Supercritical Fluid Chromatography and Extraction

Current status, technology, regulation and future perspectives of essential oils usage in the food and drink industry

Nowadays, essential oils (EOs) have a wide use in many applications such as in food, cosmetics, pharmaceutical and animal feed products. Consumers' preferences concerning healthier and safer foodstuffs lead to an increased demand for natural products, in replacement of synthetic substances, used as preservatives, flavourings etc. EOs, besides being safe, are promising alternatives as natural food additives, and much research has been carried out on their antioxidant and antimicrobial activity. The initial purpose of this review is to discuss conventional and 'green' extraction techniques along with their basic mechanism for the isolation of EOs from aromatic plants. This review aims to provide a broad overview of the current knowledge about the chemical constitution of EOs while considering the existence of different chemotypes, since bioactivity is attributed to the chemical composition - qualitative and quantitative - of EOs. Although the food industry primarily uses EOs as flavourings, an overview on recent applications of EOs in food systems and active packaging is provided. EOs exhibit poor solubility in water, oxidation susceptibility, negative organoleptic effect and volatility, restricting their use. Encapsulation techniques have been proven to be one of the best approaches to preserve the biological activities of EOs and minimize their effects on food sensory qualities. Herein, different encapsulation techniques and their basic mechanism for loading EOs are discussed. EOs are highly accepted by consumers, who are often under the misconception that 'natural' means safe. This is, however, an oversimplification, and the possible toxicity of EOs should be taken into consideration. Thus, in the final section of the current review, the focus is on current EU legislation, safety assessment and sensory evaluation of EOs. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Flavor of rapeseed oil: An overview of odorants, analytical techniques, and impact of treatment

As one of the three major vegetable oils in the world, rapeseed oil is appreciated for its high nutritional value and characteristic flavor. Flavor is an essential attribute, determining rapeseed oil quality and consumer acceptance. The present manuscript provides a systematic literature review of recent advances and knowledge on the flavor of rapeseed oil, which focuses on aroma-active as well as off-flavor compounds, flavor analysis techniques (i.e., extraction, qualitative, quantitative, sensory, and chemometric methods), and effects of treatments (storage, dehulling, roasting, microwave, flavoring with herbs, refining, and oil heating) on flavor from sensory and molecular perspectives. One hundred thirty-seven odorants found in rapeseed oil from literature are listed and possible formation pathways of some key aroma-active compounds are also proposed. Future flavor analysis techniques will evolve toward time-saving, portability, real-time monitoring, and visualization, which aims to obtain a "complete" flavor profile of rapeseed oil. The changes of volatile compounds in rapeseed oil under different treatments are summarized in this view. Studies to elucidate the influence of different treatments on the formation of aroma-active compounds are needed to get a deeper understanding of factors leading to the variations of rapeseed oil flavor.

Colchicine: Isolation, LC-MS QTof Screening, and Anticancer Activity Study of Gloriosa superba Seeds

Colchicine was extracted from Gloriosa superba seeds using the Super Critical Fluid (CO2) Extraction (SCFE) technology. The seeds were purified upto 99.82% using column chromatography. Colchicine affinity was further investigated for anticancer activity in six human cancer cell lines, i.e., A549, MCF-7, MDA-MB231, PANC-1, HCT116, and SiHa. Purified colchicine showed the least cell cytotoxicity and antiproliferation and caused no G2/M arrest at clinically acceptable concentrations. Mitotic arrest was observed in only A549 and MDA-MB231 cell lines at 60nM concentration. Our finding indicated the possible use of colchicine at a clinically acceptable dose and provided insight into the science behind microtubule destabilization. However, more studies need to be conducted beforethese findings could be established.

Revision: Extracción con CO2 a alta presión. Fundamentos y aplicaciones en la industria de alimentos / Review: High pressure CO2 extraction. Fundamentals and applications in the food industry

Supercritical extraction (SFE) is a unit operation that exploits the dissolving power of supercritical fluids (SF) under conditions above their critical temperature and pressure. It is possible to obtain solvent-free extracts using SF and the extraction is faster than using conventional organic solvents. These advantages are due to the high volatility of SF (gases under normal environmental conditions) and improved transport properties (i.e., high diffusivity and low viscosity). When using carbon diox ide (CO,) in particular, moderate-temperature processing and high selectivity towards valuable microconstituents in natural products can be achieved. This article presents a review of transport properties and solubilities in SF, particularly CO2, as well as other underlying factors that are respon sible for the kinetics and phase equilibrium in SFE processes. It also describes the selective CO 2 ex traction of essential oils, pungent principles, carotenoid pigments, antioxidants, antimicrobials, and related substances to be used as ingredients for the food, drug and perfume industries, from spices, herbs and other plant materials. These very important applications are discussed from the point of view of the potential applications of SFE in Latin America. The two most important commercial ap plications of SFE in the food industry, namely hop extraction and coffee decaffeination, are reviewed to a limited extent. Some other potential applications briefly described include extraction and frac tionation of edible fats and oils, purification of solid matrices, and concentration of fermentation broths, fruit juices and other extracts. In most cases CO2 extracts are compared with counterparts obtained using conventional methods.

Selective extraction of astaxanthin from crustaceans by use of supercritical carbon dioxide

An on-line supercritical fluid extraction (SFE) system coupled to a continuous flow manifold including a UV detector was used as a screening system to extract astaxanthin from crayfish, which was found to be the major carotenoid present in the samples. This compound constitutes the principal additive used to dye salmon flesh. The flow manifold was used to confirm the presence of astaxanthin in the crustacean samples. Also, an HPLC/UV-vis method was used to ascertain that this compound was the major carotenoid extracted under the optimum SFE conditions employed. The influence of SFE operating variables such as pressure, temperature, equilibration time, extraction time, trap temperature, and volume of CO(2) modifier was examined in order to maximize the efficiency of analyte extraction. The use of supercritical CO(2) enables the expeditious, selective, quantitative extraction of astaxanthin from crustaceans.

Determination of additives in cosmetics by supercritical fluid extraction on-line headspace solid-phase microextraction combined with gas chromatography-mass spectrometry

A new hyphenated technique couples supercritical fluid extraction in situ derivatization and on-line headspace solid-phase microextraction to gas chromatography-mass spectrometry (SFE in situ derivatization on-line HS-SPME-GC-MS) for the determination of paraben preservatives and polyphenolic antioxidants in cosmetics. The preservatives and antioxidants were extracted from the cosmetic matrices with supercritical carbon dioxide at a pressure of 13,840 kPa. The supercritical fluid extraction was performed at 55 degrees C for 10 min of static extraction then 15 min of dynamic extraction. The extractant subsequently was derivatized in situ with the silylation reagent N,O-bis(trimethylsilyl)trifluoroacetamide with 0.1% trimethylchlorosilane. The product was then adsorbed on a polyacrylate solid-phase microextraction (SPME) fiber in the headspace. Sea sand was used as a dispersive material in the SFE step. The analytical linear ranges for the preservatives and antioxidants were found to be from 10 to 1000 ng g(-1) with RSD values below 7.8%. The detection limits ranged from 0.5 to 8.3 ng g(-1). These results are better than those obtained by using only SPME or SFE for trace preservatives and antioxidants analysis in cosmetic matrices. The new method was successfully utilized to determine the amounts of preservatives and antioxidants in real cosmetics without the need for tedious pretreatments.

Use of specially designed columns for antioxidants and antimicrobials enrichment by preparative supercritical fluid chromatography

A new, specially designed column has been developed for fractionation of supercritical fluid extract of rosemary by using a preparative supercritical fluid chromatography system (Prep-SFC). The column evaluated in this work was prepared using a new packing method consisting of a combination of slurry and supercritical CO2 with commercial silica particles coated with a stationary phase commonly used in gas chromatography, such as SE-54 (5% phenyl-, 95% methylsilicone). The new packing procedure provided columns with reasonable efficiencies, with high stability and useful at high-pressure range. A 25 cm x 10 mm i.d. column packed with silica particles coated with 3% of SE-54 was prepared, and its separation power was tested for isolating fractions with high antioxidant and/or antimicrobial activity from a supercritical rosemary extract. The SFC conditions were selected based on a previous work done with a commercial LC-Diol packed column (130 bar, 80 degrees C), and different percentages of modifier in the mobile phase were tested (5 and 10%). Two cyclones were employed to collect the fractions which were then characterized by HPLC-diode array detection (DAD), GC, and in vitro antioxidant and antimicrobial assays. The use of coated packed columns allowed the fractionation of a complex mixture of rosemary supercritical extract with a minimum amount of modifier in the mobile phase (5% ethanol). At the optimum conditions it was possible to obtain two very active fractions in terms of antioxidant and antimicrobial activity, with no residual rosemary aroma and with improved activities compared to the original supercritical extract.

Determination of total safranal by in situ acid hydrolysis in supercritical fluid media: Application to the quality control of commercial saffron

A procedure allowing hydrolysis reactions to be conducted in a dynamic supercritical-CO2 medium was developed for quantifying total safranal (viz. free safranal present in the sample+safranal resulting from picrocrocin hydrolysis), which are the main component of the essential oil and responsible for the characteristic aroma of saffron. The proposed method allows total safranal amounts over the ranges 0.05-1.5 mg mL(-1) to be determined. The standard deviation achieved was 2%. This method was applied to the determination of safranal in natural saffron samples. The results obtained were compared with the "safranal value" total index, which is widely used as a quality measure of saffron products. The comparison revealed that the proposed method provides useful information not contained in the safranal value, based on the fact that, some samples with a high "safranal index" contain low concentrations of safranal. The proposed method is very useful for quality control in commercial saffron samples.

Enantioselective separations by packed column subcritical and supercritical fluid chromatography

Enantioselective separations have been one of the most successful applications of supercritical fluid chromatography (SFC). Although analytical scale separations have dominated the literature, the use of SFC for preparative chiral separations is growing. Both analytical and preparative scale SFC separations seek to take advantage of the high efficiency, high throughput, and rapid method development associated with the technique. This review will cover recent developments in the application of SFC to enantioseparations.

Separation of rosemary antioxidant compounds by supercritical fluid chromatography on coated packed capillary columns

Antioxidant compounds in rosemary extracts obtained by supercritical fluid extraction (SFE) were separated by supercritical fluid chromatography (SFC) on packed capillary columns. The columns contained silica particles coated with SE-54 (5% phenyl, 95% methyl silicone) and Carbowax 20 M [poly(ethylene glycol)]. The use of coated packed capillary columns allowed the separation of polar compounds by SFC with neat CO2. The SFC conditions were selected on the basis of previous work. High pressures (up to 370 atm; 1 atm = 10,325 Pa) and moderate temperatures (up to 100 degrees C) were used to separate the compounds responsible for the antioxidant activity such as carnosic acid and camosol while lower pressures were sufficient to separate the compounds of the essential oil.

Determination of thermodynamic properties by supercritical fluid chromatography

This survey attempts to summarise thermodynamic applications of supercritical fluid chromatography (SFC) with an emphasis on the results published during the last 10 years. In addition to a review of thermodynamic measurements by SFC, it contains brief sections on instrumental considerations and on the sources of auxiliary information needed when processing the retention data.

Derivatization of Chiral Amino Acids in Supercritical Carbon Dioxide

A new method is proposed to perform the derivatization of chiral amino acids occurring in complex samples using supercritical carbon dioxide as both the reaction medium and the agent used to extract the obtained derivatives prior to accomplishing the subsequent enantiomeric chromatographic analysis. The derivatization step under supercritical conditions involves the esterification of the carboxyl group and the acylation of the amino group of the amino acids without using a catalyst. A Chirasil-L-Val capillary column enabled the separation of the D- and L-forms of the amino acids as their N(O)-pentafluoropropionyl 1-propyl esters. Relative standard deviation values obtained from the gas chromatographic analysis for the derivatized amino acids ranged from 5 to 15%.

Supercritical carbon dioxide extraction of colchicine and related alkaloids from seeds of Colchicum autumnale L

A method for the extraction of the alkaloids colchicine, 3-demethylcolchicine and colchicoside from seeds of Colchicum autumnale by supercritical carbon dioxide has been established. Several parameters such as pressure, temperature, percentage of modifier and extraction time have been examined. Two extraction steps with constant carbon dioxide density (0.90 g/mL) and flux (1.5 mL/min) were required to extract the alkaloids in 110 min using 3% methanol as modifier. The quantitative determination of the alkaloids was performed by HPLC; the percentages of recovery were higher than 98% for the three alkaloids. This extraction procedure was compared with a conventional method involving maceration and sonication, and the same levels of alkaloids were obtained in each case. The supercritical carbon dioxide method is, however, very efficient, more rapid and more environmentally friendly than conventional methods.

Supercritical fluid extraction of all-trans-lycopene from tomato

A procedure is proposed for the supercritical fluid extraction of all-trans-lycopene from tomato using carbon dioxide at 40 degrees C without modifier. The present method minimizes the risk of degradation via isomerization and oxidation of health-promoting ingredients, such as lycopene. The effect of different experimental variables on the solvating power of the supercritical fluid was evaluated in terms of both the selectivity achievable in the process and the yield of the extraction of all-trans-lycopene. Satisfactory separations of the all-trans-lycopene isomers from the cis counterparts were achieved using a C(30) column. The obtained extract contained 88% all-trans-lycopene and 12% cis-lycopene.

Supercritical fluid extraction of potential migrants from paper and board intended for use as food packaging materials

The optimization of supercritical fluid extraction using CO2 for the extraction of contaminants in 15 samples of recycled paper and board (P&B) has been studied. An experimental design was used for simultaneous optimization of the variables involved in both the extraction step and the collection of the extract. Methanol was used as modifier. Several plastisizers such as diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, dioctyl adipate, and diethylhexyl phthalate (from 2 to 100 microg/g of paper) were found in the recycled P&B samples. A discriminate analysis applied to all results obtained allow us to classify the samples in three different groups according to the content of recycled pulp (0, 10-30, and > 80% of recycled pulp), the sample thickness (from <300 to >600 microm), and the surface treatment of the paper. The analytical behavior and the results are discussed.

Supercritical fluid extraction: an innovative tool for a fly ash-like model support

The performance of the supercritical fluid extraction (SFE) technique to obtain a new and more appropriate model support for PCDD/F formation studies was investigated. To characterize fly ash and model supports and relate their chemical-physical properties, surface area and pore size were determined. To evaluate the influence on reactivity of the different model supports with respect to raw fly ash, a kinetic study of the thermal behavior of dibenzofuran (DF) was performed. Rate constants as well as the activation and thermodynamic parameters for the different systems were also compared. The model support obtained from SFE was very similar to raw fly ash from the structural, physical-chemical, and kinetic points of view.

Extraction of pharmaceutical components from Ginkgo biloba leaves using supercritical carbon dioxide

Ginkgo biloba extract (GBE) has many remarkable pharmacological and clinical effects, and it is the most frequently used product as a phytomedicine in many countries. The combination of primary extraction with 70% ethanol followed by extraction using supercritical carbon dioxide provides an efficient and economical means for obtaining flavonoids and terpenoids from Ginkgo biloba leaves. The supercritical fluid extraction (SFE) is affected by pressure, temperature, and the concentration of modifier in the extractant. At the most favorable experimental conditions of 300 MPa, 60 degrees C, and carbon dioxide containing 5% ethanol as modifier, the yield of GBE powder is 2.1% (based on the air-dry weight of Ginkgo biloba leaves) compared to a yield of only 1.8% by conventional solvent extraction. The contents of flavonoids and terpenoids in SFE products are 35.9% and 7.3%, respectively, which are significantly higher than the general standards of 24% and 6%, respectively.

Supercritical fluid extraction and chromatography for fat-soluble vitamin analysis

Extraction and chromatographic separation of fat-soluble vitamins is a challenging task, due to the sensitivity of these compounds towards light, oxygen, heat and pH. In light of this, supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC) are attractive techniques as they function at considerably milder conditions than conventional solvent-based analytical techniques. Moreover, supercritical techniques consume much less amounts of organic solvents than conventional ones. This review gives a brief description of suitable supercritical media as well as basic theory on SFE and SFC processes. Furthermore, guidelines are provided for optimizing the important extraction and separation parameters to facilitate a successful method development. Finally, applications employing SFE and/or SFC for fat-soluble vitamin enrichment and final determination are reviewed.

Supercritical fluid extraction for liquid chromatographic determination of carotenoids in Spirulina Pacifica algae: a chemometric approach

An experimental design procedure was used to investigate the effects of some operating parameters on the supercritical fluid extraction of carotenoids beta-carotene, beta-cryptoxanthin and zeaxanthin from Spirulina Pacifica algae, a carotenoid-rich dietary product. Variables tested were temperature and pressure of the supercritical fluid, dynamic extraction time and percentage of ethanol added as the modifier. Each variable was tested at three levels; 31 experiments were performed in random order. Analyses of the extracts were performed by high-performance liquid chromatography with UV-Vis photodiode array detection. Analytical responses (chromatographic peak areas) were processed by using a stepwise multiple regression analysis, in order to find polynomial functions describing the relationships between variables and responses. For all the analytes the experimental conditions providing the highest extraction yield inside the experimental domain considered were found. Supercritical fluid extraction results obtained in these conditions were compared with those obtained by performing solvent extraction in order to evaluate the effectiveness of the supercritical fluid extraction procedure.

Enantioseparations in super- and subcritical fluid chromatography

The separation of chiral compounds by sub- and supercritical fluid chromatography has been a field of great progress since the first demonstration of a chiral separation by SFC in 1985. Almost all of the chiral selectors used in gas or liquid chromatography have been successfully applied to sub-/supercritical chromatography. Easier and faster method development, high efficiency, superior and rapid separations of a wide variety of analytes, extended-temperature capability, analytical and preparative-scale equipment improvements and a selection of detection options have been reported.

Determination of solubilities of uranium complexes in supercritical CO2 by on-line laser-induced fluorescence

A new approach to the measurement of solubilities in supercritical CO2 is reported, utilizing laser-induced fluorescence. This selective technique was found to be capable of rapid multipoint solubility measurements with high sensitivity (10(-9) M). The sensitivity enables measurements to be performed with small amounts of analytes and at low pressure, 80-130 atm, typically below the range of other methods. Four uranyl complexes were investigated using this method, UO2(TTA)2.H20, UO2(TTA)2.TBP, UO2(TTA)2.TOPO, and UO2(NO3)2.2TBP (where TTA = thenoyltrifluoroacetone, TBP = tributyl phosphate, and TOPO = trioctyl phosphine oxide). Comparison with solubility data previously obtained with UV-visible spectroscopy shows good agreement between the techniques. We have shown that the Chrastil solubility equation is equally valid at lower ScF densities, and consequently, solubility values determined at high pressures can be extrapolated to the low-pressure regions and vice versa for solid materials.

Supercritical fluid extraction and accelerated solvent extraction of dioxins from high- and low-carbon fly ash

This study investigates the replacement of Soxhlet extraction by supercritical fluid extraction (SFE) or accelerated solvent extraction (ASE) for the removal of dioxins from municipal waste incinerator fly ash. SFE is very matrix dependent; higher percent recoveries versus Soxhlet extraction can be obtained for low-carbon-level fly ash, but only a few percent of dioxins can be extracted from high-carbon-level fly ash. The addition of large quantities of toluene in the extraction cell prior to extraction of high-carbon fly ash improves the recovery of the lowest chlorinated dioxins (approximately 90%), but a maximum of 20% of the octachlorodibenzo-p-dioxins can be extracted. Since large quantities of toluene are needed to improve the recoveries, ASE with toluene was tested. Recoveries similar to Soxhlet extraction can be obtained in 2 h at 80 degrees C. Increasing the temperature to 150 degrees C increases the extraction rate and yields recoveries of approximately 110-160% compared to 48-h Soxhlet extraction for all congeners for both low- and high-carbon fly ashes. These results question the choice of Soxhlet extraction as a reference method for dioxin determination.

Strategies for supercritical fluid extraction of hyoscyamine and scopolamine salts using basified modifiers

The supercritical fluid extraction behaviors of hyoscyamine and scopolamine were investigated and found to be highly dependent upon the chemical nature of the compounds. Free bases of hyoscyamine and scopolamine were freely soluble in supercritical CO2 with increasing temperature and pressure; however, the salts of these alkaloids were not soluble under any experimental conditions. It was found that alkaline modifiers such as methanol basified with diethylamine could enhance the solubilities and extraction yields of these alkaloids from plant matrices as compared to other modifiers.

Analytical and preparative supercritical fluid extraction of chamomile flowers and its comparison with conventional methods

Supercritical fluid extraction (SFE) was compared with Soxhlet extraction, steam distillation and maceration for the isolation of the active components present in chamomile flowerheads. The obtained fractions were analysed by GC-MS and reversed-phase HPLC. The yield of essential oil achieved by a 30-min extraction with pure CO2 at 90 atm and 40 degrees C was 4.4 times higher than that produced by steam distillation performed for 4 h. The recovery of the flavonoid apigenin obtained by supercritical CO2 after a 30-min extraction at 200 atm and 40 degrees C was 71.4% compared to Soxhlet extraction performed for 6 h and 124.6% compared to maceration performed for 3 days. However, the highly polar flavonoid apigenin-7-glucoside was not extracted by 100% CO2 (recovery values < 1.1%). Its extraction efficiency was markedly improved by the addition of the polar modifier methanol (5%, v/v) to the CO2 fluid, yet the obtained recoveries were unsatisfactory (14.6-19.5%). The SFE method was scaled-up for preparative applications using a pilot plant with three separation stages operating in series. Large-scale SFE was technically feasible with pure CO2 as the extracting fluid. However, the use of CO2 modified with organic solvents was not effective at the pilot-plant scale.

Determination of imidazole antimycotics in creams by supercritical fluid extraction and derivative UV spectroscopy

A supercritical fluid extraction (SFE) method was developed for the isolation of imidazole antimycotic drugs (miconazole, econazole, clotrimazole and bifonazole) from cream preparations. The SFE process involved static (1 min) and dynamic (4 min) extraction steps using pure and 10% methanol modified carbon dioxide. The SFE step was then followed by derivative UV spectrophotometric analysis. The method proved to be suitable for quality control assays of the examined antimycotics in commercial cream formulations.