•In average conditions, modern SFC systems possess σext2 of ∼85μL2.•3mm I.D. is the ideal column geometry for the current SFC technology.•Viscosity for various mixtures of CO2/MeOH were ...determined.•Kinetic plot methodology was experimentally found to be reliable in SFC.•Considering an upper pressure limit of 400bar, 1.7μm particles provide better performance than 3.5 or 5μm particles.
Recently, there has been a renewed interest in supercritical fluid chromatography (SFC), due to the introduction of state-of-the-art instruments and dedicated columns packed with small particles. However, the achievable kinetic performance and practical possibilities of such modern SFC instruments and columns has not been described in details until now. The goal of the present contribution was to provide some information about the optimal column dimensions (i.e. length, diameter and particle size) suitable for such state-of the-art systems, with respect to extra-column band broadening and system upper pressure limit. In addition, the reliability of the kinetic plot methodology, successfully applied in RPLC, was also evaluated under SFC conditions. Taking into account the system variance, measured at ∼85μL2, on modern SFC instruments, a column of 3mm I.D. was ideally suited for the current technology, as the loss in efficiency remained reasonable (i.e. less than 10% decrease for k>6). Conversely, these systems struggle with 2.1mm I.D. columns (55% loss in N for k=5). Regarding particle size, columns packed with 5μm particles provided unexpectedly high minimum reduced plate height values (hmin=3.0–3.4), while the 3.5 and 1.7μm packing provided lower reduced plate heights hmin=2.2–2.4 and hmin=2.7–3.2, respectively. Considering the system upper pressure limit, it appears that columns packed with 1.7μm particles give the lowest analysis time for efficiencies up to 40,000–60,000 plates, if the mobile phase composition is in the range of 2–19% MeOH. The 3.5μm particles were attractive for higher efficiencies, particularly when the modifier percentage was above 20%, while 5μm was never kinetically relevant with modern SFC instruments, due to an obvious limitation in terms of upper flow rate value. The present work also confirms that the kinetic plot methodology could be successfully applied to SFC, without the need for isopycnic measurements, as the difference in plate count between predicted and experimental values obtained by coupling several columns in series (up to 400mm) was on average equal to 3–6% and with a maximum of 13%.
•Immobilized polysaccharide-derived columns SFC use with extended solvent range.•Elution patterns with such solvents and the role of additives were studied.•New solvents increase the resolution ...success rate achieved with alcohols in SFC.•Non-protic solvents can overcome racemization, solubility and stability issues.
Polysaccharide-derived selectors are often used in the separation of enantiomers by supercritical fluid chromatography (SFC). Their recognition patterns are normally investigated with alcohols and acetonitrile as modifiers. The present paper describes the results of a research program designed by Pfizer and Chiral Technologies Inc. to explore the potential of other solvents (i.e. ethyl acetate, tetrahydrofuran, dichloromethane) in SFC by using a series of polysaccharide-derived supports with broad solvent versatility (CHIRALPAK IA, IB, IC, ID, IE and IF). The contribution of such extended solvent range to the overall success rate, as well as to overcome racemization, solubility and stability issues was confirmed by using standard non-proprietary samples and research molecules. Elution patterns with such lower polarity solvents, compared to alcohols, and the role of the different additives were also investigated.
This study used reversed-phase liquid chromatography-tandem mass spectrometry and supercritical fluid chromatography-tandem mass spectrometry for determination of the stereoisomers of chlorfenvinphos ...and dimethylvinphos in tobacco. Tobacco samples were extracted and purified with a modified quick, easy, cheap, effective, rugged, and safe technique using spherical carbon. The performance of both methodologies was comprehensively compared in terms of methods validation parameters (separation efficiency, linearity, selectivity, recovery, repeatability, sensitivity, matrix effect, etc.). Under optimized conditions, the calibration curves of the stereoisomers of chlorfenvinphos and dimethylvinphos in the range of 10-500 ng/mL showed excellent linearity with R
≥ 0.997 in both methods. The adequate recoveries of analytes from three different spiked tobaccos were obtained using reversed-phase liquid chromatography-tandem mass spectrometry (86.1-95.7%) as well as supercritical fluid chromatography-tandem mass spectrometry (86.5-94.0%). The relative standard deviations for spiked samples were all below 7.0%. Compared with supercritical fluid chromatography-tandem mass spectrometry, lower matrix effects and LODs can be obtained in reversed-phase liquid chromatography-tandem mass spectrometry.
Currently, little information has been published on the application of ternary eluent compositions in supercritical fluid chromatography for separating peptides. This work investigates the benefits ...of adding acetonitrile to methanol as the modifier. Three cyclic antibiotic peptides (bacitracin, colistin, and daptomycin) ranging between 1000 and 2000 Da were chosen as model substances. The ternary mixture of carbon dioxide, methanol, and acetonitrile is optimized to increase the resolution of the peptide's fingerprint. In addition, varying compositions of methanol and acetonitrile were found to change the elution order of the analytes, which is a valuable tool during method development. An individual gradient method using two Torus 2‐PIC columns (each 100 × 3.0 mm, 1.7 μm), carbon dioxide, and a modifier consisting of acetonitrile/methanol/water/methanesulfonic acid (60:40:2:0.1, v:v:v:v) was optimized for each of the peptides. Subsequently, a generic method development protocol applicable to polypeptides is proposed.
Empirical heat transfer correlations serve as indispensable tools for predicting and optimizing the thermal performance of a wide range of engineering devices, like for example in energy conversion ...and propulsion applications. Although a remarkable number of correlations exist for systems at low (atmospheric) pressures, accurately quantifying heat transfer under high-pressure transcritical conditions poses a notable challenge, especially at low Reynolds numbers due to the scarcity of correlations available in the literature. This difficulty has prompted the widespread use of general empirical correlations, which are inadequate for such flow conditions, and hold significant implications, for instance, in fields like microfluidics technology. In this regard, the aim of this study is to develop novel heat transfer correlations tailored for high-pressure transcritical fluids at relatively low Reynolds numbers. These correlations are derived from a dataset of 18 direct numerical simulations of carbon dioxide confined between differentially heated walls, which induce a transcritical trajectory through the pseudo-boiling region. The correlations are developed for both the cold liquid-like and hot gas-like regions, resulting in a total of 6 correlations that encompass the laminar, transitional, and turbulent flow regimes. In particular, as a function of Reynolds, Prandtl, Eckert and Mach numbers, the proposed empirical correlations provide accurate estimations with relative errors below 8%, which significantly surpass existing literature correlations.
•Novel heat transfer correlations proposed for high-pressure transcritical fluids.•Correlations developed for supercritical liquid- (cold) and gas-like (hot) regions.•Heat transfer covering wide regime range: laminar, transitional and turbulent.•Accurate correlation estimations with relative errors below 8%.
•Column screening on six orthogonal stationary phases for vitamin D analysis.•Nine vitamin D metabolites (D2 and D3 forms) are baseline separated in 8min.•The effect of co-solvent, temperature, ...pressure and flow rate is studied.•ESI+ is 6-fold more sensitive than APCI+ in SFC–MS.
In this study, a new supercritical fluid chromatography–mass spectrometry (SFC–MS) method has been developed for the separation of nine vitamin D metabolites within less than eight minutes. This is the first study of analysis of vitamin D and its metabolites carried out by SFC–MS. Six columns of orthogonal selectivity were examined, and the best separation was obtained by using a 1-aminoanthracene (1-AA) column. The number and the position of hydroxyl groups in the structure of the studied compounds as well as the number of unsaturated bonds determine the physiochemical properties and, thus the separation of vitamin D metabolites that is achieved on this column. All D2 and the D3 forms were baseline separated with resolution values>1.5. The effects of pressure, temperature, flow rate and different gradient modes were studied. Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were compared in positive mode, both by direct infusion and after SFC separation. The results showed that the sensitivity in APCI+ was higher than in ESI+ using direct infusion. In contrast, the sensitivity in APCI+ was 6-fold lower than in ESI+ after SFC separation. The SFC–MS method was validated between 10 and 500ng/mL for all analytes with coefficient of determination (R2)≥0.999 for all calibration curves. The limits of detection (LOD) were found to range between 0.39 and 5.98ng/mL for 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) and 1-hydroxyvitamin D2 (1OHD2), respectively. To show its potential, the method was applied to human plasma samples from healthy individuals. Vitamin D3 (D3), 25-hydroxyvitamin D3 (25OHD3) and 24,25(OH)2D3 were determined in plasma samples and the concentrations were 6.6±3.0ng/mL, 23.8±9.2ng/mL and 5.4±2.7ng/mL, respectively.
The objective of this study is to fabricate conductive carbon fiber composites with thermal and electrical properties by degradation carbon-fiber-reinforced plastics (CFRPs) and recycled carbon ...fibers using only supercritical water without any catalyst or oxidant. We focused on a recycling method that is harmless to the human body and environment-friendly, by using supercritical fluid water rather than recycling CFRP by physical or pyrolysis methods. In particular, we recycled carbon fibers (R-CFs) in which up to 99.5% of epoxy resin was removed, by optimizing the conditions of supercritical fluid water (SCF-W) treatment, and we fabricated conductive R-CFs composites with thermal and electrical properties by combining the R-CFs with cyclic butylene terephthalate (CBT), which is a polymerizable low-viscosity thermoplastic resin. The fabricated composites had a thermal conductivity of 1.35 ± 0.05 (W/mK) and an electrical conductivity of 11.23 × 10−6 (S/cm) when the added amount of recycled carbon fibers was 5 wt%.
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Ion mobility spectrometry (IMS) is a widely used analytical technique for rapid molecular separations in the gas phase. Though IMS alone is useful, its coupling with mass spectrometry (MS) and ...front-end separations is extremely beneficial for increasing measurement sensitivity, peak capacity of complex mixtures, and the scope of molecular information available from biological and environmental sample analyses. In fact, multiple disease screening and environmental evaluations have illustrated that the IMS-based multidimensional separations extract information that cannot be acquired with each technique individually. This review highlights three-dimensional separations using IMS-MS in conjunction with a range of front-end techniques, such as gas chromatography, supercritical fluid chromatography, liquid chromatography, solid-phase extractions, capillary electrophoresis, field asymmetric ion mobility spectrometry, and microfluidic devices. The origination, current state, various applications, and future capabilities of these multidimensional approaches are described in detail to provide insight into their uses and benefits.
Phenolic compounds from mango (
) seed kernels (MSK)
. Sugar were obtained using supercritical CO
and EtOH as an extraction solvent. For this purpose, a central composite design was carried out to ...evaluate the effect of extraction pressure (11-21 MPa), temperature (40-60 °C), and co-solvent contribution (5-15%
/
EtOH) on (i) extraction yield, (ii) oxidative stability (OS) of sunflower edible oil (SEO) with added extract using the Rancimat method, (iii) total phenolics content, (iv) total flavonoids content, and (v) DPPH radical assay. The most influential variable of the supercritical fluid extraction (SFE) process was the concentration of the co-solvent. The best OS of SEO was reached with the extract obtained at 21.0 MPa, 60 °C and 15% EtOH. Under these conditions, the extract increased the OS of SEO by up to 6.1 ± 0.2 h (OS of SEO without antioxidant, Control, was 3.5 h). The composition of the extract influenced the oxidative stability of the sunflower edible oil. By SFE it was possible to obtain extracts from mango seed kernels (MSK)
. Sugar that transfer OS to the SEO. These promissory extracts could be applied to foods and other products.
•Mass transfer of supercritical fluids.•Application of supercritical CO2 extraction.•Mass transfer phenomena.•Overview literature correlations mass transfer coefficients.
In many chemical engineering ...processes mass transfer is a frequently encountered phenomenon. One of the upcoming processes is extraction with supercritical fluids (SCF), especially the use of supercritical carbon dioxide (scCO2). In order to design extraction processes it is very important to understand and describe the mass transfer steps, and also to be able to determine and estimate the mass transfer coefficients. Dimensionless mass transfer correlations together with mass balance models (process models) are highly recommend to ensure a maximum versatility. However, up till now most mass transfer correlations are related and validated to regular solid–liquid, liquid–liquid or gas–liquid systems and are not automatically and directly applicable for SCF due to the unique properties of supercritical fluids. Moreover, in the case of SCF extraction, natural convection can occur and interfere with forced mass transfer. For forced convection Sherwood depends on Reynolds and Schmidt where for natural convection Sherwood depends on only Grashof and Schmidt.
In this paper an overview will be given of the dimensionless mass transfer correlations for scCO2 from experimental data in terms of Sherwood, Reynolds and Schmidt for packed bed, annular duct, liquid film and hollow fiber membranes.
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