表明,离子液体使胶束的表面电荷密度变小、粒径变大及其内核极性增大.以泼尼松、氢化可的松和泼尼松龙为分析对象,氢化可的松与泼尼松龙在十二烷基硫酸钠(SDS)胶束体系中不能实现分离.而在SDS-离子液体混合介质(20 mmol/L SDS-10 mmol/L...     

短分离柱胶束液相色谱法同时测定酱油和食醋中的苯甲酸和山梨酸

建立了胶束液相色谱同时测定酱油和食醋中苯甲酸和山梨酸的检测方法。样品经过简单的稀释和过滤后直接注入高效液相色谱仪进行分析。分析柱使用两根串联的色谱保护柱(Zorbax Extend-C₁₈ 柱, 12.5 mm×4.6 mm, 5 μm),胶束流动相为含有2%(体积分数)异丙醇的0.01 mol/L十二烷基硫酸钠-0.01 mol/L醋酸钠(pH 4.9),检测器为二极管阵列检测器,检测波长为235 nm。苯甲酸和山梨酸在3.5 min内完全分离。检测的线性范围为10~100 μ g/mL,相关系数(r)为0.9999。检出限(S/N=3)和定量限(S/N=10)分别为0.04和0.14 μ g/mL。批间和批内精密度均不高于5.2%,高、中、低3个水平的加标回收率为90.5%~103.8%。该方法简单、快速,适用于食品质量监测的日常检测。     

Identification and determination of active anthraquinones in Chinese teas by micellar electrokinetic capillary chromatography

The simultaneous determination of emodin, aloe-emodin and rhein, in Semen Cassiae, Qinghai Wild Dahuang tea, Ningxia Juemingzi tea, Lanzhou Juemingzi tea and Surong Juemingzi tea, has been investigated by micellar electrokinetic capillary chromatography for the fi rst time. With an electrolyte containing 15 mm borax, 30 mm SDS, 10% (v/v) ethanol, at pH 9.60 and 20 kV applied voltage, the three analytes were completely separated within 12 min. The effects of the concentration of borax, electrolyte pH, the concentrations of SDS and organic modifier and the applied voltage on electropheoretic behavior and separation were studied. The linear calibration range was 4-120 micro g/mL (r = 0.9921) for emodin, 10-200 micro g/mL (r = 0.9970) for aloe-emodin and 2-100 micro g/mL (r = 0.9971) for rhein, respectively. Under the optimum conditions, the relative standard deviation (RSD) values (n = 6) of the migration time and the peak area of each peak was 0.59-0.80% and 1.30-3.22%, respectively. The contents of the analytes in Rheum, Qinghai Wild Dahuang tea, Semen Cassiae and three other kinds of teas were easily determined with recoveries ranging from 95.3 to 104.4%.     

Determination of oleanolic acid and ursolic acid in cornel by cyclodextrin-modified micellar electrokinetic chromatography

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was established for the determination of oleanolic acid and ursolic acid in cornel. The two components were separated in the running buffer of 40 mmol/L sodium borate containing 5% methanol, 25 mmol/L SDS and 15 mmol/L hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The applied voltage was 24 kV. The wavelength of detection was 200 nm. The temperature was kept at 25 C. Cinnamic acid was used as the internal standard. The analytical performance of the method was tested with respect to linearity, precision and recovery. The calibration curves were linear in the range of 10.15-243.6 microg/mL, r=0.9993 (oleanolic acid) and 10.07-241.7 microg/mL, r=0.9994 (ursolic acid); the intra-day precision (RSD) was less than 3.7% (oleanolic acid) and 4.1% (ursolic acid); the inter-day precision (RSD) was less than 4.2% (oleanolic acid) and 4.9% (ursolic acid). The limits of detection were 1.6 microg/mL for both components. The method proved to be sensitive, rapid, accurate and suitable for the determination of oleanolic acid and ursolic acid in cornel.     

Simultaneous determination of ursodeoxycholic acid and its glycine-conjugate in serum as phenacyl esters using multidimensional liquid chromatography

Summary A narrowbore high-performance liquid chromatographic (HPLC) method using column switching is described for the simultaneous determination of ursodeoxycholic acid (UDCA) and glyco-UDCA (GUDCA) from serum samples as their phenacyl esters. Serum samples were subjected to a preliminary clean-up using octadecylsilane reversed-phase extraction and derivatized with phenacylbromide. The purification, fractionation and concentration of UDCA and GUDCA from the esterified serum sample were performed on-line by appropriate switching of columns. Limit of detection (LOD) of UDCA and GUDCA were 5 ng and the absolute mean recoveries averaged 84.4±8.2% and 85.2±8.4%, respectively. This method was successfully applied to the pharmacokinetic study of UDCA in rats and human.     

Cyclodextrin-modified micellar electrokinetic chromatography for the analysis of Esterom,a topical product consisting of hydrolyzed benzoylecgonine in propylene glycol

Esterom, a new drug currently in human clinical trials, is a mixture of compounds in a propylene glycol vehicle. It is being evaluated as a topical treatment to aid in the relief of muscle pain and to increase range of motion. Benzoylecgonine is the major component of Esterom and there are at least nine other minor constituents, including four hydroxypropyl esters that have multiple diasteriomers. The aim of the study was to develop a capillary electrophoresis method for the simultaneous separation of the main components in Esterom, including the multiple proposed diastereomers of the esters. Due to the complex sample composition, the use of micelles and cyclodextrins as buffer modifiers was evaluated. A cyclodextrin-modified micellar electrokinetic chromatography method was able to determine 7 of the 8 UV-active Esterom components, with baseline separation of 7 of the 10 diastereomers of the hydroxypropyl esters.     

Comparison of the performance of non-ionic and anionic surfactants as mobile phase additives in the RPLC analysis of basic drugs

Surfactants added to the mobile phases in reversed-phase liquid chromatography (RPLC) give rise to a modified stationary phase, due to the adsorption of surfactant monomers. Depending on the surfactant nature (ionic or non-ionic), the coated stationary phase can exhibit a positive net charge, or just change its polarity remaining neutral. Also, micelles in the mobile phase introduce new sites for solute interaction. This affects the chromatographic behavior, especially in the case of basic compounds. Two surfactants of different nature, the non-ionic Brij-35 and the anionic sodium dodecyl sulfate (SDS) added to water or aqueous-organic mixtures, are here compared in the separation of basic compounds (β-blockers and tricyclic antidepressants). The reversible/irreversible adsorption of the monomers of both surfactants on the stationary phase was examined. The changes in the nature of the chromatographic system using different columns and chromatographic conditions were followed based on the changes in retention and peak shape. The study revealed that Brij-35 is suitable for analyzing basic compounds of intermediate polarity, using "green chemistry", since the addition of an organic solvent is not needed and Brij-35 is a biodegradable surfactant. In contrast, RPLC with hydro-organic mixtures or mobile phases containing SDS required high concentrations of organic solvents.     

Combination of microwave-assisted micellar extraction with liquid chromatography tandem mass spectrometry for the determination of fluoroquinolone antibiotics in coastal marine sediments and sewage sludges samples

In this work, a method for the analysis of fluoroquinolone antibiotics using microwave-assisted micellar extraction combined with liquid chromatography-mass spectrometry detection has been developed. Different surfactants were tested for use as extractants in the isolation of the analytes from solid samples, and several experimental designs were evaluated for the determination and optimization of the variables that affect recovery from the matrix. Under optimal conditions, we obtained recoveries greater than 73% with relative standard deviations below 8%. Compounds were detected by liquid chromatography-electrospray ionization tandem mass spectrometry with detection limits between 0.15 and 0.55 ng g(-1) and quantification limits between 0.49 and 1.85 ng g(-1) . Finally, the optimized method was applied in the determination of antibiotics in real solid samples. Four fluoroquinolones (levofloxacin, norfloxacin, ciprofloxacin and enrofloxacin) were found in coastal marine sediments taken close to a marine outfall and in sewage sludge samples from a wastewater treatment plant. Concentrations ranged between 0.81 and 34.3 ng g(-1) in the sediments and 3.43 and 206.1 ng g(-1) in the sludge.