Orthogonal array design for the optimization of supercritical fluid extraction of baicalin from roots of Scutellaria baicalensis Georgi

Supercritical fluid was used to extract baicalin from the roots of Scutellaria baicalensis Georgi. An orthogonal array design (OAD), OA(9)(3(4)), was employed as a chemometric method for the optimization of the supercritical fluid extraction of baicalin from the herbal medicine. Four parameters, namely, modifiers, temperature and pressure of supercritical fluid, and the dynamic extraction time, were studied and optimized by a three-level OAD in which the interactions between the parameters were neglected. Determinations of the extracts were performed by high-performance liquid chromatography. The effects of parameters were studied using analysis of variance. The results showed that selection of the modifier was the main factor in attaining higher yields of baicalin. While the other three factors had some effect on the extraction of the compound, the effect was much less than that of the modifiers. 1,2-Propanediol-modified supercritical fluid was more effective than 95% ethanol-modified supercritical carbon dioxide or methanol-modified supercritical carbon dioxide for the extraction of baicalin from the solid matrix. Finally, experimental conditions were proposed which can provide the highest extraction yield with respect to the considered factors.     

Enantioseparation of atropine by capillary electrophoresis using sulfated beta-cyclodextrin: application to a plant extract

A capillary zone electrophoresis (CZE) method, with sulfated beta-CD as chiral selector, was optimized by means of an experimental design for the enantioseparation of atropine. In this study, a central composite design was used and the following factors were varied simultaneously: buffer concentration, buffer pH and sulfated beta-CD concentration. The resolutions between littorine and its positional isomer ((-)-hyoscyamine) and between atropine enantiomers, as well as the separation time and generated current were established as responses. A model was obtained for each response by linear multiple regression of a second-degree mathematical expression. The most favorable conditions were determined by maximizing the resolution between atropine enantiomers and by setting the other responses at threshold values. Successful results were obtained with a 55 mM phosphate buffer at pH 7 in the presence of 2.9 mM sulfated-beta-CD at 20 degrees C and 20 kV. Under these optimized conditions, a baseline separation of littorine and atropine enantiomers was achieved in less than 5 min. Finally, the method allowed the enantiomeric separation of atropine in a pharmaceutical formulation and was also found to be suitable for the enantiomeric purity evaluation of (-)-hyoscyamine in plant extracts, in relation with the extraction procedure. It was demonstrated that supercritical fluid extraction induced less racemization than classical liquid-solid extraction procedures.     

Packed Column SFC of Gas Oils. Part II: Experimental Design Optimization of the Group-Type Analysis using CO2-SF6 as the Mobile Phase

An optimization procedure is presented for group-type analysis of diesel fuel by supercritical fluid chromatography using packed silica column and a mixed mobile phase. A set of five responses, four values of resolution of a performance mixture and analysis time, was modeled using a Doehlert matrix for experimental design. Optimized experimental conditions for the five responses were obtained from a response surfaces optimization, taking into account various constraints on SF₆ content in mobile phase and analysis time. The predicted and experimental resolutions were in good agreement for the different optimized conditions and one of them was selected to for application to a given diesel fuel for comparison with the results obtained by SFC using pure CO₂ and by HPLC. The conditions found in this study provide an alternative method for the determination of mono-, di-, and polyaromatic compounds in middle distillates.     

Supercritical fluid extraction of ecdysterone from the roots of Achyranthes bidentata BL

Ecdysterone has been found in a great many plants and animals and has some valuable pharmaceutical properties. The present study was conducted to investigate optimal conditions for the extraction of the compound by supercritical fluid extraction from the roots of Achyranthes bidentata BL. An orthogonal array design (OAD), OA(9)(3(4)), was employed as a chemometric method for optimization of the extraction of ecdysterone from the herbal medicine. Four parameters, namely, pressure and temperature of the supercritical fluid, the dynamic extraction time, and the flow rate of dimethyl sulfoxide, were studied and optimized by a three-level OAD. Determinations of the extracts were performed by high-performance liquid chromatography. The effects of the parameters were studied using analysis of variance. The results shown that the yield of ecdysterone could be influenced by the four parameters to a similar degree. The yield for DMSO-modified supercritical CO(2) was in the range from 0.65 to 1.03 mg/g under the selected conditions. In comparison with methanol-modified supercritical CO(2 )and Soxhlet extraction, a higher yield was obtained when DMSO-modified supercritical CO(2) was used.     

Optimization of extraction of evodiamine and rutaecarpine from fruit of Evodia rutaecarpa using modified supercritical CO(2)

Evodiamine and rutaecarpine have been intensively studied due to their pharmacological actions and clinical applications. In this report, supercritical fluid was used to extract evodiamine and rutaecarpine from the unripe fruit of Evodia rutaecarpa. Response surface methodology using Box-Behnken experimental design was utilized to optimize parameters for supercritical carbon dioxide extraction with methanol as co-solvent. The effect of various values of dynamic extraction time (30-90min), temperature (50-70°C) and pressure (200-400bar) on extraction yields of the two compounds was evaluated. Determinations of the extracts were performed by high-performance liquid chromatography. The experimental data obtained were fitted to second-order polynomial equations and analyzed by analysis of variance. The highest yields predicted were 1.217mg/g for evodiamine and 0.969mg/g for rutaecarpine at the optimal values (time 78min, temperature 62°C, pressure 280bar and co-solvent flow rate 0.4mL/min), based on the selected range of experimental conditions.     

Near infrared thermal lens spectrometry for the real-time monitoring of supercritical fluid extraction

A commercially available supercritical fluid extractor provided with carbon dioxide was coupled to a dual-beam thermal lens spectrometer with a pumpprobe coaxial configuration, pumped by a pulsed Nd-YAG laser operating at the fundamental wavelength of 1064 nm. As a preliminary step, several compounds were studied in batch regime using carbon tetrachloride as solvent, in order to observe the influence of overtones and combinations involving distinct chemical bonds on thermal lens spectrometry (TLS). Several factors related with supercritical fluid extraction (SFE) under hydrodynamic conditions were studied in order to establish their influence both in the extraction yield and thermal lens signal magnitude obtained. The advantages and limitations of the hyphenated SFE-TLS technique proposed are discussed, and the possibility of on-line detection in SFE with a pulse thermal lens spectrometer was demonstrated.     

Monitoring supercritical fluid extraction by thermal lens spectrometry with pulsed laser excitation

A dual-beam thermal lens spectrometer (TLS) with a pulse pump–probe coaxial configuration was coupled to commercially available supercritical fluid extraction equipment using a high-pressure flow cell interface. Because of its feasible critical parameters, moderate cost and good thermooptical properties, carbon dioxide was used as supercritical solvent. Using trans-β-carotene as analyte, several factors related with the extraction process under continuos flow conditions were studied in order to establish their influence in the thermal lens signal magnitude. Under the optimum experimental conditions, the relative TLS signal area showed a linear relationship with the concentration of trans-β-carotene from 1.5×10⁻⁶ to 8×10⁻⁸ M (n=5, r=0.998) in the supercritical phase. Thus, the viability of on-line detection for supercritical fluid extraction with a pulse thermal lens spectrometer was demonstrated.     

The analysis of chlorinated dibenzofurans in municipal fly ash: Supercritical fluid extraction vs Soxhlet

A multiresidue supercritical fluid extraction procedure for chlorinated dibenzofurans (PCDFs) has been optimized as an efficient method for the determination of these compounds in fly ash samples. The results were compared with those obtained by Soxhlet extraction. Extracts from the two procedures were analyzed by gas chromatography–mass spectrometry (HRGC–MS) Statistical analysis of the results confirmed that supercritical fluid extraction provides data with a relative standard deviation of less than 10% while Soxhlet extraction data show a much greater spread.     

Extraction of norflurazon residues in cotton seeds with supercritical CO2

Summary A new method for the extraction of Norflurazon residues in cotton seeds using supercritical CO₂ as the extracting fluid is described. The supercritical fluid extraction results were compared with those of the classical procedure using liquid extraction. All SFE experiments were performed using a home-made system. The method presented, besides being faster and more economical than existing methods, showed better recovery, with higher selectivity for Norflurazon extraction.     

Reactive supercritical fluid extraction and chromatography of arsenic species

Reactive supercritical fluid extraction has been used for the speciation of organic (DMA and MMA) and inorganic (As(III) and As(V)) arsenic compounds in solid samples. Derivatization with thioglycolic acid methylester (TGM) was performed in supercritical carbon dioxide. Different extraction conditions have been tested. The arsenic derivatives have been analyzed by GC. A capillary-SFC method was evaluated for the analysis of the TGM derivatives and compared with GC.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Solid-phase extraction with supercritical fluid elution as a sample preparation technique for the ultratrace analysis of flavone in blood plasma.

A new sample preparation technique, solid-phase extraction with supercritical fluid elution, was developed for the selective isolation of ultratrace levels of drugs from plasma. Plasma samples spiked with a drug were applied to octadecylsilane cartridges and the cartridges were then washed, briefly dried and directly fitted into cells for subsequent supercritical fluid elution. The absolute recovery was studied by using a radiolabeled model compound. The extraction selectivity was examined by chromatographing the extracts with a reversed-phase high-performance liquid chromatographic method with ultraviolet detection. The effects of extraction pressure and the length of capillary restrictors on drug recovery were examined in order to determine the optimal conditions for supercritical fluid elution. The performance of the method was compared to that of conventional solid-phase extraction in terms of recovery, selectivity, precision and accuracy of analysis. Flavone was used as the model compound and dog plasma as the biological matrix for these studies.     

Extraction of carotenoids and chlorophyll from microalgae with supercritical carbon dioxide and ethanol as cosolvent

The extraction of carotenoids and chlorophylls using carbon dioxide modified with ethanol as a cosolvent is an alternative to solvent extraction because it provides a high-speed extraction process. In the study described here, carotenoid and chlorophyll extraction with supercritical CO(2 )+ ethanol was explored using freeze-dried powders of three microalgae (Nannochloropsis gaditana, Synechococcus sp. and Dunaliella salina) as the raw materials. The operation conditions were as follows: pressures of 200, 300, 400 and 500 bar, temperatures of 40, 50 and 60 degrees C. Analysis of the extracts was performed by measuring the absorbance and by using empirical correlations. The results demonstrate that it is necessary to work at a temperature of 50-60 degrees C and a pressure range of 300-500 bar, depending on the type of microalgae, in order to obtain the highest yield of pigments. The best carotenoid/chlorophyll ratios were obtained by using supercritical fluid extraction + cosolvent instead of using conventional extraction. The higher selectivity of the former process should facilitate the separation and purification of the two extracted pigments.     

Optimization of parameters for the supercritical fluid extraction in the determination of N-nitrosamines in rubbers

The study of the possibilities of supercritical fluid extraction (SFE) with N-nitrosamines in rubbers has been carried out. Home-made materials fortified with several N-nitrosamines were prepared in order to optimize the SFE parameters. A Plackett-Burman design was employed to evaluate the influence of those parameters to be controlled in SFE, such as pressure, temperature, static and dynamic time, restrictor temperature and volume of modifier while CO2 was used as the extraction fluid. An extra central composite design for the main factors (according to the previously obtained results) was also developed in order to refine the best supercritical conditions for the extraction of N-nitrosamines from rubbers. Gas chromatography with a nitrogen and phosphorus sensitive detector was used to achieve sensitivity and limits of detection for the concentrations expected in plastic materials. The proposed analytical method has shown to be useful in the determination of N-nitrosamines even for complex matrices.     

Determination of lipid mediators in breast cancer cells using lyophilization‒supercritical fluid extraction online coupled with supercritical fluid chromatography‒quadrupole tandem mass spectrometry

A lyophilization?supercritical fluid extraction coupled with supercritical fluid chromatography?quadrupole tandem mass spectrometry online method was developed for the determination of lipid mediators in breast cancer cells. Supercritical fluid extraction was applied to the cell samples for the first time due to the use of lyophilization. The conditions of supercritical fluid extraction and supercritical fluid chromatography?quadrupole tandem mass spectrometry were investigated systematically. Under the optimized conditions, all the calibration curves for the lipid mediators showed good linearity (correlation coefficient > 0.99). The limits of detection and the limits of quantification were in the range of 0.190?5.36 pg and 0.560?16.2 pg, respectively. The recoveries were in the range of 70.3?125%. The relative standard deviations of the precision ranged from 1.49?18.7% and the accuracies were higher than 84%. Compared with liquid?liquid extraction coupled with liquid chromatography and tandem mass spectrometry method, the present approach reduced the manual labor and obtained higher sensitivity as well as higher extraction recoveries for all 15 lipid mediators. Finally, the online method was applied to the quantification of lipid mediators in breast cancer cells and normal mammary epithelial cells. On the basis of the results, this lyophilization?supercritical fluid extraction online coupled with supercritical fluid chromatography?quadrupole tandem mass spectrometry method showed great promise in the analysis of lipid mediators in complex biological samples.     

Optimisation and characterisation of marihuana extracts obtained by supercritical fluid extraction and focused ultrasound extraction and retention time locking GC‐MS

The optimisation of focused ultrasound extraction and supercritical fluid extraction of volatile oils and cannabinoids from marihuana has been accomplished by experimental design approach. On the one hand, the focused ultrasound extraction method of volatile compounds and cannabinoids was studied based on the optimisation of cyclohexane and isopropanol solvent mixtures, and the instrumental variables. The optimal working conditions were finally fixed at isopropanol/cyclohexane 1:1 mixture, cycles (3 s^?1), amplitude (80%) and sonication time (5 min). On the other hand, the supercritical fluid extraction method was optimised in order to obtain a deterpenation of the plant and a subsequent cannabinoid extraction. For this purpose, pressure, temperature, flow and co‐solvent percentage were optimised and the optimal working conditions were set at 100 bar, 35°C, 1 mL/min, no co‐solvent for the terpenes and 20% of ethanol for the cannabinoids. Based on the retention time locking GC‐MS analysis of the supercritical fluid extracts the classification of the samples according to the type of plant, the growing area and season was attained. Finally, three monoterpenes and three cannabinoids were quantified in the ranges of 0.006–6.2 μg/g and 0.96–324 mg/g, respectively.     

Simultaneous analysis of antioxidants and preservatives in cosmetics by supercritical fluid extraction combined with liquid chromatography-mass spectrometry

This study evaluated supercritical fluid extraction (SFE) combined with liquid chromatography-mass spectrometry (LC-MS) to determine trace preservatives and antioxidants including methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol (alpha-t) and alpha-tocopherol acetate (alpha-ta) in cosmetic products. A supercritical fluid extraction procedure was used to isolate four paraben preservatives and four antioxidants from the cosmetic matrix before quantitative analysis. The optimum extraction condition was performed with static extraction for 5 min, then dynamic extraction for 20 min by using carbon dioxide supercritical fluid at 14,000 kPa and 65 degrees C. Methanol was used as collection solvent and the sea sand was chosen as a filling material. The analytes were separated on a C18 reversed-phase column using methanol-water as mobile phase and quantified by measuring its mass spectrometry. The linearity range is from 10 to 20,000 ng/g with RSD values below 18%. Detection limits are achieved at the level of 4.7-142 ng/g. It was successfully applied to the determination of paraben preservatives and antioxidants in cosmetics without tedious pretreatment.     

Microcalorimetric determination of the activity of supercritical extracts of wormwood (Artemisia absinthium L.) over Spodoptera littoralis

The aim of this study is to develop a method and to determine by means of isothermal microcalorimetry the activity of supercritical extracts obtained from growth-controlled wormwood (Artemisia absinthium L.) over Spodoptera littoralis L. (S. littoralis), a polyphagous pest of the Mediterranean crops. In order to achieve this goal, a three-step microcalorimetric method has been developed to insure the quality of the measurements and the validity of the results. Once optimized, different extracts of wormwood obtained by means of supercritical fluid extraction and by traditional methods have been used to investigate their effects over S. littoralis. The microcalorimetric method serves as a tool to complement other bioassays found in the literature. Several extracts from supercritical extractions with solvent density ranging from 485.5 to 819.5 kg m^?3 have been tested. The influence of an entrainer addition to the supercritical fluid has also been investigated. The traditional extracts were obtained by hydrodistillation and organic Soxhlet extraction. The supercritical extracts were more efficient against S. littoralis than the traditionally obtained extracts.     

Supercritical CO2 extraction of emodin and physcion from Polygonum cuspidatum and subsequent isolation by semipreparative chromatography

Emodin and physcion are abundant anthraquinone compounds found in the traditional Chinese medicinal herb Polygonum cuspidatum Sied. et Zucc. In this paper, emodin and physcion were successfully extracted with supercritical CO2 plus ethanol modifier after the extraction conditions were optimized with uniform design-sequential optimization. Results showed that the ethanol modifier concentration was the main factor for the effective extraction of the emodin. The optimal extraction condition was obtained: 20 MPa, 30 degrees C, and 95% ethanol, at which the yields of emodin and physcion were 0.616 and 0.178 g/100 g, respectively. The yield obtained by supercritical fluid extraction (SFE) was a little lower than that obtained by sonication extraction (SE). The crude extract obtained by SFE was further isolated and purified by semipreparative chromatography with the mobile phase composed of methanol-water (90:1, v/v). Emodin and physcion were obtained with purity 98.6 and 99.1%, respectively, when determined by HPLC, and identification was performed by retention time and UV spectra of the standards. The result suggested that SFE is an alternative and promising method for extraction of the two compounds from P. cuspidatum owing to its environment-friendly properties and fewer coextracts.     

Determination of major aromatic constituents in vanilla using an on‐line supercritical fluid extraction coupled with supercritical fluid chromatography

An on‐line supercritical fluid extraction coupled with supercritical fluid chromatography method was developed for the determination of four major aromatic constituents in vanilla. The parameters of supercritical fluid extraction were systematically investigated using single factor optimization experiments and response surface methodology by a Box–Behnken design. The modifier ratio, split ratio, and the extraction temperature and pressure were the major parameters which have significant effects on the extraction. While the static extraction time, dynamic extraction time, and recycle time had little influence on the compounds with low polarity. Under the optimized conditions, the relative extraction efficiencies of all the constituents reached 89.0–95.1%. The limits of quantification were in the range of 1.123–4.747 μg. The limits of detection were in the range of 0.3368–1.424 μg. The recoveries of the four analytes were in the range of 76.1–88.9%. The relative standard deviations of intra‐ and interday precision ranged from 4.2 to 7.6%. Compared with other off‐line methods, the present method obtained higher extraction yields for all four aromatic constituents. Finally, this method has been applied to the analysis of vanilla from different sources. On the basis of the results, the on‐line supercritical fluid extraction‐supercritical fluid chromatography method shows great promise in the analysis of aromatic constituents in natural products.     

Direct online extraction and determination by supercritical fluid extraction with chromatography and mass spectrometry of targeted carotenoids from red Habanero peppers (Capsicum chinense Jacq.)

Recently, supercritical fluid chromatography coupled to mass spectrometry has gained attention as a fast and useful technology applied to the carotenoids analysis. However, no reports are available in the literature on the direct online extraction and determination by supercritical fluid extraction with chromatography and mass spectrometry. The aim of this research was the development of an online method coupling supercritical fluid extraction and supercritical fluid chromatography for a detailed targeted native carotenoids characterization in red habanero peppers. The online nature of the system, compared to offline approaches, improves run‐to‐run precision, enables the setting of batch‐type applications, and reduces the risks of sample contamination. The extraction has been optimized using different temperatures, starting from 40°C up to 80°C. Multiple extractions, until depletion, were performed on the same sample to evaluate the extraction yield. The range of the first extraction yield, carried out at 80°C, which was the best extraction temperature, was 37.4–65.4%, with a %CV range of 2–12. Twenty‐one targeted analytes were extracted and identified by the developed methodology in less than 17 min, including free, monoesters, and diesters carotenoids, in a very fast and efficient way. Quantification of the β‐carotene was carried out by using the optimized conditions.