Simulation of Multicomponent Distillation Using a Nonequilibrium Stage Model

Abstract

A nonequilibrium stage model is used to predict composition profiles for binary and multicomponent distillation in a column of spheres and cylinders with a known interfacial area. The profiles generated by the model are compared with experimental data for the binary systems methanol—isopropanol, methanol—water, and isopropanol—water, and for the ternary systems methanol—isopropanol—water and acetone—n—hexane—cyclohexane. The model predicts with a high accuracy the experimental data with an average deviation lower than 1 mol%.     

Retention models of capacity factor with different compositions of organic modifier in RP-HPLC

A Chromatographic retention behavior of five deoxyribonucleosides (dCyd, dUrd, dGuo, dThd, and dAdo) with respect to the mobile phase composition was studied under isocratic conditions of reversed phase High Performance Liquid Chromatography (RP-HPLC). The volume fraction (F) of organic modifier was changed from 0.05 to 0.30, and to 0.12 for methanol and acetonitrile, respectively. The experimental data of nitro and steroid compound were also considered for comparison of five retention models with various class of samples. The Langmuir-type retention model (k′= A+B/F) with two parameters shows excellect agreements between the experimental capacity factors and calculated values although the values by the log-scale quadratic model with three parameters (log k′= LF₂+MF+N) are closer. Unlike the other four retention models, the slope B of the Langmuir-type retention model can characterize the properties of solute and organic modifier simultaneously. For each solute, the intercepts A calculated for acetonitrile and methanol as organic modifiers are coincident closely.     

High Performance Liquid Chromatographic Analysis of Soybean Phospholipids

An HPLC method was optimized to analyze soybean phospholipids. It uses a silica column with UV detection at 210 nm, and a mobile phase consisting of hexane, isopropanol and water. Separation is achieved by keeping the hexane to isopropanol ratio constant and varying the water concentration in a gradient elution program. Components in the HPLC chromatogram were identified by comparison with retention times of authentic compounds. The method was quantitative for phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and lyso-phosphatidylcholine (LPC). To determine these components quantitatively, standard curves of authentic compounds were prepared. The peak area of the compound in the mixture was converted into weight percent with the standard curves. Unsaturation was the functional group measured by the detector, therefore, the accuracy of the quantitative results depended upon the degree of unsaturation in the standard compounds. Unsaturation in triglycerides and phospholipids may vary depending upon the season of harvest and the climate of location and production. Two commercial samples of granular soybean lecithin were analyzed. Soybean lecithin was extracted with alcohol and the alcohol-soluble and alcohol-insoluble fractions were analyzed. The results differed both qualitatively and quantitatively.     

高效液相色谱直接光学拆分手性农药(英文)

Enantiomer separation is one of the most important prerequisites for the investigation of environmental enantioselective behavior for chiral pesticides.The enantiomeric separation of three chiral pesticides,indoxacarb,lambda-cyhalothrin,and simeconazole,were studied on cellulose tris-(3,5-dimethylphenyl-carbamate)-coated chiral stationary phase(CDMPC-CSP) using high-performance liquid chromatography under normal phase condition.The effects of chromatographic conditions,such as the mobile phase composition including the concentration and type of alcohol modifiers in hexane,flow rate and column temperature,on enantiomer separation were examined.The thermodynamical mechanism of enantioseparation and chiral recognition mechanism were discussed.Better separation were achieved using 20% n-propanol for indoxacarb,2% iso-butanol for lambda-cyhalothrin,and 20% iso-propanol for simeconazole as modifiers in hexane at 25℃ with the selectivity factor(a) of 1.69,1.82 and 1.70,respectively.The resolution factor(Rs) decreased as the flow rate increased from 0.4 to 1.1 ml·min-1.The retention factor(k’) and selectivity factor for the enantiomers of analytes decreased as temperature increased.The lna-1/T plots for racemic chiral pesticides were linear in the range of 15-35℃ in hexane/iso-propanol and the chiral separation was controlled by enthalpy.Hydrogen bonding,π-π and dipole-dipole interactions between enantiomers and CDMPC-CSP play an important role in chiral identification,and the fitting of the asymmetric portion of solutes in a chiral cavity or channel of the CSP is also important.     

Separation of phospholipids from soybean by NP-HPLC with ELSD

Phospholipids of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) from lecithin were separated on gradient steps by NP-HPLC with ELSD. The ternary mobile phases of hexane, IPA, and water were used, and the optimum mobile phase conditions were experimentally determined. The calibration curves of phospholipids were constructed to analyze quantitatively the amounts of PE and PC. The responses of PE by ELSD showed linearity with the injected amount range but a logarithmic relationship of PC was observed. By quantitative analysis, 14.2% of PE and 36.6% (w/w) of PC were contained in the sample of lecithin. Finally, in the separation of phospholipids, the detection by ELSD was better than that by UV. This paper is dedicated to Dr. Youn Yong Lee on the occasion of his retirement from Korea Institute of Science and Technology.     

Separation of neutral lipid,free fatty acid and phospholipid classes by normal phase HPLC

Normal phase high performance liquid chromatography methods are described for the separation of neutral lipid, fatty acid and five phospholipid classes using spectrophotometric detection at 206 nm. Separations were accomplished in less than 10 min for each lipid class. A mobile phase consisting of hexane/methyltertiarybutylether/acetic acid (100∶5∶0.02) proved effective in separating cholesteryl ester and triglyceride with recoveries of 100% for radiolabeled cholesteryl oleate and 98% for radiolabeled triolein. Free fatty acid and cholesterol were separated by two different mobile phases. The first, hexane/methyltertiarybutylether/acetic acid (70∶30∶0.02) effectively separated free fatty acids and cholesterol, but did not separate cholesterol from 1,2-diglyceride. A mobile phase consisting of hexane/isopropanol/acetic acid (100∶2∶0.02) effectively separated free fatty acid, cholesterol, 1,2-diglyceride and 1,3-diglyceride. Recoveries of oleic acid and cholesterol were 100% and 97%, respectively. Five phospholipid classes were separated using methylteriarybutylether/methanol/aqueous ammonium acetate (pH 8.6) (5∶8∶2) as the mobile phase. The recoveries of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were each greater than 96%.     

Thermodynamic Study of Enantioseparation of Mitotane by Supercritical Fluid Chromatography

Enantioseparation data of mitotane (o,p′-DDD) have been obtained and thermodynamically analyzed. A diallyl-L-tartardiamide-based stationary phase (Kromasil CHI-TBB column) was used for chiral separation and CO₂ added to 14% of methanol at 160 bar was used as mobile phase in a temperature range of 303.15–313.15 K. The thermodynamic parameters accounting for the retention and the separation were determined by means of van't Hoff plots. The isoenantioselective temperature was calculated to be 331.55 K. The enantioseparation process was enthalpically driven under experimental conditions.     

Optimization of the column loadability for the preparative HPLC Separation of soybean phospholipids

A simple and rapid preparative-scale separation method was investigated in order to obtain pure soybean phospholipids. Because of technical and economical reasons, two coarse, irregular silica gels were selected. Comparing both stationary phases, a ternary mixture of hexane, 2-propanol and water yielded a different elution order of the phospholipids at analytical sample loads, in spite of the chemical similarity of these packing materials. During scaleup, it became obvious that the retention characteritics were largely influenced by the sample load, thus making the 15–35 μm RSiL inappropriate for preparative-scale separations of phospholipids. Moreover, the column loadability could be increased by controlling the flow rate. Hence, a solvent program was elaborated which enabled a column loadability of up to 2% by weight of the stationary phase. Using analytical high performance liquid chromatography, it was shown that the method proposed yielded over 90% pure phospholipids at a recovery of nearly 80%. Research assistant of the Belgian National Fund for Scientific Research (N.F.W.O.).     

Investigation of ofloxacin enantioseparation by ligand exchange chromatography

BACKGROUND: There is much interest in the recognition and determination the two ofloxacin enantiomers, not only from the point of view of investigating the pharmacokinetics of the enantiomers in vitro but also in the design and development of new chiral pharmaceutics. RESULTS: Chiral separation was performed on a C₁₈ column, in which the mobile phase consisted of a methanol–water solution (containing different concentrations of L ‐phenylalanine and copper sulfate) and its flow rate was set at 0.7 mL min^?1. The effect of different kinds and concentration of ligands, bivalent copper ion, organic modifier, ionic liquid modifier, pH of mobile phase, and temperature on enantioseparation were evaluated and the results show that the enantioselectivity was strongly affected by the pH and ligand concentration of the mobile phase. Under optimal conditions, baseline separation of the two enantiomers was obtained with a resolution of 4.69 in less than 40 min. CONCLUSION: The mechanism of chiral discrimination is based on the stabilities of the copper(II) binary complexes and their ternary diastereomeric complexes with amino acids formed in solution and stationary phase. The proposed method could be used for the quality evaluation of ofloxacin enantiomers. Copyright © 2009 Society of Chemical Industry     

外消旋单硒代缩水甘油醚在纤维素-三(4-甲基苯甲酸酯)手性固定相上反相模式下的手性拆分

在Chiralcel OJ-H色谱手性柱上,反相条件下拆分了5种外消旋单硒代缩水甘油醚,考察了流动相的组成、溶质的结构对手性拆分的影响。实验结果表明,样品在甲醇/水中的保留时间较强,分离情况较好。样品4~5始终未获分离。样品在Chiralcel OJ-H柱上正反相模式下的拆分结果有差别,拓宽了该固定相的应用。     

Chromatographic analysis of ceramide III ofSaccharomyces cerevisiae

Ceramide was prepared by the cultivation ofSaccharomyces cerevisiae from cell extracts by solvent exfraction and analyzed by NP-HPLC using a UV detector. The mobile phase was composed of hexane, methanol, and IPA. From the experimental conditions, the composition of mobile phase was 72/5/23 (hexane/IPA/methanol, vol%). Quantitative analysis of ceramide was performed. Based on the analytical conditions, the effect of cultivation temperature for the production of ceramide was investigated and the optimum cultivation temperature was found to be 35°C. This paper is dedicated to Dr. Youn Yong Lee on the occasion of his retirement from Korea Institute of Science and Technology.     

双手性识别HPLC法拆分3-(2-氯乙基)-2-(2-氯乙基氨基)四氢-2H-1,3,2-噁嗪磷-2-氧化物对映体

建立了拆分3-(2-氯乙基)-2-(2-氯乙基氨基)四氢-2H-1,3,2-口恶嗪磷-2-氧化物(异环磷酰胺)对映体的双手性识别HPLC方法。以三苯基氨基甲酸酯-纤维素(CTPC)为手性固定相,以添加N-苄氧羰基-S-苯基-L-半胱胺酸(BPC)为手性添加剂的正己烷、异丙醇为手性流动相,V(正己烷)∶V(异丙醇)=90∶10,c(BPC)=0.4 mmol/L,流动相流速为0.8 mL/m in,检测波长为254 nm,异环磷酰胺对映体的分离选择性系数为1.12,分离度为1.91,质量浓度测定的线性范围为0.5~2.6 mg/mL,相对标准偏差为0.21%~0.59%,最小检测限为0.86μg。     

Preparative-Scale Separation of Anticancer Triterpenes from Eucalyptus hybrid by Centrifugal Partition Chromatography

Centrifugal partition chromatography was successfully applied in the separation of close R _f complex anticancer triterpenes directly from a fraction of Eucalyptus hybrid (Myrtaceae). The experiment was performed with a two-phase solvent system composed of hexane/ethyl acetate/methanol/water (1:2:1.5:1 v/v/v) where 2% ammonia solution was added in lower aqueous mobile phase to achieve pH 9.5. From 1.5 g of a fraction, 145 mg of ursolic acid and 72 mg of ursolic acid lactone were obtained in 95.4% and 94.8% purities. The total yield recovery was >94% and the isolated triterpenes were characterized on the basis of their ¹H, ¹³C-NMR, and ESI-MS data.     

高效液相色谱直链淀粉手性固定相拆分奥美拉唑对映体

建立了奥美拉唑对映体的高效液相色谱拆分方法。使用Chiralpak AD-H手性色谱柱,考察了流动相中极性调节剂的种类和体积分数、流动相中二乙胺体积分数、柱温以及流速对拆分奥美拉唑对映体的影响。确定了最佳拆分条件:流动相为V(正己烷)∶V(异丙醇)∶V(二乙胺)=75∶25∶0.05;流速为0.8 mL/min;检测波长302nm;柱温30℃,计算了奥美拉唑与固定相相互作用的焓变差值Δ(ΔH0)和熵变差值Δ(ΔS0),分别为-2.845 kJ/mol和-6.233 J/(mol.K),所建立的方法简便快速,重复性好,可用于奥美拉唑的质量研究和控制。该研究以(R)-联二萘酚作为包结拆分剂,拆分后的奥美拉唑对映体过量值(ee)可达96.7%以上。通过峰面积的显著差异,考察了在以乙醇或异丙醇为极性调节剂流动相中两对映体的出峰顺序。结果发现,在这两种流动相中出峰顺序是相反的。     

Migration behavior of aromatic amines on alumina thin layers developed with water-in-oil microemulsion

Water-in-oil (w/o) microemulsions consisting of surfactant [sodium dodecyl sulfate (SDS) or N-Cetyl-N,N,N-trimethyl ammonium bromide], water, heptane or hexane, and a cosurfactant (1-pentanol or butanol) have been used as a mobile phase in combination with alumina, microcrystalline cellulose, silica gel G, silica gel H, and Kieselguhr thin layers to study the retention efficiency of amines. The separation of amines from their ternary and binary mixtures is achieved. Thin layers of alumina as the stationary phase and SDS/water/heptane/1-pentanol microemulsion as mobile phase is identified as the best chromatographic system for amine analysis. The limits of identification and dilution are reported for amines. Effects of heavy metals, anions, and phenols on the separation efficacy of diphenylamine-p-chloroaniline-p-nitroaniline have also been examined. The effect of electrolyte in the microemulsion on amine mobility is investigated. The o- and p-isomers move faster compared to the m-isomer of aniline.     

Production of porous polylactic acid monoliths via nonsolvent induced phase separation

Polylactic acid (PLA) is one of the most promising polymers for use as the matrix of a bone scaffold. In this work, porous PLA monoliths are fabricated via nonsolvent induced phase separation using dichloromethane as a solvent and hexane as a nonsolvent. The PLA-dichloromethane-hexane compositions which undergo liquid–liquid phase separation followed by gelation are shown to allow for the production of high quality foams. Solvent exchange with methanol after aging the gel is found to substantially reduce shrinkage during drying. Using this simple, versatile and template-free method we produced PLA foams with porosities as high as ∼90.8%, specific surface area up to 54.14 m²/g, crystallinity up to 62.6% and compressive modulus ranging from 1.8 to 57 MPa. Depending on ternary mixture concentration and standing temperature a range of mesoporous and combined meso/macroporous morphologies suitable for use as a bone scaffold are produced.     

Supercritical Fluid Chromatography Applied to the Characterization of a Siloxane-Based Gas Chromatographic Stationary Phase

Abstract

Supercritical fluid chromatography using n-pentane as a mobile phase and Porasil C as a column packing was applied to the characterization of Dow-Corning 710 fluid, a commonly used gas chromatographic stationary phase. Under the experimental conditions, decomposition of the polymer was observed on columns of alumina, and derivatized Porasil packings were found to be unstable. Linear pressure programming variables were studied at 206 and 216°C by normalizing the total analysis time on a fixed length of column. A series of homologous polymer components was used to demonstrate the effects upon resolution of density-isotherm nonlinearity associated with the mobile phase. The results showed that optimal temperature conditions existed for the use of linear pressure programming, with the choice of temperature conditions dependent upon the molecular weight range. Operational guidelines are suggested. Mixed solvent behavior was investigated for this separation. The effect of changing the polarity of the mobile phase by adding 0 to 20% v/v isopropanol to n-pentane was studied under isothermal and isobaric conditions. The alcohol was shown to change adsorption characteristics and alter critical constants. The effect upon the critical constants appeared to conform to Kay's approximation. The results suggest that mixed solvents can be used to speed up separations for mixtures having components of widely different adsorption energies. The pseudocritical concept using Kay's approximation was tested for its qualitative ability to estimate state effects when solvents are mixed. The effect of temperature upon migration behavior was compared for equimolar amounts of isopropanol and methanol, each in n-pentane. Kay's approximation appeared to be useful for qualitative predictions regarding changes in critical pressure. However, an attempt to predict density isotherm behavior for 20 % isopropanol in n-pentane relative to pure n-pentane suggested that Kay's approximation may not be as useful for predicting criticla temperature effects.     

A preferred solvent system for high-performance liquid chromatographic analysis of soybean phospholipids with evaporative light-scattering detection

Normal-phase high-performance liquid chromatography separations of phospholipids (PL) depend heavily on the variation in mobile phases. Incorporation of pure tetrahydrofuran to a mobile phase of chloroform, methanol, and ammonium hydroxide improved the separation of polar phospholipids. However, impurities were often found to be present in tetrahydrofuran that caused severe peak interferences with PL analytes. The use of a common chromatographic solventtert.-butyl methyl ether, in lieu of tetrahydrofuran in mobile phases, eliminated problems associated with solvent contamination and yielded reproducible results. The modified method has been applied for the quantitative analysis of phospholipids in crude soybean oils.     

纤维素-三(3,5-二甲基苯基氨基甲酸酯)对烯唑醇对映体的直接拆分

制备了纤维素-三(3，5-二甲基苯基氨基甲酸酯)手性固定相(CDMPC)，以正己烷为流动相，添加异丙醇为改性剂，在高效液相色谱上实现了对烯唑醇光学异构体的直接拆分，探讨了改性剂的含量及色谱柱长对拆分效果的影响，从而优化了拆分条件。试验结果显示，流动相中异丙醇含量的减少有利于对映体的拆分，但保留增强；长色谱柱也有利于对映体的分离。使用两色谱柱串连，当流动相中正己烷与异丙醇的比例为95：5时可达到最佳分离效果，分离因子为1．17。     

HPLC method for quantitation of cholesterol and four of its major oxidation products in muscle and liver tissues

A fast, sensitive, high performance liquid chromatographic method was developed for the quantitation of cholesterol and four of its major oxidation products: 3β-hydroxycholest-5-en-7-one (7-ketocholesterol), cholest-5-ene-3β, 7α-diol (7α-hydroxycholesterol), cholest-5-ene-3β,7β-diol (7β-hydroxycholesterol), and cholest-5-ene-3β,25-diol (25-hydroxycholesterol). In this procedure 2∶1 chloroform:methanol (v/v) extracts of tissue homogenate were combined, dried over anhydrous Na₂SO₄, filtered, evaporated to dryness under N₂ and dissolved with a mobile phase of either 97∶3 or 93∶7 hexane:isopropanol (v/v). After membrane filtration and without further purification, aliquots were directly injected onto a 10-μm pore size, 30×0.39 cm μ-Porasil normal phase column. The separation of cholesterol and its oxidation products was monitored by a UV detector at 206 and 233 nm. This method was successfully applied to pork muscle as well as mouse liver tissues and was able to detect cholesterol oxidation products (COP) in the ppm range. The identity of the COP was confirmed by mass spectroscopy.