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  • 11
    Digitale Medien
    Digitale Medien
    Heterogenic catalytic hydrolysis and analysis of natural pyrethrins in subcritical water coupled with solid phase microextraction (SPME) and GC-MS (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 625-630 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The natural pyrethrins, cinerin I, jasmolin I and pyrethrin I, have been hydrolyzed to chrysanthemic acid (CA) in subcritical water in the presence of basic alumina. The hydrolysis and extraction was performed in situ with subcritical water. The conversion to acid is reproducible at 200 °C and 30 min with an RSD of 19% (n = 16) at a concentration level of 1.2 × 10–8 mol/L CA and 12% (n = 12) at concentration level of 1.2 × 10–7 mol/L CA. An analytical method using Solid Phase Micro Extraction (SPME) combined with GC-FID or -MSD was developed and optimized. For SPME an equilibration time of 20 min at pH of 2 was required. Three fibers, 100 μm polydimethylsiloxane (PDMS), 85 μm polyacrylate (PA) and 65 μm carbowax/divinylbenzene (CW) were evaluated. The Carbowax/divinylbenzene fiber has the highest affinity for CA, but the capacity decreases significantly from experiment to experiment. The most reproducible and most stable one was the PDMS fiber. Two internal standards, octanoic acid and cis-chrysanthemic acid, were used because CA degrades slowly at 200 °C in water. This method was applied to analyze some products which contain pyrethrum as an active ingredient, such as insect spray, shampoo against lice, and dried chrysanthemum flowers. The results are comparable to SFC-FID data and correspond to the values given by the manufacturer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051398
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  • 12
    Digitale Medien
    Digitale Medien
    Analysis of volatile varnishes of coated wires by SPME (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 641-642 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Metal wires coated with varnishes emit organic compounds with increasing of temperature. The use of headspace-GC/MS in the full scan modus is required to identify these compounds. Solid phase microextraction (SPME) allows to analyze the emissions by GC/MS. The response for headspace/SPME-GC/MS is larger than for headspace-GC/FID although the FID detector is very sensitive.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051402
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  • 13
    Digitale Medien
    Digitale Medien
    Extraction of PCDD/PCDF from soil with supercritical CO2: Optimization by a three-level factorial design approach (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 378-383 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Two factors (pressure and temperature) varied over three levels were optimized for the extraction of PCDD/F from native contaminated soil with toluene-modified supercritical carbon dioxide. Temperature had a strong positive effect on the recovery. The most efficient extraction was achieved at 120 °C. This is in contrast to the influence of the temperature on the extraction of HCH, where a higher recovery is obtained at 60 °C than at 150 °C. The optimized conditions found for this soil were applied to the analysis of a BCR (European Commission) reference material prepared from contaminated industrial soil. The results are in good agreement with those of an interlaboratory study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160000446
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  • 14
    Digitale Medien
    Digitale Medien
    Supercritical fluid extraction of polycyclic aromatic hydrocarbons (PAH) from native soil and fly ash with pure and modified carbon dioxide and dimethylether (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 1128-1132 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polycyclic aromatic hydrocarbons (PAH) and alkyl-PAH in the lower mg/kg range were extracted from soil and fly ash. Extraction yields were measured for toluene Soxhlet, supercritical carbon dioxide, toluene modified carbon dioxide, and toluene modified dimethylether (DME) extractions. Pure DME similarly to toluene Soxhlet extraction enhances extraction yields (32 mg/kg) as compared to pure carbon dioxide (21 mg/kg). In particular, higher molecular weight PAH are extracted with pure DME. 5% Toluene modified carbon dioxide (43 mg/kg) and toluene modified DME (50 mg/kg) yield much better extraction yields than Soxhlet (32 mg/kg) or pure supercritical fluid extractions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160050318
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  • 15
    Digitale Medien
    Digitale Medien
    Rhodium and palladium β-diketonate determination with on-line supercritical fluid extraction-high performance liquid chromatography via solid phase extraction (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 471-474 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract  An on-line system of supercritical fluid extraction (SFE) and high performance liquid chromatography (HPLC) via solid phase extraction (SPE) is described for the determination of palladium and rhodium 2,2,6,6-tetramethyl-3,5-heptanedione-(thd) as well as rhodium-acetylacetonate-(acac) and benzylacetonate-(bzac) chelates. The chelates were extracted with supercritical CO2 from sand and humic acid, concentrated on SPE cartridges and analysed with HPLC. Two cartridge materials were tested and compared to off-line trapping. The percentage of the breakthrough and cartridge retained material were measured in liquid dichloromethane. The SFE conditions could be optimized to separate metal chelates during the extraction. The supercritical fluid (SF) behaviour of different ligands on rhodium were investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160050448
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  • 16
    Digitale Medien
    Digitale Medien
    Superheated water extraction, steam distillation and SFE of peppermint oil (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 650-653 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Superheated water extraction, steam distillation and supercritical fluid extraction (SFE) are compared for extraction of l-menthol, menthone, eucalyptol and other components of peppermint (mentha piperita) leaves. Different temperatures and pressures were investigated. SFE results at 25/40 °C and 6.5/8/10 MPa were comparable with those reported in the literature. Although SFE is a gentle way of extracting thermally unstable compounds, this method is too slow for commercial use in comparison with steam distillation at 100 °C. Superheated water extraction at 125/150 °C and 1–2 MPa exhibits higher extraction efficiency than the SFE method. Comparison of all experiments under the chosen conditions shows steam distillation to be the most effective extraction method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051406
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  • 17
    Digitale Medien
    Digitale Medien
    Ultrasonic/Soxhlet/supercritical fluid extraction kinetics of pyrethrins from flowers and allethrin from paper strips (1999)
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 472-474 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Three different extraction methods (ultrasonic extraction (USE), Soxhlet extraction (SOX) and supercritical fluid extraction (SFE)) were compared for the extraction of pyrethrins from chrysanthemic flowers and commercial insecticide powder. Allethrin was extracted from paper strips. All extracts and the kinetics were analyzed by supercritical fluid chromatography and flame ionization detector.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051644
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  • 18
    Digitale Medien
    Digitale Medien
    Copper-complexation index as a polarographic summation parameter for the determination of chelating agents in water (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 250-255 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Polarography of the copper(II)-complexes of chelating agents is shown to be a suitable basis for a summation parameter for the total concentration of these chemicals in water (expressed as the copper-complexation index). Using 12 chelating agents (ATMP, BAED, CDTA, DTPA, DTPMP, EDTA, EDTMP, EDTP, EGTA, HEDP, NTA, PBTC) all listed in DIN 38409-H26 and DIN 38413-P5 a satisfactory reproducibility of the method used was obtained. In addition several commercial tensides, detergents in washing and deliming products were investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160000545
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  • 19
    Digitale Medien
    Digitale Medien
    Investigation of SFE/SFC grade carbon dioxide (1999)
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 355-360 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Carbon dioxide, the most used substance for supercritical fluid extraction, was investigated for its purity. The carbon dioxide containing impurities were concentrated in a cold trapping system and analyzed by GC-FID, -ECD and -MS. It was possible to identify several of these impurities. For some SFE pumps a helium headpressure is required. The influence of different headpressures and different types of gases on impurity level was also investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051499
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  • 20
    Digitale Medien
    Digitale Medien
    Extraction of polychlorinated biphenyl with supercritical carbon dioxide, sulfur hexafluoride and subcritical water (2000)
    Springer
    Fresenius' journal of analytical chemistry 367 (2000), S. 89-90 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the extraction of spiked PCB from soil, three extracting fluids were investigated: supercritical carbon dioxide (CO2), supercritical sulfur hexafluoride (SF6) and subcritical water. Among the tested fluids SF6 appeared to be appropriate especially for the extraction of low polar PCB. CO2 and water were found to be suitable for the quantitative extraction of all PCB. Water was judged as the best because of its low price, good availability and environmental safety.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051605
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