Supercritical Fluid Carbon Dioxide Research Articles

The Potential Antinociceptive Effect and Mechanism of Cannabis sativa L. Extract on Paclitaxel-Induced Neuropathic Pain in Rats Uncovered by Multi-Omics Analysis.

Cannabis sativa L. (hemp) is a herbaceous plant rich in cannabinoids with a long history of use in pain treatment. The most well-characterized cannabinoids, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC), garnered much attention in chemotherapy-induced peripheral neuropathy (CIPN) treatment. However, few studies have investigated the biological benefits and mechanism of hemp extract on CIPN. In the present study, hemp extract (JG) rich in cannabinoids was extracted by supercritical fluid carbon dioxide extraction (SFCE). The antinociceptive efficacy was evaluated using a paclitaxel-induced peripheral neuropathy (PIPN) rat model based on behavioral tests. Further omics-based approaches were applied to explore the potential mechanisms. The results showed that JG decreased mechanical allodynia, thermal hyperalgesia, and inflammatory cytokines in PIPN rats significantly. Transcriptome analysis identified seven key genes significantly regulated by JG in PIPN model rats, mainly related to the neuroactive ligand-receptor interaction pathway, PPAR signaling pathway, and cAMP signaling pathway. In metabolomic analysis, a total of 39 significantly altered metabolites were identified, mainly correlated with pentose and glucuronate interconversions and the glycerophospholipid metabolism pathway. Gut microbiota analysis suggested that increased community Lachnoclostridium and Lachnospiraceae_UCG-006 in PIPN rats can be reversed significantly by JG. In conclusion, hemp extract exhibited antinociceptive effects on PIPN. The analgesic mechanism was probably related to the regulation of inflammation, neuroactive ligand-receptor interaction pathway, sphingolipid metabolism, etc. This study provides novel insights into the functional interactions of Cannabis sativa L. extract on PIPN.

Comparison of antimicrobial activities of oregano, lavender, sage, anise and clove extracts obtained by supercritical fluid carbon dioxide extraction and essential oils obtained by hydrodistillation

ABSTRACT The aim of the study was to compare the extraction yields, chemical compositions and antimicrobial activities of essential oils obtained by hydrodistillation (HD) and volatile extracts obtained by supercritical fluid extraction extraction (SFE) from oregano (Origanum onites), lavender (Lavandula angustifolia), sage (Salvia officinalis), anise (Pimpinella anisum) and clove (Syzygium aromaticum). Essential oil compounds (EOCs) of the obtained materials from both techniques (HD and SFE) were determined by GC-MS/FID. Agar well diffusion method was used for the determination of antimicrobial activities on five different foodborne microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli Enterococcus faecalis and Klebsiella pneumoniae). According to the results; extraction yields of SFE were found to be higher than HD for all tested aromatic plants. Active ingredient ratios (carvacrol, camphor, anethole, eugenole and linalol) varied depending on the extraction methods. SFE extracts were higher antimicrobial activity than HD essential oils, except clove extract on E. faecalis.

Effects of different preparation methods on the physical, chemical and functional properties of protein powders from Skipjack tuna (Katsuwonus pelamis) liver

Tuna livers (TL), which are often discarded as waste, are a valuable source of protein for human consumption. However, the preparation method used affects the nutritional and functional characteristics of protein powders. This work aimed to investigate the effects of different preparation methods on the physical, chemical, and functional properties of tuna liver protein powders (TLPPs) following heat (H) treatment, heat and ultrasound-assisted (HU) extraction, alkaline pH shift (APS) process, and supercritical carbon dioxide fluid (SC-CO2 ) extraction. H at 85°C (H85), HU at 80 kHz and 100 W (HU-80-100), APS at pH 11.5 (APS 11.5), and SC-CO2 at 350 bars (SC-CO2 -350) resulted in the remarkably highest total protein content among the different preparation conditions. All TLPPs, except for APS 11.5, showed lighter color characteristics. The most abundant amino acids in all TLPPs were glutamic acid, aspartic acid and alanine. The protein solubility and foaming capacity were efficiently improved by SC-CO2-350. Nevertheless, the emulsion properties and oil holding capacity were greatly enhanced by H85 and HU-80-100, and a significant foaming stability and water holding capacity were found in APS 11.5. Therefore, the TLPPs obtained following different preparation methods are unique and could be potentially utilized as a source of protein ingredients in several food systems.

A universal ANN-based approach predicting PCHEs’ off-design performance across various operating conditions of sCO2 RCBCs

This paper proposes a universal approach that employs artificial neural networks (ANN) to predict the off-design performance of printed circuit heat exchangers (PCHEs) using supercritical carbon dioxide (sCO2) fluid. PCHEs are widely studied precoolers and recuperators of sCO2 power cycles, for which predicting their off-design heat transfer performance is challenging due to the fluid’s dramatic non-linear property variations. Due to their narrow valid range and constrained expressing ability, the existing empirical correlations might introduce significant out-of-scope errors that result in diverged simulation results, slow convergence and abnormal quitting. This work addresses the issue by proposing an ANN-based Nusselt number correlation, ANNu, to predict the off-design performance of PCHEs quickly and universally over the vast operating range of sCO2 cycles. Multiple techniques were adopted to promote ANNu’s prediction accuracy and generalization, such as consolidating 494 training data, data-driven input selection, and global optimization for the networks’ architecture and hyperparameters. This paper comprehensively evaluates ANNu’s performance by comparing its predictions with ten empirical correlations over four typical real-world scenarios, where ANNu features an overall MSE of 83.4222 and overall MAPE of 16.285 % that rank the second best and third best among eleven candidates (even overpassing two references), respectively. Moreover, ANNu exhibits good generalization and reliability, featuring MAPEs ranging from 9.89 % to 27.73 % when processing unmet experiment data from sCO2 PCHE applications.

Solvent-Free Method for Masking the Bitter Taste of Azithromycin Dihydrate Using Supercritical Fluid Technology

ABSTRACT Introduction and purpose The unpleasant extremely bitter taste of the orally administered broad-spectrum antibiotic azithromycin decreases patient compliance, especially in pediatrics. This issue can be overcome by decreasing drug interaction with the tasting buds using insoluble polymers at salivary pH (6.8 -7.4), like the cationic polymer Eudragit EPO. Supercritical fluid technology is a green synthesis method for preparing pharmaceutical preparations that replace organic solvents with safe supercritical CO2. This study aimed to mask the bitter taste of azithromycin using the supercritical fluid method and a pH-sensitive Eudragit EPO polymer. Methods: A foaming process was investigated for preparing a formulation (TEST), which comprises treating the polymer with supercritical carbon dioxide (CO2) fluid to prepare a taste-masked dosage form without employing organic solvents or flavors. Results: The use of the supercritical technique at 40 °C and 10 MPa for two hours allowed the manufacturing of solvent-free polymeric foam with azithromycin dispersions; the average calculated percentage of apparent volume change was 62.5 ± 5.9% with an average pore diameter of 34.879 Å. The formulated sample showed low drug release in simulated salivary fluid while keeping its crystalline nature. Moreover, clinical studies on healthy subjects showed that the formula successfully masked azithromycin's bitter taste. Conclusions: Overall, it has been shown herein that the supercritical fluid technology foaming method is promising in masking the bitter taste of bitter ingredients.

Hydrophobic modification of polyvinylidene fluoride membranes in supercritical carbon dioxide fluids

Polyvinylidene fluoride (PVDF) membranes exhibit exceptional chemical stability and find applications in various fields, including building membranes, flexible sensors, blood purification, and seawater desalination. Nevertheless, the hydrophobic performance of PVDF membranes in these applications is subpar and requires enhancement. Supercritical carbon dioxide (scCO2) fluid demonstrates a beneficial expansion effect on PVDF membranes and exhibits good solubility with fluorine reagents. This study employs scCO2 as a medium to introduce a fluorine reagent onto the surface of PVDF membranes, forming a layer of low surface energy substance that significantly improves the membrane's hydrophobicity. The results indicate the feasibility of hydrophobic modification of PVDF membranes using scCO2 as a medium, leading to improved hydrophobic properties. When using a fluorine reagent with a relatively large molecular weight, PVDF membranes in scCO2 fluid at 110 °C and 20–25 MPa for 4 h results in a substantial improvement in the hydrophobicity of the PVDF membrane, with the contact angle reaching 117.2° (compared to the primitive membrane's 80°). Scanning electron microscopy (SEM) analysis confirms the presence of a layer of low surface energy material on the modified PVDF membrane surface. Thermogravimetric (TG) and differential thermogravimetric (DTG) analyses demonstrate that the hydrophobic modification using scCO2 enhances the crystallinity and thermal stability of the PVDF membrane, raising the thermal cracking temperature from 425.3 °C to 450.5 °C. Fourier-transform infrared spectroscopy (FT-IR) reveals clear absorption peaks of the fluorine reagent at 1740 cm−1 and 1211 cm−1. Nuclear magnetic resonance (NMR) confirms the presence of characteristic peaks of hydrogen on the fluorine reagent, confirming the embedding of the hydrophobic reagent onto the PVDF membrane surface. This modification method holds significant potential for guiding the development of hydrophobic surfaces, contributing to carbon neutrality, and meeting environmental sustainability goals.

Research on the Electrodeposition of Graphene Quantum Dots under Supercritical Conditions to Enhance Nickel-Based Composite Coatings

A graphene quantum dots (GQDs)-reinforced nickel-based composite coating was electrodeposited on the surface of a copper plate with a supercritical carbon dioxide fluid (SC-CO2)-assisted DC power supply. The effect of the current density on surface morphology, microstructure, average grain size, hardness, and corrosion resistance of the resulting coatings was investigated in detail. It was found that the GQDs composite coating showed a more compact surface, a smaller grain size, higher microhardness, and stronger corrosion resistance than the pure Ni coating produced in SC-CO2 and a texture coefficient indicative of a (111) preferred orientation. When the current density was 8 A/dm2, the surface morphology of the GQDs composite coating showed a high density, and the grain size was about 23 nm. In addition, the micro-hardness and corrosion resistance of the GQDs composite coating was greatly improved compared with those of the pure nickel coating; at the same time, its wear rate, friction coefficient, and self-corrosion current density were decreased by 73.2%, 17.5%, and 9.2%, respectively.

Characterization and stability evaluation of Egyptian propolis extract nano-capsules and their application

The increasing demand for natural products and biotechnological activities from bees facilitate their widespread use in food preservation and beneficial effects on humans. This study aimed to prepare and characterize the nano-capsules of Qaluiobia (PQG) governorates propolis extracted with water, ethanol and supercritical fluid-carbon dioxide at 50 °C with co-solvent. Propolis bioavailability was analyzed and introduced to prepare crackers to extend their shelf life. Nano-encapsulation was examined using transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and antioxidant activity. Ethanol and supercritical fluid-carbon dioxide (SCF-CO2) at 50 °C with ethanol as co-solvent recorded higher yield, antioxidant activities, total phenolics and total flavonoids. SCF-CO2 extracts had a higher flavonoid concentration. It was revealed that propolis nano-capsules had high-temperature stability and cytotoxic effects against the three tested human cancer cell lines (i.e. PC3, MCF7 and HePG2). The higher overall acceptability of crackers fortified with PQG was achieved with SCF-CO2 at 50 °C and ethanol extract nano-capsules, i.e. 86.57% and 86.29% respectively. The higher ability to retain antioxidant activity reduces the increase of peroxide value (PV), preventing rancidity and increasing the shelf life of crackers during the storage period. Practical application: This study can provide a suitable method for extracting bioactive compounds from propolis, and improve the biological properties and activities by nano-encapsulation, also reveals the extent of its use as a natural antioxidant and anticancer and its application in bakery products as a functional food.

Supercritical extraction technique of agarwood essential oil induced by plant hormones

Samples of agilawood (agarwood), which were studied in this work, were produced in Zhongshan City, Guangdong Province, China. To enhance incense production, a specific concentration of plant hormone is employed for induction. The extraction technology of agilawood essential oil was explored using supercritical carbon dioxide fluid, which exhibited a more pronounced induction effect. The pressure, temperature, and flow rate, respectively, were 8, 16, and 24 MPa; 35, 45, and 55 °C; and 20, 30, and 40 L/h. A Box-Behnken analysis was adopted for experimental data, which involved 33 experiments. The data were fitted with the equation Y = 2.18 + 0.1312X1 – 0.025X2 + 0.1236X3 – 0.0025X1X2 – 0.0125X2X3 + 0.0175X12 + 0.035X22 – 0.1275X32. Hence, the optimal process parameters in the supercritical extraction of agarwood essential oil were as follows: the pressure, temperature, and flow rate of 24 MPa, 35 °C, and 33 L/h, respectively. An analysis was conducted with the statistical analysis software Design-Expert 11, which indicated that the extraction yield of agarwood essential oil by supercritical carbon dioxide was mainly affected by the pressure and flow rate. The yield was proportional to the pressure and flow, and inversely proportional to the temperature.

Evaluation of control of additive concentration in gradient analysis of supercritical fluid chromatography-coupled to tandem mass spectrometry

Mobile phase additives are used to improve retention behavior in chromatography. In supercritical fluid chromatography (SFC), for which supercritical fluid carbon dioxide (SF-CO2) is used as the main mobile phase, additives can only be added into the modifier. For that reason, when gradient analysis is performed by changing the modifier ratio to SF-CO2, the additive concentration in the mobile phase increases in parallel with the modifier ratio. In a preliminary study performed using the conventional SFC system, ammonium acetate was necessary to improve the peak shape of a polar steroid, dehydroepiandrosterone sulfate (DHEA-S), while the peak intensity of a non-polar steroid, progesterone, decreased by 78% compared to that in the absence of the additive in mobile phase when gradient elution was performed. Since ammonium acetate had both favorable and unfavorable effects on sensitive and simultaneous analysis of these two steroid compounds, a compromise between these effects had to be sought. A three-pump configuration of SFC was developed by adding a pump unit to SFC instrument, which enabled control of the additive concentration independently of the modifier ratio, for the purpose of investigating the additive effect in detail using both steroids as model compounds. The putative cause of the decrease in peak intensity of progesterone was excessively elevated additive concentration in gradient analysis. When the additive concentration in the mobile phase was controlled to ensure that it did not increase during gradient analysis, the peak intensities of progesterone, cortisol, corticosterone, and testosterone were 55%, 40%, 25%, and 17% higher than when the additive concentration was not controlled, respectively. On the other hand, the peak intensity of DHEA-S was almost identical between the conditions, with an increase of 2% with three-pump instrument. The three-pump configuration showed the potential to solve problems relating to the use of modifier additives by keeping their concentration constant in gradient SFC analysis.

Optimization of Supercritical Carbon Dioxide Fluid Extraction of Medicinal Cannabis from Quebec

Research on cannabis oil has evolved to encompass the pharmaceutical industry for the therapeutic potential of the active compounds for pathologies such as Alzheimer, auto-immune disorders, and cancer. These debilitating diseases are best treated with cannabinoids such as tetrahydrocannabinol (∆9-THC), cannabigerol (CBG), and cannabinol (CBN), which relieve neuropathic pain and stimulate the immune system. We extracted cannabinoids from plants with supercritical CO2 and produced an extract with a total yield close to 26%. The three-level Box–Behnken experimental design considered four factors: Temperature, pressure, CO2 flow rate, and processing time, with predetermined parameters at low, medium, and high levels. The mathematical model was evaluated by regression analysis. The yield of ∆9-THC and CBG reached a maximum after 2 h and 15 g/min of CO2, 235 bar, 55 °C (64.3 g THC/100 g of raw material and 4.6 g CBG/100 g of raw material). After another 2 h of extraction time, the yield of CBN reached 2.4 g/100 g. The regression analysis identified pressure and time as the only significant factors for total yield while pressure was the only significant factor for ∆9-THC and CBG. Time, temperature, pressure, and flow rate were all significant factors for CBN.

Optimization of Supercritical Fluid CO2 Extraction from Yellow Horn Seed and Its Anti-Fatigue and Antioxidant Activity.

A supercritical fluid carbon dioxide (SF-CO2) extraction method was used to obtain the optimum process for extracting yellow horn seed oil. The anti-fatigue and antioxidant properties of the extracted oil were investigated through animal experiments. The optimum process conditions for SF-CO2 extraction of the yellow horn oil were 40 MPa, 50 °C and 120 min, with an extraction yield of 31.61%. The high-dose group of yellow horn oil could significantly increase the weight-bearing swimming time, the hepatic glycogen (HG) content and decrease the lactic acid (LA) content and blood urea nitrogen (BUN) content (p < 0.05) in mice. Moreover, it improved the antioxidant ability by reducing the malondialdehyde (MDA) content (p < 0.01) and raising the glutathione reductase (GR) content and superoxide dismutase (SOD) content (p < 0.05) in mice. Yellow horn oil has the effects of being an anti-fatigue and antioxidant substance, which provides a basis for its further utilization and development.

Evolution of Supercritical Fluid Carbon Dioxide Dyeing Technology: Comparison of Predictive and Experimental Affinity and Dyeability between PET Fiber and Various Disperse Dyes

Evolution of Supercritical Fluid Carbon Dioxide Dyeing Technology: Comparison of Predictive and Experimental Affinity and Dyeability between PET Fiber and Various Disperse Dyes

Evaluation of carbon dioxide supercritical fluid extraction (CO2-SFE) on carotenoids recovery from red yeast cells

AbstractIn this work, the performance of carotenoids extraction from Rhodotorula spp red yeast (strain ELP2022) using supercritical CO2 (CO2-SFE) was compared to the traditional technique with organic solvent. For this purpose, the yeast was cultured in liquid medium, pre-treated with glass beads in 0.1 M NaHCO3, and lyophilized. The extraction by CO2-SFE was carried out using a bench scale equipment at 300, 400, and 500 bar whilst maintaining a constant CO2 flow rate (6 mL/min) and temperature (40 °C) resulting in an average extraction yields of 60.8 ± 1.1, 68.0 ± 1.4, and 67.6 ± 1.4 µg of total carotenoids per g of yeast (dry weight), respectively. Based on these results, three other experiments at 400 bar and a CO2 flow rate of 6 L/min were also performed. In specific, the temperature was increased up to 60 °C, and ethanol as a co-solvent was added at 40 and 60 °C. The results showed that the temperature does not have a significant effect on the extraction of carotenoids. On the contrary, the yields improved significantly in the presence of the co-solvent, and the percentage of recovery reached the mean values of 71.70% ± 1.4 and 73.86% ± 1.9 at 40 and 60 °C, respectively. Furthermore, from chromatographic analysis, four major peaks were observed and identified as torularhodin, torulene, γ-carotene, and β-carotene which represented about 53.4%, 6.4%, 8.3%, and 26.9% of total carotenoids, respectively. Therefore, these promising results show the potential of this green technique for obtaining high-value products, such as carotenoids, from yeasts and therefore avoiding the use of dangerous solvents.

Subcritical liquified dimethyl ether and supercritical fluid carbon dioxide extraction of gamma oryzanol from rice bran acid oil

Gamma oryzanol (γ-oryzanol) is a bioactive compound in rice bran acid oil, a by-product of the rice bran oil refining process that possesses various pharmacological properties. This study investigated the effect of green technology supercritical fluid carbon dioxide extraction (SF–CO2) and subcritical liquified dimethyl ether extraction (SUBLDME) of γ-oryzanol from rice bran acid oil. Results showed that subcritical liquified dimethyl ether extracted oryzanol at 4865.25 mg/100 g from rice bran acid oil without pretreatment by hexane and ethyl acetate compared with supercritical fluid carbon dioxide extraction (2569.04 mg/100 g), with high extraction efficiency (62.73 vs 18.86%). Further extraction of the filter cake remaining from supercritical fluid carbon dioxide extraction from rice bran acid oil without pretreatment using subcritical liquified dimethyl ether extraction gave the highest percentage yield and γ-oryzanol contents (8128.51 mg/100 g). Supercritical fluid carbon dioxide extraction together with subcritical liquified dimethyl ether extraction showed promise as a green technology to extract γ-oryzanol from rice bran acid oil. Further studies are required to optimize both SF-CO2 and SUBLDME extraction methods to increase the γ-oryzanol content.

Comparison of Single Control Loop Performance Monitoring Methods

Well-performing control loops have an integral role in efficient and sustainable industrial production. Control performance monitoring (CPM) tools are necessary to establish further process optimization and preventive maintenance. Data-driven, model-free control performance monitoring approaches are studied in this research by comparing the performance of nine CPM methods in an industrially relevant process simulation. The robustness of some of the methods is considered with varying fault intensities. The methods are demonstrated on a simulator which represents a validated state-space model of a supercritical carbon dioxide fluid extraction process. The simulator is constructed with a single-input single-output unit controller for part of the process and a combination of relevant faults in the industry are introduced into the simulation. Of the demonstrated methods, Kullback–Leibler divergence, Euclidean distance, histogram intersection, and Overall Controller Efficiency performed the best in the first simulation case and could identify all the simulated fault scenarios. In the second case, integral-based methods Integral Squared Error and Integral of Time-weighted Absolute Error had the most robust performance with different fault intensities. The results highlight the applicability and robustness of some model-free methods and construct a solid foundation in the application of CPM in industrial processes.

Super‐stable homogeneous embolic agents advance the treatment of hepatocellular carcinoma

Super‐stable homogeneous embolic agents advance the treatment of hepatocellular carcinoma

Supercritical-Assisted Ball-Milling Synthesis of Multicomponent Si/Fe3O4/C Composites for Outstanding Lithium-Storage Capability

Attributed to high theoretical capacity and abundant reserves, Si/C anodes have been commercialized in lithium-ion batteries (LIBs). However, the shortcomings of poor interfacial compatibility, low rate performance, and bad stability remain to be overcome. In this paper, a facile method for the synthesis of silicon/iron oxide/carbon (Si/Fe3O4/C) composites by ball-milling in a supercritical carbon dioxide (scCO2) fluid medium is proposed. This method utilizes the diffusion characteristics, extremely low viscosity, and excellent mass transfer properties of supercritical fluids. Under the infiltration of an scCO2 fluid, mesophase carbon microspheres (MCMB) are exfoliated into graphite flakes and achieve good interfacial fusion with silicon and Prussian blue during ball-milling. The Prussian blue is transformed into Fe3O4 by subsequent heat treatment under a nitrogen atmosphere, and Fe3O4 introduced in this way enhances the lithium-storage capacity, cycling stability, and rate performance significantly of Si/C anodes. As an anode for LIBs, the reversible capacity of Si/Fe3O4/C reaches 1363 mA h g–1 after 600 cycles at 1 A g–1. This study provides an idea for the design and fabrication of Si-based anode materials with high capacity and long cycle life.

Supercritical carbon dioxide fluid cleaning of extracellular polymeric substance surrogates on seawater reverse osmosis membranes

Fouling of seawater reverse osmosis (SWRO) membranes cause of reduced water flux and increased energy usage, which requires frequent cleaning to maintain performance. We demonstrate Supercritical carbon dioxide (sCO2) fluid, as an alternative membrane cleaning reagent, can effectively remove extracellular polymeric substances (EPS) that form on SWRO membranes. Carbon dioxide (CO2) gas was turned into sCO2 fluid by elevating the pressure (to 7.5 MPa) and temperature (to 35 °C). The SWRO membrane coupons were fouled by EPS surrogate materials (sodium alginate or bovine serum albumin), and the sCO2 cleaning was conducted to recover the deteriorated water permeation flux. We present that the sCO2 cleaning can effectively eliminate the EPS surrogate materials from the membrane surface with a great cleaning efficiency (75–90 %). In addition, it was observed that sCO2 cleaning does not alter the properties (i.e., surface functional groups and salt-rejecting performance) of polyamide-based SWRO. Our findings suggest that sCO2 is applicable to remove EPS surrogate materials from the membrane.

On-line SFC-UV/Vis-MS using flow selection interfaces to monitor continuous flow single and sequential stage organic reactions in supercritical carbon dioxide

Two flow selection interfaces have been developed for connecting single or linked reactors with on-line SFC equipped with UV/Vis diode-array (DAD) and mass spectrometer detectors coupled in series (SFC-DAD-MS). This process analytical technology system, enabled the study of reactions performed in supercritical fluid carbon dioxide (SF-CO2). Each interface is designed to obtain on-line samples at different reaction progress points. Three single stage electrophilic annulation reactions performed in SF-CO2 using aniline, indole and pyrrole as amine reactants to synthesize N-heterocyclic products within a stirred continuous flow reaction vessel containing montmorillonite K-10 catalyst were monitored. Also, both stages of a two step synthetic procedure conducted within two connected continuous flow reaction coil systems were monitored using on-line SFC-DAD-MS. The first step involved a Knoevenagel reaction in SF-CO2 that provided a continuous feed to perform a second stage acetylation reaction. Use of on-line SFC-DAD-MS enabled early detection and characterization of unexpected by-products.