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Steven B Hawthorne - One of the best experts on this subject based on the ideXlab platform.
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simple method for estimating polychlorinated biphenyl concentrations on soils and sediments using subcritical water Extraction coupled with solid phase microExtraction
Journal of Chromatography A, 1998Co-Authors: Steven B Hawthorne, Kimberly J Hageman, Carol B Grabanski, David J. MillerAbstract:Abstract A rapid method for estimating polychlorinated biphenyl (PCB) concentrations in contaminated soils and sediments has been developed by coupling static subcritical water Extraction with solid-phase microExtraction (SPME). Soil, water, and internal standards are placed in a sealed Extraction Cell, heated at 250°C for 15 to 60 min, cooled, and the PCB concentrations in the extractant water determined by SPME and GC–electron-capture detection. When PCB 103 and 169 (not found in contaminated samples) are used as internal standards to calibrate for the soil/water and water/SPME equilibria, quantitative results for individual PCB congeners typically agree within 80 to 130% of the concentrations based on Soxhlet Extraction and conventional GC analysis. The reproducibility of replicate subcritical water Extraction/SPME determinations is typically 10 to 15% relative standard deviation. Analysis of water extracts stored for 24 h agrees with fresh extracts, demonstrating that extracts can be stored for later SPME analysis without significant loss of the PCBs from the extractant water. The method is simple to perform, uses field-rugged and inexpensive apparatus, and generates no organic solvent waste.
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Coupled Subcritical Water Extraction with Solid-Phase MicroExtraction for Determining Semivolatile Organics in Environmental Solids
Analytical Chemistry, 1996Co-Authors: Kimberly J Hageman, Carol B Grabanski, Laurent Mazeas, And David J. Miller, Steven B HawthorneAbstract:Efficient Extractions of semivolatile organic pollutants from solid samples can be obtained using subcritical (hot/liquid) water by simply placing the sample in an Extraction Cell, filling the Cell with water, and heating the system in an oven. After a 15−60-min Extraction, the Cell is cooled, the water is removed from the Extraction Cell, and the solubilized organics are analyzed using solid-phase microExtraction (SPME). Quantitative determinations (recoveries typically ranging from ∼60 to 140% compared to conventional solvent Extraction) of polycyclic aromatic hydrocarbons (PAHs) from soil and air particulate matter were achieved using a 250 °C Extraction step and isotopically labeled PAHs as internal standards. Quantitative determinations of more volatile (e.g., alkylbenzenes) and more polar compounds (e.g., aromatic amines) from contaminated soil using external standards of pure target analytes also showed good general agreement with conventional solvent Extraction. Relative standard deviations (RSDs)...
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Method for determining the density of pure and modified supercritical fluids
Analytical Chemistry, 1992Co-Authors: John J. Langenfeld, David J. Miller, Steven B Hawthorne, Joseph. TehraniAbstract:Densities of three pure supercritical fluids (Co 2 , N 2 O, and CHCIF 2 ) and one modified fluid (Co 2 modified with 5 volume % methanol) were determined over a wide range of pressures (60-600 atm) and temperatures (40-150 o C) using a simple device constructed from a conventional supercritical fluid Extraction Cell
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Effects of collection solvent parameters and Extraction Cell geometry on supercritical fluid Extraction efficiencies
Journal of Chromatography A, 1992Co-Authors: John J. Langenfeld, Steven B Hawthorne, Mark D. Burford, David J. MillerAbstract:Abstract Supercritical fluid Extraction (SFE) collection efficiences of 66 compounds with a wide range of volatility and polarity were examined. Good collection efficiencies required efficient partitioning of the analyte into the collection solvent after depressurization, and factors including collection solvent polarity and temperature were found to be more important than collection solvent volume and height. Heating the collection solvent with a heat gun to avoid plugging of the outlet restrictor resulted in 20−50% losses of the more volatile analytes, while > 90% trapping of all test analytes could be attained by controlling the solvent temperature at 5°C. Extraction Cell geometry (“long, narrow” versus “short, broad” vessel) at constant internal volume and the orientation of the Extraction Cell were found to have negligible effects on the Extraction rates of polycyclic aromatic hydrocarbons (PAHs) from railroad bed soil and flavor and fragrance compounds from lemon peels. The supercritical fluid flow-rate also had little effect on the Extraction rate of native PAHs provided that it was sufficient to sweep the Cell dead volume every ca. 3 min.
Vlastimil Kubáň - One of the best experts on this subject based on the ideXlab platform.
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A two-step supercritical fluid Extraction of polycyclic aromatic hydrocarbons from roadside soil samples.
Journal of separation science, 2005Co-Authors: Lea Lojková, Jitka Sedláková, Vlastimil KubáňAbstract:A two-step procedure for the supercritical fluid Extraction (SFE) of polycyclic aromatic hydrocarbons from soil samples was developed. The procedure consists of a static supercritical fluid treatment in a closed Extraction Cell at a high temperature (T=250 or 340degreesC for 20 min) and an SFE with a solvent trapping. During the static phase, the sample is exposed to a supercritical organic solvent (methanol, toluene, dichloromethane, ACN, acetone, and hexane). The solvent penetrates particles of the matrix to substitute strongly bonded molecules and dissolves the analytes in the supercritical phase. At ambient temperature, supercritical fluids became liquid and lost their solvation abilities. Most of the analytes condense on the surface of the particles or on the Extraction Cell walls without forming strong bonds or penetrating deep into the matrix. Thus, the pretreatment liberates the analytes and they behave similar to those in freshly spiked samples. The common SFE with toluene-modified CO2 as an Extraction fluid follows the static phase. With the use of the most suitable Extraction phases (toluene, ACN), the Extraction efficiency of the combined procedure is much higher (approximately100%). The results of the combined procedure are compared to the SFE procedure of the same untreated sample (difference less than 5%) and to the Soxhlet Extraction. The extracts were analyzed using a GC with the flame ionization detection.
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liquid chromatographic mass spectrometric determination of genistin and daidzin in soybean food samples after accelerated solvent Extraction with modified content of Extraction Cell
Analytica Chimica Acta, 2004Co-Authors: Bořivoj Klejdus, Radka Mikelova, Vojtěch Adam, Josef Zehnalek, Jan Vacek, Rene Kizek, Vlastimil KubáňAbstract:Abstract A newly elaborated accelerated solvent Extraction (ASE) procedure allowed more accurate (
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Liquid chromatographic–mass spectrometric determination of genistin and daidzin in soybean food samples after accelerated solvent Extraction with modified content of Extraction Cell
Analytica Chimica Acta, 2004Co-Authors: Bořivoj Klejdus, Radka Mikelova, Vojtěch Adam, Josef Zehnalek, Jan Vacek, Rene Kizek, Vlastimil KubáňAbstract:Abstract A newly elaborated accelerated solvent Extraction (ASE) procedure allowed more accurate (
David J. Miller - One of the best experts on this subject based on the ideXlab platform.
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simple method for estimating polychlorinated biphenyl concentrations on soils and sediments using subcritical water Extraction coupled with solid phase microExtraction
Journal of Chromatography A, 1998Co-Authors: Steven B Hawthorne, Kimberly J Hageman, Carol B Grabanski, David J. MillerAbstract:Abstract A rapid method for estimating polychlorinated biphenyl (PCB) concentrations in contaminated soils and sediments has been developed by coupling static subcritical water Extraction with solid-phase microExtraction (SPME). Soil, water, and internal standards are placed in a sealed Extraction Cell, heated at 250°C for 15 to 60 min, cooled, and the PCB concentrations in the extractant water determined by SPME and GC–electron-capture detection. When PCB 103 and 169 (not found in contaminated samples) are used as internal standards to calibrate for the soil/water and water/SPME equilibria, quantitative results for individual PCB congeners typically agree within 80 to 130% of the concentrations based on Soxhlet Extraction and conventional GC analysis. The reproducibility of replicate subcritical water Extraction/SPME determinations is typically 10 to 15% relative standard deviation. Analysis of water extracts stored for 24 h agrees with fresh extracts, demonstrating that extracts can be stored for later SPME analysis without significant loss of the PCBs from the extractant water. The method is simple to perform, uses field-rugged and inexpensive apparatus, and generates no organic solvent waste.
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Method for determining the density of pure and modified supercritical fluids
Analytical Chemistry, 1992Co-Authors: John J. Langenfeld, David J. Miller, Steven B Hawthorne, Joseph. TehraniAbstract:Densities of three pure supercritical fluids (Co 2 , N 2 O, and CHCIF 2 ) and one modified fluid (Co 2 modified with 5 volume % methanol) were determined over a wide range of pressures (60-600 atm) and temperatures (40-150 o C) using a simple device constructed from a conventional supercritical fluid Extraction Cell
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Effects of collection solvent parameters and Extraction Cell geometry on supercritical fluid Extraction efficiencies
Journal of Chromatography A, 1992Co-Authors: John J. Langenfeld, Steven B Hawthorne, Mark D. Burford, David J. MillerAbstract:Abstract Supercritical fluid Extraction (SFE) collection efficiences of 66 compounds with a wide range of volatility and polarity were examined. Good collection efficiencies required efficient partitioning of the analyte into the collection solvent after depressurization, and factors including collection solvent polarity and temperature were found to be more important than collection solvent volume and height. Heating the collection solvent with a heat gun to avoid plugging of the outlet restrictor resulted in 20−50% losses of the more volatile analytes, while > 90% trapping of all test analytes could be attained by controlling the solvent temperature at 5°C. Extraction Cell geometry (“long, narrow” versus “short, broad” vessel) at constant internal volume and the orientation of the Extraction Cell were found to have negligible effects on the Extraction rates of polycyclic aromatic hydrocarbons (PAHs) from railroad bed soil and flavor and fragrance compounds from lemon peels. The supercritical fluid flow-rate also had little effect on the Extraction rate of native PAHs provided that it was sufficient to sweep the Cell dead volume every ca. 3 min.
J. R. Dean - One of the best experts on this subject based on the ideXlab platform.
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Extraction of pharmaceuticals using pressurised carbon dioxide
Journal of pharmaceutical and biomedical analysis, 1997Co-Authors: J. R. Dean, Sharmin KhundkerAbstract:This paper reviews the applications of super- and sub-critical carbon dioxide for the Extraction of pharmaceuticals from various matrices. The matrices covered are divided into the following types: animal feed, formulations, biological and misCellaneous, with various sub-divisions as appropriate. The polar nature of most pharmaceuticals often precludes the use of carbon dioxide only, so it is common to find the addition of a more polar solvent, as modifier. As the majority of sample types covered are solid, little if any pre-treatment is required, with the exception of grinding, prior to insertion in the sample Extraction Cell. For liquid-type matrices, sample pre-treatment is the normal. Often this may involve adsorption on an inert support e.g. Celite or diatomaceous earth, or immobilisation on a functionalised silica surface, e.g. C18. The later may take the form of a solid phase Extraction cartridge or disk. An attempt has also been made to sample from liquid matrices directly using a modified Extraction Cell. The variety of sample types, matrices and analyte polarity places stringent requirements on the use of pressurised carbon dioxide. Its potential for effective recovery is examined in this review.
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Extraction of surfactants from aqueous media by supercritical fluid Extraction
The Analyst, 1995Co-Authors: M. O`kane, J. R. Dean, Chris J Dowle, Steven Hitchen, R.l. TranterAbstract:Two methods for the supercritical fluid Extraction (SFE) of analytes from aqueous media were evaluated: direct Extraction and solid-phase Extraction (SPE) discs. SPE discs were used to isolate an alcohol phenol ethoxylate (APE) non-ionic surfactant from an aqueous matrix prior to Extraction using supercritical CO2. This method was compared with the direct SFE of surfactant from the aqueous matrix. The second method allowed the continuous Extraction of analyte from water using a modified Extraction Cell. The Extraction Cell was designed to maximize the exposure of the analyte to supercritical CO2 interactions and thereby allow the continuous Extraction of the analyte from an aqueous sample. The results suggest that there is a difference in the effects of diffusion and equilibrium on the Extraction process for the two methods of Extraction studied.
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Supercritical fluid Extraction of organochlorine pesticides from an aqueous matrix
Journal of Chromatography A, 1994Co-Authors: Ian J. Barnabas, J. R. Dean, Steven Hitchen, Susan P. OwenAbstract:Abstract Supercritical fluid Extraction (SFE) conditions were optimised for the removal of organochlorine pesticides (OCPs) from water. OCPs were collected and extracted from sofid-phase Extraction disks (Empore) and also directly from a water sample using a modified Extraction Cell. High recoveries (>90%) were obtained for two of the three OCPs with Empore disks. Despite the good solubility of OCPs in pure CO2, the analyte recoveries decreased when they were extracted directly from water. Three different flow-rates were used in the direct SFE with no apparent change in recovery, indicating that Extraction was diffusion-controlled. The effect of increasing the ionic strength of the aqueous sample on analyte recovery was investigated.
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Experimental design approach for supercritical fluid Extraction
Analytrca Chotuca Acta Elsevler Science Pubhshers B V, 1993Co-Authors: M. O`kane, S M Hltchen, Chris J Dowle, J. R. Dean, R.l. TranterAbstract:Expenmental design with multlhnear regression has been used to examme the relative contriiutlon of the main experimental vanables durmg supercntlcal fluid Extraction SLX steroidal compounds of vanous solubditles m supercntlcal CO, were considered The results indicate that the density of the supercntlcal flurd has the greatest effect on the solubdlsation and transfer of steroid from Extraction Cell to collectlon device The nununum number of Cell volumes of supercntlcal CO, requued for effective Extraction was expenmentally determmed
R Cela - One of the best experts on this subject based on the ideXlab platform.
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pressurized liquid Extraction with in Cell clean up followed by gas chromatography tandem mass spectrometry for the selective determination of parabens and triclosan in indoor dust
Journal of Chromatography A, 2007Co-Authors: P Canosa, D Perezpalacios, Alvaro Garridolopez, Maria Teresa Tena, I Rodriguez, E Rubi, R CelaAbstract:Abstract A sample preparation method based on the use of pressurized liquid Extraction is proposed for the determination of four alkyl parabens and triclosan in indoor dust. Extraction of analytes and removal of interfering species were achieved in the same step, by placing an appropriate sorbent in the Extraction Cell and by choosing a right combination of washing and elution solvents. Compounds, as silylated derivatives, were determined by gas chromatography in combination with tandem mass spectrometry (GC–MS/MS). Factors affecting the yield and selectivity of the sample preparation procedure were carefully evaluated. Under final conditions, dried samples (0.5 g of dust and 1 g of sodium sulphate) were dispersed with 3 g of Florisil and loaded into an 11 mL stainless-steel Extraction Cell containing 1 g of the same material as clean-up sorbent. Non-polar species were removed with n -hexane under mild conditions (40 °C, 3.4 MPa) and then analytes were extracted with ethyl acetate. The best compromise Extraction conditions were 103 °C, 13.8 MPa and 3 static Extraction cycles of 1 min. The proposed method provided recoveries from 76 to 98%, relative standard deviations under 11% (operating under reproducibility conditions) and quantification limits from 1 to 4 ng/g. The analysis of dust samples from private houses and office buildings confirmed the ubiquitous presence of target bactericides in these environments.
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Pressurized liquid Extraction with in-Cell clean-up followed by gas chromatography-tandem mass spectrometry for the selective determination of parabens and triclosan in indoor dust.
Journal of chromatography. A, 2007Co-Authors: P Canosa, Maria Teresa Tena, I Rodriguez, E Rubi, D Pérez-palacios, A Garrido-lópez, R CelaAbstract:A sample preparation method based on the use of pressurized liquid Extraction is proposed for the determination of four alkyl parabens and triclosan in indoor dust. Extraction of analytes and removal of interfering species were achieved in the same step, by placing an appropriate sorbent in the Extraction Cell and by choosing a right combination of washing and elution solvents. Compounds, as silylated derivatives, were determined by gas chromatography in combination with tandem mass spectrometry (GC-MS/MS). Factors affecting the yield and selectivity of the sample preparation procedure were carefully evaluated. Under final conditions, dried samples (0.5 g of dust and 1g of sodium sulphate) were dispersed with 3g of Florisil and loaded into an 11 mL stainless-steel Extraction Cell containing 1g of the same material as clean-up sorbent. Non-polar species were removed with n-hexane under mild conditions (40 degrees C, 3.4 MPa) and then analytes were extracted with ethyl acetate. The best compromise Extraction conditions were 103 degrees C, 13.8 MPa and 3 static Extraction cycles of 1 min. The proposed method provided recoveries from 76 to 98%, relative standard deviations under 11% (operating under reproducibility conditions) and quantification limits from 1 to 4 ng/g. The analysis of dust samples from private houses and office buildings confirmed the ubiquitous presence of target bacteriocides in these environments.
