| 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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