Evaluation of supercritical fluid extraction for isotope dilution gas chromatography-mass spectrometric quantification of polychlorinated biphenyls in sediment.
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Supercritical fluid extraction (SFE) has been evaluated as an extraction technique for the isotope-dilution quantification of polychlorinated biphenyls (PCBs) in a sediment sample. A high-resolution mass-spectrometric system equipped with a gas chromatograph was employed for the determination of seven target PCB congeners. The effect of the operation parameters on the SFE efficiency was investigated, in which the analytical values of five target PCB congeners significantly increased with increases in the extraction temperature and pressure, and that of 4,4'-dichlorobiphenyl further increased by applying static extraction. The following conditions were found to be optimal: extraction temperature, 140 degrees C; pressure, 30 MPa; time and mode, static for 15 min then dynamic for 30 min. Under these conditions, the addition of modifiers influenced the extraction of polar compounds, but did not affect the analytical values of the PCB congeners. The optimized method was suitable for high-throughput analysis as well as for providing accurate analytical results, which were comparable to or better than the analytical results obtained by Soxhlet extraction. (+info)
Supercritical carbon dioxide: putting the fizz into biomaterials.
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This paper describes recent progress made in the use of high pressure or supercritical fluids to process polymers into three-dimensional tissue engineering scaffolds. Three current examples are highlighted: foaming of acrylates for use in cartilage tissue engineering; plasticization and encapsulation of bioactive species into biodegradable polyesters for bone tissue engineering; and a novel laser sintering process used to fabricate three-dimensional biodegradable polyester structures from particles prepared via a supercritical route. (+info)
Antidepressant-like effect of Cordyceps sinensis in the mouse tail suspension test.
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Cordyceps sinensis (CS) has been known as a component of traditional medicines that elicit various biological effects such as anti-fatigue, immunomodulatory, and hypoglycemic actions. Since it has been well-established that fatigue is closely related to depression, we used the tail suspension test (TST) in mice to examine the antidepressant-like effects of hot water extract (HWCS) and supercritical fluid extract (SCCS) of CS. Immobility time in the TST was reduced by administration of SCCS (2.5-10 ml/kg, p.o.) dose-dependently though it was not reduced by treatment with HWCS (500-2000 mg/kg, p.o.). Neither HWCS nor SCCS altered locomotor activity in the open field test, excluding the possibility that the effect of SCCS is due to activation of locomotion. Pretreatment with prazosin (an adrenoreceptor antagonist) or sulpiride (a dopamine D2 receptor antagonist) reduced the effect of SCCS on the immobility time. In contrast, pretreatment with p-chlorophenylalanine (p-CPA, a serotonin synthesis inhibitor) did not alter the anti-immobility effect of SCCS. The last finding is consistent with an additional observation that SCCS had no effect on head twitch response induced by 5-hydroxy-L-tryptophan in mice. Taken altogether, these results suggest that SCCS may elicit an antidepressant-like effect by affecting the adrenergic and dopaminergic systems, but not by affecting the serotonergic system. (+info)
Determination of total biodiesel fatty acid methyl, ethyl esters, and hydrocarbon types in diesel fuels by supercritical fluid chromatography-flame ionization detection.
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A method for determining total biodiesel methyl and ethyl ester content in diesel fuels by supercritical fluid chromatography-flame ionization detection (SFC-FID) is developed. A silica column typically used for determining aromatics in conventional diesel fuels by ASTM D5186 is back-flushed after separation of the hydrocarbons to allow elution of the various esters as a single "total biodiesel" distinct peak. The modification concurrently allows the determination of total aromatic hydrocarbons and their distribution as mono- and polynuclear compounds, as described in the current version of D5186. The instrument response is linear from 1.0% to 50% biodiesel esters with a signal-to-noise ratio of 25 at the 0.1% level. The short-term relative standard is 0.8%. Normalized percent quantitation using a hydrocarbon response factor of 1.00 and an ester response factor of 1.19 provide an average percentage error of 1.8% when measuring actual biodiesel/hydrocarbon fuel blends. The ester response factor is the average of the response factors of 10 pure ester compounds. These responses are calculated from respective solutions of each ester and the four compounds, hexadecane, toluene, tetralin, and naphthalene, as used for the D5186 response factor mixture. (+info)
Production of cromolyn sodium microparticles for aerosol delivery by supercritical assisted atomization.
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