Ultrafiltration of soybean oil/hexane extract by porous ceramic membranes

This study investigated the ultrafiltration of soybean oil/hexane extract (miscella) using porous ceramic membrane. The evaporation energy can be saved in the soybean oil production by pre-separating a portion of hexane through the ceramic membrane. Raw soybean oil/hexane extract with 33 wt% of oil was used without pretreatment. A cross-flow ultrafiltration was performed using an anodisc membrane with a pore diameter of 0.02 μm and thickness of ∼1 μm. The concentrations of oil/hexane mixture were measured by UV adsorption at a wavelength of 458 nm. The separation mechanism was suggested to be the hindrance diffusion of soybean oil. Agitation in the feed side significantly increased the rejection of soybean oil. A small stage cut could also yield a higher rejection. Above observations were attributed to the reduction of concentration polarization by increasing the shear rate and small permeate flux, respectively. The optimum separation was achieved under the conditions of 4 kg/cm² transmembrane pressure, 0.04 stage cut and 120 rpm agitation speed. The concentration of soybean oil decreased from 33 wt% of feed to 27 wt% in permeate, that is, near 20% rejection. A gel-layer polarization model was proposed to estimate the gel concentration and thickness. The gel concentration was found 43–53 wt%. Agitating feed side reduced gel thickness, thus enhanced the rejection and permeate flux.     

Phase behavior of polymer/diluent/diluent mixtures and their application to control microporous membrane structure

Rechargeable battery separators containing controlled pores were fabricated via the thermally-induced phase separation (TIPS) process. Based on the idea that pores could be manipulated by controlling the liquid–liquid phase separation temperature in the TIPS process, phase boundaries of the polymer–diluent systems were controlled by using diluent mixtures. Phase behaviors of the polymer/diluent/diluent ternary blends consisting of polyethylene (PE) as polymer, and soybean oil (SBO) and dioctyl phthalate (DOP) as diluents were explored. PE/SBO and PE/DOP binary blends, and PE/SOB/DOP ternary blends exhibited typical upper critical solution temperature (UCST) type phase behaviors, and the phase separation temperatures of the PE/SBO blends were higher than those of the PE/DOP blends. When the mixing ratio of the polymer and diluent-mixture was fixed, the phase separation temperature of the PE/SBO/DOP blend initially increased with increasing SBO content in the diluent-mixture passing through a maximum centered at about 80 wt% SBO and decreased beyond this point. Furthermore, the phase separation temperature of the PE/diluent-mixture blend was always higher than that of the PE/SBO blend when the diluent-mixture contained more than or equal to 50 wt% SBO. To understand the observed phase behavior of the blends, thermodynamic analyses based on the lattice-fluid theory were performed. Larger pore membranes were fabricated from the blend when higher phase separation temperatures of the blend were exhibited.     

Coupled SFE/SFC/GC for the trace analysis of pesticide residues in fatty food samples

An on-line SFE-chromatographic system, where SFE has been coupled with SFC and GC, was developed and utilized for trace analyses of organochlorine and organophosphorus pesticide residues from gram-sized complex sample matrices, such as chicken fat, ground beef, and lard. The SFE process and chromatographic techniques were instrumentally integrated for efficient and automated on-line analysis, having minimal sample handling between the sample preparation and separation steps. A cleanup step, incorporating packed column SFC, allowed the fractionation of relatively small-sized, non-polar pesticides from the co-extracted fatty materials. This permitted final high-resolution separation of analytes on a capillary GC column. Detection of pesticides was accomplished using selective electron-capture and nitrogen-phosphorus detectors. Pesticide concentrations determined with the on-line system were accurate and reproducible, for fatty samples containing both fortified and incurred pesticides. This method, utilizing supercritical carbon dioxide, was considerably faster and less laborious than the conventional analytical procedures based on liquid extraction.     

On-line monitoring of trihalomethanes in drinking water using continuous-flow purge and cryofocusing gas chromatography-mass spectrometry

A continuous-flow purge-and-trap-GC-MS system was developed for on-line monitoring of THMs (trihalomethanes) in drinking water. Three systems with different traps and purging flow-rates are discussed. In order to minimize interference from water vapor, total purge gas volume and injection temperature were controlled during analysis. Shorter sample concentration time and GC separation time reduced total cycle time to less than 5 min. The detection limits of the system could be lowered to 10 ppt, 25 ppt, 40 ppt, and 50 ppt (w/w) for CHCl3, CHCl2Br, CHClBr2, and CHBr3, respectively. This system could detect changes in sample concentration when applied to the on-line monitoring of THMs in drinking water.     

Determination of ultratrace impurity elements in high purity niobium materials by on-line matrix separation and direct injection/inductively coupled plasma mass spectrometry

The determination of 52 impurity elements in niobium materials (niobium metal, niobium oxide (V), and niobium pentaethoxide) was performed by inductively coupled plasma mass spectrometry (ICP-MS) with on-line anion exchange matrix separation as well as direct nebulization. Niobium material samples were decomposed with a mixture of hydrofluoric acid and nitric acid to prepare 10% niobium solutions. In the on-line anion exchange matrix separation/ICP-MS, the niobium and hydrofluoric acid concentrations in sample solution were adjusted to 5% and ca. 8 M, respectively. The solution was then injected into the carrier stream from the sample loop of injection valve to pass through an anion exchange resin column. In the anion exchange separation, niobium in the fluoro-complex form was adsorbed on the resin, while impurity elements were eluted. The eluted elements were introduced into ICP-MS for the determination of 25 impurity elements. On the other hand, 27 impurity elements could not be separated well from niobium matrix under the above anion exchange conditions, and then the sample solution with the niobium concentration of max. 0.2% containing internal standard elements was injected from the sample loop of injection valve directly to introduce into ICP-MS. As a result, 52 impurity elements in three kinds of niobium materials could be determined at the ng g⁻¹ level.     

基于巯基-烯点击化学法的β-环糊精固定相多模式色谱保留行为研究

基于巯基硅胶与单取代-6A-烯丙氨基-β-环糊精的巯基-烯点击化学反应,制备了β-环糊精(Click TE-CD)共价键合固定相。元素分析结果表明β-环糊精被成功键合到硅胶表面。以黄酮苷类化合物为模型,考察了Click TE-CD固定相在亲水、反相和超临界流体色谱等分离模式下的色谱保留行为。黄酮苷类化合物保留时间随流动相中乙腈含量的变化呈现典型的U型曲线,表明Click TE-CD固定相具有亲水/反相的双重保留特性。应用几何学方法测得Click TE-CD固定相在反相/亲水、亲水/超临界、反相/超临界混合模式下的正交性分别为69.8%、50.8%、50.8%。对比复杂中药样品降香提取物在反相、亲水、超临界等模式下的分离情况,结果表明Click TE-CD固定相在分离中药复杂样品方面具有极大潜力,可以在一根色谱柱上通过分离模式的改变,实现二维液相色谱的分离。Click TE-CD固定相不同分离模式的分离性能和较好的正交性表明该固定相具有在液相色谱方法发展和二维液相色谱分离方面应用的潜力。     

Microcolumn liquid chromatography with thermionic detection of the enantiomers of O-ethyl S-2-diisopropylaminoethyl methylphosphonothioate (VX)

An improved interface for the on-line coupling of microcolumn liquid chromatography (micro-LC) with thermionic detection (TID) is described. Modifications have been made to enable separate adjustment of the eluent introduction and the detector flame temperature in order to improve the sensitivity and ease of use of the system. The micro-LC-TID was used for the chiral separation of the nerve agent O-ethyl S-2-diisopropylaminoethyl methylphosphonothioate (VX). Baseline separation for the enantiomers of VX was obtained on Chiralcel OD using 1% isopropanol in hexane as the eluent. The detection limit of VX using 60 nl injections is ca. 5 μg/ml (ppm range). However, when using large-volume injections (10 μl) the detection limit is ca. 25 ng/ml (ppb range).     

Nelumbo nucifera leaves as source of water-repellent wax: Extraction through polar and non-polar organic solvents

Nelumbo nucifera leaves are rich source of natural wax possessing super-hydrophobic properties. It provides protection to them from ecological turbulences and climatic wear and tear. In this study, various experiments have been conducted to observe the yield of extraction and the determination of various functional groups, which are present in natural wax, derived from Nelumbo nucifera leaves. The natural wax has been extracted from lotus leaves through non-polar (hexane) and polar (ethanol) solvent via different extraction methods. The superhydrophobic wax has been successfully extracted with hexane. Whereas, ethanol did not extract the water-repellent wax of lotus leaf. Considering the cumulative amount, i.e. (desired + undesired), the maceration shows the extraction of 2.9% (%w/w, through hexane) and 10.2% (%w/w, through ethanol), while it was found 2.5% (%w/w, cycle period 15 min) and 9.0% (%w/w, cycle period 26 min) respectively, in case of Soxhlet extraction technique. For this specific case of natural wax recovery from biomass (lotus leaf), the maceration (traditional method) resulted a little bit superior extraction yield in comparison to the Soxhlet extraction method for extraction of crude wax. In the case of non-polar solvent (hexane), an extraction yield of 1.97% (%w/w) through maceration method was observed while in the case of non-polar solvent (ethanol), an extraction yield of 1.62% (%w/w) through Soxhlet extraction was observed. The TLC analysis on both types of extracts was performed. For the detection of various hydrocarbon chains in the crude wax extracts, FTIR was also performed. Topography of wax surface and wax-coated waterproof fabric was compared through SEM.     

Chromatographic resolution of closely related species: Drug metabolites and analogs

In this study, we investigate the separation of a variety of mixtures of drugs, metabolites, and related analogs including representatives of the carbamazepine, methylated xanthine, steroid hormone, nicotine, and morphine families using several automated chromatographic method development screening systems including ultra high performance liquid chromatography, core–shell HPLC, achiral supercritical fluid chromatography (SFC), and chiral SFC. Of the 138 column and mobile phase combinations examined for each mixture, a few chromatographic conditions afford the best overall performance, with a single achiral SFC method (4.6 × 250 mm, 3.0 μm GreenSep Ethyl Pyridine, 25 mM isobutylamine in methanol/CO₂) affording good separation for all samples. Four of these mixtures were also resolved by achiral SFC on the Luna HILIC and chiral SFC Chiralpak IB columns using methanol or ethanol with 25 mM isobutylamine as polar modifiers. Modifications of standard chromatography screening conditions afforded fast separation methods (from 1 to 5 min) for baseline resolution of all components of each of these challenging sets of closely related compounds.     

β-Cyclodextrin production by simultaneous fermentation and cyclization

Production of β-cyclodextrin (CD) with high-dextrose equivalent (DE) starch hydrolysates by simultaneous fermentation and cyclization (SFC) gives higher yields than using only the enzyme CGTase, because fermentation eliminates glucose and maltose that inhibit CD production, while at the same time, produces ethanol that increases yield. A 10% (w/v) solution of cassava starch, liquefied with α-amylase, was incubated with CGTase using: only the enzyme, added ethanol (from 1 to 5%), and added yeast,S. cerevisiae (12% w/v), plus nutrients, the latter being the SFC process. Reaction conditions were: 38αC, pH 6.0, DE from 2 to 25, and 3.3 mL of CGTase/L. The yield of β-CD has decreased with an increase in DE, and maximum reaction yields were found for DE equal to 3.54, reaching 5.6, 14.7, and 11.5 mM β-CD, respectively. For an increase of DE, of approx 6 times (from 3.54 to 23.79), β-CD yield decreased 6 times for the first, and second reaction media with 3% (v/v) ethanol, and only approx 3 times for SFC (from 11.5 to 3.73 mM), showing that this process is less sensitive to variations in the DE     

Separation of divalent transition metal beta-diketonates and their adducts by supercritical fluid chromatography

A method for separation and detection of divalent transition metal beta-diketonates by adduct formation/supercritical fluid chromatography (SFC) with an open-tubular capillary column and a FID detector is described. The crystal structures of copper (Cu)-hexafluoro-acetylacetone (HFA) and Cu bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (THD) complexes have been determined by X-ray crystallography. The SFC behavior of Cu beta-diketonates shows a strong correlation with the structure of the complexes. The hydrated cu beta-diketonate complexes usually exhibit strong intermolecular interactions or decomposition in SFC. Formation of adducts with a neutral donor, such as tributyl phosphine oxide (TBPO), can greatly improve the SFC behavior and detection sensitivity of Cu(II) and Mn(II) beta-diketonates. The stoichiometry and thermal stability of the adducts Cu(II) and Mn(II) beta-diketonates with TBPO in supercritical CO(2) have also been investigated. The implications of utilizing adduct formation for supercritical fluid extraction (SFE) of divalent transition metals and for on-line coupled SFE/SFC analysis of divalent transition metals are discussed.     

On-line coupled supercritical fluid extraction and chromatography for the determination of thiolcarbamate herbicides in soil matrix

Supercritical fluid extraction (SFE) was on-line coupled with supercritical fluid chromatography (SFC) for the determination of thiolcarbamate herbicides in soil matrix. Inert ODS-silica gel packings were used as a trap column for an interface between SFE and SFC and as an analytical column for the satisfactory separation of extracts. Thiolcarbamate herbicides could be extracted satisfactorily from the soil matrix, which had different characteristics. The results indicated that the proposed system was useful for the rapid determination of thiolcarbamate herbicides in soil matrices.     

Monitoring the Progress of a Photochemical Reaction Performed in Supercritical Fluid Carbon Dioxide Using a Continuously Stirred Reaction Cell Interfaced to On-Line SFC

A high-pressure photochemical reaction cell operated with a magnetic stir drive has been directly interfaced on-line with either SFC or HPLC. The interface consisted of an oven housing a recirculation pump directly connected to a sample injection valve. The inlet of the recirculation pump and the outlet from the sample injection valve were connected to the stirred reaction cell such that a return flow circuit was established. With this arrangement, a continuous flow of fresh supercritical fluid photochemical reaction mixture was maintained through the sample injection valve. This enabled samples of reaction mixture to be conveniently analyzed at regular intervals to monitor reaction progress using either on-line SFC or HPLC. The photoreduction of benzophenone in the presence of propan-2-ol to produce 1,1,2,2-tetraphenylethane-1,2-diol and 2-methyl-1,1-diphenylpropan-1,2-diol was studied. For this reaction, on-line SFC provided significantly better performance than on-line HPLC and was therefore used to monitor overall reaction progress and the different product yields. Quantitative results for this study demonstrate that highly efficient photochemical reactions proceeded in supercritical fluid carbon dioxide at 13 and 20 MPa.     

Comparison by capillary SFC and SFC-MS of soxhlet and supercritical fluid extraction of hamster feces

Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds. SFC with flame ionization detection was used to compare Soxhlet extraction, off-line supercritical fluid extraction (SFE), and on-line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.     

Two-dimensional supercritical fluid chromatography/mass spectrometry for the enantiomeric analysis and purification of pharmaceutical samples

A new analytical two-dimensional supercritical fluid chromatography/mass spectrometry system (2D SFC/SFC/MS) has been designed and implemented to enhance the efficiency and quality of analytical support in drug discovery. The system consists of a Berger analytical SFC pump and a modifier pump, a Waters ZQ 2000 mass spectrometer, a set of switching valves, and a custom software program. The system integrates achiral and chiral separations into a single run to perform enantiomeric analysis and separation of a racemic compound from a complex mixture without prior clean up. The achiral chromatography in the first dimension separates the racemate from all other impurities, such as un-reacted starting materials and by-products. Mass-triggered fractionation is used to selectively fractionate the targeted racemic compound based on its molecular weight. The purified racemate from the achiral chromatography in the first dimension is then transferred to the chiral column in the second dimension to conduct the enantiomeric separation and analysis. A control software program, we coined SFC2D, was developed and integrated with MassLynx to retrieve acquisition status, current sample information, and real time mass spectrometric data as they are acquired. The SFC2D program also monitors the target ion signal to carry out mass-triggered fractionation by switching the valve to fractionate the desired peak. The 2D SFC/SFC/MS system uses one CO(2) pump and one modifier pump for both first and second dimension chromatographic separations using either gradient or isocratic elution. Similarly, a preparative 2D SFC/SFC/MS system has been constructed by modifying an existing Waters preparative LC/MS system. All components except the back pressure regulator are from the original LC/MS system. Applications of the 2D SFC/SFC/MS methods to the separation and the analysis of racemic pharmaceutical samples in complex mixtures demonstrated that an achiral separation (in first dimension) and a chiral separation (in second dimension) can be successfully combined into a single, streamlined process both in analytical and preparative scale.     

Extraction of gossypol

The conditions for the extraction of gossypol from cottonseed flakes and from isolated gossypol glands have been investigated. It has been established that the amount of gossypol extracted by hexane is affected mainly by the degree of stirring, the moisture content, the material, and the temperature. By steeping the flakes first with concentrated miscella and then with hexane it is possible to extract about 60–65% of the gossypol. It has been shown that hexane and miscella extract practically no gossypol either from dry or from moistened gossypol glands, and only acetone extracts it almost completely.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 157–160, March–April, 1980.     

Packed column supercritical fluid chromatography of a peroxysome proliferator-activating receptor agonist drug. Achiral and chiral purity of substance, formulation assay and its enantiomeric purity

This paper describes packed column supercritical fluid chromatography (SFC) for the analysis of a peroxysome proliferator-activating gamma-receptor agonist that is a carboxylic acid. Evaluation of conditions for the separation of this candidate drug and related compounds in bulk substance is described. A Chiralcel OD column was used for this purpose due to its high selective retention of related substances and relative inertness, though the enantioselectivity was negligible, with methanol as polar modifier. A high enantioselectivity was obtained on Chiralpak AD and it was possible to determine the enantiomeric purity within 10 min on a 5 cm short column. Both the achiral and the chiral systems were run without acid additive in the mobile phase and the level of detection of impurities by area was about 0.1%. For the analysis of samples dissolved in water, without any isolation step, 2-propanol was used as modifier. Due to the column surface activity, evidently generated by injected water, citric acid 1 mM was included as additive in the 2-propanol in order to maintain symmetric and undistorted peak shape. The detection limit for the assay was 21 microg mL(-1) (50 nmol mL(-1)) for 5 microL injected (R.S.D. 6.4%, n = 8). A 5 cm short Chiralcel OD column was used. Determination of enantiomeric purity of the drug in aqueous samples required increased sensitivity. The sample was acidified and extracted into a small volume of 1-pentanol, out of which 25 microl was analyzed by SFC. The minor enantiomer at the 3% (w/w) level added could be confirmed. Its ratio remained constant during the procedure as measured relative to a reference solution in organic media.     

Analysis of chlortetracycline by high performance liquid chromatography with postcolumn alkaline-induced fluorescence detection.

A high performance liquid chromatographic method for the analysis of chlortetracycline (CTC) using postcolumn fluorescence detection has been developed. After chromatographic separation of CTC on a polystyrene-divinylbenzene copolymer column, a highly fluorescent derivative isochlortetracycline (iso-CTC) was formed postcolumn in an on-line reaction coil with the addition of 25% NaOH (w/v). Chromatographic separation was achieved on a PRP-1 column, 15 cm x 4.6 mm, with 27:73 acetonitrile:0.2% perchloric acid (v/v), at 1.0 mL/min. Fluorescence derivatization was achieved by the on-line addition of 25% NaOH (w/v), at a flow rate of 0.2 mL/min, into the column eluant in a post-column reaction coil. The reaction coil was 9 m of teflon (1/16 in o.d., 0.3 mm i.d.) knitted into a six-sided coil. The fluorescent derivative was detected at lambda ex 355 nm and lambda em > 389 nm. Using this method after a simple sample cleanup, CTC can be detected in milk at 0.04 micrograms/mL, which is comparable to that obtained by microbiological assays. The detection method was linear between 0.02 micrograms/mL and 4 micrograms/mL. Because of the chromatographic separation, the method is more selective than microbiological assays and more sensitive than ultraviolet detection. With the chromatographic system described, the keto tautomeric forms of CTC and 4-epi-CTC are separated in a system which minimizes their formation on-column. In acidic aqueous organic solutions, the keto tautomer of CTC is the only product formed to any significant amount.     

SFC Instrument Modification to Allow Greater Flexibility in Method Development by Generating Mixtures of Solvents and Modifiers On-Line for Mobile Phase B Optimization

A binary supercritical fluid chromatography (SFC) system was further modified by the addition of a quaternary HPLC pump. The flow outlet of this pump was connected to the flow inlet of the existing modifier pump (“pump B”) by way of a custom-designed reservoir in such a way that blends of methanol with up to three additional solvents and/or additives could be delivered to pump B on-the-fly. Small amounts of modifiers (0.1–5 %) are typically mixed with mobile phase B in SFC to improve either the peak shape or to optimize the selectivity of the separation. As the critical influence of these modifiers on the separation of complex mixtures cannot a priori be predicted, incremental changes in mobile phase B compositions typically have to be evaluated on a trial-and-error basis. The instrumental modifications described in this paper eliminate the need to prepare these combinations off-line and the concomitant time requirement to re-purge supply and de-gasser solvent lines with each change in composition. By eliminating these steps, a significantly decrease in the overall SFC method development time can be achieved. Furthermore, such an on-line arrangement allows for greater flexibility in method development, that is, in the “fine-tuning” of the method once the stationary phase and gradient conditions have been established.

     

Rapid and high resolution capillary supercritical fluid chromatography (SFC) and SFC/MS of trichothecene mycotoxins

The potential application of capillary column supercritical fluid chromatography (SFC) and SFC/mass spectrometry (SFC/MS) for the separation and analysis of mycotoxins of the trichothecene group was examined. Trichothecenes present significant analytical problems for both gas and liquid chromatography with a major difficulty for the latter being the lack of sufficiently sensitive and selective detectors. Supercritical carbon dioxide mobile phases at temperatures up to 100 degrees C were used with deactivated fused silica columns coated with crosslinked stationary phases. Separations were obtained under pressure ramped conditions using long (15 m) 50-micron i.d. columns for several trichothecenes (diacetoxyscirpenol, deoxynivalenol, and T-2 toxin) and related higher molecular weight macrocyclic (roridin and verrucarin) trichothecenes. In addition, new rapid pressure programming techniques with short (less than 2m) 25- to 50-micron i.d. capillary columns were used to obtain fast separations in as little as 1 min. SFC/MS with ammonia chemical ionization provided high selectivity and sensitive detection (with approximately 1-pg detection limits) for trichothecene mixtures. The extension to complex sample matrices is discussed and the application of selective MS/MS detection is demonstrated.