| 1. |
- Macher, M.-B., et al.
(författare)
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Triacylglycerol analysis of partially hydrogenated vegetable oils by silver ion HPLC
- 2001
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Ingår i: Journal of Separation Science. - 1615-9306 .- 1615-9314. ; 24:3, s. 179-185
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Tidskriftsartikel (refereegranskat)abstract
- A fast and reliable method was developed for the analysis of positional and geometrical triacylglycerol isomers in partially hydrogenated vegetable oils. A binary gradient of heptane/acetonitrile was employed in silver ion HPLC with evaporative light scattering detection. Good resolution of native and partially hardened oils was achieved within 22 min for palm oil and within 60 min for rapeseed oil. Initial stability problems were found to be caused by decreasing acetonitrile concentration in the solvent mixture, due to selective evaporation of acetonitrile. By tightening the bottle caps and plugging the usual ventilation inlets, this could be prevented; the system then became very stable. A complementary system (heptane/acetone) was used to confirm the absence of 1,2-elaidin-3-palmitin in the hydrogenated samples. This system shows better resolution in the more saturated region (up to three double bonds). However, for less saturated species, peak-split problems occurred (e.g. for triolein), and the elution strength of acetone was not sufficient for the elution of the most polyunsaturated triacylglycerols of rapeseed oil. This would have required a ternary gradient with an additional, stronger solvent, e.g. acetonitrile. Hence, the original heptane/acetonitrile system was retained as the method of choice. It is sufficiently fast and accurate over a wide range of unsaturation to make it suitable for hydrogenation process control, especially of continuous processes with rapidly changing product composition.
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| 2. |
- Ahlström, Lars-Henric, et al.
(författare)
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Standard addition - A way of improving quantification of banned azo dyes in leather
- 2005
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 28:17, s. 2407-2412
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Tidskriftsartikel (refereegranskat)abstract
- An analytical procedure based on supercritical-fluid extraction and microwave-assisted extraction was applied on six different real leather samples for the determination of banned azo dyes. Determination of the dyes was performed indirectly by measuring their corresponding harmful aromatic amines, formed after reduction. A comparative study between external standard calibration and standard addition using both the dyes as well as the corresponding amines showed that the latter quantification method provided the highest accuracy.
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| 3. |
- Al-Jarah, S. Y., et al.
(författare)
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Capillary electrophoretic and mass spectrometric analysis of a polydisperse fluorosurfactant
- 2005
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 28:3, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- A fluorosurfactant has been studied using capillary electrophoresis and mass spectrometry. The fluorosurfactant, FC134, can be used as a buffer additive in capillary electrophoresis in order to decrease wall adsorption of proteins and in micellar electrokinetic chromatography. However, it has been discovered that this fluorosurfactant is polydisperse, thus containing substances with different lengths and structures. In this work, the fluorosurfactant sample components were separated by capillary electrophoresis. An uncoated as well as a poly(vinyl alcohol)-coated capillary were used with running electrolytes containing methanol and acetic acid. Following the capillary electrophoretic separation, fractions were collected for further analysis by MALDI-MS. Non-fractionated samples were also analyzed both by MALDI-MS and by ESI-MS.
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| 4. |
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| 5. |
- Amini, Ahmad
(författare)
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Separation of somatropin charge variants by multiple-injection CZE with Polybrene/chondroitin sulfate A double-coated capillaries
- 2013
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 36:16, s. 2686-2690
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Tidskriftsartikel (refereegranskat)abstract
- The performance of dynamic double-coated fused-silica capillaries with Polybrene and chondroitin sulfate A has been compared with uncoated fused-silica capillaries for the determination of recombinant human growth factor (somatropin) charge variants. The separations were carried out under the same electrophoretic conditions as described in the European Pharmacopoeia, i.e. at pH 6.0 and 30 degrees C. The coating significantly reduced the interactions between the proteins and the surface of the fused-silica capillary. The first five separations performed in a new bare fused-silica capillary were discarded because of very poor separation performance as a result of protein-surface interactions. There was an approximate twofold increase in the interday migration time precision (%RSD 6.5%) in the double-coated capillaries. The method was successfully transferred to a multiple CZE mode where two samples were analyzed in a single electrophoretic run. The average purity of somatropin certified reference standard was 98.0% (%RSD 0.3%) determined by using uncoated and coated capillaries.
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| 6. |
- Andersson, Maria, et al.
(författare)
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Synthesis and bioanalytical evaluation of morphine-3-O-sulfate and morphine-6-O-sulfate in human urine and plasma using LC-MS/MS
- 2012
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 35:3, s. 367-375
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to synthesize morphine-3-O-sulfate and morphine-6-O-sulfate for use as reference substances, and to determine the sulfate conjugates as possible heroin and morphine metabolites in plasma and urine by a validated LC-MS/MS method. Morphine-6-O-sulfate and morphine-3-O-sulfate were prepared as dihydrates from morphine hydrochloride, in overall yields of 41 and 39% with product purities of >99.5% and >98%, respectively. For bioanalysis, the chromatographic system consisted of a reversed-phase column and gradient elution. The tandem mass spectrometer was operated in the positive electrospray mode using selected reaction monitoring, of transition m/z 366.15 to 286.40. The measuring range was 5500?ng/mL for morphine-3-O-sulfate and 4.5454?ng/mL for morphine-6-O-sulfate in plasma. In urine, the measuring range was 505000?ng/mL for morphine-3-O-sulfate and 45.44544?ng/mL for morphine-6-O-sulfate. The intra-assay and total imprecision (coefficient of variation) was below 11% for both analytes in urine and plasma. Quantifiable levels of morphine-3-O-sulfate in authentic urine and plasma samples were found. Only one authentic urine sample contained a detectable level of morphine-6-O-sulfate, while no detectable morphine-6-O-sulfate was found in plasma samples.
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| 7. |
- Appelblad, Patrik, et al.
(författare)
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Fast hydrophilic interaction liquid chromatographic separations on bonded zwitterionic stationary phase
- 2008
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 31:9, s. 1529-1536
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Tidskriftsartikel (refereegranskat)abstract
- Separation science is an art of obtaining adequate resolution of the desired compounds in minimum time, and with minimum effort in terms of sample preparation and data evaluation. In LC, where selectivity is a main driving force for separation, the availability of different separation modes capable of operating at high flow rates is a way to make combined optimal use of selectivity, efficiency, and speed. The separation of polar and hydrophilic compounds is problematic in RP LC due to the poor retention. Hydrophilic interaction liquid chromatography (HILIC) is a more straightforward separation mode to address this problem. Herein, it is shown that separations in HILIC mode are equally efficient as for RP, providing a potential for very fast separations on short columns. This is not only facilitated by the low viscosity of the mobile phase compositions used, compared to typical RP eluents, but also due to higher column permeability. To exemplify this, baseline separations of uracil and cytosine are shown in less than 4 s and of Tamiflu® and its main metabolite in less than 40 s, both under isocratic conditions. HILIC must therefore be considered having potential for high throughput purposes, and being an attractive candidate as the second separation dimension in 2-D HPLC.
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| 8. |
- Bartolome, Luis, et al.
(författare)
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Determination of trace levels of dinitrophenolic compounds by microporous membrane liquid-liquid extraction in environmental water samples
- 2007
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 30:13, s. 2144-2152
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Tidskriftsartikel (refereegranskat)abstract
- A fast and simple hollow fibre-based microporous membrane liquid-liquid extraction (MMLLE) method is proposed for the determination of trace levels of dinitrophenolic compounds in water samples. The optimization step was performed using a three-variables Doehlert matrix design, involving the fibre length, the quantity of trioctylphosphine oxide (TOPO) in the acceptor phase and the extraction time. Using the established experimental conditions, some other parameters such as stirring speed, salt content, humic acids and different organic solvents as the acceptor phase were studied. Validation of the method included calibration experiments, linearity studies and determination of method LOD (MLD). The RSD was around 11% in all the experiments on different days at different concentrations. Separation and detection of four dinitrophenols were performed in 10 min with an RP-LC and a C-8 column ACN-citric buffer gradient elution and diode array detection.
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| 9. |
- Bertucci, Carlo, et al.
(författare)
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HSA binding of HIV protease inhibitors : a high-performance affinity chromatography study
- 2009
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 32:10, s. 1625-1631
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Tidskriftsartikel (refereegranskat)abstract
- The binding of HIV protease inhibitors, drugs important for anti-HIV chemotherapy, to HSA was examined by high-performance affinity chromatography. Frontal analysis was first used to determine the amount of anchored protein and the binding capacity for selected markers on this column. Zonal elution experiments then ranked the HSA bound fraction of the examined compounds. Information on the g region was obtained by competitive zonal elution experiments using probe binding compounds with known sites on HSA. An allosteric competition between HIV protease inhibitors (PIs) and valproate (a probe for the bilirubin site) was detected, consistent with a noncooperative binding mechanism. No significant competition was observed between the examined compounds and salicylate or ibuprofen, probes for sites I and II, respectively. The observations were confirmed by circular dichroism spectroscopy, based on the change in the induced circular dichroism signals of selected markers for the main binding sites of HSA when ritonavir was added as the competitor. These results were in good agreement with previous literature reports and provide more details on how PIs are transported in plasma and how they may compete with other drugs in the body.
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| 10. |
- Bui, Nhat Thi Hong, et al.
(författare)
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Synthesis of poly(N-[tris(hydroxymethyl)methyl]acrylamide) functionalized porous silica for application in hydrophilic interaction chromatography
- 2012
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 35:23, s. 3257-3269
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Tidskriftsartikel (refereegranskat)abstract
- Porous silica coated by a highly hydrophilic and nonionic tentacle-type polymeric layer was synthesized by free radical "grafting from" polymerization of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-2-propenamide (TRIS-acrylamide) in partly aqueous solutions. The radical initiator sites were incorporated on the silica surfaces via a two-step reaction comprising thionyl chloride activation and subsequent reaction with tert-butyl hydroperoxide. The surface-bound tert-butylperoxy groups were then used as thermally triggered initiators for graft polymerization of TRIS-acrylamide. The synthesized materials were characterized by diffusive reflectance Fourier transform infrared specotroscopy, X-ray photoelectron spectroscopy, and CHN elemental analysis. Photon correlation spectroscopy was used to determine changes in ζ-potentials resulting from grafting, (29) Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) spectroscopy was used to assess the ratio of silanol to siloxane groups in the substrate and the grafted material, and the changes in surface area and mesopore distribution were determined by nitrogen cryosorption. Chromatographic evaluation in hydrophilic interaction chromatography (HILIC) mode showed that the materials were suitable for use as stationary phases, featuring good separation efficiency, a comparatively high retention, and a selectivity that differed from most commercially available HILIC phases. A comparison of this neutral phase with a previously reported N-(2-hydroxypropyl)-linked TRIS-type hydrophilic tentacle phase with weak anion exchange functionality revealed substantial differences in retention patterns.
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| 11. |
- Bui Thi Hong, Nhat, et al.
(författare)
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Tris(hydroxymethyl)aminomethane-functionalized silica particles and their application for hydrophilic interaction chromatography
- 2010
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Ingår i: Journal of Separation Science. - : John Wiley & Sons. - 1615-9306 .- 1615-9314. ; 33:19, s. 2965-2976
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Tidskriftsartikel (refereegranskat)abstract
- A new method is presented for synthesizing a highly hydrophilic silica-based material for use in hydrophilic interaction chromatography. Porous silica particles used as a starting substrate were modified with 3-bromopropyl trichlorosilane and grafted with glycidyl methacrylate by controlled (“living”) atom transfer radical polymerization in order to introduce an oxirane-carrying reactive tentacle layer on the silica surface. The grafted material was thereafter subject to an oxirane ring opening reaction with tris(hydroxy-methyl)aminomethane in dimethylformamide to yield a polymer-bound equivalent of the well known and highly hydrophilic “TRIS” buffering substance. Chemical characterization was done by diffuse reflectance FT-IR, X-ray photoelectron spectroscopy, elemental analysis, and 1H NMR. Porosity and surface area examination was done with Brunauer–Emmett–Teller. Chromatographic application of the material was evaluated by separations of nucleic bases, small organic acids, and common nucleotides under mixed hydrophilic interaction chromatography and weak anion exchange conditions.
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| 12. |
- Byström, Emil, 1980-, et al.
(författare)
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Differences in porous characteristics of styrenic monoliths prepared by controlled thermal polymerization in molds of varying dimensions
- 2010
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 33:2, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- Nitroxide-mediated polymerization was used as a model system for preparing styrenic monolithic materials with significant mesopore contents in different mold formats, with the aim of assessing the validity of pore characterization of capillary monoliths by analysis of parallel bulk polymerized precursor solution. Capillary monoliths were prepared in 250 mm id fused silica tubes (quadruplicate samples, in total 17 m), and the batch polymerizations were carried out in parallel in 100 mL microvials and regular 2mL glass vials, both in quintuplicate. The monoliths recovered from the molds were characterized for their meso- and macroporous properties by nitrogen sorptiometry (three repeated runs on each sample), followed by a single analysis by mercury intrusion porosimetry. A total of 14 monolith samples were thus analyzed. A Grubbs’ test identified one regular vial sample as an outlier in the sorptiometric surface area measurements, and data from this sample were consequently excluded from the pore size calculations, which are based on the same nitrogen sorption data, and also from the mercury intrusion data set. The remaining data were subjected to single factor analyses of variance analyses to test if the porous properties of the capillary monoliths were different from those of the bulk monoliths prepared in parallel. Significant differences were found between all three formats both in their meso and macroporous properties. When the dimension was shrunk from conventional vial to capillary size, the specific surface area decreased from 52.274.7 to 34.671.7m2/g. This decrease in specific surface area was accompanied by a significant shift in median diameter of the through-pores, from 31073.9 to 544713 nm. None of these differences was obvious from the scanning electron micrographs that were acquired for each sample type. The common practice of determining the mesopore characteristics from analysis of samples prepared by parallel bulk polymerization and looking for changes in the macropore structure by visual assessment of SEMs are therefore both rather questionable, at least for monoliths of the kind used in this study.
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| 13. |
- Byström, Emil, et al.
(författare)
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Plasma brominated polymer particles as grafting substrate for thiol-terminated telomers
- 2010
-
Ingår i: Journal of Separation Science. - Weinheim : WILEY-VCH Verlag GmbH & Co. KGaA. - 1615-9306 .- 1615-9314. ; 33:11, s. 1563-70
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Tidskriftsartikel (refereegranskat)abstract
- A combined surface activation and "grafting to" strategy was developed to convert divinylbenzene particles into weak cation exchangers suitable for protein separation. The initial activation step was based on plasma modification with bromoform, which rendered the particles amenable to further reaction with nucleophiles by introducing Br to a surface content of 11.2 atom-%, as determined by X-ray photoelectron spectroscopy. Grafting of thiol-terminated glydicyl methacrylate telomers to freshly plasma activated surfaces was accomplished without the use of added initiator, and the grafting was verified both by reduction in bromine content and the appearance of sulfur-carbon linkages, showing that the surface grafts were covalently bonded. Following grafting the attached glydicyl methacrylate telomer tentacles were further modified by a two-step procedure involving hydrolysis to 2,3-hydroxypropyl groups and conversion of hydroxyl groups to carboxylate functionality by succinic anhydride. The final material was capable of baseline separating four model proteins in 3 min by gradient cation exchange chromatography in a fully aqueous eluent.
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| 14. |
- Bårdstu, Kari Folde, et al.
(författare)
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Supported liquid membranes in hollow fiber liquid-phase microextraction (LPME) - Practical considerations in the three-phase mode
- 2007
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 30:9, s. 1364-1370
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Tidskriftsartikel (refereegranskat)abstract
- In this work, three-phase liquid-phase microextraction (LPME) based on a supported liquid membrane (SLM) sustained in the wall of a hollow fiber was investigated with special focus on optimization of the experimental procedures in terms of recovery and repeatability. Recovery data for doxepin, amitriptyline, clomipramine, and mianserin were in the range of 67.8-79.8%. Within-day repeatability data for the four basic drugs were in the range of 4.1-7.7%. No single factor was found to be responsible for these variations, and the variability was caused by several factors related to the LPME extractions as well as to the final HPLC determination. Although the volume of the SLM varied within 0.4-3.1% RSD depending on the preparation procedure, and the volume of the acceptor solution varied within 4.8% RSD, both recoveries and repeatability were found to be relative insensitive to these variations. Thus, the handling of microliters of liquid in LPME was not a very critical factor, and the preparation of the SLM was accomplished in several different ways with comparable performance. Reuse of hollow fibers was found to suffer from matrix effects due to built-up of analytes in the SLM, whereas washing of the hollow fibers in acetone was beneficial in terms of recovery, especially for the extraction of the most hydrophobic substances. Several of the organic solvents used in the literature as SLM suffered from poor long-term stability, but silicone oil AR 20 (polyphenyl-methylsiloxane), 2-nitrophenyl octyl ether (NPOE), and dodecyl acetate (DDA) all extracted with unaltered performance even after 60 days of storage at room temperature.
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| 15. |
- Chen, Xiao-Jia, et al.
(författare)
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Effect of ion adsorption on CEC separation of small molecules using hypercrosslinked porous polymer monolithic capillary columns
- 2012
-
Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 35:12, s. 1502-1505
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Tidskriftsartikel (refereegranskat)abstract
- Both poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) and poly(4-methylstyrene-co-vinylbenzyl chloride-co-divinylbenzene) monolithic columns have been hypercrosslinked and for the first time used to achieve capillary electrochromatographic separations. Although these columns do not contain ionizable functionalities, electroosmotic flow was observed due to adsorption of ions from a buffer solution contained in the mobile phase on the surface of the hydrophobic polymer. An increase of more than one order of magnitude was observed with the use of both monolithic polymers. The hypercrosslinking reaction creates a large surface area thus enabling adsorption of a much larger number of ions. Alkylbenzenes were successfully separated using the hypercrosslinked monolithic columns.
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| 16. |
- Courtois, Julien, et al.
(författare)
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A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries.
- 2006
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29:1, s. 14-24
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Tidskriftsartikel (refereegranskat)abstract
- Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3-((trimethoxysilyl)propyl) methacrylate (gamma-MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6-butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.
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| 17. |
- Ekström, Jörgen, 1944, et al.
(författare)
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RP-HPLC-ESI-MS characterization of novel peptide fragments related to rat parotid secretory protein in parasympathetic induced saliva.
- 2009
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Ingår i: Journal of separation science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:17, s. 2944-52
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Tidskriftsartikel (refereegranskat)abstract
- Two peptides (MW 1211.7 and 928.5 Da) were detected by RP-HPLC-ESI-MS analysis of parotid saliva secreted upon continuous parasympathetic stimulation. The peptide with the higher mass (PSPFr-A) corresponded to the N-terminal dodecapeptide (Fragment 1-12) of rat parotid secretory protein (PSP), while the peptide with the lower mass (PSPFr-B) corresponded to the 4-12 fragment of the same protein. During stimulation, the PSPFr-A secretion increased, while the PSPFr-B secretion decreased (HPLC-ESI-MS). In the presence of cycloheximide, PSPFr-A was not demonstrated, while the PSPFr-B secretion decreased. In the presence of aprotinin, the PSPFr-B secretion was almost abolished, while the PSPFr-A secretion increased to higher levels than those observed in the absence of the inhibitor. In vitro perfusion, with artificial solution, of stimulated rat parotid glands excluded that the fragments were derived from the circulation. Neither peptide occurred in enriched granule preparations from unstimulated glands. The results suggest that at least two pathways - granular and vesicular - are responsible for the generation of the two peptides. PSPFr-A is the first cleavage product in both pathways. PRPFr-B is probably generated from granular PSPFr-A only and, at the end of the granule mediated pathway, by the action of an enzyme of the serine protease class.
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| 18. |
- El-Beqqali, Aziza, 1966-, et al.
(författare)
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Determination of dopamine and serotonin in human urine samples utilizing microextraction online with liquid chromatography/electrospray tandem mas spectrometry
- 2007
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 30:3, s. 421-424
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Tidskriftsartikel (refereegranskat)abstract
- A specific LC-MS-MS method for the determination of dopamine and serotonin (5-hydroxytryptamine; 5HT) in human urine is described. The analytes were extracted from urine and preconcentrated by microextraction in a packed syringe (MEPS). The new method is very promising, very easy to use, fully automated, of low cost, and rapid in comparison to previously used methods. The method was validated and the standard curves were evaluated by means of quadratic regression and weighted by the inverse of the concentration: 1/x for the calibration range 50–4000 μg/L. The MEPS applied polymer (silica-C8) could be used more than 300 times. The extraction recovery was about 50%. The results showed close correlation coefficients (r2 A0.999) for all analytes in the calibration range studied. The accuracy of MEPS-LC-MS-MS was 100–101% for dopamine and 99–100% for 5HT. The interday precision (n = 3 days), expressed as the RSD%, was 6.0–7.7% for dopamine and 6.1–11% for 5HT. MEPS reduced the handling time by 12 times compared to a published method.
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| 19. |
- El-Beqqali, Aziza, 1966-, et al.
(författare)
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Quantitative analysis of methadone in human urine samples by microextraction in packed syringe-gas chromatography-mass spectrometry (MEPS-GC-MS)
- 2007
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 30:15, s. 2501-2505
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Tidskriftsartikel (refereegranskat)abstract
- A method for the simultaneous analysis of methadone in urine samples by microextraction in a packed syringe online with GC-MS (MEPS-GC-MS) is described. The new method reduced the sample handling and the detection limit by two- to seven-fold compared to published methods. Using a quantitation method based on the calculation of analyte concentration by comparison to an internal standard, we were able to measure methadone levels consistent with values reported for healthy individuals. The intra-assay precisions (RSD) of the method using quality control (QC) samples at three different concentration levels were about 11-14% (n = 6). The interassay precisions (RSD) were 11–15% for methadone in urine samples (n = 18). The accuracy varied from 89 to 109% for intra-assay (n = 6), and 97 to 107% for inter-assay (n = 18). The regression correlation coefficients (r2) were over 0.99 in all experiments.
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| 20. |
- Feás, Xesús, et al.
(författare)
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Application of dummy molecularly imprinted solid-phase extraction in the analysis of cyproheptadine in bovine urine.
- 2009
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:10, s. 1740-1747
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Tidskriftsartikel (refereegranskat)abstract
- Due to the difficulty of monitoring trace levels of cyproheptadine (CYP) residues in complicated biological matrices, specific adsorption materials for the preconcentration and clean-up of CYP are indispensable. In this work, CYP was extracted from urine using dummy molecularly imprinted SPE (DMISPE) to avoid leakage of the imprinting molecules during the desorption phase. For synthesis of DMISPE, azatadine (AZA) was employed as the dummy template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator, and dichloromethane as the porogen solvent. An LC-MS/MS method was used to analyze CYP. Two MRM (multiple reaction monitoring) transitions for each analyte were monitored using diphenylpyraline hydrochloride (DPP.HCl), which was used as an internal standard. The advantages of DMISPE include obtaining less complex chromatograms and reducing ion suppression in ESI. The process efficiencies for DMISPE and SPE were 80% and 12%, respectively. In addition, the demonstrated reusability of the DMISPE cartridges is an advantage compared with single-use SPE cartridges or immunoaffinity materials.
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| 21. |
- Forssén, Patrik, 1966-, et al.
(författare)
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Impact of column and stationary phase properties on the productivity in chiral preparative LC
- 2018
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 41:6, s. 1346-1354
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Tidskriftsartikel (refereegranskat)abstract
- By generating 1500 random chiral separation systems, assuming two-site Langmuir interactions, we investigated numerically how the maximal productivity (P-R,P-max) was affected by changes in stationary phase adsorption properties. The relative change in P-R,P-max, when one adsorption property changed 10%, was determined for each system and for each studied parameter the corresponding productivity change distribution of the systems was analyzed. We could conclude that there is no reason to have columns with more than 500 theoretical plates and larger selectivity than 3. More specifically, we found that changes in selectivity have a major impact on P-R,P-max if it is below similar to 2 and, interestingly, increasing selectivity when it is above similar to 3 decreases P-R,P-max. Increase in relative saturation capacity will have a major impact on P-R,P-max if it is below similar to 40%, but only modest above this percent. Increasing total monolayer saturation capacity, or decreasing the first eluting enantiomer's retention factor, will have a modest effect on P-R,P-max and increased efficiency will have almost no effect at all on P-R,P-max unless it is below similar to 500 theoretical plates. Finally, we showed that chiral columns with superior analytic performance might have inferior preparative performance, or vice versa. It is, therefore, not possible to assess columns based on their analytical performance alone.
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| 22. |
- Fred, Charlotta, et al.
(författare)
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Characterization of alkyl-cobalamins formed in trapping of epoxide metabolites of 1,3-butadiene
- 2004
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 27:7-8, s. 607-612
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Tidskriftsartikel (refereegranskat)abstract
- Analytical methods facilitating studies of electrophilically reactive and genotoxic compounds in vitro and in vivo are needed. The strong nucleophile, cob(I)alamin, formed by reduction of Vitamin B12 [cob(III)alamin], may be used for trapping and analysis of 1,2-epoxides and other electrophiles. In the present study, cob(I)alamin is evaluated as an analytical tool for 1,2-epoxide metabolites (oxiranes) of 1,3-butadiene. Products of reaction of cob(I)alamin with 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB), and 1,2-epoxy-3,4-butanediol (EBdiol) have been analyzed by reversed phase high performance liquid chromatography (HPLC) coupled on-line to electrospray ionization mass spectrometry (ESI-MS) and ultraviolet diode array detection (UV-DAD). It was shown that a specific alkyl-Cbl complex is formed for each metabolite and that it was possible to discriminate between the products by HPLC-UV and by LC-MS. Quantification of DEB with the method by use of another 1,2-epoxide as an internal standard was successfully performed. The possibility of using cob(I)alamin for trapping and analysis of the three oxirane metabolites of 1,3-butadiene will facilitate quantitative comparisons of species in vitro with regard to metabolism of 1,3-butadiene.
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| 23. |
- Fredriksson, Mattias, et al.
(författare)
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An automatic peak finding method for LC-MS data using Gaussian second derivative filtering
- 2009
-
Ingår i: Journal of Separation Science. - Weinheim : Wiley-VCH Verlag. - 1615-9306 .- 1615-9314. ; 32:22, s. 3906-3918
-
Tidskriftsartikel (refereegranskat)abstract
- A highly automated procedure for localising and characterising peaks in the chromatographic time domain of LC-MS data has been developed. The work was initiated by an identified need to facilitate the detection and tracking of chromatographic peaks during method development for the analysis of impurities in pharmaceutical products. The algorithm is mainly based on a digital filter for which the settings are automatically adapted to the data set under study. The procedure was evaluated for synthetic data sets with various S/N levels, peak widths and baseline properties. It was found that even for the worst case tested with S/N=10 and a high variability in the baseline, 94% of the simulated analytical peaks could be detected without producing any false-positive identifications. Furthermore, the number of correctly estimated peak heights and peak widths falling within a 10% error of the true values were 94 and 91%, respectively. For experimental data sets, peak height, and width estimations were more difficult, but the processed reconstructions showed an excellent agreement with the analytical signals of the raw data, and also a clearly improved visualisation in total ion- and base-peak chromatograms.
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| 24. |
- Gao, Min, et al.
(författare)
-
Separation of polyphenols using porous polyamide resin and assessment of mechanism of retention
- 2011
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 34:15, s. 1853-1858
-
Tidskriftsartikel (refereegranskat)abstract
- A porous polyamide resin is shown to possess hydrogen bond acceptor properties suitable for the separation of polyphenolic solutes such as phenolic acids, flavonols and flavonoids. The separation is achieved in the presence of solvent mixtures of acetic acid and ethanol. The extent of hydrogen bond adsorption is reviewed based on data obtained from the elution behaviour of a variety of simple polyphenolic solutes. Polyamide adsorption chromatography was applied for the purification of resveratrol and polydatin from Polygonum cuspidatum Sieb. & Zucc.
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| 25. |
- Ghasemzadeh, Nasim, et al.
(författare)
-
Highly selective artificial gel antibodies for detection and quantification of biomarkers in clinical samples : I. Spectrophotometric approach to design the calibration curve for the quantification
- 2008
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 31:22, s. 3945-3953
-
Tidskriftsartikel (refereegranskat)abstract
- High selectivity of a biomarker is a basic requirement when it is used for diagnosis, prognosis and treatment of a disease. The artificial gel antibodies, which we synthesise by a molecular imprinting method, have this property not only for proteins, but also for bioparticles, such as viruses and bacteria. However, diagnosis of a disease requires not only that the biomarker can be "fished out" from a body fluid with high selectivity, but also that its concentration in the sample can rapidly be determined and preferably by a simple technique. This paper deals primarily with the development of a spectrophotometric method, which is so simple and fast that it can be used with advantage in a Doctor's Office. The development of this method was not straight-forward. However, by modifications of the performance of these measurements we can now design standard curves in the form of a straight line, when we plot the true (not the recorded "apparent" absorption) against known protein concentrations. In an additional publication (see the following paper in this issue of JSS) we show an application of such a plot: determination of the concentration of albumin in serum and cerebrospinal fluid from patients with neurological disorders to investigate whether albumin is a biomarker for these diseases.
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| 26. |
- Ghasemzadeh, Nasim, et al.
(författare)
-
Highly selective artificial gel antibodies for detection and quantification of biomarkers in clinical samples : II. Albumin in body fluids of patients with neurological disorders
- 2008
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 31:22, s. 3954-3958
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously used the molecular-imprinting method for the synthesis of artificial gel antibodies, highly selective for various proteins. In the present work, we have synthesized artificial gel antibodies against human albumin with the aim to develop a simple and rapid procedure to measure the concentration of this protein in samples of clinical interest. The procedure, based on the design of a standard curve (see the preceding paper), was applied on a quantitative analysis of albumin in human plasma and cerebrospinal fluid (CSF). We found that our technique permitted detection of albumin in these body fluids with high precision and that the concentration of this protein was significantly enhanced in CSF from patients with amyotrophic lateral sclerosis (ALS), compared to control samples. This finding is in agreement with results from earlier studies, which confirms the validity of our analysis technique and suggests that the barrier permeability may be affected in ALS, perhaps also for other proteins. No enhancement in plasma levels of albumin was seen in patients with ALS, but rather a decrease. The results further indicate that our approach might also apply well to other biomarkers for the actual neurological disease and other disorders.
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| 27. |
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| 28. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Composite cryogel with immobilized concanavalin A for affinity chromatography of glycoproteins.
- 2012
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 35:21, s. 2978-2985
-
Tidskriftsartikel (refereegranskat)abstract
- Composite cryogels containing porous adsorbent particles were prepared under cryogelation conditions. The composites with immobilized concanavalin A (Con A) were used for capturing glycoproteins. Adsorbent particles were introduced into the structure in order to improve the capacity and to facilitate the handling of the particles. The monolithic composite cryogels were produced from suspensions of polyvinyl alcohol particles and porous adsorbent particles and cross-linked under acidic conditions at sub-zero temperature. The cryogels were epoxy activated and Con A was immobilized as an affinity ligand. Binding and elution of horseradish peroxidase (HRP) was studied in batch experiment and in a chromatographic setup. Increasing adsorbent concentration in composite cryogels will increase ligand density, which therefore enhances the amount of bound HRP from 0.98 till 2.9 (milligram enzyme per milliliter of gel) in the chromatographic system. The material was evaluated in 10 cycles for binding and elution of HRP.
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| 29. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Evaluation of selective composite cryogel for bromate removal from drinking water.
- 2010
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 33, s. 1752-1759
-
Tidskriftsartikel (refereegranskat)abstract
- Bromate, which is a potential carcinogen, should be removed from drinking water to levels of less than 10 mug/L. A chitosan-based molecularly imprinted polymer (MIP) and a sol-gel ion-exchange double hydrous oxide (Fe(2)O(3).Al(2)O(3).xH(2)O) adsorbent (inorganic adsorbent) were prepared for this purpose. The sorption behavior of each adsorbent including sorption kinetics, isotherms, effect of pH and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had better selectivity for bromate, even in the presence of high concentrations of nitrate, as compared to the inorganic adsorbent. It was found that pH does not affect the adsorption of bromate when using the inorganic adsorbent. Additionally, both adsorbents were immobilized in a polymeric cryogel inside plastic carriers to make them more practical for using in larger scale. Regeneration of the cryogels either containing MIP or inorganic adsorbents were carried out by 0.1 M NaOH and 0.1 M NaCl, respectively. It was found that the regenerated MIP and inorganic adsorbents could be used at least three and five times, respectively, without any loss in their sorption capacity.
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| 30. |
- Hansson, Helena, et al.
(författare)
-
Study of mass transfer in a dynamic hollow-fibreliquid phase microextraction system
- 2010
-
Ingår i: Journal of Separation Science. - : Wiley Interscience. - 1615-9306 .- 1615-9314. ; 33:1, s. 112-119
-
Tidskriftsartikel (refereegranskat)abstract
- The extraction characteristics of a dynamic hollow-fibre liquid phase microextractionsystem were investigated by studying the mass transfer and diffusion rates of dinitrophenolsfrom plasma samples over the liquid membrane (dihexylether). The measureddiffusion coefficients were compared with theoretical values calculated from Stokesdiameters. The diffusion mechanism was simulated by computer and the most polarcompounds, 2,4-dinitrophenol and 4,6-o-dinitrocresol, had associated diffusion coefficientsthat were close to the calculated theoretical values. 2-sec-Butyl-4,6 dinitrophenoland 2-tert-butyl-4,6-dinitrophenol, the compounds with the highest log P values, wereretained by the polypropylene membrane, which reduced the experimentally observeddiffusion rates to about half of the theoretical values. The retention was most likely due todispersive forces interacting with the pore inner walls. Extraction was linearly correlatedwith time for all compounds and the repeatability was high (RSDs 7–11%), even for theshortest extraction times. Method LOD as the amount injected ranged between 0.3 and3.1 ng for an extraction cycle of 213 s.
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| 31. |
- Hemström, Petrus, et al.
(författare)
-
Alternative organic solvents for HILIC separation of cisplatin species with on-line ICP-MS detection
- 2008
-
Ingår i: Journal of Separation Science. - : John Wiley & Sons. - 1615-9306 .- 1615-9314. ; 31:4, s. 599-603
-
Tidskriftsartikel (refereegranskat)abstract
- Several low volatile organic solvents were evaluated as organic modifiers in eluents for HILIC separations of cisplatin species to optimize the on-line coupling of HILIC to inductively coupled plasma MS (ICP-MS). The aim was to identify a solvent giving low solvent vapor loading of the ICP, to maximize analyte sensitivity and minimize carbon depositions on instrumental parts, while retaining chromatographic performance. The best overall performance of the HILIC-ICP-MS system for the analysis of cisplatin was achieved using 1,4-dioxane as eluent, yielding high retention and an HILIC type retention mechanism, at the expense of a 50% drop in column efficiency due to the higher viscosity of 1,4-dioxane compared to the more commonly used HILIC solvent ACN. Using 1,4-dioxane as solvent in HILIC provides the best compromise between carbon deposition and separation efficiency among a series of high-boiling water-miscible solvents tested.
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| 32. |
- Hemström, Petrus, et al.
(författare)
-
Hydrophilic interaction chromatography
- 2006
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29, s. 1784-1821
-
Tidskriftsartikel (refereegranskat)abstract
- Separation of polar compounds on polar stationary phases with partly aqueous eluents is by no means a new separation mode in LC. The first HPLC applications were published more than 30 years ago, and were for a long time mostly confined to carbohydrate analysis. In the early 1990s new phases started to emerge, and the practice was given a name, hydrophilic interaction chromatography (HILIC). Although the use of this separation mode has been relatively limited, we have seen a sudden increase in popularity over the last few years, promoted by the need to analyze polar compounds in increasingly complex mixtures. Another reason for the increase in popularity is the widespread use of MS coupled to LC. The partly aqueous eluents high in ACN with a limited need of adding salt is almost ideal for ESI. The applications now encompass most categories of polar compounds, charged as well as uncharged, although HILIC is particularly well suited for solutes lacking charge where coulombic interactions cannot be used to mediate retention. The review attempts to summarize the ongoing discussion on the separation mechanism and gives an overview of the stationary phases used and the applications addressed with this separation mode in LC.
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| 33. |
- Hemström, Petrus, et al.
(författare)
-
Polymer-based monolithic microcolumns for hydrophobic interaction chromatography of proteins.
- 2006
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29:1, s. 25-32
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic capillary columns for hydrophobic interaction chromatography (HIC) have been prepared by thermally initiated, single-step in situ polymerization of mixtures of monovinyl monomers including butyl methacrylate and/or 2-hydroxyethyl methacrylate, with a divinyl crosslinker glycerol dimethacrylate or 1,4-butanediol dimethacrylate using two different porogen systems. Two porogenic solvent mixtures were used; one "hydrophilic", consisting of water, butanediol, and propanol, and one "hydrophobic," comprising dodecanol and cyclohexanol. The porous structures of the monoliths were characterized and their performance was demonstrated with a separation of a mixture of myoglobin, ribonuclease A, and lysozyme under conditions typical of HIC.
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| 34. |
- Hyötyläinen, Tuulia, 1971-
(författare)
-
Analytical challenges in human exposome analysis with focus on environmental analysis combined with metabolomics
- 2021
-
Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 44:8, s. 1769-1787
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental factors such as chemical exposures are likely to play a crucial role in the development of several human chronic diseases. However, how the specific exposures contribute to the onset and progress of various diseases is still poorly understood. In part, this is because comprehensive characterization of the chemical exposome is a highly challenging task, both due to its complex dynamic nature as well as due to the analytical challenges. Herein, the analytical challenges in the field of exposome research are reviewed, with specific emphasis on the sampling, sample preparation and analysis, as well as challenges in the compound identification. The primary focus is on the human chemical exposome, i.e., exposures to mixtures of environmental chemicals and its impact on human metabolome. In order to highlight the recent progress in the exposome research in relation to human health and disease, selected examples of human exposome studies are presented.
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| 35. |
- Jacksén, Johan, et al.
(författare)
-
Capillary electrophoretic separation and fractionation of hydrophobic peptides onto a pre-structured matrix assisted laser desorption/ionization target for mass spectrometric analysis
- 2006
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29:2, s. 288-295
-
Tidskriftsartikel (refereegranskat)abstract
- A CE separation of hydrophobic peptides followed by fractionation onto a prestructured MALDI target and off-line MS analysis was performed. An improved and partially automated manufacturing procedure of the previously described MALDI target is presented. This target is structurally coated with silicone and especially developed for hydrophobic peptides and proteins. Here, the target plate was designed specifically for the CE fraction collection. Different solvents were evaluated to meet the requirements of peptide solubility and compatibility to both the CE and MALDI methods and to the fractionation procedure. CE-MALDI-MS analysis of nine highly hydrophobic peptides from cyanogen bromide-digested bacteriorhodopsin is demonstrated.
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| 36. |
- Jamshidi, Sara, et al.
(författare)
-
Using magnetic core-shell nanoparticles coated with an ionic liquid dispersion assisted by effervescence powder for the micro-solid-phase extraction of four beta blockers from human plasma by ultra high performance liquid chromatography with mass spectrometry detection
- 2019
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 42:3, s. 698-705
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a novel, efficient, and green sorbent, SiO2@Fe3O4 has been created and functionalized with 1-butyl-3-methylimidazolium hexafluorophosphate as an ionic liquid. This sorbent was applied for microextraction of four beta blockers, propranolol, metoprolol, atenolol, and alprenolol with bupivacaine as internal standard from human plasma followed by liquid chromatography with mass spectrometric detection. A mixture of sodium bicarbonate and sodium dihydrogen phosphate was used as an extractant dispersive agent (effervescent power) to enhance the interaction between the magnetic sorbent and analytes. Main affecting parameters on microextraction and elution were optimized. Figures of merit for dispersive solid phase extraction with ionic liquid coated magnetic nanoparticles assisted by effervescent powder were calculated under the optimized conditions. The detection limits for propranolol, metoprolol, atenolol, and alprenolol were found at 0.33, 0.62, 0.03, and 0.44 ng/mL, respectively. For all analytes, good linearity was obtained. Intra-(n = 5) and interday (n = 10) precision were both under 6.3% while the preconcentration factors were obtained in the range between 15-18. The extraction efficiencies for each analyte ranged from 75 to 91%. The method was successfully applied for determination of trace amounts of the beta blockers in human plasma samples.
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| 37. |
- Jansson, Erik T.
(författare)
-
Strategies for analysis of isomeric peptides
- 2018
-
Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 41:1, s. 385-397
-
Forskningsöversikt (refereegranskat)abstract
- This review presents an overview and recent progress of strategies for detecting isomerism in peptides, with focus on D/L epimerization and the various isomers that the presence of an aspartic acid residue may yield in a protein or peptide. While mass spectrometry has become a majorly used method of choice within proteomics, isomerism is inherently difficult to analyze because it is a modification that does not yield any change in mass of the analyte. Here, several techniques used for analysis of peptide isomerism are discussed, including enzymatic assays, liquid chromatography, and capillary electrophoresis. Recent progress in method development using mass spectrometry is also discussed, including labeling strategies, fragmentation techniques, and ion-mobility spectrometry.
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| 38. |
- Josefsson, Leila, et al.
(författare)
-
Analysis of polyvinyl alcohol microbubbles in human blood plasma using capillary electrophoresis
- 2016
-
Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 39:8, s. 1551-1558
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, a new type of ultrasound contrast agent that consists of air-filled microbubbles stabilized with a shell of polyvinyl alcohol was developed. When superparamagnetic nanoparticles of iron oxide are incorporated in the polymer shell, a multimodal contrast agent can be obtained. The biodistribution and elimination pathways of the polyvinyl alcohol microbubbles are essential to investigate, which is limited with today's techniques. The aim of the present study was, therefore, to develop a method for qualitative and quantitative analysis of microbubbles in biological samples using capillary electrophoresis with ultraviolet detection. The analysis parameters were optimized to a wavelength at 260 nm and pH of the background electrolyte ranging between 11.9 and 12. Studies with high-intensity ultrasonication degraded microbubbles in water showed that degraded products and intact microbubbles could be distinguished, thus it was possible to quantify the intact microbubbles solely. Analysis of human blood plasma spiked with either plain microbubbles or microbubbles with nanoparticles demonstrated that it is possible to separate them from biological components like proteins in these kinds of samples.
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| 39. |
- Khataei, Mohammad Mahdi, et al.
(författare)
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Applications of porous frameworks in solid-phase microextraction
- 2021
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 44:6, s. 1231-1263
-
Forskningsöversikt (refereegranskat)abstract
- Porous frameworks are a term of attracting solid materials assembled by interconnection of molecules and ions. These trendy materials due to high chemical and thermal stability, well-defined pore size and structure, and high effective surface area gained attention to employ as extraction phase in sample pretreatment methods before analytical analysis. Solid-phase microextraction is an important subclass of sample preparation technique that up to now different configurations of this method have been introduced to get adaptable with different environments and analytical instruments. In this review, theoretical aspect and different modes of solid-phase microextraction method are investigated. Different classes of porous frameworks and their applications as extraction phase in the proposed microextraction method are evaluated. Types and features of supporting substrates and coating procedures of porous frameworks on them are reviewed. At the end, the prospective and the challenges ahead in this field are discussed.
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| 40. |
- Kuklinski, Nicholas J., et al.
(författare)
-
Micellar capillary electrophoresis - Electrochemical detection of neurochemicals from Drosophila
- 2010
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 33:3, s. 388-393
-
Tidskriftsartikel (refereegranskat)abstract
- The fruit fly is one of the most heavily studied model organisms for genetics research and has significantly contributed to the molecular, cellular, and evolutionary understandings of human behavior Recent research in the analytical chemistry of the fruit fly has focused on developing methods to obtain highly sensitive chemical quantification information of Drosophila melanogaster, especially looking at the nervous system We provide a brief overview of work in the area of CE of the fly head and brain
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| 41. |
- Kumric, Ksenija R., et al.
(författare)
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Mass transfer resistance in a liquid-phase microextraction employing a single hollow fiber under unsteady-state conditions
- 2012
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 35:18, s. 2390-2398
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the mass transport resistance in liquid-phase microextraction (LPME) in a single hollow fiber was investigated. A mathematical model has been developed for the determination of the overall mass transfer coefficient based on the acceptor phase in an unsteady state. The overall mass transfer coefficient in LPME in a single hollow fiber has been estimated from time-dependent concentration of extracted analyte in the acceptor phase while maintaining a constant analyte concentration in the donor phase. It can be achieved either using a high volume of donor to acceptor phase ratio or tuning the extraction conditions to obtain a low-enrichment factor, so that the analyte concentration in the sample is not significantly influenced by the mass transfer. Two extraction systems have been used to test experimentally the developed model: the extraction of Lu(III) from a buffer solution and the extraction of three local anesthetics from a buffer or plasma solution. The mass transfer resistance, defined as a reciprocal values of the mass transfer coefficient, was found to be 1.2 x 103 cm-1 min for Lu(III) under optimal conditions and from 1.96 to 3.3 x 103 cm-1 min for the local anesthetics depending on the acceptor pH and the hydrophobicity of the drug.
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| 42. |
- Lakade, Sameer S., et al.
(författare)
-
Hypercrosslinked particles for the extraction of sweeteners using dispersive solid-phase extraction from environmental samples
- 2018
-
Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 41:7, s. 1618-1624
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract This work presents a new extraction material, namely, Q-100, based on hypercrosslinked magnetic particles, which was tested in dispersive solid-phase extraction for a group of sweeteners from environmental samples. The hypercrosslinked Q-100 magnetic particles had the advantage of suitable pore size distribution and high surface area, and showed good retention behavior toward sweeteners. Different dispersive solid-phase extraction parameters such as amount of magnetic particles or extraction time were optimized. Under optimum conditions, Q-100 showed suitable apparent recovery, ranging in the case of river water sample from 21 to 88% for all the sweeteners, except for alitame (12%). The validated method based on dispersive solid-phase extraction using Q-100 followed by liquid chromatography with tandem mass spectrometry provided good linearity and limits of quantification between 0.01 and 0.1Â ÎŒg/L. The method was applied to analyze samples from river water and effluent wastewater, and four sweeteners (acesulfame, saccharin, cyclamate, and sucralose) were found in both types of sample.
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| 43. |
- Le Noir, Mathieu, et al.
(författare)
-
Removal of endocrine-disrupting compounds from water using macroporous molecularly imprinted cryogels in a moving-bed reactor.
- 2009
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:9, s. 1471-1479
-
Tidskriftsartikel (refereegranskat)abstract
- Highly efficient removal of endocrine-disrupting compounds (EDCs) such as 17beta-estradiol (E2), 4-nonylphenol (NP) and atrazine from water was achieved using a novel macroporous adsorption medium. The medium consisted of a macroporous poly(vinyl alcohol) (PVA) cryogel with molecularly imprinted polymer (MIP) particles embedded in it. The MIP was prepared using E2, NP and atrazine as templates. The macroporous composite molecularly imprinted cryogels were formed inside the open-ended protective shells, known as Kaldnes carriers. These adsorbents (defined as Macroporous Gel Particles, MGPs) were evaluated on the removal of E2, NP and atrazine from water using different column configurations, namely column filled with the MGPs (packed-bed column) and in moving-bed reactors (defined here as moving-bed MGPs reactor). Complete binding (> 99%) of E2 from a spiked aqueous solution (1 mg/L) was achieved using E2-MIP/MGPs in a moving-bed MGPs reactor at the retention time in the reactor of 4 min, while only 77% was bound to the nonimprinted medium (NIP/MGPs). Similar results were also obtained for the adsorption medium imprinted with atrazine. All contaminants studied (E2, atrazine and NP) were effectively removed from water at low (environmentally relevant) concentrations by the respective adsorption medium.
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| 44. |
- Liu, Dan, et al.
(författare)
-
Liquid-liquid/solid three-phase high-speed counter-current chromatography, a new technique for separation of polyphenols from Geranium wilfordii Maxim
- 2012
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 35:16, s. 2146-2151
-
Tidskriftsartikel (refereegranskat)abstract
- High-speed counter-current chromatography using a new liquidliquid/solid three-phase system was used for the separation of the polyphenols corilagin and geraniin from a crude extract of Geranium wilfordii Maxim in one step. The optimized three-phase system was composed of n-hexane/ethyl acetate/methanol/acetic acid/water and to which was added 10-mu m average diameter microspheres of cross-linked 12% agarose at the ratio of 0.2:10:2:1:5 and 0.1 g/mL, respectively. The purities of geraniin and corilagin were 82 and 90%, which were determined by HPLC at 280 nm. A 14.5 and 7 mg of geraniin and corilagin were purified from 160 mg crude extract with the yields of 70 and 78%, respectively.
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| 45. |
- Liu, Dan, et al.
(författare)
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One-step separation and purification of hydrolysable tannins from Geranium wilfordii Maxim by adsorption chromatography on cross-linked 12% agarose gel
- 2011
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 34:9, s. 995-998
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrolysable tannins corilagin and geraniin, the major active components of the traditional Chinese medicine Geranium wilfordii Maxim, have been separated and purified from crude extracts in one step by adsorption chromatography on cross-linked 12% agarose gel (Superose 12 10/300 GL). The separation was achieved by gradient elution using mobile phase A composed of 5% ethanol and 5% acetic acid and mobile phase B composed of 30% ethanol and 30% acetic acid. The gradients were composed as follows: 0-240 mL, 0-25% B; 240-480 mL, 25-40% B; after 480 mL, 100% B. The purities of the collected corilagin and geraniin were 92.4 and 87.2%, and the corresponding yields were 88.0 and 76.8%, respectively.
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| 46. |
- Moein, Mohammad Mahdi, et al.
(författare)
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On-line determination of sarcosine in biological fluids utilizing dummy molecularly imprinted polymers in microextraction by packed sorbent
- 2015
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 38:5, s. 788-795
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Tidskriftsartikel (refereegranskat)abstract
- Several years ago, sarcosine received attention as a prostate-cancer marker. Prostate cancer is one of the most widespread types of tumor diseases in men. The prostate-specific antigen is normally used as a marker, and it can only be detected in blood with a sensitivity of approximately 80%. In the present study, dummy molecularly imprinted polymers in microextraction by packed sorbent with on-line liquid chromatography coupled to tandem mass spectrometry was used for the determination of sarcosine in human plasma and urine samples. The polymer network glycine was used for the dummy molecularly imprinted polymers. The selectivity of the method was evaluated using similar prostate-cancer biomarkers. In addition, various parameters affecting the extraction performance were investigated. The method limits of detection and quantification in the plasma and urine were 1.0 and 3.0 ng/mL, respectively. The values of the coefficient of determination were over 0.99 for all runs in the studied concentration range (3.0-10 000 ng/mL). The method recovery was 87 and 89% in plasma and urine, respectively. The intraday and interday precisions of sarcosine in the plasma and urine samples were in the ranges of 4.0-7.1, 3.0-6.3, 2.9-4.7, and 5.0-6.7, respectively.
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| 47. |
- Nemulenzi, Olga, et al.
(författare)
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Potential of combining of liquid membranes and molecularly imprinted polymers in extraction of 17 beta-estradiol from aqueous samples
- 2009
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 32:11, s. 1941-1948
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Tidskriftsartikel (refereegranskat)abstract
- The potential of combination of liquid membranes (microporous membrane liquid-liquid extraction) and molecularly imprinted polymers (MIPs) was performed using 17 beta-estradiol (E2) as model compound. The model compound was extracted from aqueous sample through a hydrophobic porous membrane that was impregnated with hexane/ethyl acetate (3:2), which also formed part of the acceptor phase. In the acceptor phase, the compound was bound onto MIP particles that were also part of the organic phase. The potential of such combination was optimised for the type and amount of MIP particles in the organic acceptor phase, the extraction time, and the type of organic acceptor solvent. Ultrasound assisted binding of E2 onto MIP particles was also investigated. MIPs prepared by precipitation polymerization were found to be superior to those prepared by bulk polymerization. Increase in the extraction time and the amount of MIP particles in the acceptor phase led to more E2 binding onto the MIP particles. Hexane/ethyl acetate (3:2) as an organic acceptor was found to give higher E2 binding onto MIP particles compared to toluene, diethyl ether, and hexane. Ultrasound was furthermore found to increase the binding of E2 onto MIP particles. The selectivity of the technique was demonstrated by extracting wastewater and where clean chromatograms were obtained compared to liquid membrane extractions (SLMs) alone.
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| 48. |
- Nguyen, Anh Mai, et al.
(författare)
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Preparation and characterization of sizable macroporous epoxy resin-based monolithic supports for flow-through systems
- 2009
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Ingår i: Journal of Separation Science. - : Wiley InterScience. - 1615-9306 .- 1615-9314. ; 32:15-16, s. 2608-2618
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents further results from our efforts to prepare sizable macroporous monolithic materials from epoxy resins and polyamines by emulsion polymerization. For their uses as supports in flow systems, the study aimed at developing materials possessing maximum fluid permeability, high mechanical stability, and a controlled porosity and surface area. Characterization of the materials has been carried out using different techniques, focusing on morphological and mechanical features, and on the surface chemistry. Morphology and porosity were studied with SEM, nitrogen adsorption/desorption, mercury intrusion porosimetry (MIP), and (2)H NMR cryoporosimetry. The chemical composition of the bulk structures and their surfaces was studied by means of bulk elemental analysis and X-ray photoelectron spectroscopy, and potentiometric titration was used to assess the relative amounts of amines and epoxy groups. Essentially, the morphological features were a high fluid permeability, but rather low specific surface area. Convective flow was facilitated by large, interconnected, and evenly spaced macropores which were formed by nonporous skeletons of the connected-rod type. Despite the interfacial nature of the polymerization, the bulk and the surface of the fully cured materials showed similar elemental compositions. All materials were found to have a high surface density of hydroxyl groups, which facilitates functionalization reactions.
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| 49. |
- Nguyen, Anh Mai, et al.
(författare)
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Thermally induced dissolution/precipitation : A simple approach for the preparation of Macroporous Monoliths from Linear Aliphatic Polyamides
- 2009
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Ingår i: Journal of Separation Science. - : Wiley InterScience. - 1615-9306 .- 1615-9314. ; 32:15-16, s. 2619-2628
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Tidskriftsartikel (refereegranskat)abstract
- A versatile way of preparing macroporous monolithic materials from linear aliphatic polyamides is presented. Simply, polyamide pellets were treated in benzyl alcohol (BA) at elevated temperature, causing dissolution by interchain hydrogen bond disruption. Subsequent cooling below the upper critical solution temperature (UCST) resulted in precipitation and partial restoration of the semicrystalline polymer, which is organized into network structures. The final steps were a solvent exchange of BA for methanol, followed by drying to form monolithic entities. A number of polyamides ranging from hydrophilic to hydrophobic were tested and under the experimental conditions, poly(1-aza-2-cycloheptanone (PA6) and (poly-[imino-1,6-hexanediylimino{1,10-dioxo-1,10-decanediyl}] (PA610) yielded entities with macroporous properties that were deemed useful for liquid chromatography. The morphological features and porous properties of the monoliths produced by this dissolution-precipitation procedure were studied by scanning electron microscopy, adsorption/desorption of N2(g) according to the Brunauer-Emmett-Teller (BET) principle, and mercury intrusion porosimetry. Degradation of the polymer backbone was noticeable when the dissolution time was extended and shortening of the polymer chains was confirmed by MALDI-MS, viscosity measurements, X-ray photoelectron spectroscopy (XPS), and potentiometric titration. When the heating was limited to the time it took to dissolve the polymers, mechanically stable monoliths could be obtained. The dissolution/heat treatment time further seemed to be useful for controlling the macroporous morphology.
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| 50. |
- Nilsson, Ulrika Nilsson, et al.
(författare)
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SPE and HPLC/UV of resin acids in colophonium-containing products.
- 2008
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Ingår i: Journal of separation science. - Weinheim, Fed. Rep. of Germany : Wiley. - 1615-9314 .- 1615-9306. ; 31:15, s. 2784-90
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Tidskriftsartikel (refereegranskat)abstract
- A new method, involving SPE and HPLC/UV diode-array detection (DAD), was developed for the quantification of colophonium components in different consumer products, such as cosmetics. Colophonium is a common cause of contact dermatitis since its components can oxidize into allergens on exposure to air. Three different resin acids were used as markers for native and oxidized colophonium, abietic acid (AbA), dehydroabietic acid (DeA), and 7-oxodehydroabietic acid (7-O-DeA). The SPE method, utilizing a mixed-mode hydrophobic and anion exchange retention mechanism, was shown to yield very clean extracts. The use of a urea-embedded C(12) HPLC stationary phase improved the separation of the resin acids compared to common C(18). Concentrations higher than 2 mg/g of both AbA and DeA were detected in wax strips. In this product also 7-O-DeA, a marker for oxidized colophonium, was detected at a level of 28 microg/g. The LODs were in the range of 7-19 microg/g and the LOQs 22-56 microg/g. The method is simple to use and can be applied on many types of technical products, not only cosmetics. For the first time, a method for technical products was developed, which separates AbA from pimaric acid.
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