| 1. |
- Ghaffarzadegan, Tannaz, et al.
(författare)
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Determination of bile acids by hollow fibre liquid-phase microextraction coupled with gas chromatography.
- 2014
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Ingår i: Journal of Chromatography. B. - : Elsevier BV. - 1873-376X .- 1570-0232. ; 944, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- A method based on hollow-fibre liquid phase microextraction combined with gas chromatography was developed for determination of specific bile acids in caecal materials of rats. Nine unconjugated bile acids, including the primary bile acids (cholic acid, chenodeoxycholic acid and α-muricholic acid) and the secondary bile acids (lithocholic acid, deoxycholic acid, ursodeoxycholic acid, hyodeoxycholic acid, β-muricholic acid and ω-muricholic acid) were quantified. Extraction conditions were evaluated, including: sample pH, type of organic solvent and amount of caecal material to be extracted. To compensate for sample matrix effects during extraction the method of standard addition was applied. The satisfactory linearity (r(2)>0.9840), high recovery (84.2-108.7%) and good intra-assay (6.3-10.6%) and inter-assay (6.9-11.1%) precision illustrated the good performance of the present method. The method is rapid, simple and capable of detecting and determining bile acids with limit of detection (LOD) ranged from 0.002 to 0.067μg/mL and limits of quantification (LOQ) varied from 0.006 to 0.224μg/mL. The results indicated that the concentration of some secondary bile acids, which usually are associated with health problems, were lower in rats fed with fermentable dietary fibre compared with a fibre free control diet, while the concentration of primary bile acids, usually connected with positive health effects, were higher in rats fed with diets containing dietary fibre. Of the dietary fibres, guar gum and to some extent the mixture of pectin+guar gum had the most positive effects. Thus, it was concluded that the composition of bile acids can be affected by the type of diet.
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| 2. |
- Ghaffarzadegan, Tannaz, et al.
(författare)
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Determination of free and conjugated bile acids in serum of Apoe(−/−) mice fed different lingonberry fractions by UHPLC-MS
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Bile acids (BAs) are known to be involved in cholesterol metabolism but interactions between the diet, BA profiles, gut microbiota and lipid metabolism have not been extensively explored. In the present study, primary and secondary BAs including their glycine and taurine-conjugated forms were quantified in serum of Apoe−/− mice by protein precipitation followed by reversed phase ultra-high-performance liquid chromatography and QTOF mass spectrometry. The mice were fed different lingonberry fractions (whole, insoluble and soluble) in a high-fat setting or cellulose in a high and low-fat setting. Serum concentrations of BAs in mice fed cellulose were higher with the high-fat diet compared to the low-fat diet (20–70%). Among the lingonberry diets, the diet containing whole lingonberries had the highest concentration of chenodeoxycholic acid (CDCA), ursodeoxycholic acid (UDCA), tauro-ursodeoxycholic acid (T-UDCA), α and ω-muricholic acids (MCA) and tauro-α-MCA (T-α-MCA), and the lowest concentration of tauro-cholic acid (T-CA), deoxycholic acid (DCA) and tauro-deoxycholic acid (T-DCA). The glycine-conjugated BAs were very similar with all diets. CDCA, UDCA and α-MCA correlated positively with Bifidobacterium and Prevotella, and T-UDCA, T-α-MCA and ω-MCA with Bacteroides and Parabacteroides.
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| 3. |
- Ghaffarzadegan, Tannaz, et al.
(författare)
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Postprandial Responses of Serum Bile Acids in Healthy Humans After Ingestion of Turmeric Before Medium /High‐Fat Breakfasts
- 2019
-
Ingår i: Molecular Nutrition and Food Research. - : Wiley. - 1613-4133 .- 1613-4125.
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Tidskriftsartikel (refereegranskat)abstract
- Scope: Bile acids (BAs) are known to regulate a number of metabolic activities in the body. However, very little is known about how BAs are affected by diet. This study aimed to investigate whether a single-dose of turmeric-based beverage (TUR) before ingestion of medium- (MF) or high-fat (HF) breakfasts would improve the BA profile in healthy subjects. Methods and results: Twelve healthy subjects were assigned to a randomized crossover single-blind study. The subjects received iso-caloric MF or HF breakfasts after a drink containing flavored water with or without an extract of turmeric with at least one-week wash-out period between the treatments. Postprandial BAs were measured using protein precipitation followed by ultra-high-performance liquid chromatography-mass spectrometry analysis (UHPLC-MS). The concentration of BAs was generally higher after HF than MF breakfasts. Ingestion of TUR before MF breakfast increased the serum concentrations of free and conjugated forms of cholic and ursodeoxycholic acids, as well as the concentrations of chenodeoxycholic acid and its taurine-conjugated form. However, the concentration of conjugated forms of deoxycholic acid decreased when TUR was taken before HF breakfast. Conclusion: TUR ingestion before MF and HF breakfasts improved BA profiles and may therefore have potential health-promoting effects on BA metabolism.
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| 4. |
- Abdelaziz, Omar Y., et al.
(författare)
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Biological valorization of low molecular weight lignin
- 2016
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 34:8, s. 1318-1346
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Forskningsöversikt (refereegranskat)abstract
- Lignin is a major component of lignocellulosic biomass and as such, it is processed in enormous amounts in the pulp and paper industry worldwide. In such industry it mainly serves the purpose of a fuel to provide process steam and electricity, and to a minor extent to provide low grade heat for external purposes. Also from other biorefinery concepts, including 2nd generation ethanol, increasing amounts of lignin will be generated. Other uses for lignin – apart from fuel production – are of increasing interest not least in these new biorefinery concepts. These new uses can broadly be divided into application of the polymer as such, native or modified, or the use of lignin as a feedstock for the production of chemicals. The present review focuses on the latter and in particular the advances in the biological routes for chemicals production from lignin. Such a biological route will likely involve an initial depolymerization, which is followed by biological conversion of the obtained smaller lignin fragments. The conversion can be either a short catalytic conversion into desired chemicals, or a longer metabolic conversion. In this review, we give a brief summary of sources of lignin, methods of depolymerization, biological pathways for conversion of the lignin monomers and the analytical tools necessary for characterizing and evaluating key lignin attributes.
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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. |
- Al Hamimi, Said, et al.
(författare)
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Screening of stationary phase selectivities for global lipid profiling by ultrahigh performance supercritical fluid chromatography
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1548, s. 76-82
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Tidskriftsartikel (refereegranskat)abstract
- The performance of seven sub-2-μm particle packed columns (2-picolylamine, 2-PIC; charged surface hybrid fluoro-phenyl, CSH-FP; high strength silica C18 SB, HSS-C18; diethylamine, DEA; 1-aminoanthracene, 1-AA; high density diol and ethylene bridged hybrid; BEH) was examined for lipid separation in ultra-high performance supercritical fluid chromatography (UHPSFC) coupled to quadrupole time-of-flight mass spectrometry. Based on the results of the column screening a method for profiling of multiple lipid species from the major lipid classes was developed. Stationary phases containing β-hydroxy amines, i.e. 1-AA, DEA and 2-PIC, yielded strong retention and poor peak shapes of zwitterionic lipids with primary amine groups, such as phosphatidylserines, phosphatidylethanolamines and its lyso forms. The BEH and HSS-C18 columns showed strong retention of polar and nonpolar lipids, respectively. The Diol column retained the majority of major lipid classes and also produced symmetric peaks. In addition, this column also produced the highest resolution within and between major lipid classes. An injection solvent composed of methanol:chloroform (1:2, v:v) and the addition of 20 mM ammonium formate in the mobile phase improved chromatographic separation and mass spectrometry detection in comparison to ammonium acetate or absence of additive. Finally, chromatographic and mass spectrometric parameters were optimized for the Diol column using a design of experiments approach. The separation mechanism on the Diol column depended on the lipid functionality and the length and degree of unsaturation of the acyl groups. The developed method could resolve 18 lipid classes and multiple lipids within each class, from blood serum and brain tissue in 11 min.
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| 7. |
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| 8. |
- Azeem, Hafiz Abdul, et al.
(författare)
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Extending the scope of dispersive liquid–liquid microextraction for trace analysis of 3-methyl-1,2,3-butanetricarboxylic acid in atmospheric aerosols leading to the discovery of iron(III) complexes
- 2019
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 411:13, s. 2937-2944
-
Tidskriftsartikel (refereegranskat)abstract
- 3-Methyl-1,2,3-butanetricarboxylic acid (MBTCA) is a secondary organic aerosol and can be used as a unique emission marker of biogenic emissions of monoterpenes. Seasonal variations and differences in vegetation cover around the world may lead to low atmospheric MBTCA concentrations, in many cases too low to be measured. Hence, an important tool to quantify the contribution of terrestrial vegetation to the loading of secondary organic aerosol may be compromised. To meet this challenge, a dispersive liquid–liquid microextraction (DLLME) method, known for the extraction of hydrophobic compounds, was extended to the extraction of polar organic compounds like MBTCA without compromising the efficiency of the method. The extraction solvent was fine-tuned using tri-n-octyl phosphine oxide as additive. A multivariate experimental design was applied for deeper understanding of significant variables and interactions between them. The optimum extraction conditions included 1-octanol with 15% tri-n-octyl phosphine oxide (w/w) as extraction solvent, methanol as dispersive solvent, 25% NaCl dissolved in 5 mL sample (w/w) acidified to pH 2 using HNO 3 , and extraction time of 15 min. A limit of detection of 0.12 pg/m 3 in air was achieved. Furthermore, unique complexation behavior of MBTCA with iron(III) was found when analyzed with ultra-high-performance liquid chromatography coupled with electrospray ionization–quadrupole time-of-flight mass spectrometry (UHPLC–ESI–QToF). A comprehensive overview of this complexation behavior of MBTCA was examined with systematically designed experiments. This newly discovered behavior of MBTCA will be of interest for further research on organometallic photooxidation chemistry of atmospheric aerosols. [Figure not available: see fulltext.].
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| 9. |
- Azeem, Hafiz Abdul, et al.
(författare)
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Towards the isolation and estimation of elemental carbon in atmospheric aerosols using supercritical fluid extraction and thermo-optical analysis
- 2017
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 409:17, s. 4293-4300
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Tidskriftsartikel (refereegranskat)abstract
- Air-starved combustion of biomass and fossil fuels releases aerosols, including airborne carbonaceous particles, causing negative climatic and health effects. Radiocarbon analysis of the elemental carbon (EC) fraction can help apportion sources of its emission, which is greatly constrained by the challenges in isolation of EC from organic compounds in atmospheric aerosols. The isolation of EC using thermo-optical analysis is however biased by the presence of interfering compounds that undergo pyrolysis during the analysis. EC is considered insoluble in all acidic, basic, and organic solvents. Based on the property of insolubility, a sample preparation method using supercritical CO2 and methanol as co-solvent was developed to remove interfering organic compounds. The efficiency of the method was studied by varying the density of supercritical carbon dioxide by means of temperature and pressure and by varying the methanol content. Supercritical CO2 with 10% methanol by volume at a temperature of 60 °C, a pressure of 350 bar and 20 min static mode extraction were found to be the most suitable conditions for the removal of 59 ± 3% organic carbon, including compounds responsible for pyrolysis with 78 ± 16% EC recovery. The results indicate that the method has potential for the estimation and isolation of EC from OC for subsequent analysis methods and source apportionment studies.
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| 10. |
- Cui, Jingwen, et al.
(författare)
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Extraction with Water-in-Carbon Dioxide Microemulsions : A Case Study on Steviol Glycosides
- 2019
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Ingår i: Journal of Surfactants and Detergents. - : Wiley. - 1097-3958 .- 1558-9293. ; 22:6, s. 1505-1514
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Tidskriftsartikel (refereegranskat)abstract
- This work explores the use of water-in-supercritical carbon dioxide (scCO2) microemulsions for the extraction of polar metabolites from plants. Stevia rebaudiana Bertoni leaves and polyethylene glycol trimethylnonyl ether (TMN) surfactants were selected for a case study. A CO2-water-TMN 10 mixture at 35 °C and 30.0 MPa extracted 7 mg target analyte/g dry leaves. The extraction was proven to occur due to a water-surfactant liquid solution rather than a water-in-CO2 microemulsion. Using a modified extraction setup, the microemulsion was created prior to extraction. TMN 6 was able to dissolve enough water in CO2 to extract steviol glycosides, in detectable but very small amounts.
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| 11. |
- Cui, Jingwen, et al.
(författare)
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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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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446 .- 1872-8162. ; 171
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Enhanced distribution kinetics in liquid-liquid extraction by CO2-expanded solvents
- 2020
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 163
-
Tidskriftsartikel (refereegranskat)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.
(författare)
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Reactivity of dissolved organic matter in response to acid deposition
- 2016
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Ingår i: Aquatic Sciences. - : Springer. - 1015-1621 .- 1420-9055. ; 78:3, s. 463-475
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Journal of chromatography. A. - 0021-9673. ; 1706, s. 464267-464267
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Tidskriftsartikel (refereegranskat)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.
(författare)
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Comparison of different extraction techniques for isolation of antioxidants from sweet grass (Hierochloe odorata)
- 2005
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 33:3, s. 223-233
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Tidskriftsartikel (refereegranskat)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. |
- Hyder, Murtaza, et al.
(författare)
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Determination of polycyclic aromatic hydrocarbons (PAHs) from organic aerosols using hollow fiber micro - porous membrane liquid - liquid extraction (HF-MMLLE) followed by gas chromatography-mass spectrometry analysis.
- 2011
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Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 85:2, s. 919-926
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Tidskriftsartikel (refereegranskat)abstract
- A method for determination of polycyclic aromatic hydrocarbons (PAHs) from aerosols was developed. Instead of conventionally used non-polar or slightly polar phenylmethylpolysiloxane column a highly polar, highly substituted, cyanopropyl column (VF-23 MS) was used for separation of PAHs. Based on hollow fiber micro-porous membrane liquid-liquid extraction (HF-MMLLE) a method was developed for sample clean up and pretreatment. An enrichment factor of 617-1022 was obtained with extraction efficiency 10.2-18.9% for different PAHs analyzed in this study. The optimized method was successfully applied to aerosol samples and limits of detection between 1.2pgm(-3) and 180pgm(-3) was obtained. Almost all PAHs were found in most of the aerosol samples.
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| 17. |
- Hyder, Murtaza, et al.
(författare)
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Yearly trend of dicarboxylic acids in organic aerosols from south of Sweden and source attribution
- 2012
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 57, s. 197-204
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Tidskriftsartikel (refereegranskat)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.
(författare)
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A fast and sensitive method for the separation of carotenoids using ultra-high performance supercritical fluid chromatography-mass spectrometry
- 2016
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 408:21, s. 5883-5894
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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
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Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1440, s. 191-200
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Tidskriftsartikel (refereegranskat)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.
(författare)
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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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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 65:37, s. 8220-8228
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Tidskriftsartikel (refereegranskat)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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| 21. |
- Jumaah, Firas, et al.
(författare)
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Supercritical Fluid Extraction and Chromatography of Lipids in Bilberry.
- 2015
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Ingår i: Journal of the American Oil Chemists Society. - : Wiley. - 0003-021X .- 1558-9331. ; 92:8, s. 1103-1111
-
Tidskriftsartikel (refereegranskat)abstract
- A supercritical fluid extraction (SFE) method has been developed for the extraction of lipids in bilberry. Experimental design was used to optimize pressure, temperature and extraction time using CO2 as solvent. Best SFE condition for total lipids was 450 bar, 60 °C and 45 min. The SFE method was compared to conventional Bligh & Dyer (B&D) extraction. The amount of fatty acid methyl esters (FAME) was found to be 4.84 ± 0.06 mg and 4.564 ± 0.003 mg per g of the freeze-dried bilberry sample for the developed SFE and B&D methods, respectively, while the amount of total lipids was found to be 54.40 ± 6.06 mg and 65.70 ± 0.67 mg per g of sample for SFE and B&D, respectively. This discrepancy between FAME and total lipids could be explained by the presence of wax esters, sterol esters, carotenoids and phospholipids, as determined by supercritical fluid chromatography.
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| 22. |
- Li, Kena, et al.
(författare)
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Investigating lignin-derived monomers and oligomers in low-molecular-weight fractions separated from depolymerized black liquor retentate by membrane filtration
- 2021
-
Ingår i: Molecules. - : MDPI AG. - 1420-3049. ; 26:10
-
Tidskriftsartikel (refereegranskat)abstract
- Base-catalyzed depolymerization of black liquor retentate (BLR) from the kraft pulping process, followed by ultrafiltration, has been suggested as a means of obtaining low-molecular-weight (LMW) compounds. The chemical complexity of BLR, which consists of a mixture of softwood and hardwood lignin that has undergone several kinds of treatment, leads to a complex mixture of LMW compounds, making the separation of components for the formation of value-added chemicals more difficult. Identifying the phenolic compounds in the LMW fractions obtained under different depolymerization conditions is essential for the upgrading process. In this study, a state-of-the-art nontargeted analysis method using ultra-high-performance supercritical fluid chromatography coupled to high-resolution multiple-stage tandem mass spectrometry (UHPSFC/HRMSn ) combined with a Kendrick mass defect-based classification model was applied to analyze the monomers and oligomers in the LMW fractions separated from BLR samples depolymerized at 170–210◦ C. The most common phenolic compound types were dimers, followed by monomers. A second round of depolymerization yielded low amounts of monomers and dimers, while a high number of trimers were formed, thought to be the result of repolymerization.
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| 23. |
- Liu, Jiayin, et al.
(författare)
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Pressurised hot water extraction in continuous flow mode for thermolabile compounds : extraction of polyphenols in red onions
- 2014
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 406:2, s. 441-445
-
Tidskriftsartikel (refereegranskat)abstract
- Extraction and analysis of labile compounds in complex sample matrices, such as plants, is often a big analytical challenge. In this work, the use of a "green and clean" pressurised hot water extraction (PHWE) approach performed in continuous flow mode is explored. Experimental data for extraction and degradation kinetics of selected compounds were utilised to develop a continuous flow extraction (CFE) method targeting thermolabile polyphenols in red onions, with detection by high-performance liquid chromatography (HPLC)-diode array detection (DAD)-mass spectrometry (MS). Water containing ethanol and formic acid was used as extraction solvent. Method performance was focused on extraction yield with minimal analyte degradation. By adjusting the flow rate of the extraction solvent, degradation effects were minimised, and complete extraction could be achieved within 60 min. The CFE extraction yields of the polyphenols investigated were 80-90 % of the theoretically calculated quantitative yields and were significantly higher than the yields obtained by conventional methanol extraction and static batch extraction (70-79 and 58-67% of the theoretical yields, respectively). The precision of the developed method was lower than 8 % expressed as relative standard deviation.
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| 24. |
- Madsen, Dan, et al.
(författare)
-
Levoglucosan as a Tracer for Smouldering Fire
- 2018
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Ingår i: Fire Technology. - : Springer Science and Business Media LLC. - 0015-2684 .- 1572-8099. ; 54:6, s. 1871-1885
-
Tidskriftsartikel (refereegranskat)abstract
- Detecting fires at an early stage is crucial for mitigating and extinguishing fires. The increased use of biofuels in Northern Europe has led to an increased number of fires in storage facilities. These fires are often caused by self-heating in the interior of the stored materials and slowly develop to smouldering fires. Consequently, these smouldering fires are usually detected several days or weeks after the initial smouldering fire had started. At this point, measures to extinguish the smouldering fire inside the material are difficult as the fire has grown for a long time and is located inside the material. This makes it difficult to gain a successful effect of any extinguishing agents. This paper presents a pilot study in lab scale suggesting levoglucosan as an early tracer for smouldering fires using 600 g cotton as the biomass source. The advantage of detecting levoglucosan as a fire signature is that it serves as a tracer compound for biomass burning and is produced at temperatures of 200–400°C reducing the risk of false alarms from emissions produced at lower temperatures. In this paper, levoglucosan was detected in aerosols emitted in an early stage from smouldering fires and was analyzed by ultrasonic assisted extraction followed by gas chromatographic separation and mass spectrometric detection. First detection of levoglucosan was made in the first sample, collected after 30 min when the smouldering fire was only a few cubic centimeters of the cotton package. In addition, levoglucosan was found in the solid residues of carbonized cotton after the initial smouldering process had moved through the material. The findings should be regarded as screening results to be used for the development of sensors and technology for smouldering fire detection.
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| 25. |
- Nardella, Federica, et al.
(författare)
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Native lignin extraction from soft- and hardwood by green and benign sub/supercritical fluid extraction methodologies
- 2023
-
Ingår i: RSC Advances. - 2046-2069. ; 13:32, s. 21945-21953
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin constitutes an impressive resource of high-value low molecular weight compounds. However, robust methods for isolation of the extractable fraction from lignocellulose are yet to be established. In this study, supercritical fluid extraction (SFE) and CO2-expanded liquid extraction (CXLE) were employed to extract lignin from softwood and hardwood chips. Ethanol, acetone, and ethyl lactate were investigated as green organic co-solvents in the extractions. Additionally, the effects of temperature, CO2 percentage and the water content of the co-solvent were investigated using a design of experiment approach employing full factorial designs. Ethyl lactate and acetone provided the highest gravimetric yields. The water content in the extraction mixture had the main impact on the amount of extractable lignin monomers (LMs) and lignin oligomers (LOs) while the type of organic solvent was of minor importance. The most effective extraction was achieved by using a combination of liquid CO2/acetone/water (10/72/18, v/v/v) at 60 °C, 350 bar, 30 min and 2 mL min−1 flow rate. The optimized method provided detection of 13 LMs and 6 lignin dimers (LDs) from the hardwood chips. The results demonstrate the potential of supercritical fluids and green solvents in the field of mild and bening lignin extraction from wood.
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| 26. |
- Nermark, Fiona M., et al.
(författare)
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Optimization of coal desulfurization method by sub/supercritical fluid extraction with binary mixtures of carbon dioxide and ethyl lactate as a solvent
- 2024
-
Ingår i: Green Analytical Chemistry. - 2772-5774. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Coal combustion for energy results in the emission of air pollutants such as NOx and SOx, which negatively affect human health and the environment. Reducing toxic gas emissions and ash production is needed to achieve cleaner coal. This study aimed to develop an extraction method for desulfurizing coal with non-toxic solvents before combustion. Mixtures of sub/supercritical carbon dioxide and ethyl lactate (EL) were used at temperatures of 60–80 °C and extraction times of 15–45 min. Box-Behnken design (BBD) was used to assess the influence of the extraction parameters and to optimize the extraction method. The results show that higher temperatures and lower EL content significantly increased desulfurization. The optimal conditions for desulfurization were CO2/EL (95:5, v/v) at 80 °C, 300 bar and 15 min, reducing total sulfur in coal from 1.90 to 0.13% by weight. The extraction was efficient for removing organic sulfur, sulfones and sulfates, whereas there were still traces of sulfoxides and sulfides remaining in the coal after extraction. Moreover, the ash content slightly decreased while the calorific value increased by 8% and 3% by weight, respectively. The use of a temperature less than 100 °C and an extraction time of 15 min make this method "greener" in comparison to other proposed "green" methods, which use temperatures above 200 °C. Thus, the method has the potential to produce clean coal.
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| 27. |
- Papp, Daniel, et al.
(författare)
-
A Complementary Multitechnique Approach to Assess the Bias in Molecular Weight Determination of Lignin by Derivatization-Free Gel Permeation Chromatography
- 2024
-
Ingår i: Analytical Chemistry. - 0003-2700. ; 96:26, s. 10612-10619
-
Tidskriftsartikel (refereegranskat)abstract
- The growing interest in lignin valorization in the past decades calls for analytical techniques for lignin characterization, ranging from wet chemistry techniques to highly sophisticated chromatographic and spectroscopic methods. One of the key parameters to consider is the molecular weight profile of lignin, which is routinely determined by size-exclusion chromatography; however, this is by no means straightforward and is prone to being hampered by considerable errors. Our study expands the fundamental understanding of the bias-inducing mechanisms in gel permeation chromatography (GPC), the magnitude of error originating from using polystyrene standards for mass calibration, and an evaluation of the effects of the solvent and type of lignin on the observed bias. The developed partial least-squares (PLS) regression model for lignin-related monomers revealed that lignin is prone to association mainly via hydrogen bonding. This hypothesis was supported by functional group-based analysis of the bias as well as pulse field gradient (pfg) diffusion NMR spectroscopy of model compounds in THF-d8. Furthermore, although the lack of standards hindered drawing conclusions based on functionalities, direct infusion electrospray ionization mass spectrometry indicated that the relative bias decreases considerably for higher molecular weight species. The results from pfg-diffusion NMR spectroscopy on whole lignin samples were comparable when the same solvents were used in both experiments; in addition, the comparison between results obtained by pfg-diffusion NMR in different solvents gives some additional insights into the aggregation.
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| 28. |
- Papp, Daniel, et al.
(författare)
-
Single-Standard Quantification Strategy for Lignin Dimers by Supercritical Fluid Chromatography with Charged Aerosol Detection
- 2022
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 95:2, s. 1436-1445
-
Tidskriftsartikel (refereegranskat)abstract
- The increased interest in utilizing lignin as a feedstock to produce various aromatic compounds requires advanced chemical analysis methods to provide qualitative and quantitative characterization of lignin samples along different technology streamlines. However, due to the lack of commercially available chemical standards, routine quantification of industrially relevant lignin oligomers in complex lignin samples remains a challenge. This study presents a novel method for universal quantification of lignin dimers based on supercritical fluid chromatography with charged aerosol detection (CAD). A series of lignin-derived dimeric compounds that have been reported from reductive catalytic fractionation (RCF) were synthesized and used as standards. The applicability of using linear regression instead of quadratic calibration curves was evaluated over a concentration range of 15-125 mg/L, demonstrating that the former calibration method is as appropriate as the latter. The response factors of lignin dimeric compounds were compared to assess the uniformity of the CAD signal, revealing that the CAD response for the tested lignin dimers did not differ substantially. It was also found that the response factors were not dependent on the number of methoxy groups or linkage motifs, ultimately enabling the use of only one calibrant for these compounds. The importance of chromatographic peak resolution in CAD was stressed, and the use of a digital peak sharpening technique was adopted and applied to address this challenge. The developed method was verified and used for the quantification of lignin dimers in an oil obtained by a RCF of birch sawdust.
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| 29. |
- Pilařová, Veronika, et al.
(författare)
-
Analysis of vitamin D and its metabolites in biological samples – Part I : Optimization and comparison of UHPSFC-MS/MS and UHPLC-MS/MS methods
- 2024
-
Ingår i: Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences. - 1570-0232. ; 1237
-
Tidskriftsartikel (refereegranskat)abstract
- Fat-soluble vitamin D is an essential bioactive compound important for human health. Insufficient vitamin D levels can result not only in bone disease but also in other disorders, such as cancer, metabolic disorders, and diseases related to poor immune function. The current methods commonly used for vitamin D analysis are often applied to determine the levels of the most abundant metabolite in plasma, i.e., 25-OH-D2/D3. These methods do not consider the presence of other hydroxylated and esterified metabolites, including isomers and epimers, which are typically found in low concentrations. In this study, we developed a fast and selective ultra-high performance supercritical fluid chromatography (UHPSFC) method using a 150 mm long 1-amino anthracene (1-AA) column and a mobile phase consisting of carbon dioxide and methanol/isopropanol (1/1, v/v) mixed with 8 % water. After thorough optimization of column temperature and back pressure, the separation of four vitamin D3 esters, vitamin D3 and D2, and eight mono- and di-hydroxylated metabolites, including three groups of isomers, was achieved in 10 min. Two ion sources, atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization optimized within this study, were compared in tandem mass spectrometry (MS/MS) detection. No significant sensitivity differences were observed. Subsequently, the same 1-AA column chemistry was examined in ultra-high performance liquid chromatography (UHPLC) as the stationary phase that could hypothetically bring different selectivity in the separation of vitamin D and its metabolites. However, this hypothesis was rejected, and C18 was used as a stationary phase in the final optimized UHPLC-MS/MS method. Despite detailed optimization, the final 15 min UHPLC method was not able to separate di-hydroxylated isomers of vitamin D3, while it enabled better resolution of esterified forms compared to UHPSFC. Optimized methods provided similar repeatability of retention times and peak areas, with RSD < 2 % and 10 %, respectively. The lowest limits of quantification were in the range of 1.2 – 4.9 ng/mL for UHPSFC-APCI-MS/MS, while for UHPLC-APCI-MS/MS, they were typically in the range of 2.6 – 9.6 ng/mL. Based on the obtained results, the UHPSFC-APCI-MS/MS method was the most promising approach for fast, selective, and sensitive analysis that could be applied in the analysis of biological samples with emphasis on the separation of both hydroxylated and esterified metabolites, including isomeric forms.
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| 30. |
- Pilařová, Veronika, et al.
(författare)
-
Analysis of vitamin D and its metabolites in biological samples – Part II : Optimization of a sample preparation method for liver tissue
- 2024
-
Ingår i: Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences. - 1570-0232. ; 1237
-
Tidskriftsartikel (refereegranskat)abstract
- Extraction of vitamin D, including its hydroxylated and esterified metabolites, from soft tissues such as the liver is challenging due to the lipophilic character of matrix and analytes that are expected in very low concentration levels. In this study, we aimed at the optimization of two-step extraction using solid–liquid extraction as the first step, followed by solid-phase extraction. Various solvents, including ethanol, acetonitrile, methanol, acetone, heptane, and heptane with isopropanol, were investigated to isolate vitamin D compounds from liver tissue in the first step. Acetone was finally selected as the most suitable solvent for the solid–liquid extraction, with the highest recovery in the range of 67 – 98% for polar hydroxylated forms and 3 – 28% for lipophilic vitamin D and esters. Two solid phase extraction (SPE) based on the (i) “bind and elute strategy” and (ii) “removal strategy” using hydrophilic-lipophilic balanced SPE sorbent were optimized as a proceeding step for acetone extracts to increase the method selectivity. Finally, two optimized methods, combining solid–liquid extraction and individual SPE strategy, were examined in terms of sensitivity, recovery, matrix effect, accuracy, and precision. The limits of quantification were in the range of 1 – 10 ng/mL and 3 – 20 ng/mL analyzed by ultra-high performance supercritical fluid chromatography and ultra-high performance liquid chromatography hyphenated a with tandem mass spectrometer, respectively. The absolute recovery determined for the “bind and elute strategy” protocol was in the range of 3 – 24 %. Nevertheless, this method was free of matrix effects, which were determined to be in the 73 – 120 % range. On the contrary, the “removal strategy” approach provided higher recovery values for all compounds (47 – 123 %), but the results for nonpolar vitamin D and esters were strongly affected by signal suppression (matrix effects 3 – 51 %). Both methods fulfilled the criteria for accuracy and precision requested by the European Medicine Agency Guideline on Bioanalysis. “Removal strategy” SPE with decreased manual intervention and lower solvent consumption was finally applied to mouse liver tissue to determine vitamin D and its hydroxylated and esterified metabolites for the first time. The results, i.e., vitamin D esters detected in liver tissue, supported the notion that esters of vitamin D can be stored in lipophilic tissues to release vitamin D.
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| 31. |
- Plaza, Merichel, et al.
(författare)
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Characterization of antioxidant polyphenols from Myrciaria jaboticaba peel and their effects on glucose metabolism and antioxidant status : A pilot clinical study
- 2016
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146. ; 211, s. 185-197
-
Tidskriftsartikel (refereegranskat)abstract
- Brazilian berries, such as Myrciaria jaboticaba (jaboticaba), are good sources of polyphenols with a recognized function in oxidative stress attenuation proved in non-clinical studies. In the present study, the polyphenols profile and their contribution to the antioxidant capacity of the jaboticaba peel were analyzed using high-performance liquid chromatography (HPLC) with photodiode array (DAD), electrochemical (ECD), charged aerosol (CAD), and mass spectrometry (MS) detections. Anthocyanins, ellagitannins and gallotannins, ellagic acid and derivatives, and flavonols were found in jaboticaba. Anthocyanins were the phenolics found in higher concentrations. However, ellagitannins were the main contributors to the total antioxidant capacity. Moreover, the effect of jaboticaba peel intake on antioxidant and glucose parameters in a single-blind placebo-controlled crossover study was investigated. The serum antioxidant capacity was significantly higher when the subjects had consumed the test meal containing jaboticaba. Serum insulin decreased subsequent to the second meal at 4 h after jaboticaba peel consumption.
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| 32. |
- Prothmann, Jens, et al.
(författare)
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Identification of lignin oligomers in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn)
- 2018
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 410:29, s. 7803-7814
-
Tidskriftsartikel (refereegranskat)abstract
- Kraft lignin is the main source of technically produced lignin. For the development of valuable products based on Kraft lignin, its molecular structure is important. However, the chemical composition of Kraft lignin is still not well known. So far, the analysis of Kraft lignin by mass spectrometry (MS) has been mainly focused on monomeric compounds. Previous MS studies on lignin oligomers (LOs) considered only synthesised LO standards and/or lignins produced by processes other than the Kraft process. Furthermore, published MS methods suffer from using high resolution only in the MS1 stage in multiple-stage tandem MS methods. A high resolution in all MSn stages would provide more detailed information about LO fragmentation pathways. Since lignin samples are complex mixtures of a large number of similar phenolic compounds, the selection of tentative LOs in the MS data is challenging. In this study, we present a method for non-targeted analysis of LOs in Kraft lignin using ultra-high-performance liquid chromatography/high-resolution multiple-stage tandem mass spectrometry (UHPLC/HRMSn). A pre-selection strategy for LOs has been established based on a data-dependent neutral loss MS3 method in combination with a principal component analysis-quadratic discriminant analysis classification model (PCA-QDA). The method was optimised using a design of experiments (DOE) approach. The developed approach improved the pre-selection of tentative LOs in complex mixtures. From 587 detected peaks, 36 peaks were identified as LOs.
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| 33. |
- Prothmann, Jens, et al.
(författare)
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Non-targeted analysis strategy for the identification of phenolic compounds in complex technical lignin samples
- 2020
-
Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 13:17, s. 4605-4612
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin is the second most abundant biopolymer in nature and a promising renewable resource for aromatic chemicals. For the understanding of different lignin isolation and conversion processes, the identification of phenolic compounds is of importance. However, due to the vast number of possible chemical transformations, the prediction of produced phenolic structures is challenging, and a non-targeted analysis method is therefore needed. In this study, we present a non-targeted analysis method for the identification of phenolic compounds using ultra-high-performance supercritical fluid chromatography/high-resolution multiple stage tandem mass spectrometry combined with a Kendrick mass defect-based classification model. The method was applied to a Lignoboost Kraft lignin (LKL), a sodium Lignosulphonate lignin (SLS) and a depolymerised Kraft lignin (DKL) sample. In total, 260 tentative phenolic compounds were identified in the LKL sample, 50 in the SLS sample and 77 in the DKL sample.
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| 34. |
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| 35. |
- Prothmann, Jens, et al.
(författare)
-
Separation of monomeric and dimeric phenolic compounds in lignosulphonate lignin on different stationary phases using ultrahigh-performance supercritical fluid chromatography
- 2021
-
Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1653
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin is a promising renewable resource and its valorization could help to reduce our dependency on fossil carbon resources. Especially the production of small molecular weight and economically valuable compounds, such as vanillin, are of interest. A good separation of the sample components is crucial for a confident identification of compounds in complex sample mixtures using for instance mass spectrometry. In this work, the resolving power and selectivity of five different stationary phases for ultrahigh-performance supercritical fluid chromatography were studied for the class separation of lignin monomers (LMs) and dimers (LDs). A separation of LMs and LDs will help to identify such compounds in complex technical lignin samples. It could be shown that stationary phases with both hydrogen-bonding acceptor and donator groups offer high overall resolving power, while π-π-interactions are advantageous for the separation of the two compound classes. An almost complete separation combined with an improved overall resolving power was achieved with the 1-aminoanthracene stationary phase, which offers both hydrogen-bonding interactions and π-π-interactions.
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| 36. |
- Prothmann, Jens, et al.
(författare)
-
Ultra-high-performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC/QTOF-MS) for analysis of lignin-derived monomeric compounds in processed lignin samples
- 2017
-
Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 409:30, s. 7049-7061
-
Tidskriftsartikel (refereegranskat)abstract
- The conversion of lignin to potentially high-value low molecular weight compounds often results in complex mixtures of monomeric and oligomeric compounds. In this study, a method for the quantitative and qualitative analysis of 40 lignin-derived compounds using ultra-high-performance supercritical fluid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UHPSFC/QTOF-MS) has been developed. Seven different columns were explored for maximum selectivity. Makeup solvent composition and ion source settings were optimised using a D-optimal design of experiment (DoE). Differently processed lignin samples were analysed and used for the method validation. The new UHPSFC/QTOF-MS method showed good separation of the 40 compounds within only 6-min retention time, and out of these, 36 showed high ionisation efficiency in negative electrospray ionisation mode. [Figure not available: see fulltext.]
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| 37. |
- Sandahl, Margareta, et al.
(författare)
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Automated determination of Vinclozolin at the ppb level in aqueous samples by a combination of microporous membrane liquid-liquid extraction and adsorption chromatography
- 2000
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Ingår i: Analytica Chimica Acta. - 1873-4324. ; 424:1, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- An automated system with microporous membrane liquid-liquid extraction (MMLLE) combined with HPLC has been designed for the determination of Vinclozolin in aqueous matrices. In MMLLE a porous hydrophobic membrane separates an aqueous phase from an organic phase. The pores are filled with the organic solvent. In this work, MMLLE was performed in a flow system and coupled on-line to normal phase HPLC. The performance of the system was evaluated with respect to enrichment when processing large sample volumes. Enrichment factors of 118 times were obtained and the limit of detection was around 1 ng/ml. This technique is an alternative to classical LLE and offers advantages such as reduced solvent consumption, possibility of automation and avoidance of emulsion formations. (C) 2000 Elsevier Science B.V.
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| 38. |
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| 39. |
- Sandahl, Margareta, et al.
(författare)
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On-line automated sample preparation for liquid chromatography using parallel supported liquid membrane extraction and microporous membrane liquid-liquid extraction
- 2002
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 975:1, s. 211-217
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Tidskriftsartikel (refereegranskat)abstract
- An automated system was developed for analysis of non-polar and polar ionisable compounds at trace levels in natural water. Sample work-up was performed in a flow system using two parallel membrane extraction units. This system was connected on-line to a reversed-phase HPLC system for final determination. One of the membrane units was used for supported liquid membrane (SLM) extraction, which is suitable for ionisable or permanently charged compounds. The other unit was used for microporous membrane liquid-liquid extraction (MMLLE) suitable for uncharged compounds. The fungicide thiophanate methyl and its polar metabolites carbendazim and 2-aminobenzimidazole were used as model compounds. The whole system was controlled by means of four syringe pumps. While extracting one part of the sample using the SLM technique, the extract from the MMLLE extraction was analysed and vice versa. This gave a total analysis time of 63 min for each sample resulting in a sample throughput of 22 samples per 24 h. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 40. |
- Sandahl, Margareta
(författare)
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Surface Sampling and Automated Liquid Membrane Extraction of Fungicides
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A number of approaches for fungicide determination are presented. A surface sampling technique is utilised for the determination of fungicide foliar residues on greenhouse surfaces, mainly leaves. The procedure is based on solvation of the fungicides on the leaf surface with ethanol and HPLC analysis. It was applied to studies of the environment in greenhouses including investigations of decline rates of the fungicides. Occupational hazards, such as respiratory exposure and dermal uptake were investigated. Another environmental aspect on application of fungicides is the discharge of the compounds and their degradation products to water recipients. The actual concentrations are often quite low (usually below 1 µg/L) necessitating sensitive and selective analytical procedures involving enrichment. This can be met by membrane-based extraction techniques also providing possibilities for automation and closed systems. The supported liquid membrane (SLM) extraction and microporous membrane liquid-liquid extraction (MMLLE), are used for sample preparation of natural water samples. Automated systems on-line to reverse- and to normal phase HPLC have been realised. A combination of these techniques offers extraction conditions, which makes it possible to determine a wide variety of compounds.
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| 41. |
- Socas-Rodríguez, Bárbara, et al.
(författare)
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Recent advances in the analysis of vitamin D and its metabolites in food matrices
- 2020
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Ingår i: separations. - : MDPI AG. - 2297-8739. ; 7:2
-
Forskningsöversikt (refereegranskat)abstract
- Vitamin D and its analogues are fat-soluble vitamins that carry out important functions in human and animal organisms. Many studies have pointed out the relationship between the deficiency of these substances and the development of both skeletal-and extra-skeletal diseases. Although vitamin D is fundamentally derived from the bio-transformation of its precursor, 7-dehydrocholesterol, through the action of UV-B radiation in the skin, dietary intake also plays an important role in the regulation of its status in an organism. For this reason, the application of reliable methodologies that enable monitoring the content of vitamin D and its analogues in food and supplements constitutes an aspect of special relevance to establish adequate habits, which avoid the deficiency of these substances in organisms and, consequently, the appearance of related diseases. The use of chromatographic techniques in combination with conventional and novel sample pre-treatments has become a suitable strategy to achieve this aim. This review compiles the most relevant methodologies reported in the last ten years for vitamin D analogues analysis in food matrices. Particular attention has been paid to provide a general overview of the most suitable approaches in terms of reliability, sensitivity and simplicity, used in the field of food analysis.
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| 42. |
- Socas-Rodríguez, Bárbara, et al.
(författare)
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Simultaneous Determination of Vitamin D and Its Hydroxylated and Esterified Metabolites by Ultrahigh-Performance Supercritical Fluid Chromatography-Tandem Mass Spectrometry
- 2022
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 94:7, s. 3065-3073
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an analytical method has been developed that, for the first time, allows simultaneous determination of vitamin D2and vitamin D3along with their hydroxylated and esterified forms. A group of 12 vitamin D analogues including vitamin D2and vitamin D3, seven hydroxylated metabolites, and three ester forms were separated in a single 8.0 min run using ultrahigh-performance supercritical fluid chromatography coupled with triple quadrupole tandem mass spectrometry. Electrospray ionization and atmospheric pressure chemical ionization were investigated as ion sources, of which the latter showed a higher ionization efficiency. Chromatographic conditions were thoroughly evaluated by a step-by-step method, whereas an experimental design was applied for the optimization of the ionization parameters. Calibration and repeatability studies were carried out to validate the instrumental methodology showing determination coefficients higher than 0.9992 and good intra-and interday precision with relative standard deviations for areas and retention times lower than 10 and 2.1%, respectively, for all target analytes. Limits of quantification were below 3.03 μg/L for all compounds. The methodology was then validated and applied for the evaluation of human plasma samples in order to demonstrate its applicability to the analysis of vitamin D analogues in biological samples. Samples of five individuals were analyzed. Results show that linoleate-D3, vitamin D2, vitamin D3, 25-hydroxyvitamin D2, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3could be detected in most samples, while the two latter also were quantified in all analyzed samples.
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| 43. |
- Sun, Mingzhe, et al.
(författare)
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Comprehensive on-line two-dimensional liquid chromatography × supercritical fluid chromatography with trapping column-assisted modulation for depolymerised lignin analysis
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1541, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- Lignin depolymerisation produces a large variety of low molecular weight phenolic compounds that can be upgraded to value-added chemicals. Detailed analysis of these complex depolymerisation mixtures is, however, hampered by the lack of resolving power of traditional analysis techniques. In this study, a novel online comprehensive two-dimensional reversed-phase liquid chromatography (RPLC) × supercritical fluid chromatography (SFC) method with trapping column interface was developed for the separation of phenolic compounds in depolymerised lignin samples. The trapping capacities of different trapping columns were evaluated. The influence of large volume water-containing injection on SFC performance was studied. The relation between peak capacity and first dimension flow rate and gradient was investigated. The optimized method was applied for the analysis of a depolymerised lignin sample. The RPLC × SFC system exhibited high degree of orthogonality. Compared with traditional loop based interface, trapping column interface can significantly shorten the analysis time and offer higher detectability, with the disadvantage of more severe undersampling in the first dimension.
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| 44. |
- Sun, Mingzhe, et al.
(författare)
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Dynamic extraction coupled on-line to liquid chromatography with a parallel sampling interface—a proof of concept for monitoring extraction kinetics
- 2019
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 411:16, s. 3675-3683
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Tidskriftsartikel (refereegranskat)abstract
- On-line hyphenation of extraction with chromatography has been explored in several different types of combinations. However, monitoring the complete process of a dynamic, continuous-flow extraction is not possible with any hyphenated system reported so far. The current work demonstrates that this challenging task can be effectively fulfilled by using a parallel sampling interface, which mimics the concept of comprehensive two-dimensional chromatography. In this study, pressurised hot water extraction was coupled on-line with ultra-high-performance liquid chromatography. The set-up was utilised in a kinetic study of dynamic pressurised hot water extraction of curcuminoids from turmeric powder. Compound-specific extraction curves were obtained, which clearly indicated the rate-limiting factors of the extraction processes under different conditions. Additionally, thermal degradation of curcumin during the extraction could also be demonstrated in some of the extractions.
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| 45. |
- Sun, Mingzhe, et al.
(författare)
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Signal enhancement in supercritical fluid chromatography-diode-array detection with multiple injection
- 2019
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 42:24, s. 3727-3737
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Tidskriftsartikel (refereegranskat)abstract
- To circumvent the detrimental effects of large-volume injection with fixed-loop injector in modern supercritical fluid chromatography, the feasibility of performing multiple injection was investigated. By accumulating analytes from a certain number of continual small-volume injections, compounds can be concentrated on the column head, and this leads to signal enhancement compared with a single injection. The signal to noise enhancement of different compounds appeared to be associated with their retention on different stationary phases and with type of sample diluent. The diethylamine column gave the best signal to noise enhancement when acetonitrile was used as sample diluent and the 2-picolylamine column showed the best overall performance with water as the sample diluent. The advantage of multiple injection over one-time large-volume injection was proven with sulfanilamide, with both acetonitrile and water as sample diluents. The multiple injection approach exhibited comparable within- and between-day precision of retention time and peak area with those of single injections. The potential of the multiple injection approach was demonstrated in the analysis of sulfanilamide-spiked honey extract and diclofenac-spiked ground water sample. The limitations of this approach were also discussed.
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| 46. |
- Sun, Mingzhe, et al.
(författare)
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Ultra-high performance supercritical fluid chromatography of lignin-derived phenols from alkaline cupric oxide oxidation
- 2016
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 39:16, s. 3123-3129
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Tidskriftsartikel (refereegranskat)abstract
- Traditional chromatographic methods for the analysis of lignin-derived phenolic compounds in environmental samples are generally time consuming. In this work, an ultra-high performance supercritical fluid chromatography method with a diode array detector for the analysis of major lignin-derived phenolic compounds produced by alkaline cupric oxide oxidation was developed. In an analysis of a collection of 11 representative monomeric lignin phenolic compounds, all compounds were clearly separated within 6 min with excellent peak shapes, with a limit of detection of 0.5–2.5 μM, a limit of quantification of 2.5–5.0 μM, and a dynamic range of 5.0–2.0 mM (R2 > 0.997). The new ultra-high performance supercritical fluid chromatography method was also applied for the qualitative and quantitative analysis of lignin-derived phenolic compounds obtained upon alkaline cupric oxide oxidation of a commercial humic acid. Ten out of the previous eleven model compounds could be quantified in the oxidized humic acid sample. The high separation power and short analysis time obtained demonstrate for the first time that supercritical fluid chromatography is a fast and reliable technique for the analysis of lignin-derived phenols in complex environmental samples.
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| 47. |
- Svenberg, Linus
(författare)
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Sample preparation and analysis of metabolites from plants in the families of Cyperaceae, Poaceae and Apiaceae
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An important aspect of understanding how plants effect their environmentis the study of volatile compounds and how these influence interactions between plants and other living organisms. The study of these secondary metabolites from plants can be used in practical applications, such as behaviour control of insects, and is an important part in the search for novel compounds that can be used to influence the behaviour of disease spreading vectors. The study of secondary metabolites can also be used as tools for introducing and teaching chemical ecology and analytical chemistry. The proper use of sample preparation methods and analysis has a key role in both these applications.In this thesis, different sample collection methods are combined with gas chromatography-mass spectrometry to investigate the diversity of secondary metabolites emitted from plants. In paper I, two different sample collection methods, ultrasound assisted extraction and solid-phase microextraction, were used as a basis to collect six metabolites as a metric of comparison of the methods. The work compares the ultrasound assisted extraction and solid-phase microextraction of stored Cyperus rotundus, and also compares solid-phase microextraction collections from stored and live plant samples.The static headspace solid-phase microextraction method used in paper I was then used to analyse the headspace samples of three other graminoid plants, namely Cynodon dactylon, Cyperus exaltatus and Panicum repens. In paper III, the identification of the headspace volatiles of the graminoid plants were determined, and the relative peak area percentages were analysed using one-way ANOVA. The result of this work allowed for a comparison between the three different plants to determine significant differences between the compounds detected based on relative peak area percentages.Adding to the results of paper I and III, the results from paper II offers more insight into the chemicals present in the gas phase above the plants by employing dynamic headspace sampling from live plants. This adds another sampling method to the body of the work, which expands the knowledge of what volatile compounds are present around the plants. Further, in paper II, the use of two-port olfactometric and semi-field bioassays were used to compare which plants have the largest impact on the behaviour of the malaria vector Anopheles gambiae.In Paper IV, the ultrasound assisted extraction method from paper I was used in order to evaluate the allelopathy of Aegopodium podagraria. This work was used as an inquiry-based learning project for Swedish highschool students, and the feedback of the students were collected for development of the project. The results of the work in paper IV demonstrated the implementation of the developed experimental methods as tools for teaching students of different academic levels about analytical chemistry and chemical ecology.
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