Characterization of biopartitioning micellar chromatography system using monolithic column by linear solvation energy relationship and application to predict blood–brain barrier penetration

The linear solvation energy relationship (LSER) was applied to characterize biopartitioning micellar chromatography (BMC) system using monolithic column, and was utilized to compare the above system with other physicochemical and biological processes in this study. The solute volume and HB basicity had the maximum influence on the retention of the solutes, and an increase in the dipolarity/polarizability, HB basicity, HB acidity or excess molar refraction of the solutes decreased the retention. Principal component analysis of LSER coefficients showed that the system had certain similarity to drug biomembrane transport processes, such as blood–brain barrier penetration, transdermal and oral absorption. The quantitative retention–activity relationship (QRAR) of drug penetration across blood–brain barrier was established and its predictive capability for this biological process was evaluated. With the aid of the high flow rate, the monolithic column significantly facilitated the high-throughput analysis of large compounds’ bank without changing the mechanism of the retention in BMC and without impairing good predictive capability of the biological processes. Accordingly, the BMC system, together with monolithic column, allows for high-throughput profiling the biological processes, such as blood–brain barrier penetration.     

Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration

Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of vapor phase calibration —VPC where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Analysis of selected designer benzodiazepines by ultra high performance liquid chromatography with high‐resolution time‐of‐flight mass spectrometry and the estimation of their partition coefficients by micellar electrokinetic chromatography

A new ultra high performance liquid chromatography with electrospray ionization time of flight mass spectrometry method for the selective and sensitive separation, identification, and determination of selected designer benzodiazepines (namely, pyrazolam, phenazepam, etizolam, flubromazepam, diclazepam, deschloroetizolam, bentazepam, nimetazepam, and flubromazolam) in human serum was developed. The separation of the studied designer benzodiazepines was achieved on C₁₈ chromatographic column using gradient elution within 6 min without any significant matrix interferences. Liquid–liquid extraction with butyl acetate was applied for serum samples cleanup and preconcentration of studied designer benzodiazepines. The method was validated in terms of linearity, limit of detection, limit of quantification, matrix effects, specificity, precision, accuracy, recovery, and sample stability. The limit of detection values were 0.10–0.15 ng/mL. The method was applied to a spiked serum sample to demonstrate its applicability for systematic toxicology analysis. Furthermore, a capillary chromatographic method with micellar electrokinetic chromatography was used for the estimation of partition coefficients of studied designer benzodiazepines as important parameters to evaluate their pharmacological and toxicological properties.     

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.     

Determination of partition coefficients and residual solvent for polymer drying applications

Summary Gas-solid partition coefficients (K) for n-hexane in high density polyethylene (HDPE) have been measured at conditions applicable to large-scale drying utilizing a novel headspace method. The method features considerable versability and simplicity due to the control of experimental conditions designed to favor full extraction of the analyte into the headspace. By combining this full extraction technique with a traditional static headspace experimental scheme, a method which measuresK and residual concentration is achieved. The results show that partition coefficients differ significantly between HDPE in its virgin powder and pellet forms, as well as among various HDPE grades. The differences are shown to be attributable to differences in % crystallinity of the specific polymer. Data collected over a wide range of hexane concentrations reveals saturation levels (solubilities) which correspond to crossover from evaporative to diffusion-controlled drying.     

Porous polymers coated with stationary phases. Contribution of the support to retention behaviour in gas chromatography. Chromosorb 102 coated with ethofat 60/25, squalane and fractonitril VI. Calculation of the experimental partition constants

Summary Following previous work on the solute-stationary phase-adsorbent interaction phenomena associated with the use of Chromosorb 101 support in gas chromatography, the retention of different polarity compounds on columns of Ethofat, squalane and Fractonitril VI on Chromosorb 102 has been studied. The experimental partition coefficients in these three liquid phases have been compared with those ones obtained earlier on Chromosorb 101 and Chromosorb P. The values have been related to the geometry of the support surface and the different coating of the liquid phases by scanning electron microscopy.     

Determination of S-adenosylmethionine,S-adenosylhomocysteine,and methylthioadenosine in urine using solvent-modified micellar electrokinetic chromatography

A new approach for direct determination of S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and methylthioadenosine (MTA) in urine was developed based on MEKC by using SDS modified with isobutanol in the presence of PEG-300. Analytes were first extracted with grafted phenylborononic acid. Using a 50 µm internal diameter silica capillary of 32 cm total length filled with 0.05 M SDS, 0.05 M H₃PO₄, 5% (v/v) isobutanol, and 10% (v/v) PEG-300, LOQ of 0.15 µM for SAM and SAH, and 0.2 µM for MTA was reached. Accuracy was 92% for MTA, 109% for SAH, and 105% for SAM, intra- and interday imprecision were <2.5 and ≤3%, respectively. The total time of analysis for one sample was 10 min. Analysis of 30 urine samples from healthy volunteers showed that the median SAM and SAH levels were 12.1 and 0.73 µM, respectively. MTA levels, which were determined in urine for the first time (according to our data), were 0.43 µM, and these values correlated well with the SAM level (r = 0.748, p < 0.01).     

Reversed-phase ion-pair systems to predict partition coefficients of β-carbolines by HPLC and TLC

Summary A group of 17 β-carbolines was studied in HPLC and TLC systems in order to predict their partition coefficients (log P values). On account of the basic or acid character of some of these compounds, an ion pairing system gave the best results. Both HPLC and TLC data were comparable for log P prediction but severe pH conditions required the use of TLC plates. Retention data are quantitatively related to lipophilicity (expressed as the Hansch constant) and polarity (as the inductive constant) of the solute molecule.     

胶束液相色谱法同时测定血浆中的苯巴比妥、艾司唑仑和氯硝西泮

采用胶束液相色谱法(MLC)分离测定血浆中苯巴比妥、艾司唑仑和氯硝西泮,运用三相平衡理论探讨了流动相中表面活性剂浓度(CM)、氢离子浓度(CH)、助表面活性剂浓度(Cφ)对溶质保留行为的影响,同时运用多元线性回归建立了保留因子的对数(log k)与溶质性质参数和流动相组成之间的相关模型。结果表明,溶质保留因子(k)随CM、Cφ和CH的增加而减小,与理论模型完全一致。而且log k与溶质的疏水性常数的对数(log P)和电离常数(Ka)以及CM、CH和Cφ之间呈现良好的多元线性关系。在确定的色谱条件下,血浆中的3种药物与其他组分之间有较好的分离效果。3种药物的血药浓度分别在2.5～50 mg/L、0.25～5.0 mg/L和0.05～5.0 mg/L间具有良好的线性关系。本方法简便、准确、重现性良好、灵敏度高。3种药物的最低检出限(S/N=3)分别为10.27、1.17、0.867 ng,平均加标回收率范围分别为99.80%～102.9%, 94.00%～98.20%和96.30%～98.70%。     

Comparison between micellar liquid chromatography and capillary zone electrophoresis for the determination of hydrophobic basic drugs in pharmaceutical preparations

The determination of highly hydrophobic basic compounds by means of conventional reversed-phase liquid chromatographic methods has several drawbacks. Owing to the characteristics of micellar liquid chromatography (MLC) and capillary electrophoresis (CE), these techniques could be advantageous alternatives to reversed-phase chromatographic methods for the determination of these kinds of compounds. The objective of this study was to develop and compare MLC and CE methods for the determination of antipsychotic basic drugs (amitryptiline, haloperidol, perphenazine and thioridazine) in pharmaceutical preparations. The chromatographic determination of the analytes was performed on a Kromasil C(18) analytical column; the mobile phase was 0.04 m cetyltrimethylammonium bromide (CTAB), at pH 3, containing 5% 1-butanol, at a flow rate of 1 mL/min. The CE separation was performed in a fused-silica capillary with a 50 mm tris-(hydroxymethyl)-aminomethane buffer, pH 7, at an applied voltage of 20 kV, using barbital as internal stardard. The proposed methods are suitable for a reliable quantitation of these compounds in the commercial tablets and drops in terms of accuracy and precision and require a very simple pre-treatment of the samples. By comparing the performance characteristics and experimental details of the MLC and CE methods we conclude that CE seems to be slightly better than MLC in the determination of highly hydrophobic compounds in pharmaceuticals in terms of resolution and economy, taking into account that the limits of detection are not a handicap in pharmaceutical samples.     

胶束电动毛细管色谱法同时测定西洋参中人参皂苷Rg1、Re和Rb1

建立了西洋参中人参皂苷Rg1、Re及Rb1同时分离测定的胶束电动毛细管色谱新方法,以解决西洋参样品中难溶于水的3种人参皂苷的准确定量问题。以40.2 cm(有效长度30 cm)×50 μm的熔融石英毛细管柱为分离柱,分离缓冲液的组成为V(15 mmol/L Na2B4O7+30 mmol/L H3BO3 (pH 9.0)+100 mmol/L十二烷基硫酸钠(SDS)+30 g/L聚乙二醇35000):V(甲醇):V(异丙醇)=2:1:1,于214 nm下检测。详细研究了影响分离的因素。Rg1、Re及Rb1检出限(信噪比(S/N)为3)分别为30、40及30 mg/L,定量限(S/N=9)分别为90、120及90 mg/L,加标回收率为87.4%～95.2%。用该法测定了西洋参标准物质,并与高效液相色谱法的检测结果进行了比对,结果吻合。应用该方法分别测定了中国、加拿大及美国的西洋参,获得满意的结果。     

Distribution ratio, distribution constant and partition coefficient. Countercurrent chromatography retention of benzoic acid

There is some confusion in chromatography between terms such as solute distribution ratio, distribution constant and partition coefficient. These terms are very precisely defined in the field of liquid-liquid systems and liquid-liquid extraction as well as in the field of chromatography with sometimes conflicting definitions. Countercurrent chromatography (CCC) is a chromatographic technique in which the stationary phase is a support-free liquid. Since the mobile phase is also liquid, biphasic liquid systems are used. This work focuses on the exact meaning of the terms since there are consequences on experimental results. The retention volumes of solutes in CCC are linearly related to their distribution ratios. The partition coefficient that should be termed (IUPAC recommendation) distribution constant is linked to a single definite species. Using benzoic acid that can dimerize in heptane and ionize in aqueous phase and an 18 mL hydrodynamic CCC column, the role and relationships between parameters and the consequences on experimental peak position and shape are discussed. If the heptane/water distribution constant (marginally accepted to be called partition coefficient) of benzoic acid is 0.2 at 20 °C and can be tabulated in books, its CCC measured distribution ratio or distribution coefficient can change between zero (basic aqueous mobile phase) and more than 25 (acidic aqueous mobile phase and elevated concentration). Benzoic acid distribution ratio and partition coefficient coincide only when both dimerization and ionization are quenched, i.e. at very low concentration and pH 2. It is possible to quench dimerization adding butanol in the heptane/water system. However, butanol additions also affect the partition coefficient of benzoic acid greatly by increasing it.     

二维毛细管区带电泳/胶束电动毛细管色谱分离尿样中的药物及其对映体

建立了毛细管区带电泳(CZE)/胶束电动毛细管色谱(MEKC)二维毛细管电泳分离平台,CZE毛细管和MEKC毛细管通过一段带微孔的聚四氟乙烯(polytetrafluoroethylene, PTFE)套管固定。样品在CZE毛细管中分离后进入MEKC毛细管进一步分离,在二维转换过程中采用动态pH连接-胶束扫集法避免第一维分离区带在接口处扩散。将该方法成功用于鼠尿样品中4种药物及其对映体的分离,各组分的理论塔板数为(2.8～4.3)×104/m,检出限为0.015～0.052 mg/L,实际样品中峰面积和迁移时间的相对标准偏差(n=7)分别为1.7%～3.8%和1.3%～4.6%。方法重现性好、灵敏度和分离度高、峰容量大,适用于尿样中多种药物组分及其对映体的同时分离检测。     

胶束电动毛细管色谱法同时测定复方化学消毒剂及日化产品中邻苯二甲醛、对氯间二甲基苯酚及三氯生

建立了邻苯二甲醛(OPA)、对氯间二甲基苯酚(PCMX)和三氯生3种杀菌剂同时分离测定的胶束电动毛细管色谱(MEKC)新方法。详细研究了影响上述3种杀菌剂同时分离与准确定量的因素: 如分离缓冲溶液的浓度及pH,十二烷基硫酸钠(SDS)浓度、样品缓冲溶液等。以40.2 cm (有效长度: 30 cm)×50 μm未涂层熔融石英毛细管为分离柱,20 mmol/L硼砂-80 mmol/L SDS(无需调pH)为分离缓冲溶液,2 mmol/L硼砂-8 mmol/L SDS (含体积分数为10%甲醇)为样品缓冲溶液,检测波长为214 nm。3种杀菌剂的校正峰面积的相对标准偏差(RSD)在1.1%～ 3.8%范围内,迁移时间的RSD均小于0.9%, OPA、PCMX和三氯生的检出限(LOD,信噪比为3)分别为4.0、0.4、0.4 mg/L,定量限(LOQ,信噪比为10)分别为12、1.2、1.2 mg/L,校正峰面积与相应的质量浓度分别在12～2 000 mg/L、1.2～200 mg/L和1.2～200 mg/L范围内具有良好的线性关系,相关系数分别为0.9994、0.9993和0.9995。该法前处理简单,可快速、准确地同时测定3种组分,非常适合常规实验室分析。     

Determination of ticagrelol in rat plasma and tablets by micellar electrokinetic chromatography coupled with large volume sample stacking: Application to a pharmacokinetic study

A method using micellar electrokinetic chromatography coupled with large-volume sample stacking for the determination of ticagrelol was developed and validated. The analysis was performed in a fused silica capillary (41.5 cm effective length, 50 μm diameter) with ultraviolet detection at 195 nm. The background electrolytes were 30 mM phosphate buffer of pH 3.0 with 120 mM sodium dodecylsulfate and 10 % (v/v) acetonitrile (120 s X 50 mbar; 20°C; -18 kV) and 30 mM borate buffer of pH 8.5 with 75 mM sodium dodecylsulfate (120 s X 50 mbar; 20°C; 25 kV); under acidic and alkaline conditions, respectively. The method was found to be reliable with respect to specificity, linearity of the calibration line (R² > 0.99), repeatability (relative standard deviation 2.56%–3.34%), and accuracy (recovery in the range 101.21%–102.67%). The limits of detection and quantitation were 0.032, 0.071, and 0.087, 0.188 μg/mL, respectively. The method was successfully applied for the determination of ticagrelol concentrations in rat plasma and tablets with good recoveries and reproducibility. The presented method proved to be suitable for monitoring ticagrelor in rat plasma.     

Monitoring of cefepime in human serum and plasma by micellar electrokinetic capillary chromatography: Improvement of sample preparation and validation by liquid chromatography coupled to mass spectrometry

Cefepime monitoring in deproteinized human serum and plasma by micellar electrokinetic capillary chromatography and liquid chromatography coupled to mass spectrometry in presence of other drugs is reported. For micellar electrokinetic capillary chromatography, sample preparation comprised dodecylsulfate protein precipitation at pH 4.5 using an increased buffer concentration compared to that of a previous assay and removal of hydrophobic compounds with dichloromethane. This provided robust conditions for cefepime analysis in the presence of sulfamethoxazole and thus enabled its determination in samples of patients that receive cotrimoxazole. The liquid chromatography assay is based upon use of a column with a pentafluorophenyl‐propyl modified and multiendcapped stationary phase and the coupling to electrospray ionization with a single quadrupole detector. The performances of both assays with multilevel internal calibration were assessed with calibration and control samples and both assays were determined to be robust. Cefepime levels monitored by micellar electrokinetic capillary chromatography in samples from patients that were treated with cefepime only and with cefepime and cotrimoxazole were found to compare well with those obtained by liquid chromatography coupled to mass spectrometry. Cefepime drug levels determined by micellar electrokinetic capillary chromatography could thereby be validated.     

Simple and rapid analysis of nitrofurazone from blood,milk, urine and meat samples

Summary Nitrofurazone is an effective chemotherapeutic drug in the treatment of infections of the urinary tract. In order to study its occurrence and metabolism, a simple and sensitive method was developed.     

Simultaneous determination of aliphatic hydrocarbons,PCBs and PCTs in pork liver by gas chromatography

Summary A multicomponent extraction/concentration procedure has been developed for the enrichment of PCBs, PCTs and aliphatic hydrocarbons (pristane, C₁₈, C₁₉, C₂₀, C₂₂, C₂₄, C₂₈, C₃₂ and C₃₆) in pork liver. These components of the enriched extract were then simultaneously determined by gas chromatography. Mean recoveries ranged from 81.5% for pristane to 93% for PCBs;CV% (0.9–6.7) indicated the method to be both precise and reproducible.