| 11. |
- Cui, Jingwen, et al.
(author)
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Measurement of relative static permittivity and solvatochromic parameters of binary and ternary CO2-expanded green solvents
- 2021
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In: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446 .- 1872-8162. ; 171
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Journal article (peer-reviewed)abstract
- CO2-expanded liquids (CXLs) is a class of solvent systems giving relatively low viscosity in comparison to neat organic solvents. The challenge is to achieve a high overall polarity of the CXL, despite the presence of compressed liquid CO2. In this study, the relative static permittivity (εr) was measured for binary and ternary one-phase mixtures of CO2 + green solvent using an in-line microfluidic device. In addition, Kamlet-Taft solvatochromic parameters were experimentally determined, allowing the characterization of the polarizability, acidity, and basicity. Novel data is shown for binary and ternary systems of CO2 expanded ethanol and ethyl lactate, with or without glycerol or water added, at moderate conditions of pressure and temperature (8 MPa and 35 °C). One-phase CXLs systems of a wide relative permittivity range (7.7–75.3) at lowered viscosity were enabled, by mixing different green solvents with CO2.
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| 12. |
- Cunico, Larissa P., et al.
(author)
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Enhanced distribution kinetics in liquid-liquid extraction by CO2-expanded solvents
- 2020
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In: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 163
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Journal article (peer-reviewed)abstract
- Liquid-liquid extraction (LLE) is a useful extraction technique for highly complex samples, however, it suffers from being slow due to mass transfer limitations. Carbon dioxide expanded liquids (CXL) is a good replacement of traditional organic solvents for extraction, and for the first time, the use of CXL in LLE was evaluated. An equipment consisting of a high-pressure view cell with on-line gas chromatography analysis was built and validated, and thereafter used to obtain novel phase equilibria data of the CO2/n-octanol/water system. The system was connected on-line to HPLC to study the potential of CO2-expanded liquid-liquid extraction (CXLLE) of pharmaceutical contaminants in water. In comparison with traditional LLE performed under similar experimental conditions, the addition of CO2 as a viscosity-lowering entrainer significantly increased the speed of mass transfer. Changes in compound log D (octanol-water distribution ratio) values brought by the CO2 expansion also proved the possibility of selectivity-tuning in CXLLE.
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| 13. |
- Ekström, Sara M., et al.
(author)
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Reactivity of dissolved organic matter in response to acid deposition
- 2016
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In: Aquatic Sciences. - : Springer. - 1015-1621 .- 1420-9055. ; 78:3, s. 463-475
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Journal article (peer-reviewed)abstract
- Fluvial export of organic matter from the terrestrial catchment to the aquatic system is a large and increasing carbon flux. The successful reduction in sulfuric acid deposition since the 1980s has been shown to enhance the mobility of organic matter in the soil, with more terrestrially derived dissolved organic matter (DOM) reaching aquatic systems. Changes in soil acidity also affect the quality of the DOM. In this study we explore the consequences this may have on the reactivity and turnover of the terrestrially derived DOM as it reaches the aquatic system. DOM of different quality (estimated by absorbance, fluorescence and size exclusion chromatography) was produced through extraction of boreal forest O-horizon soils from podzol at two sulfuric acid concentrations corresponding to natural throughfall in spruce forest in Southern Sweden around 1980 and today. Extraction was done using two different methods, i.e. field leaching and laboratory extraction. The DOM extracts were used to assess if differences in acidity generate DOM of different reactivity. Three reactivity experiments were performed: photodegradation by UV exposure, biodegradation by bacteria, and biodegradation after UV exposure. Reactivity was assessed by measuring loss of dissolved organic carbon and absorbance, change in fluorescence and molecular weight, and bacterial production. DOM extracted at lower sulfuric acid concentration was more susceptible to photooxidation, and less susceptible to bacterial degradation, than DOM extracted at a higher sulfuric acid concentration. Thus the relative importance of these two turnover processes may be altered with changes in acid deposition.
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| 14. |
- Gondo, Thamani Freedom, et al.
(author)
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Extractability, selectivity, and comprehensiveness in supercritical fluid extraction of seaweed using ternary mixtures of carbon dioxide, ethanol, and water
- 2023
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In: Journal of chromatography. A. - 0021-9673. ; 1706, s. 464267-464267
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Journal article (peer-reviewed)abstract
- It is well-known that an ideal extraction method enabling quantitative analysis should give complete extraction of the target analytes as well as minimal co-extraction of unwanted matrix substances. If the extraction method is part of a nontarget screening protocol, the desired analytes can differ widely in terms of chemical properties. In chromatography, terminologies such as recovery, selectivity, and comprehensiveness are well-established and can easily be determined. However, in extraction, these concepts are much less developed. Hence, the aim of our research is to develop and scrutinize theory in extraction with respect to numerical descriptors for extractability, selectivity, and comprehensiveness. Our approach is based on experiments determining the extractability of target analytes and selected interferences. As a case study, we use a pooled sample of three species of seaweed (Alaria esculenta, Laminaria digitata and Ascophyllum nodosum). Target analytes are β-carotene, fucoxanthin, δ-tocopherol, and phloroglucinol; and selected interferences are carbohydrates, proteins, ash, arsenic, and chlorophyll a. As a "green and clean" extraction technique, supercritical fluid extraction (SFE) using mixtures of CO 2, ethanol and water were explored using a design of experiment. The temperature was varied between 40-80°C, and the pressure was held constant at 300 bar. Obtained results clearly demonstrate that highest relative selectivity was achieved with CO 2 containing only 5 vol% of ethanol and no water, which primarily enabled high extractability of β-carotene, and yielding an extract free of carbohydrates, proteins, and toxic metals such as arsenic. Best methods for highest extractability of the other target analytes varied quite widely. Analytes requiring the highest water content (fucoxanthin and phloroglucinol), also resulted in the lowest relative selectivity. Maximum relative comprehensiveness was achieved using CO 2/ethanol/water (40/55/5, v/v/v) at 70°C and 300 bar. Our study demonstrates the feasibility of using relative quantitative descriptors for extractability, selectivity, and comprehensiveness, in optimization strategies for analytical extractions.
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| 15. |
- Grigonis, D, et al.
(author)
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Comparison of different extraction techniques for isolation of antioxidants from sweet grass (Hierochloe odorata)
- 2005
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In: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 33:3, s. 223-233
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Journal article (peer-reviewed)abstract
- Strong antioxidants, 5,8-dihydroxycoumarin and 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone were extracted from sweet grass (Hierochloe odorata L.) by using Soxhlet (SE), microwave-assisted (MAE) and supercritical fluid carbon dioxide (SFE) extractions at different extraction schemes and parameters. One-step MAE gave the most concentrated extract with 8.15% of 5,8-dihydroxycoumarin (extract yield 0.42%). Comparable results were obtained by one-step SFE and Soxhlet extraction. A two-step extraction was applied in order to increase the concentration of active compounds. Taking into account antioxidant recovery and concentration as well the extraction time and environmental aspects, two-step SFE was considered as a preferable method. The obtained crude extract contained 20.31% of 5,8-dihydroxycoumarin and 2.18% of 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone. The extraction yields were 0.46 and 0.06%, respectively. First-step of SFE extraction was performed from dried herb at 35 MPa and 40degreesC with 20% of ethanol as a modifier; the second extraction step was performed from the crude extract at 25 MPa and 40degreesC.
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| 16. |
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| 17. |
- Hyder, Murtaza, et al.
(author)
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Yearly trend of dicarboxylic acids in organic aerosols from south of Sweden and source attribution
- 2012
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 57, s. 197-204
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Journal article (peer-reviewed)abstract
- Seven aliphatic dicarboxylic acids (C3-C9) along with phthalic acid, pinic acid and pinonic acid were determined in 35 aerosol (PM10) samples collected over the year at Vavihill sampling station in south of Sweden. Mixture of dichloromethane and methanol (ratio 1:3) was preferred over water for extraction of samples and extraction was assisted by ultrasonic agitation. Analytes were derivatized using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) containing 1% trimethylsilyl chloride and analyzed using gas chromatography/mass spectrometry. Among studied analytes, azelaic acid was found maximum with an average concentration of 6.0 +/- 3.6 ng m(-3) and minimum concentration was found for pimelic acid (1.06 +/- 0.63 ng m(-3)). A correlation coefficients analysis was used for defining the possible sources of analytes. Higher dicarboxylic acids (C7-C9) showed a strong correlation with each other (correlation coefficients (r) range, 0.96-0.97). Pinic and pinonic acids showed an increase in concentration during summer. Lower carbon number dicarboxylic acids (C3-C6) and phthalic acid were found strongly correlated, but showed a poor correlation with higher carbon number dicarboxylic acids (C7-C9), suggesting a different source for them. Biomass burning, vehicle exhaust, photo-oxidation of volatile organic compounds (natural and anthropogenic emissions) were possible sources for dicarboxylic acids. (C) 2012 Elsevier Ltd. All rights reserved.
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| 18. |
- Jumaah, Firas, et al.
(author)
-
A fast and sensitive method for the separation of carotenoids using ultra-high performance supercritical fluid chromatography-mass spectrometry
- 2016
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In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 408:21, s. 5883-5894
-
Journal article (peer-reviewed)abstract
- In this study, a rapid and sensitive ultra-high performance supercritical fluid chromatography-mass spectrometry (UHPSFC-MS) method has been developed and partially validated for the separation of carotenoids within less than 6 min. Six columns of orthogonal selectivity were examined, and the best separation was obtained by using a 1-aminoanthracene (1-AA) column. The length of polyene chain as well as the number of hydroxyl groups in the structure of the studied carotenoids determines their differences in the physiochemical properties and thus the separation that is achieved on this column. All of the investigated carotenoids were baseline separated with resolution values greater than 1.5. The effects of gradient program, back pressure, and column temperature were studied with respect to chromatographic properties such as retention and selectivity. Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were compared in both positive and negative mode, using both direct infusion and hyphenated with UHPSFC. The ESI in positive mode provided the highest response. The coefficient of determination (R2) for all calibration curves were greater than 0.998. Limit of detection (LOD) was in the range of 2.6 and 25.2 ng/mL for α-carotene and astaxanthin, respectively, whereas limit of quantification (LOQ) was in the range of 7.8 and 58.0 ng/mL for α-carotene and astaxanthin, respectively. Repeatability and intermediate precision of the developed UHPSFC-MS method were determined and found to be RSD <3 % and RSD <6 %, respectively. The method was applied in order to determine carotenoids in supercritical fluid extracts of microalgae and rosehip. [Figure not available: see fulltext.]
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| 19. |
- Jumaah, Firas, et al.
(author)
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A rapid method for the separation of vitamin D and its metabolites by ultra-high performance supercritical fluid chromatography-mass spectrometry.
- 2016
-
In: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1440, s. 191-200
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Journal article (peer-reviewed)abstract
- 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 (R(2))≥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.
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| 20. |
- Jumaah, Firas, et al.
(author)
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Rapid and Green Separation of Mono- and Diesters of Monochloropropanediols by Ultrahigh Performance Supercritical Fluid Chromatography-Mass Spectrometry Using Neat Carbon Dioxide as a Mobile Phase
- 2017
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In: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 65:37, s. 8220-8228
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Journal article (peer-reviewed)abstract
- This study demonstrates the effect of column selectivity and density of supercritical carbon dioxide (SC-CO2) on the separation of monochloropropanediol (MCPD) esters, known as food toxicants, using SC-CO2 without addition of cosolvent in ultrahigh performance supercritical fluid chromatography-mass spectrometry (UHPSFC-MS). This study shows that over 20 2-monochloropropanediol (2-MCPD) and 3-monochloropropanediol (3-MCPD) mono- and diesters are separated on a 2-picolylamine column in less than 12 min. The presence and position of a hydroxyl group in the structure, the number of unsaturated bonds, and the acyl chain length play a significant role in the separation of MCPD esters. The flow rate, backpressure, and column oven temperature, which affect the density of the mobile phase, were shown to have a substantial impact on retention, efficiency, and selectivity. The developed method was successfully applied for the determination of MCPD esters in refined oils and showed a close to excellent green analysis score using the Analytical Eco-Scale.
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