PubMed · 4736421
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N Sakauchi. 1973. [Gas chromatography].. https://pubmed.ncbi.nlm.nih.gov/4736421/
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The swing system is designed for introducing large volumes of water-containing samples into a gas chromatograph. Sample evaporation and solvent-solute separation are performed in separate compartments. This widens the application range to compounds of higher volatility. Sample evaporation takes place in a hot chamber packed with Carbofrit. Solvent-solute separation is performed in a cascade of increasing powers of retention. While high boiling solutes are retained in an oven-thermostatted retaining precolumn, the more volatile components are retained by a packed bed of sorbents of increasing powers of retention situated in a programmed temperature vaporiser. For elution, the gas flow is reversed and the solutes are discharged from the heated packed bed through the retaining precolumn into the separation column.
Accelerated solvent extraction was studied as a method for the extraction of hydrocarbon contamination from wet and dry soils. Temperatures from 125 to 200 degrees C and six different solvents were investigated. Nonpolar solvents could not achieve complete recovery from wet soils at the temperatures studied. Optimum conditions were found to be 175 degrees C with dichloromethane-acetone (1:1, v/v) with 8 min heat-up time and 5 min static time. Quantitative recoveries for diesel range organics (DROs) and waste oil organics (WOOs) were obtained using the optimized conditions. The recovery of DROs and WOOs from three matrices at two concentrations (5 and 2000 mg/kg) averaged 115%. These results show that accelerated solvent extraction can generate results comparable to those obtained using Soxhlet or sonication.
Migration and dispersion in chromatography are modeled by analogy to an effective eddy diffusion process. On the basis of this model, the spatial rates of temporal statistical moment change are derived for general chromatography in linear media. In most practical cases, these equations can be simplified so that temporal statistical moments can be calculated by solving a system of ordinary differential equations that depend only on the local HETP, solute velocity, and initial values of the temporal statistical moments. The calculations of temporal centroid, temporal variance, temporal skew, and temporal excess are demonstrated for the case of linear solvent strength gradients. It is shown for the case of temporally invariant separation environments, such as isocratic liquid chromatographic systems and isothermal gas chromatographic systems, that temporal variance contributions are spatially additive and that the temporal third normalized central moment is unaffected by spatial variations in the medium. A refined explanation is given for how peak symmetry is improved in gradient forms of chromatography.