Influence of Modifiers on Supercritical Fluid Chromatography (SFC) and Supercritical Fluid Extraction (SFE), Part I

It is important to understand the mechanism and implications of different modifiers on analytical and preparative processes under chromatography with supercritical fluids (SFs) and under extraction with SFs. Supercritical fluid chromatography (SFC) and supercritical fluid extraction are generally carried out with neat supercritical carbon dioxide (SCCO2) or with SCCO2 containing modifiers (or cosolvents), especially for strongly polar compounds. For example, methanol is added as a cosolvent/modifier to SCCO2 for the extraction/separation of polar compounds. This paper discusses the influence of the modifier on the colligative properties of the principal mobile phase, which may define the situation in the total mobile phase in a chromatography column or in parts of a column under SFC. No colligative behavior of solutions reflects individual properties of the solutes. Their cross-interactions with solvents are discussed.

Influence of Modifiers, Extractants, and Trappers on Lipid Composition with Liquids in Standard State Extraction, Supercritical Fluid Extraction and Trapping by Supercritical Fluid Extraction, Part II

Modifiers have a broad array of influences on extraction with liquids in standard state, supercritical fluid extraction (SFE), trapping by SFE and supercritical fluid chromatography (SFC). They can significantly change the qualitative and quantitative results. Quantitative and qualitative results can be influenced by different extractants and modifiers in different ways as it was shown by Brondz et al. at 2007 in “The real nature of the indole alkaloids in Cortinarius infractus: Evaluation of artifact formation through solvent extraction method development”, J. Chromatography A, 1148, 1-7. The choice of correct extractant, modifier, and trapper to the bulk mobile phase for supercritical fluids (SFs) or for liquids in subcritical or in the liquids in standard state is a challenge in any extraction procedure. This is the second paper in a sequence that describes the influence of extractants and modifiers on the performance of SFs and results of extraction with liquids in standard state and SFE. Here, attention is given to possible mistakes in qualitative and quantitative results by poor understanding of the influence of extractants, modifiers, and trappers on extraction and trapping process by a careless choice of extractant, modifier, and trapper for extraction with liquids in standard state and SFE. The SF chosen for discussion in the paper is CO2. However, similar effects can be observed with use of other SFs and fluids in subcritical and standard states. In this paper, the discussion of lipids, fatty and carboxylic acids have been chosen as target analytes for extraction, trapping and analysis. Some examples from extraction with liquids in the standard state and trapping in the supercritical state (collection) have been furnished with the wrong extractant, modifier, or trapper which is presented for illustration of inappropriate choice of extractants, modifiers, and trappers.

Simultaneous determination of amino acids in different teas using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) was developed to simultaneously determine 11 amino acids in different types of tea (green teas, Oolong tea, black tea and Pu-erh tea). The separation conditions for the analysis of the selected amino acids including the column type, temperature and backpressure as well as the type of additive, were carefully optimized. The best separation of the 11 amino acids was obtained by adding water (5%, v/v) and trifluoroacetic acid (0.4%, v/v) to the organic modifier (methanol). Finally, the developed SFC-MS method was fully validated and successfully applied to the determination of these amino acids in six different tea samples. Good linearity (r ≥ 0.993), precision (RSDs≤ 2.99%), accuracy (91.95%-107.09%) as well as good sample stability were observed. The limits of detection ranged from 1.42 to 14.69 ng/mL, while the limits of quantification were between 4.53 and 47.0 ng/mL. The results indicate that the contents of the 11 amino acids in the six different tea samples are greatly influenced by the degree of fermentation. The proposed SFC-MS method shows a great potential for further investigation of tea varieties.

Advances of supercritical fluid chromatography in lipid profiling

Supercritical fluid chromatography(SFC) meets with great favor due to its high efficiency, low organic solvent consumption, and the specialty for the identification of the isomeric species. This review describes the advances of SFC in targeted and untargeted lipid profiling. The advancement of the SFC instruments and the stationary phases are summarized. Typical applications of SFC to the targeted and untargeted lipid profiling are discussed in detail. Moreover, the perspectives of SFC in the lipid profiling are also proposed. As a useful and promising tool for investigating lipids in vitro and in vivo, SFC will predictably obtain further development.

THEORY FOR STEP AND PULSE METHOD OF SUPERCRITICAL FLUID CHROMATOGRAPHY

1 INTRODUCTIONSupercritical fluid chromatography(SFC),employing supercritical fluid as mobilephase,originated in the 1960’s [1-4].Since 1980’s extensive research work has beenperformed on SFC,chiefly for analytical purposes [5,6].SFC was then adopted for thedetermination of thermodynamic properties such as partial molar volume,and partialmolar enthalpy of solutes in both mobile phase and stationary phase and the solutedistribution coefficient between two phases [7- 11].Partial molar properties can be de-

In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China

We re-evaluate the Raman spectroscopic quantification of the molar ratio and pressure for CH4–CO2 mixtures.Firstly,the Raman quantification factors of CH4 and CO2 increase with rising pressure at room temperature,indicating that Raman quantification of CH4/CO2 molar ratio can be applied to those fluid inclusions(FIs)with high internal pressure(i.e.,>15 MPa).Secondly,the v1(CH4)peak position shifts to lower wavenumber with increasing pressure at constant temperature,confirming that the v1(CH4)peak position can be used to calculate the fluid pressure.However,this method should be carefully calibrated before applying to FI analyses because large discrepancies exist among the reported v1(CH4)-P curves,especially in the highpressure range.These calibrations are applied to CH4-rich FIs in quartz veins of the Silurian Longmaxi black shales in southern Sichuan Basin.The vapor phases of these FIs are mainly composed of CH4 and minor CO2,with CO2 molar fractions from4.4%to 7.4%.The pressure of single-phase gas FI ranges from 103.65 to 128.35 MPa at room temperature,which is higher than previously reported.Thermodynamic calculations supported the presence of extremely high-pressure CH4-saturated fluid(218.03–256.82 MPa at 200°C),which may be responsible for the expulsion of CH4 to adjacent reservoirs.

Separation of Enantiomers of Clopidogrel on Chiral Stationary Phases by Packed Column Supercritical Fluid Chromatography

A packed column supercritical fluid chromatography (SFC) method for the separation of clopidogrel enantiomers on a chiral stationary phase and CO2 with modifier as mobile phase has been developed at an analytical scale. Among 11 different 2 stationary phases the Chiral cel OD-H column showed by far the best separation properties. The influence of different modifiers, injection solvents, temperature, and pressure, and density of the fluid, respectively, on the separation behaviour has been studied. It was found that the separation behaviour strongly depends on the type of modifier and the modifier content. Temperature and pressure are of less influence.

Evolution of Diagenetic Fluid of the Dawsonite-Bearing Sandstone in the Jiyang Depression,Eastern China

Based on the petrology,isotope geochemistry and fluid inclusions analysis,we established the evolutionary mode of the diagenetic fluid of dawsonite-bearing sandstone in the Jiyang Depression.Dawsonite-bearing sandstone is characterized by double injection of CO_(2)and oil-gas in the Jiyang Depression that have experienced a relatively complex diagenetic fluid evolution process.The diagenetic sequence of secondary minerals involves secondary enlargement of quartz,kaolinite,first-stage calcite,dawsonite,second-stage calcite,ferrocalcite,dolomite and ankerite.Hydrocarbon charging in the dawsonite-bearing sandstone occurred at around 2.6–0 Myr.The CO_(2)charging event occurred during Dongying tectonism,forming the Pingfangwang CO_(2)gas reservoir,which provided an abundant carbon source for dawsonite precipitation.Carbon and oxygen isotopic compositions of dawsonite demonstrate that CO_(2)forming the dawsonite was of an inorganic origin derived from the mantle,and that water mediating the proc-ess during dawsonite precipitation was sequestered brine with a fluid temperature of 82℃.The evolutionary sequence of the diagenetic fluid in the dawsonite-bearing sandstone was:alkaline syngenetic fluids,weak alkaline fluids during organic acid forma-tion,acidic fluids in the early stage of CO_(2)injection,alkaline fluids in the late stage of CO_(2)injection,and weak alkaline fluids during oil and gas charging.The mode indicates an increase in-HCO_(3)because of the CO_(2)injection,and the loss of Ca^(2+)and Mg^(2+)due to the precipitation of carbonate minerals.Therefore,the evolutionary mode of diagenetic fluids is in good agreement with high HCO_(3)^(-),low Ca^(2+)and low Mg^(2+)composition of the present formation water in the dawsonite-bearing sandstone.

Current research into the use of supercritical CO2 technology in shale gas exploitation

The use of supercritical CO2 for shale gas extraction is a promising new technology.This paper explores current research into this process,looking at analysis of the mechanism of CH4 displacement in nanoporous shale,the positive and negative effects accompanying its use for sequestration as well as organic extraction,the migration of elements and the swelling process,and the macro and micro control mechanisms involved in permeability enhancement in reservoirs.Fruitful directions for future research are also considered through comparison with hydraulic fracturing.The research findings indicate that ScCO2 fluid replacement can be used to increase gas production and seal up greenhouse gases as an effective,clean and safe method of shale gas exploitation.It is particularly effective for promoting the desorption of CH4 in shale reservoirs that have developed fine neck-wide body pores,and the subtle structural changes effected by ScCO2 fluid in sensitive minerals in reservoirs with a high brittle mineral content also have a positive effect on permeability and storage capacity.The adsorption process has been characterized as consisting of three stages:short-term shrinkage,slow swelling,and stability;an expansion equation has been proposed for CO2/CH4 that incorporates competitive adsorption,collision desorption,and impingement re-adsorption.ScCO2 fracturing has been found to be more effective than hydraulic fracturing for dense reservoirs and more effective at linking up pore-micro-fissure-fracture systems.

Kinetics of Extraction of <i>β</i>-Carotene from Tray Dried Carrots by Using Supercritical Fluid Extraction Technique

β-carotene acts as an antioxidant and is receiving growing interest due to its ability as protecting agent against heart diseases, cancer and strengthening effect on red blood cells. The main aim of this work was to study the kinetics of the supercritical fluid extraction of β-carotene from tray dried carrots at 40℃, 50℃ and 55℃ and 30, 35 and 40 MPa at SC-CO2 flow rate of 2.0 L/min for extraction time of up to 6 h. It was observed that the concentration of β-carotene in the extract increased with pressure, temperature and extraction time. The results indicated that yield was found to be maximum at 45℃ and 35 MPa at 2 L/min SC-CO2 flow rate. Concentration of β-carotene in the extract increased with SC-CO2 flow rate. Weibull distribution model described adequately the kinetics of extraction of β-carotene from carrots.

“Special Issue—Supercritical Fluids” Literatures on Dyeing Technique of Supercritical Fluid Carbon Dioxide

The supercritical fluid is used extensively, especially in substance extraction. The extraction of many substances has reached the economic-scale industrial bulk production stage. However, the research on the wastewater-free dyeing technique replacing water as dissolvent is still at a development stage. This study introduced the development situation of supercritical fluid dyeing technique, and described the evolution of stock dyeing, measurement of solubility of dye, studies of dyeing kinetics and instrument application studies, in order to provide related data for relevant studies in further development of this technique.

The Equilibrium Thermal Physics of Supercritical Fluids

To discover particular features of pure supercritical fluids, important for the supercritical fluid extraction and cleaning technologies, the preprocessed and generalized experimental data from the US National Institute of Standards and Technology (NIST) online database have been analyzed. The soft transition between gas-like and liquid-like structures in pure supercritical fluids has been considered in comparison with the abrupt vapor-liquid phase transition. A rough, diffused and boiling boundary between these structures in conditions of extra high gravity is opposed to a flat vapor-liquid boundary at a moderate gravity. The model for molecular diffusivity in carbon dioxide at temperatures near the critical temperature discovers its proportionality to the monomer fraction density. The cluster fraction based model for small molecular weight solids’ solubility in supercritical fluids has been suggested and successfully compared with the well-known experimental results for the solubility of silica in water.The model shows that at growing pressure the dissolution process has already startedin a real gas and discovers the cluster fractions’ role in the solubility process.

Parametric resonance of axially functionally graded pipes conveying pulsating fluid

Based on the generalized Hamilton's principle,the nonlinear governing equation of an axially functionally graded(AFG)pipe is established.The non-trivial equilibrium configuration is superposed by the modal functions of a simply supported beam.Via the direct multi-scale method,the response and stability boundary to the pulsating fluid velocity are solved analytically and verified by the differential quadrature element method(DQEM).The influence of Young's modulus gradient on the parametric resonance is investigated in the subcritical and supercritical regions.In general,the pipe in the supercritical region is more sensitive to the pulsating excitation.The nonlinearity changes from hard to soft,and the non-trivial equilibrium configuration introduces more frequency components to the vibration.Besides,the increasing Young's modulus gradient improves the critical pulsating flow velocity of the parametric resonance,and further enhances the stability of the system.In addition,when the temperature increases along the axial direction,reducing the gradient parameter can enhance the response asymmetry.This work further complements the theoretical analysis of pipes conveying pulsating fluid.

Demonstration of a small‐scale power generator using supercritical CO_(2)

The supercritical CO_(2)(sCO_(2))power cycle could improve efficiencies for a wide range of thermal power plants.The sCO_(2)turbine generator plays an important role in the sCO_(2)power cycle by directly converting thermal energy into mechanical work and electric power.The operation of the generator encounters challenges,including high temperature,high pressure,high rotational speed,and other engineering problems,such as leakage.Experimental studies of sCO_(2)turbines are insufficient because of the significant difficulties in turbine manufacturing and system construction.Unlike most experimental investigations that primarily focus on 100 kW‐or MW‐scale power generation systems,we consider,for the first time,a small‐scale power generator using sCO_(2).A partial admission axial turbine was designed and manufactured with a rated rotational speed of 40,000 rpm,and a CO_(2)transcritical power cycle test loop was constructed to validate the performance of our manufactured generator.A resistant gas was proposed in the constructed turbine expander to solve the leakage issue.Both dynamic and steady performances were investigated.The results indicated that a peak electric power of 11.55 kW was achieved at 29,369 rpm.The maximum total efficiency of the turbo‐generator was 58.98%,which was affected by both the turbine rotational speed and pressure ratio,according to the proposed performance map.

Correlation and Prediction of the Solubility of Solid Solutes in Chemically Diverse Supercritical Fluids Based on the Expanded Liquid Theory

For the proper design of any extraction procedure based on supercritical solvents, it is essential to have a sound knowledge of the solubility data of different compounds and the accurate way to represent it. The solute’s solubility in a supercritical solvent is dependent on the solute, the solvent, and the operating conditions (temperature and pressure). Developing a comprehensive experimental data set is an onerous task and time consuming and, thus, the incentive to develop predictive tools is substantial. In this paper, a technique is presented and tested to correlate and predict solute’s solubility in different supercritical fluids with a methodology based on the expanded liquid theory, in which the solid-fluid equilibrium is modeled using the local composition model of UNIQUAC in which the interaction parameters are related to the solvent reduced density with empiric equations. The most advantages of this model include: it does not require the knowledge of critical properties and sublimation pressure of solid solutes and does take into account the binary interaction between solid solute and solvent. The evaluation of the proposed model capabilities is done by testing it on a large data base consisting of experimental solubility data taken from literature of 33 binary systems solid-SC fluid. The results obtained for both correlation and prediction show good agreement with the experimental data used. For the comparison we have considered some literature models that account for effect of the system conditions (temperature and pressure) in addition to the sublimation pressure of the solute through their introduction of the enhancement factor and a model based on a modified Peng-Robinson equation of state.

Multi-objective optimization and evaluation of supercritical CO_(2) Brayton cycle for nuclear power generation

The supercritical CO_(2) Brayton cycle is considered a promising energy conversion system for Generation IV reactors for its simple layout,compact structure,and high cycle efficiency.Mathematical models of four Brayton cycle layouts are developed in this study for different reactors to reduce the cost and increase the thermohydraulic performance of nuclear power generation to promote the commercialization of nuclear energy.Parametric analysis,multi-objective optimizations,and four decision-making methods are applied to obtain each Brayton scheme’s optimal thermohydraulic and economic indexes.Results show that for the same design thermal power scale of reactors,the higher the core’s exit temperature,the better the Brayton cycle’s thermo-economic performance.Among the four-cycle layouts,the recompression cycle(RC)has the best overall performance,followed by the simple recuperation cycle(SR)and the intercooling cycle(IC),and the worst is the reheating cycle(RH).However,RH has the lowest total cost of investment(C_(tot))of$1619.85 million,and IC has the lowest levelized cost of energy(LCOE)of 0.012$/(kWh).The nuclear Brayton cycle system’s overall performance has been improved due to optimization.The performance of the molten salt reactor combined with the intercooling cycle(MSR-IC)scheme has the greatest improvement,with the net output power(W_(net)),thermal efficiencyη_(t),and exergy efficiency(η_(e))improved by 8.58%,8.58%,and 11.21%,respectively.The performance of the lead-cooled fast reactor combined with the simple recuperation cycle scheme was optimized to increase C_(tot) by 27.78%.In comparison,the internal rate of return(IRR)increased by only 7.8%,which is not friendly to investors with limited funds.For the nuclear Brayton cycle,the molten salt reactor combined with the recompression cycle scheme should receive priority,and the gas-cooled fast reactor combined with the reheating cycle scheme should be considered carefully.

PURIFICATION OF BILIRUBIN AND MICRO-PARTICLE FORMATION WITH SUPERCRITICAL FLUID ANTI-SOLVENT PRECIPITATION

1 INTRODUCTIONA supercritical fluid is one existing at temperatures and pressures above its criticalpoint values(T_c,p_c) [1].Supercritical fluid has unconventional thermophysical prop-erties,exhibiting higher density,greater compressibility,lower viscosity between the gasand liquid extremes.Its solute binary diffusion coefficient is considerably higher thanthat in liquids[2-4].Supercritical fluid extraction(SFE)has been suggested as a viablealternative to other separation technologies.

Separation of Sesamin and Sesamolin by a Supercritical Fluid-Simulated Moving Bed

This work shows how the sesamin and sesamolin in sesame seed can be extracted, enriched and purified by the related technologies of supercritical carbon dioxide. Sesame oil is first obtained from the sesame seeds by supercritical carbon dioxide extraction (SFE);lignans in the oil are enriched and precipitated as the top product by supercritical fluid fractionation technology (SFF);the crude lignans are then separated by supercritical fluid-simulated moving bed chromatography (SF-SMB) to obtain pure sesamin and sesamolin. The simulated moving bed is a continuous chromatography;the use of supercritical carbon dioxide as the desorbent simplifies the downstream treatment. By experimental validation, this work also shows that replacing liquid by SF as the desorbent for the SMB automatically creates a gradient operation for the SMB and enlarges the separable range of the operating conditions. Both the design and operation of the SF-SMB are introduced in this paper. The application of SF-SMB to the separation of sesamin and sesamolin provides a novel example for demonstrating the diversity of SF and the potential applications for the production of natural products and the development of botanical drugs.

Effect of process parameters on the recrystallization and size control of puerarin using the supercritical fluid antisolvent process

The purpose of this study was to investigate the influence of the supercritical CO2 processing on the particle size and morphology of puerarin crystals. The process parameters included solvents, temperature, pressures, antisolvent times, addition volumes, antisolvent addition rates and solute concentrations. After being processed, the dramatic reduction of the dimensions and the change of the crystal shape were noticed. Decreasing the antisolvent addition rate, increasing the temperature and the addition volume below 50 ml led to a decrease in size. The new crystal of puerarin generated at the optimal conditions was 30.34 μm.The solvent of methanol and the concentration of 60 mg/ml were found to determine the type and degree of crystallinity of particles. These results showed that this process has the potential to produce a drug recrystallization product with newly generated crystal forms and the size of drug particles could be controlled through the tuning of various experimental conditions.

超临界流体萃取气相色谱法测定鱼肉中的毒死蜱残留

建立了利用离线超临界CO2萃取气相色谱(SFE-GC)测定鱼肌肉中毒死蜱残留量的分析方法.超临界CO2萃取鱼肌肉中毒死蜱的适宜条件为: 温度100℃,压力41.370 MPa,CO2流量为1 mL/min,动态萃取30 min,静态萃取时间15 min,调节剂甲醇(添加量0.5 mL),收集液丙酮.最小检出量为0.01 ng;添加回收率为77.3%～105.1%;相对标准偏差(RSD)为2.4%～15.4%,符合残留分析要求.全程分析时间小于2 h.