| 1. |
- Adeyemi, David, et al.
(författare)
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Electrospun Nanofibers Sorbents for Pre-Concentration of 1,1-dichloro-2,2 bis-(4-chlorophenyl)ethylene with Subsequent Desorption by Pressurized Hot Water Extraction
- 2011
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 73:9-10, s. 1015-1020
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Tidskriftsartikel (refereegranskat)abstract
- Electrospun polystyrene (PS) nanofibers (130-500 nm) incorporating a potassium salt of imidazole-1-carbodithioate were evaluated as potential sorbents for the pre-concentration of a model organochlorine pesticide; 1,1-dichloro-2,2bis-(4-chlorophenyl)ethylene (DDE). The efficiencies of DDE (0.25-1.0 mu g L-1) adsorption by the nanofiber sorbent followed by desorption employing pressurized hot water extraction (PHWE) were investigated and monitored using gas chromatography with electron capture detection (GC-ECD). Parameters such as time, temperature and pressure of extraction, sample volume, DDE concentration and sorbent mass were optimized. The maximum adsorption of DDE (0.50 mu g L-1) on electrospun PS and carbodithioate incorporated PS nanofibers was at 43.7 and 94.6%, respectively, in 20 min. Incorporation of carbodithiote doubled the adsorption efficiency of PS and achieved LOD of 0.000234 mu g L-1 for DDE. The optimal DDE desorption on the PHWE system was 93.8% in 10 min. It would seem that the use of electrospun nanofibers as sorbent material with subsequent desorption by PHWE has great potential and thus warrants further investigations. This approach as it uses water as an extraction solvent for an organochlorine pesticide provides an opportunity to eliminate organic solvents, especially for procedures aimed at monitoring organic pollutants in the environment.
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| 2. |
- Amini, A., et al.
(författare)
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Determination of Ephedrine, Pseudo-Ephedrine and Caffeine in a Dietary Product by Capillary Electrophoresis
- 2006
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 63:3/4, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the determination of caffeine, ephedrine and pseudo-ephedrine in a dietary product by two rapid and simple methods utilising capillary electrophoresis (CE). The solutes were extracted from the product using 0.2 M HCl and determined by CE with background electrolytes containing 7.5% highly sulfated-β-cyclodextrin (7–11 sulfate groups per β-CD molecule) at pH 2.5 and pH 7.6. Determination of ephedrine and pseudo-ephedrine was accomplished at pH 2.5 with the anode at the detection side of the capillary whereas caffeine was quantified at pH 7.6 with a normal electrophoresis polarity mode. Triethanolamine was added to the running buffer at pH 2.5 in order to reverse the electroosmotic flow (EOF) and thereby speed up the separation of ephedrine and pseudo-ephedrine.
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| 3. |
- Andersson, LI, et al.
(författare)
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Towards molecular-imprint based SPE of local anaesthetics
- 2002
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Ingår i: Chromatographia. - 0009-5893. ; 55, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- The use of imprinted polymers for selective solid-phase extraction of local anaesthetics from human plasma was investigated. Methacrylic acid-ethylene glycol dimethacrylate based MIPs were developed by the alternative template approach using a structural analogue, pentycaine, as the template. The influence of the type and concentration of detergent in the buffer on selective and non-specific binding was investigated. Tween 20, Triton X-100 and Brij 35 were found to eliminate non-specific adsorption and leave selective imprint-onalyte binding essentially unaffected. Efficient pre-concert ration of ropivacaine and bupivacaine from plasma samples, both off-line prior to GC and in-line with LC-MS-MS, was demonstrated.
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| 4. |
- Barri, Thaer, et al.
(författare)
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Supported liquid membrane work-up of blood plasma samples coupled on-line to liquid chromatographic determination of basic antidepressant drugs
- 2004
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Ingår i: Chromatographia. - 0009-5893. ; 59:3-4, s. 161-165
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Tidskriftsartikel (refereegranskat)abstract
- An automated sample pretreatment of human blood plasma for liquid chromatographic determination of three antidepressant drugs, dibenzepine; a tricyclic antidepressant (TCA), reboxetine; a selective noradrenaline reuptake inhibitor (SNRI) and fluvoxamine; a selective serotonin reuptake inhibitor (SSRI), based on supported liquid membrane (SLM) for unsurpassed sample clean-up and analyte enrichment, has been developed. The chromatograms after enrichment of plasma blank and aqueous blank are virtually indistinguishable. The entire analytical procedure revealed good linearity and low detection limits of 5, 15 and 20 ng mL(-1) for dibenzepine, reboxetine and fluvoxamine, respectively. No carry-over effects were noted. The repeatability of extraction at three concentrations in the range 40-150 ng mL(-1) for the three drugs was between ca. 3% and 7% as relative standard deviation. The reproducibility relative standard deviation during three different days (replacing the membrane each day) was not significantly higher.
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| 5. |
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| 6. |
- Burestedt, E., et al.
(författare)
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Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples
- 1995
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Ingår i: Chromatographia. - Heidelberg : Springer Berlin/Heidelberg. - 0009-5893 .- 1612-1112. ; 41:3-4, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25μg L−1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations. © 1995 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.
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| 7. |
- Bylund, Dan, et al.
(författare)
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Optimisation of chromatographic separations by use of a chromatographic response function, empirical modelling and multivariate analysis
- 1997
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Ingår i: Chromatographia. - 0009-5893. ; 44:1/2, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The chiral separation of the drug substance R,S-oxybutynin chloride on a reversed phase HPLC system has been optimised by use of empirical modelling and multivariate analysis. The separation was characterised by a new chromatographic response function developed to modulate both quality of separation and retention time. The study includes a comparison between three different multivariate techniques (multi-layer feed-forward neural networks, multiple linear regression and partial least squares regression) of their capabilities to model the new chromatographic response function and predict its value for new experiments. It was indicated that the most accurate models were achieved with neural networks, although partial least squares regression could also be used to solve the problem since it gives the major directions for the optimal settings of the variables.
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| 8. |
- Bång, Joakim, et al.
(författare)
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Blue Chitin columns for the extraction of heterocyclic amines from urine samples
- 2004
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 60:11-12, s. 651-655
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Tidskriftsartikel (refereegranskat)abstract
- During normal cooking of meat, a class of mutagenic/carcinogenic compounds called heterocyclic amines is formed. Heterocyclic amines are rapidly absorbed and metabolised in the human body, and for estimation of the intake of heterocyclic amines, it is useful to determinate their levels in the urine. Blue Chitin columns were used for the extraction and purification of heterocyclic amines from urine samples spiked with 14 different heterocyclic amines. The samples were analysed using LC-MS. The results show that Blue Chitin columns provide a straightforward and rapid means of extracting heterocyclic amines from urine samples, and that Blue Chitin column are also useful in the purification of urinary metabolites.
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| 9. |
- Carlsson, Björn, et al.
(författare)
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Optimization and Characterization of the Chiral Separation of Citalopram and its Demethylated Metabolites by Response Surface Methodology
- 2001
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Ingår i: Chromatographia. - 0009-5893. ; 53:5/6, s. 266-272
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Tidskriftsartikel (refereegranskat)abstract
- Response-surface modelling and sequential optimization have been used for optimization and characterization of the separation of the enantiomers of citalopram, desmethylcitalopram, and didesmethylcitalopram on an acetylated ▀-cyclodextrin column. In the model chosen the separation conditions mobile phase methanol content, buffer concentration, column temperature, and pH were varied to investigate their influence on the chromatography. It was found that what is good for selectivity within an enantiomer pair is bad for selectivity between enantiomer pairs. Because within-pair and between-pair selectivity does not reach its optimum at the same conditions, a middle course approach has to be followed. Use of an experimental design for this investigation enabled understanding of the mechanisms of within- and between-pair separation for citalopram, desmethylcitalopram, and didesmethylcitalopram. Sequential optimization can be a quicker means of optimizing a chromatographic separation, response-surface modelling, in addition to enabling optimization of the chromatographic process, also serves as a tool for learning more about the separation mechanism.
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| 10. |
- Cohen, Arieh, et al.
(författare)
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Automated solid-phase extraction and liquid chromatography tandem mass spectrometry determination of N-methyl-2-pyrrolidone and its metabolites in urine and plasma
- 2007
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 65:7-8, s. 407-412
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Tidskriftsartikel (refereegranskat)abstract
- A method for the simultaneous determination of N-methyl-2-pyrrolidone (NMP) and its metabolites 5-hydroxyl-N-pyrrolidone (5HNMP), N-methylsuccinimide (MSI) and 2-hydroxy-N-methylsuccinimide (2HMSI) in plasma and urine has been developed. Samples were purified by SPE using an ASPEC XL4. Analysis was performed using LC-MS equipped with an APCI interface. The analysis provided linear responses in the range of 0.125-12 mu g mL(-1) for all of the analytes and up to 150 mu g mL(-1) for 5HNMP and 2HMS1. The within day precision was in the range of 0.9-19.1% for plasma samples and 1.9-10.4% for urine samples whereas the between day precisions were 4.5-11.9% and 1.2-17.5%, respectively. The method was deemed to be suitable for monitoring the levels of NMP and its metabolites in the plasma and urine of occupationally exposed persons.
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