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  • 1
    Electronic Resource
    Electronic Resource
    Nile Red as a solvatochromic dye for measuring solvent strength in normal liquids and mixtures of normal liquids with supercritical and near critical fluids [Erratum to document cited in CA112(18):171383n] (1990)
    s.l. : American Chemical Society
    Analytical chemistry 62 (1990), S. 1552-1552 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00213a042
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  • 2
    Electronic Resource
    Electronic Resource
    Nile Red as a solvatochromic dye for measuring solvent strength in normal liquids and mixtures of normal liquids with supercritical and near critical fluids (1990)
    s.l. : American Chemical Society
    Analytical chemistry 62 (1990), S. 615-622 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00205a015
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  • 3
    Electronic Resource
    Electronic Resource
    Feasibility of screening large aqueous samples for thermally unstable pesticides using high efficiency packed column supercritical fluid chromatography with multiple detectors (1995)
    Springer
    Chromatographia 41 (1995), S. 471-484 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Packed columns ; Aqueous samples ; On-line extraction ; Pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Nearly 100 pesticides were eluted with good peak shapes from silica columns using methanol/carbon dioxide mobile phases. The pesticides included organophosphorus, organochlorine, phenylurea, sulfonylurea, triazine, carbamate and phenoxyacid pesticides, demonstrating the wide applicability of SFC to pesticide analysis. A subset of 31 pesticides were on-line extracted from large water samples, typically 10 to 20 ml, but up to 100 ml. The extracts were separated on a 1.6 meter long column packed with 5 μm particles, then detected simultaneously with a photodiode array UV detector plus an electron capture (ECD) and a nitrogen-phosphorus (NPD) detector. Recovery, reproducibility, linearity, response factors and detection limits were determined. Detection limits from a 5 ml water sample were in the range of 100 to 500 parts per trillion (1/1012). Larger samples appear capable of lowering these limits to below 10 ppt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02318624
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  • 4
    Electronic Resource
    Electronic Resource
    Separation of a gasoline on an open tubular column with 1.3 million effective plates (1996)
    Springer
    Chromatographia 42 (1996), S. 63-71 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; High efficiency open tubular columns ; Columns connected in series ; Gasoline analysis ; Detailed hydrocarbon analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary More than 1.3 million effective plates were produced by a column 450 meters long, 200 μm inner diameter. The column was built up by connecting nine 50 meter columns in series. The sum of the efficiencies of the individual pieces equalled the efficiency of the combined column. Up to 970 components were differentiated in a gasoline standard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02271057
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  • 5
    Electronic Resource
    Electronic Resource
    Development and Evaluation of Consensus-Based Sediment Quality Guidelines for Freshwater Ecosystems (2000)
    Springer
    Archives of environmental contamination and toxicology 39 (2000), S. 20-31 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Numerical sediment quality guidelines (SQGs) for freshwater ecosystems have previously been developed using a variety of approaches. Each approach has certain advantages and limitations which influence their application in the sediment quality assessment process. In an effort to focus on the agreement among these various published SQGs, consensus-based SQGs were developed for 28 chemicals of concern in freshwater sediments (i.e., metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and pesticides). For each contaminant of concern, two SQGs were developed from the published SQGs, including a threshold effect concentration (TEC) and a probable effect concentration (PEC). The resultant SQGs for each chemical were evaluated for reliability using matching sediment chemistry and toxicity data from field studies conducted throughout the United States. The results of this evaluation indicated that most of the TECs (i.e., 21 of 28) provide an accurate basis for predicting the absence of sediment toxicity. Similarly, most of the PECs (i.e., 16 of 28) provide an accurate basis for predicting sediment toxicity. Mean PEC quotients were calculated to evaluate the combined effects of multiple contaminants in sediment. Results of the evaluation indicate that the incidence of toxicity is highly correlated to the mean PEC quotient (R2= 0.98 for 347 samples). It was concluded that the consensus-based SQGs provide a reliable basis for assessing sediment quality conditions in freshwater ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002440010075
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of mobile phase density gradients on efficiency in packed column supercritical fluid chromatography (1990)
    Springer
    Chromatographia 30 (1990), S. 57-60 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography, (SFC) ; Packed columns ; Density gradients ; Effect on efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of packed columns was measured as a function of flow rate, temperature, outlet density, and the density differential across the column, unsing pure carbon dioxide as the mobile phase. Although density differentials are often blamed for a serious loss in efficiency in packed column supercritical fluid chromatography, the results show that efficiency was not a function of the density differential. Peak shapes suggest that apparent loss in efficiency is actually due to inadequate solubility of the solute in carbon dioxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02270449
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  • 7
    Electronic Resource
    Electronic Resource
    High efficiency packed column supercritical fluid chromatography of sulfonylurea herbicides and metabolites from large water samples (1995)
    Springer
    Chromatographia 41 (1995), S. 133-140 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography, SFC ; Packed columns ; Sulfonylurea ; Pesticide metabolites ; Selective detectors ; Water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Five sulfonylurea herbicides were separated by SFC on both a 25 cm and a 1.6 meter packed column. The former produced rapid analysis, the latter allowed high resolution of a complex mixture containing the solutes of interest. The solutes were simultaneously detected with UV, nitrogen-phosphorus (NPD), and electron capture (ECD) detectors. Peaks of breakdown products of sulfonylureas were characterized by their UV spectra and the presence or absence of nitrogen and chlorine from their NPD and ECD response. Both parent and breakdown products of sulfonylureas were on-line extracted from large water samples with detection limits as low as 50 parts per trillion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267944
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  • 8
    Electronic Resource
    Electronic Resource
    Efficiency in packed column supercritical fluid chromatography using a modified mobile phase (1991)
    Springer
    Chromatographia 31 (1991), S. 529-534 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Density gradients ; Modified mobile phase ; Vapor-liquid equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Large density differentials across small particle packed columns failed to produce losses in chromatographic efficiency. The mobile phase consisted of carbon dioxide modified with methanol. The largest density differential across the column involved an outlet density below 0.2 g/ cm3 while the density at the inlet was simultaneously above 0.9 g/cm3. Absolute efficiencies were similar to those found using the same particle size in reversed-phase liquid chromatography and were very near theoretically predicted values. In related experiments, two cases were found where low outlet pressures or densities caused degraded peak shapes. Experimental conditions were compared to vapor-liquid equilibria data. Poor peak shapes were likely caused by the mobile phase separating into two phases and/or solubility problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279470
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of adsorbed mobile phase components on the retention mechanism, efficiency, and peak distortion in supercritical fluid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 645-652 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Adsorption of mobile phases ; Efficiency ; Peak distortion ; Partition ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This report attempts to link several previously unassociated phenomena to the formation of a thick film of adsorbed mobile phase acting as part of the effective stationary phase in SFC. Plots of log k′ vs density were found to have a different shape than is generally accepted. The plots of highly retained solutes appear linear at both low and high densities with a change in slope at intermediate densities where adsorption is know to be most extensive. Efficiency degrades under identical conditions that produce significant adsorption of the mobile phase. Van Deemter curves change shape consistent with an additional “C” term, suggesting the formation of a thick stationary phase under the same conditions known to result in multi-layer adsorption of carbon dioxide onto stationary phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274117
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  • 10
    Electronic Resource
    Electronic Resource
    Efficiency losses caused by gradients in solute velocity in packed column supercritical fluid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 5-11 
    Details
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Solute velocity gradients ; Retention gradients ; Efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Under a few sets of extreme conditions, retention gradients caused losses in apparent efficiency in packed column SFC. Under most practical chromatographic conditions no such losses occurred. The efficiency of five columns were measured both individually and connected in series. Under most conditions, no loss occurred. Under a few sets of conditions, the apparent efficiency of the five columns connected in series was as much as 66 % lower than the sum of the efficiencies of the individual columns measured under the same conditions. To observe a loss, the local retention near the column outlet must be unrealistically high and a steep non-linear change in retention is required. Under some sets of conditions, an approximate form of a recently proposed theory predicted losses similar to those observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275719
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