Neat CO2 Research Articles

Supercritical CO2 and Subcritical H2O Analysis Instrument: Automated Lipid Analysis for In Situ Planetary Life Detection.

The search for extraterrestrial extant or extinct life in our Solar System will require highly capable instrumentation and methods for detecting low concentrations of biosignatures. This paper introduces the Supercritical CO2 and Subcritical H2O Analysis (SCHAN) instrument, a portable and automated system that integrates supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), and subcritical water extraction coupled with liquid chromatography. The instrument is compact and weighs 6.3 kg, making it suitable for spaceflight missions to planetary bodies. Traditional techniques, such as gas chromatography-mass spectrometry (MS), face challenges with involatile and thermally labile analytes, necessitating derivatization. The SCHAN instrument, however, eliminates the need for derivatization and cosolvents by utilizing neat supercritical CO2 with water as an additive. This SFE-SFC-MS method gives efficient lipid biosignature separations with median detection limits of 10 pg/g (ppt) for fatty acids and 50 pg/g (ppt) for sterols. Several free fatty acids and cholesterol were among the detected peaks in biologically lean samples from the Atacama Desert, demonstrating the instrument's potential for in situ life detection missions. The SCHAN instrument addresses the challenges of conventional systems, offering a compact, portable, and spaceflight-compatible tool for the analysis of organics for future astrobiology-focused missions.

A step closer to sustainable CO2 conversion: Limonene carbonate production driven by ionic liquids

This work aims to advance the biocarbonate concept by developing the first process to produce limonene carbonate based on ionic liquids (ILs). Conventional petroleum-derived cyclic carbonates are recognized products partially composed of CO2 with the main drawback of the high energy consumption that imposes epoxide production. In contrast, natural epoxidable compounds, such as terpenes, stand out in the literature as a more sustainable open research line to enable CO2 conversion processes with better sustainable indicators. Limonene, an abundant natural compound, is identified as a key terpene in the aforementioned discussion. Ammonium-based ILs are experimentally selected and optimized, after covering massive anion and cation substituent tuning, achieving high selectivity and competitive yields to limonene carbonate. The reaction-extraction platform concept, which recovers the catalyst by liquid-liquid extraction, is envisioned and developed using a rational experimental-computational approach. The work concludes with a novel process to effectively produce limonene carbonate by using an IL catalyst and water as an extracting solvent. Ultimately, taking advance of the process simulation, a CO2 emissions assessment was conducted. Using renewable raw materials enhances the sustainability of CO2 conversion to cyclic carbonate, reducing global warming impact compared to fossil-based epoxides. However, limonene extraction and epoxidation have a tangible impact on the overall result of CO2 balance, turning efforts outside battery limits of the CO2 conversion process in the search of a limonene carbonate production line with negative neat CO2 emissions that may change the paradigm in the fixation of CO2 through cycloaddition reactions.

Spatiotemporal X-Ray Imaging of Neat and Viscosified CO2 in Displacement of Brine-Saturated Porous Media

Summary CO2 storage in saline aquifers may contribute to a 90% share in preventing emissions to the atmosphere. Due to low CO2 viscosity at the subsurface often found in supercritical (sc) conditions, the injected CO2 may spread quickly at the formation top and increase the probability of leakage. This work relates to improved CO2 storage in saline aquifers by effective viscosification of the sc-CO2 at very low concentrations of engineered oligomers and the effectiveness of slug injection of viscosified CO2 (vis-CO2). We present the results from X-ray computed tomography (CT) imaging to advance the understanding of two-phase CO2-brine flow in porous media and firmly establish the transport mechanisms. X-ray CT imaging of displacement experiments is conducted to quantify the in-situ sc-CO2 saturation spatiotemporally. In neat CO2 injection, gravity override and adverse mobility ratio may result in early breakthrough and low sweep efficiency. We find cumulative brine production from the fraction collector to be lower than X-ray CT imaging at 2 pore volume (PV) injection. The difference between the two is attributed to the solubility of the produced water in the produced CO2 at atmospheric pressure. We show that when the solubility is accounted for, there is a good agreement between direct measurements and in-situ saturation results. There are three reports (two by the same group) that oligomers of 1-decene (O1D) with six repeat units may have marginal CO2 viscosification. The majority of published work by other groups shows that O1D with six repeat units and higher are effective CO2 viscosifiers. In the past, we have demonstrated the effectiveness of an O1D in the displacement of brine by CO2 at a concentration of 1.5 wt%. The effectiveness is examined and identified by three different methods. In this work, we show that the same oligomer is effective at a low concentration of 0.6 wt%. The oligomer slows the breakthrough by 1.6 times and improves the brine production by 34% in the horizontal orientation. X-ray CT imaging results reveal that such a large effect may be from the increase in the interfacial elasticity. We also show that there is no need for continuous injection of the oligomer. A slug of 0.3 PV injection (PVI) of vis-CO2 followed by neat CO2 injection has the same effectiveness as the continuous injection of the vis-CO2. In this work, we also demonstrate the effectiveness of a new engineered molecule at 0.3 wt% that may increase residual trapping by about 35%. The combination of mobility control and residual brine saturation reduction is expected to improve CO2 storage by effective viscosification with low concentrations of oligomers.

Understanding the CO2 capture potential of tetrapropylammonium-based multifunctional deep eutectic solvent via molecular simulation

A multiscale theoretical study on the suitability of the bifunctional hydrophobic Deep Eutectic Solvent based on tetrapropylammonium chloride and acetic acid with ethanolamine is reported. Density Functional Theory quantum calculations along with classical Molecular Dynamics simulations provide a nanoscopic characterization of the properties of the studied sorbent in terms of intermolecular forces and liquid phase structuring and the characterization of the mechanism of CO2 absorption considering gas – liquid phase interfaces for neat CO2 and a realistic flue gas mixture. Results in this paper characterize the evolution of CO2 into liquid phases as well as the changes produced in the fluid upon gas capture through hydrogen bonding, void occupation and molecular clustering. The possible effect of having two different types of functionalities in the sorbent, amine and hydroxyl groups, which may lead to possible chemical and/or physical sorption is analyzed, considering their possible competing in CO2 capture. The reported study provides the first characterization of multifunctional Deep Eutectic Solvents for carbon capture from complex realistic gas mixtures.

Viscosification of CO2 to improve subsurface storage — A modeling study

In this work, we numerically investigate the potential benefits of a recently proposed functional molecule that can both significantly increase the viscosity of CO2 and reduce the residual water saturation in the context of CO2 storage in subsurface aquifers. We model different degrees of CO2 viscosification in field-scale formations at both shallow and greater depths, consider a range of permeabilities from 100 md to 2,000 md, and both homogeneous and highly heterogeneous formations. To quantify the impacts of CO2 viscosification, we track multiple domain-integrated quantitative measures such as CO2 tip velocity and dispersion widths. In all scenarios, we find that CO2 viscosification increases the total amount of CO2 retained but the degree of improvement varies. Moreover, the fraction of solubility trapping versus structural trapping is highest for neat CO2. These modeling results can inform stakeholders in CO2 viscosification technology for future large-scale CO2 storage projects.

A DFT and Matrix–Isolation IR/UV-Visible Study of High-Coordinated Lanthanide-CO Complexes

Recent joint mass spectrometric and IR photodissociation studies have provided proof on the existence of octa-coordinated ionic lanthanide-carbonyl complexes under those extreme gaseous conditions. In contrast, in older literature concerning cryogenic studies of neutral Ln(CO)x species, the highest coordination was assigned to hexa-coordinated Ln(CO)6 molecules. The present study aims to clarify the above controversy using matrix isolation spectroscopy and DFT calculations. In order to ensure the maximum possible coordination, the Ln(CO)x complexes were synthesized in neat CO cryogenic matrices at 10 K and were investigated by infrared and UV-visible spectroscopy. The formed complexes were identified on the basis of the characteristic CO stretching frequencies of the ground-state molecules predicted by DFT calculations. Our joint experimental–theoretical analysis confirmed the preference of octa-coordinated Ln(CO)8 complexes in cryogenic neat CO matrices.

Improvement in CO2 geo-sequestration in saline aquifers by viscosification: From molecular scale to core scale

Carbon dioxide (CO2) storage in the subsurface is a viable approach to mitigate climate change by reducing anthropogenic greenhouse gas emissions. The unfavorable mobility ratio in brine displacement by CO2 would lead to poor sweep efficiency. In this investigation, the efficiency of an engineered CO2 oligomer viscosifier with about twenty repeat units of 1-decene is evaluated in mobility control and sweep efficiency improvement in drainage. We have performed brine displacement experiments in sandstone rock with supercritical CO2. The viscosifier at 1.5 wt% concentration increases the viscosity of supercritical CO2 by 4.8 folds at pressure of 3500 psi and temperature of 194 ˚F. We observe significant delay of CO2 breakthrough time by 2.6 ± 0.1 folds in a large number of experiments by viscosified CO2. The molecule does not have appreciable adsorption on the rock surface. The pressure drop from displacement of neat CO2 by viscosified CO2 at 1 PV injection provides the evidence of low adsorption. Molecular simulations are conducted to investigate adsorption. Low adsorption is a key measure of the effectiveness of the molecule. The results from molecular simulations agree with the experiments. In addition to viscosification, the novelty of the molecule is that there is a significant decrease in the residual brine saturation. Consequently, the residual trapping is also increased. The combination of decrease in residual brine saturation, and mobility control are expected to significantly improve the storage capacity through increase in residual trapping and sweep efficiency in CO2 storage in saline aquifers. As a result, CO2 storage may become more efficient.

Mathematical modeling of supercritical CO2 extraction of Monteverdia aquifolia Mart. Biral leaves: Simple models approaching

The supercritical extractions of Monteverdia aquifolia leaves were conducted using neat CO2 at different temperatures, CO2 flow rates, and pressures. The highest yield was obtained at 300 bar, 6 mL min-1, and 50 °C. In this condition, extraction kinetics were obtained using mixtures of supercritical CO2 with ethanol and ethyl acetate. Other studies have proven that leaves are a good source of bioactive and antioxidant compounds. In this way, seeking to better understand obtaining these extracts via the supercritical method, simplified mathematical models were tested regarding their performance to predict the extraction kinetics. Equilibrium isotherms obtained were analytically solved and coupled to a mass balance in the extractor resulting in five simplified models that describe the extraction kinetics. The accuracy of the models was tested in the prediction of the experimental yield and compared to the results of the classic Sovová model. Results obtained demonstrated All five simplified models were able to describe the experimental supercritical extraction, still provide insights, and conduct procedures, to solve problems or optimize a situation. The Halsey-type equilibrium model was the most accurate, even when compared to the Sovová model, with an R2 of 0.981 and a relative mean deviation of 9.7%. Considering that M. aquifolia extracts are already a reality in the herbal medicine industry, the data reported here may contribute to the dissemination of the extraction methodology, as well as to the more effective acquisition of the extract, with its biological effects preserved.

Valorization by compressed fluids of Arctium lappa seeds and roots as a sustainable source of valuable compounds

An example of a sustainable and renewable but highly underused biomass with considerable potential as a source of a wide spectrum of valuable compounds is Arctium lappa, also known as burdock. In this work the feasibility and efficiency of advanced techniques applying compressed fluids to recover value from burdock seeds and roots was examined, and the influence of operating conditions and solvents on the yield, quality and composition of the extracts obtained was studied. For the seeds, compressed propane at two temperatures and pressures (6–20) MPa, and either neat supercritical CO2 (scCO2) or scCO2 with a co-solvent were tested. For the roots, extractions with scCO2 and different polarities co-solvents were performed at two temperatures and pressure 20 MPa. Pressurized liquid extractions with ethanol, methanol, water and methanol/water at 15 MPa and 353.15 K were also tested. The extracts obtained were evaluated by extraction yield, total phenolic content and antioxidant activity, and compared with Soxhlet with organic solvents. The rich spectrum of valuables - fatty acids and phenolics of different chemical complexities was identified and quantified applying GC-FID, GC–MS, LC – MS/MS. The results of this extensive study demonstrate that compressed fluids techniques are effective for value added product generation from burdock seeds and roots biomass.

Structure and single particle dynamics of the vapour-liquid interface of acetone-CO2 mixtures

Molecular dynamics computer simulations of the liquid-vapour interface of acetone-CO2 mixtures are performed in the canonical (N,V,T) ensemble at 30 thermodynamic state points, ranging from 280 to 460 K and from about 10 to 116 bar, covering the entire composition range from neat CO2 to neat acetone. The molecules forming the first layer at the molecularly rough liquid surface as well as those of the next three subsurface molecular layers have been identified by the ITIM method, and the surface properties of the liquid phase are analyzed in a layer-wise manner. The arrangement of the molecules both within the macroscopic plane of the interface and along its normal axis, as well as their surface orientation and single particle dynamics at the liquid surface are analyzed in detail. It is found that, in accordance with their higher affinity to the vapour phase, CO2 molecules are enriched at the liquid surface, moreover, even within the surface layer they prefer to occupy positions that are more exposed to the bulk vapour phase than those preferred by acetone. In other words, within the molecularly wavy surface layer, CO2 molecules prefer to stay at the crests, while acetone molecules prefer to stay in the troughs. On the other hand, the lateral arrangement of the surface molecules is found to be more or less random. Both molecules prefer to stay perpendicular to the liquid surface, but this preference only involves the first molecular layer, and this preference is governed by the electrostatic interaction of the surface molecules. Both molecules perform considerable lateral diffusion at the liquid surface during their stay there, this diffusion being faster for the CO2 than for the acetone molecules, but not as much faster than in the bulk liquid phase.

Application of supercritical fluid extraction for extraction or enrichment of phospholipids in egg and dairy products: A review

Phospholipids (PLs) are polar lipids that are found in dairy products, egg, and oilseeds. They are amphiphilic in nature and find application in many foods as a functional ingredient. As PLs are distributed in food matrix in dilute form, attempts to concentrate the same by adopting suitable technical interventions have been widely investigated. One of the more successful approaches that have been reported is the application of supercritical fluid extraction (SCFE) to extract PLs using suitable cosolvents. The extraction protocol to extract PLs from dairy products and eggs using SCFE also includes a two‐step process, namely, separation of neutral lipids using neat CO2 followed by subsequent separation of polar lipids from the residue using cosolvent and CO2. This review is an attempt to compile information on dairy and egg PLs extracted using SCFE under varied operational factors. It is expected that the compilation will serve as resource for investigators working in this research area.Practical ApplicationsMilk fat processing results in valuable by‐products which can be suitably volarized to increase profitability through processing gains and reduce environmental footprints in dairy industry. The by‐products such as buttermilk, butter serum, ghee residue, and so forth can be tapped as potential sources for phospholipid (PL). Eggs have already been recognized as a good source of PLs, which are reported to have preventive effect on pathogens, cancer protective, anti‐inflammation and cardiovascular disease. Two challenges could be anticipated in the fractionation of PLs from egg and milk by‐products. First, extraction of lipids from substrate which include polar and neutral lipids. Second, separation of neutral and polar lipids from the lipid extract. Conventional methods of extraction involve many solvents for the wide range of lipids to be extracted, which often result in incomplete extraction. Supercritical fluid extraction (SCFE) technique is reported to be useful in extraction and separation of PLs from dairy and egg products. Process intervention strategies and optimization approaches have been undertaken by various researchers to quantify and improve extractability of PLs using SCFE. The paper is a compilation of the scientific information related to extraction of dairy and egg PLs using SCFE, which will serve as a knowledge resource for researchers working in related fields.

Effects of electrode material and frequency on carbon monoxide formation in carbon dioxide dielectric barrier discharge

The transformation of carbon dioxide (CO2) to carbon monoxide (CO) employing atmospheric pressure dielectric barrier discharge (DBD) cold plasma is reported. This work is carried out with an objective to re-utilize CO2 in the form of CO, which is extremely useful in various industries. Under the study, neat CO2 gas stream is used to investigate effective conditions for achieving high yields of CO using coaxial cylindrical tube type double and single dielectric DBD reactors. The different central electrodes for example Pyrex and bare metal such as Aluminium (Al), Copper (Cu) and Stainless steel (SS) along with common outer Pyrex tube combinations respectively in double dielectric (DD) and single dielectric (SD) surface reactors are used separately. DBD outlet products such as CO and leftover CO2 are analyzed and estimated with online gas chromatograph-flame ionization detector after separating them with a suitable GC column followed by their conversion to methane using Ni-catalyzed methaniser. Furthermore, the investigation of CO production is made with gas residence time (CO2 flow), applied electric field and working frequency variations. Optical emission spectroscopy (OES) for mechanistic details and power measurement for quantitative analysis are carried out. The production of CO from 200 to 70,000 ppmv is observed with DD reactor respectively at 50 Hz and 19 kHz frequencies. In case of SD reactors, the CO yields obtained are higher with the utmost CO concentration ∼130,000 ppmv using Cu central electrode following as a minimum 13 % of CO2 transformation.

Pressurized carbon dioxide as a potential tool for decellularization of pulmonary arteries for transplant purposes

Vascular bio-scaffolds produced from decellularized tissue offer a promising material for treatment of several types of cardiovascular diseases. These materials have the potential to maintain the functional properties of the extracellular matrix (ECM), and allow for growth and remodeling in vivo. The most commonly used methods for decellularization are based on chemicals and enzymes combinations, which often damage the ECM and cause cytotoxic effects in vivo. Mild methods involving pressurized CO2-ethanol (EtOH)-based fluids, in a supercritical or near supercritical state, have been studied for decellularization of cardiovascular tissue, but results are controversial. Moreover, data are lacking on the amount and type of lipids remaining in the tissue. Here we show that pressurized CO2-EtOH-H2O fluids (average molar composition, ΧCO2 0.91) yielded close to complete removal of lipids from porcine pulmonary arteries, including a notably decrease of pro-inflammatory fatty acids. Pressurized CO2-limonene fluids (ΧCO2 0.88) and neat supercritical CO2 (scCO2) achieved the removal of 90% of triacylglycerides. Moreover, treatment of tissue with pressurized CO2-limonene followed by enzyme treatment, resulted in efficient DNA removal. The structure of elastic fibers was preserved after pressurized treatment, regardless solvent composition. In conclusion, pressurized CO2-ethanol fluids offer an efficient tool for delipidation in bio-scaffold production, while pressurized CO2-limonene fluids facilitate subsequent enzymatic removal of DNA.

Usual, unusual and unbelievable retention behavior in achiral supercritical fluid chromatography: Review and discussion

Retention rules are well known in liquid chromatography. For the mobile phase composition, retention decreases when adding organic solvent to water for reversed-phase or increasing water proportion for hydrophilic interaction liquid chromatography, and a decrease in temperature usually increases retention. For supercritical fluids, the fluid density, which is related to temperature and column back-pressure, is significant for neat CO2 and with low percentages of organic modifiers, i.e. with compressible mobile phases. The increase in the modifier percentage reduces the fluid compressibility, leading to retention behaviors close to those observed with liquid mobile phases, for instance for temperature changes. Moreover, adsorption of carbon dioxide or modifiers modify the solutes/stationary phase interactions, further complicating the understanding of the observed retention changes, either with low amount of modifier, or with specific modifiers.Besides, the polar and nonpolar stationary phases (SPs) do not always behave identically, depending on physico-chemical properties. Silica, amino or ethyl-pyridine polar phases display mostly identical behavior for classical differences of compounds of different polarity, but can provide different retention order for more subtle differences, such as the position of polar groups. Moreover, the nature of the silica, inorganic or hybrid, or the additional charges onto the silica surface can also lead to different results.Even if the C18-bonded phases are not as popular as polar SPs, the non-polar SPs provide very high separation performances for suited compounds, i.e. for non-polar compounds, which are perfectly solubilized by supercritical fluids. Recently, unusual retention behaviors were observed with some specific C18-bonded phases, which display polar interactions in addition to dispersion interactions.Whatever the SPs used, supercritical fluids appear to favor specific effects that are not observed with liquid mobile phases that are more uniform in terms of physico-chemical properties.The objective of this paper is to describe different separation behaviors observed in SFC, to improve the general understanding of the specificities of the association of supercritical fluids and varied SPs.

Pressurized carbon dioxide combined with aqueous ethanol as cosolvent induces efficient delipidation of porcine retina for their use as bioscaffolds

Retina damage results in both health and social problems. To treat retina damage, extracellular matrix technology has gained interest in the scientist community. Bioscaffolds production is based in the use of a `cleaned` tissue, free of undesired cellular components, for further recellularization using healthy cells. Removal of lipids is an important step to improve both de- and recellularization. This work shows, for the first time, the efficiency of pressurized carbon dioxide (CO2) fluids for the delipidation of porcine retina tissue. Pressurized CO2-EtOH-H2O (0.87 XCO2) at 300 bar and 37 °C for 1 h completely removed the 28 lipid species found in untreated retina (classified as phosphatidylcholines, phosphatidylethanolamines and sphingomyelins). When the ethanolic mixture was replaced by limonene at same conditions, lipid content decreased by more than a 50%, indicating reasonably good solubility of retina lipids in pressurized CO2-limonene; however, no delipidation was observed using neat supercritical CO2. In conclusion, pressurize CO2 technologies can be applied for delipidation of retina. Whether the resulting bioscaffold can be recellularized and used in transplantation remain to be shown.

Valorization of rice bran: Modified supercritical CO2 extraction of bioactive compounds

In this work, as a first step in a comprehensive strategy for the valorization of rice bran, the extraction of oil using supercritical CO2 and ethanol as cosolvent has been studied. The effect of extraction temperature (40 and 60°C), pressure (30 and 40MPa) and amount of ethanol used (0, 5 and 10%) has been considered. The quality extracted oil has been evaluated in terms of antioxidant activity, fatty acid profile and bioactive compounds such as phenolics, flavonoids, γ-oryzanols, and tocopherols content.Results revealed that, using neat CO2, the best oil in terms of antioxidant activity was obtained at 40°C and 30MPa. However, the addition of ethanol as modifier significantly increased the amount of bioactive molecules extracted and hence the overall antioxidant activity of the oil, which was maximum at 40MPa and 10% ethanol, regardless the temperature. The use of ethanol also affected the amount of fatty acids and γ-oryzanols extracted.

Vapour-liquid equilibrium of acetone-CO2 mixtures of different compositions at the vicinity of the critical point

The vapour-liquid equilibrium of acetone−CO2 mixtures is studied by computer simulation at 11 different compositions, ranging from neat CO2 to neat acetone, in a 50–100 K wide range of temperatures at the vicinity of the critical point. The composition dependence of the critical parameters is determined, for the first time, in the entire composition range. It is found that while the critical temperature changes monotonically with the composition, the critical pressure goes through a maximum around the acetone mole fraction value of 0.3, and the critical density might also exhibit a maximum in the acetone mole fraction range of 0-0.2. Temperature dependence of the surface tension is also determined in the entire composition range. The obtained results agree, in general, well with experimental data; their deviation remains below the range within which different experimental data sets deviate from each other. Since experimental data in this respect exist, unfortunately, only in limited ranges of compositions (at low acetone mole fractions) and temperatures (data above about 335 K are scarce), the present study largely extends the range of thermodynamic conditions in which we have reliable information on the liquid-vapour equilibrium and critical conditions of acetone−CO2 mixtures.

Valorization of papaya (Carica papaya L.) agroindustrial waste through the recovery of phenolic antioxidants by supercritical fluid extraction.

In this work, supercritical fluid extraction (SFE) for the recovery of phenolic antioxidants from papaya agroindustrial waste (seeds) was explored, making use of neat supercritical CO2 and CO2 added with ethanol (CO2-EtOH). A full factorial design played on in order to evaluate the effect of CO2 extraction parameters (temperature between 40 and 60°C, and pressure between 10 and 30MPa) on yield and total phenols content (TPC), then ethanol was applied as a co-solvent and its effect on the recovery of phenolics was analyzed. The SFE was compared to the conventional extraction using ethanol. The antioxidant activity of all extracts was evaluated, and the phenolic composition in selected extracts was assessed by HPLC-ESI-MS. The highest extraction yields (21.02-26.46%) and TPC (15.34-34.23mgGAE/g) were found in extracts obtained with CO2-EtOH and ethanol. Good and selective phenolic recovery was obtained by using CO2-EtOH, (44.81% of TPC recovered). The CO2-EtOH extracts showed high radical scavenging activity and higher antioxidant effect against lipid oxidation. Some phenolic acids and flavonoids were observed in the extracts with better antioxidants properties. The results showed that SFE is a suitable green technology for the phenolic recovery from papaya agroindustrial waste, and also an alternative for its valorization.

Ultrahigh-pressure supercritical fluid extraction and chromatography of Moringa oleifera and Moringa peregrina seed lipids

An ultrahigh-pressure supercritical fluid extraction method was optimized and applied to extract seed oil lipids from two moringa species, namely Moringa oleifera (MO) and Moringa peregrina (MP). A full-factorial design was used to investigate the direct and interaction influence of pressure and temperature in the range of 40 to 80 MPa and 40 to 70 °C, respectively, on the extracted amount of oil from crushed seeds. The results revealed that pressure has a significant positive influence on the extracted amount of oil. The best extraction condition using neat CO2 was found at 80 MPa and 57 °C, yielding 396 ± 23 and 529 ± 26 mg oil per gram of seeds for MO and MP, respectively. An extraction kinetics study revealed a mainly solubility-controlled extraction of oil, and 28 g of CO2 was required to extract 400 mg of oil per gram of seeds of MO using the developed method. Addition of ethanol to the sample prior to the extraction increased the proportion of extractable polar lipids as well as the total amount of extracted oil. The developed method increased the extracted amount of oil twofold compared to a reference method based on solvent sonication. The obtained oil consisted mainly of glycerolipids, sterol esters, and phospholipids. Phospholipids, campesterol, and stigmasterol ester concentrations were found to be higher in MO while cholesterol ester was more abundant in MP.

Chiral Separations Using a Modified Water Stationary Phase in Supercritical Fluid Chromatography

A novel means of achieving chiral separations in supercritical fluid chromatography (SFC) using a water stationary phase is presented. By adding various chiral selectors to the phase, different chiral analytes can be readily separated using neat CO2 as a mobile phase. For example, by adding β-cyclodextrin, it is found that certain flavanone enantiomers can be separated, while using the antibiotic vancomycin as a selector provides separation of some chiral phenoxypropionic acids. Other additives such as sodium chloride and triethylamine are also explored and found to enhance certain separations when also present in the water phase. While column pressure has a moderate impact on chiral analyte retention and separation in this SFC method, column temperature has a comparatively larger influence. In particular, relatively cooler temperatures below about 5 °C are found to markedly increase resolution and selectivity. For instance, notably large resolution of 4.7 is achieved for a phenoxypropionic acid pair at 0 °C and 150 atm CO2. Since the method does not require modifier to elute such polar species, it is also readily compatible with FID detection and does not generate organic waste. Therefore, results indicate that this approach could be a potentially simple and flexible means of achieving chiral separations in SFC.