| 1. |
- Abrahamsson, Victor, et al.
(författare)
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Continuous multicomponent quantification during supercritical fluid extraction applied to microalgae using in-line UV/Vis absorption spectroscopy and on-line evaporative light scattering detection
- 2018
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 131, s. 157-165
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative methodology based on in-line UV/Vis absorption spectroscopy and on-line evaporative light scattering detection for supercritical fluid extraction is proposed. The method was applied to the extraction of carotenoids, chlorophyll A, ergosterol and total lipids from microalgae. One regression technique and two curve resolution techniques were applied on the absorption spectroscopy data and evaluated, namely classical least squares, multivariate curve resolution by alternating least squares and parallel factor analysis (PARAFAC2). The two former both generated useful models, furthermore multivariate curve resolution also successfully enabled estimation of both spectra and concentration profiles of the analytes. The integrated extraction profiles of each analyte were compared with analysis of the collected fractions using reference analysis methods Precision, in regards to quantification of the analytes in the eluent, was better using in-line measurements compared to off-line measurements by UV/Vis absorption spectroscopy, supercritical fluid chromatography with mass spectrometry and liquid chromatography with UV/Vis detection.
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| 2. |
- Abrahamsson, Victor, et al.
(författare)
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Determination of carotenoids in microalgae using supercritical fluid extraction and chromatography.
- 2012
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Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1250, s. 63-68
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Tidskriftsartikel (refereegranskat)abstract
- A method was developed based on supercritical fluid chromatography for quantitative determination of carotenoids in extracts of Scenedesmus sp. By utilizing the low backpressure in supercritical fluid chromatography, a C18 column and a 2-ethyl pyridine column were coupled in series. It was concluded that even minor changes in temperature had a substantial effect on selectivity. A standard mixture of 8 carotenoids and microalgae extracts obtained through supercritical fluid extraction with and without 10% ethanol as a co-solvent were successfully separated. All of the carotenoids were separated within 10min, while the total analysis time was 20min. The method was validated and the carotenoids of microalgae extracts were quantified. Furthermore, the method should be seen as a more rapid and environmentally sustainable alternative to traditional high-performance liquid chromatography methods utilizing organic solvents.
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| 3. |
- Abrahamsson, Victor, et al.
(författare)
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Determination of Sulfite in Beer Based on Fluorescent Derivatives and Liquid Chromatographic Separation
- 2012
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Ingår i: Journal of the American Society of Brewing Chemists. - 0361-0470 .- 1943-7854. ; 70:4, s. 296-302
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Tidskriftsartikel (refereegranskat)abstract
- A method was developed for quantification of sulfite in beer based on derivatization with the maleimide-derived probe ThioGlo I followed by separation of fluorescent adducts by reversed-phase high-performance liquid chromatography and fluorescence detection. Sulfite gave two ThioGlo 1 derivatives and it was shown by mass spectrometry that both had identical mass spectra. Matrix effects were observed when constructing sulfite standard curves in different beers and, therefore, use of a matrix-matched calibration curve is proposed. ThioGlo I was found to generate fluorescent adducts with both bound and free sulfite, providing a quantification of the total sulfite content in beer. The limit of quantification of sulfite was 0.6 mg/L and the method can be used for quantification of sulfite in highly colored beers.
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| 4. |
- Abrahamsson, Victor
(författare)
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Fundamental research on supercritical fluid extraction kinetics : From on-line measurements to inverse modeling
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Supercritical fluid extraction is an extraction technique suitable for lipophilic compounds from solid samples. Most commonly supercritical carbon dioxide is the main component in the extraction phase, rendering the technique relatively environmentally benign. The extraction technique is rapid due to the low viscosity and the high diffusivity of analytes in the supercritical extraction phase.The selectivity can be tuned by changing the extraction conditions of pressure, temperature and co-solvent amount. These process parameters along with flow rate and extraction time make optimization of an extraction method rather cumbersome. A fundamental understanding of the extraction process can help to make wise decisions during method development. In this work extractability, partitioning, solubility and internal and external mass transfer resistancehave been studied through inverse modeling.Methods based on in-line spectrophotometric measurements and on-line evaporative light scattering detection have been developed to efficiently acquire extraction curves, i.e., the extraction yield over time. These enable a highthroughput of extractions with high temporal resolution and good precision. The methods were applied to quantify total lipids from linseed and carotenoids, chlorophyll A, ergosterol and total lipids from microalgae. An off-line method for separating carotenoids based on supercritical fluid chromatography was also developed.Methodologies have been developed to acquire models which are calibrated using all experiments, so called complete calibration. It is shown that calibrating one model per experiment does not generate models with reliable parameters with physical meaning. The models can be used for predicting extraction curves within the investigated space of process parameters.Finally, extractability and partitioning are shown to be highly influential on the extraction process. Also, partitioning can give rise to diminishing extraction rates, which has previously believed only to be caused by intraparticlediffusion.
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| 5. |
- Abrahamsson, Victor, et al.
(författare)
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Impact of injection solvents on supercritical fluid chromatography.
- 2013
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1306, s. 80-88
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Tidskriftsartikel (refereegranskat)abstract
- Even though there has been a rapid development in instrumentation and applications of supercritical fluid chromatography (SFC), relatively little is known about retention mechanisms compared to high-performance liquid chromatography (HPLC). Much effort has been made to characterize the influence of injection solvents on chromatographic efficiency in HPLC, however has been left rather uninvestigated in the domain of SFC. In this study properties of different injection solvents have been studied and correlated with properties of seven various analytes on three different columns, a C18, a 2-ethylpyridine and a bare-silica column. Aided by calculations of correlation coefficients and principal component analysis (PCA), the physical properties of injection solvents and the interactions between injection solvent, solute and stationary phase were investigated. The findings of this work shows that interactions capable of masking accessible silanol groups on a C18 column are of importance in order to maximize the plate number. While solvents with dipolar and hydrogen bond interaction properties are associated negatively with chromatographic efficiency using polar columns. Properties such as molar density, vapor pressure and boiling point were related to sharper peaks, mostly likely because of solubility issues of the injection solvent into the methanol-modified carbon dioxide. However, no additional solubility due to hydrogen interactions between the injection solvent and the carbon dioxide in SFC was observed. Surface tension and viscosity was not particularly associated with a decrease in plate numbers. By increasing the injection volume a stronger correlation between solubility related properties and plate numbers were obtained. Additional experiments showed that the resistance in solubility became an issue when performing partial-loop injection where additional washing solvent entered the system, thus providing broadened peaks.
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| 6. |
- Abrahamsson, Victor, et al.
(författare)
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Method development in inverse modeling applied to supercritical fluid extraction of lipids
- 2016
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 111, s. 14-27
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Tidskriftsartikel (refereegranskat)abstract
- Modeling of the supercritical fluid extraction of solid materials is an important aspect in order to understand and predict the process. A comparison of two empirical models, two semi-empirical models and two mechanistic models is performed using calibration of single experiments. It is concluded that the best fit is obtained using a simple empirical expression. Furthermore, single calibrations did not generate reliable parameters with physical meaning and a methodology is proposed for inverse modeling with complete calibration using several experiments. The experimental dataset contained 29 extractions of lipids from crushed linseeds with varying temperatures, pressures and flow rates. A general rate model and a proposed extension of the hot ball model were evaluated for this purpose. The methodology includes data acquisition, model structure estimation, model calibration and a cross-validation. In general, it was found that the solubility model of Sovová outperformed the other evaluated correlations, and for the general rate model the Toth partition isotherm was also found in the top model structures. However, no generalization could be made regarding the correlations describing the Nernst diffusion layer and diffusivity.
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| 7. |
- Abrahamsson, Victor, et al.
(författare)
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Multicomponent inverse modeling of supercritical fluid extraction of carotenoids, chlorophyll A, ergosterol and lipids from microalgae
- 2018
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 139, s. 53-61
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Tidskriftsartikel (refereegranskat)abstract
- The fundamentals of analyte extractable fraction, solubility, partitioning and mass transfer resistance in supercritical fluid extraction were studied using inverse modeling. These phenomena are essential for understanding, predicting and optimizing the supercritical fluid extraction process. Carotenoids, chlorophyll A, ergosterol and total lipids were extracted from the microalgae Chlorella sp. The analytes were measured continuously in-line and on-line using UV/Vis absorption spectroscopy measurements and by evaporative light scattering detection. Various pressures, temperatures, flow rates and fractions of ethanol as a co-solvent were evaluated. The extractable fraction of carotenoids, chlorophyll A and total lipids were dependent on the co-solvent fraction in the extraction phase. The additional amount that could be extracted by using more co-solvent followed a normal distribution, indicating that analytes should not simply be categorized into weakly or strongly bound. The characteristics of diminishing extraction rates over time was accounted for by analyte partitioning rather than intra-particle diffusion limitations.
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| 8. |
- Abrahamsson, Victor, et al.
(författare)
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Supercritical fluid extraction of lipids from linseed with on-line evaporative light scattering detection.
- 2015
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 853, s. 320-327
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Tidskriftsartikel (refereegranskat)abstract
- Supercritical fluid extraction (SFE) is a green alternative method of extraction for neutral lipids in seeds compared to conventional methods utilizing organic solvents. In this work, a novel method where SFE is hyphenated with an evaporative light scattering detector is presented. The method was subsequently applied to determine lipid content in crushed linseed. The new method enables rapid quantification of extracted lipids as well as be ability to continuously monitor the extraction rate in real-time, thus being able to determine the time point of completed extraction. Both the detector and the method was validated. The results show that any of several tested oils can be used to calibrate the detection method for the determination of lipids extraction from linseed. The overall method repeatability and intermediate precision was 2.6% relative standard deviations. The extracted amount was significantly less than that obtained using the standard method of Soxhlet with petroleum ether, 26.0±0.4% (95% CI, n=9) compared to 32.3±1.3% (95% CI, n=3) of extracted amounts. It was found that channeling effects were present, and by either performing sequential repeated extractions with decompression in-between or by using a relatively large vessel a more complete extraction could be obtained. Interestingly, a substantially higher extracted amount (approximately 50%) was obtained compared to both a single extraction by SFE and the Soxhlet method. Therefore, it is recommended that an additional extraction including a rapid decompression in-between should be included in the validation of a method using supercritical fluid extraction, in order to either rule out channeling effects or to acquire a full recovery.
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| 9. |
- Barbosa de Mattos, Deise Fernanda, 1985, et al.
(författare)
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Covalent incorporation of diphenylanthracene in oxotriphenylhexanoate organogels as a quasi-solid photon upconversion matrix
- 2020
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 153:21
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Tidskriftsartikel (refereegranskat)abstract
- Triplet-triplet annihilation photon upconversion (TTA-UC) in solid state assemblies are desirable since they can be easily incorporated into devices such as solar cells, thus utilizing more of the solar spectrum. Realizing this is, however, a significant challenge that must circumvent the need for molecular diffusion, poor exciton migration, and detrimental back energy transfer among other hurdles. Here, we show that the above-mentioned issues can be overcome using the versatile and easily synthesized oxotriphenylhexanoate (OTHO) gelator that allows covalent incorporation of chromophores (or other functional units) at well-defined positions. To study the self-assembly properties as well as its use as a TTA-UC platform, we combine the benchmark couple platinum octaethylporphyrin as a sensitizer and 9,10-diphenylanthracene (DPA) as an annihilator, where DPA is covalently linked to the OTHO gelator at different positions. We show that TTA-UC can be achieved in the chromophore-decorated gels and that the position of attachment affects the photophysical properties as well as triplet energy transfer and triplet-triplet annihilation. This study not only provides proof-of-principle for the covalent approach but also highlights the need for a detailed mechanistic insight into the photophysical processes underpinning solid state TTA-UC.
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| 10. |
- Börjesson, Karl, 1982, et al.
(författare)
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Photon up-conversion and molecular solar thermal energy storage: New materials and devices
- 2014
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Ingår i: 2014 IEEE Photonics Conference, IPC 2014. ; , s. 445-446
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Konferensbidrag (refereegranskat)abstract
- In a future society with limited access to fossil fuels, technologies for efficient on demand delivery of renewable energy are highly desirable. In this regard, methods that allow for solar energy storage and on demand solar driven energy generation are particularly relevant since the sun is the most abundant energy source.
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