Organic solvents desorption

When the adsorption isotherm in liquid phase can be modified by changing pH or by introducing an organic solvent, desorption can be expected to occur in a manner similar to thermal desorption in the case of gas phase adsorption operation. Desorption behavior is determined by the change of adsorption isotherm and intraparticle diffusion in the desorbent phase... 

Anasorb activated charcoal Solvent desorption. Polar organic compounds... 

Porous polymer Various types usually for solvent desorption suitable for a range of organic compounds including highly polar substances... 

Organic isocyanates in air Lab method with sampling either onto coated glass-fibre filters followed by solvent desorption, or into impingers and analysis using high performance liquid chromatography 25/3... 

BS ISO 16200 Volatile organic compounds Solvent desorption and gas chromatography... 

Desorption of analyte using organic solvent Thermal desorption... 

The carbinolamine metabolite 64 was unstable in organic solvents and on routine chromatography. It was impossible to obtain molecular ions in the mass spectra by electron impact, chemical ionization, Held desorption, or fast-atom bombardment techniques. The apparent molecular ion occurred at m/e 456, consistent with a carbinolamine such as 64, which eliminates water to form an [M — 18] peak. The H-NMR spectrum of this metabolite was similar to that of... 

Fabbri A, Crescentini G, Mangani F, et al. 1987. Advances in the determination of volatile organic solvents and other organic pollutants by gas chromatography with thermal desorption sampling and injection. Chromatographia 23 856-860. 

If n solvated nonpolar ligands simultaneously interact with the solvated peptide, then the binary complex that forms can be represented by the equilibrium shown in eq 6. When the concentration and thus the surface tension of the organic solvent reaches a critical value, then the partially solvated peptide P(+cDo)is bound to the RPC stationary phase will desorb and become re-solvated to generate the species P(+ DO)i,m- Thus, overall desorption can be represented as ... 

Two-Phase Desorption System. The mixed solvent technique has limited use for complex mixtures since it is more difficult to chromatograph, precludes determination of the polar solvent added, and may cause additional interference to other compounds present. A two-phase system has been developed which is capable of measuring both polar and non-polar organic solvents present simultaneously in work environments (19). 

Many of the charcoal tube methods are based on NIOSH Method P CAM 127 (4) for organic solvents. In this method, a known volume of air is drawn through a charcoal tube to trap organic vapors, the charcoal is transferred to a vial, and the sample is desorbed with carbon disulfide. The sample is analyzed by gas chromatography (GC) with flame ionization detection (FID). Most methods use CS2 as the desorption solvent because it yields good recoveries from charcoal and produces a very low flame response. 

In mixed organic solvents or in an emulsion electrolysis benzylic type alcohols can be converted to aldehydes as main product (Table 6). In emulsion electrolysis it seems reasonable that the intermediate aldehyde is extracted into the organic layer and thus prevented from further oxidation. In mixed organic solvents the desorption of species with intermediate degree of oxidation is assumed. A more neutral electrolyte improves the aldehyde yield too... 

Note that such a conceptualization still requires a corresponding desorption of some number, n, of water molecules from the vicinal region to make a cavity near the solid surface in which i must fit. This solvent desorption process contributes an additional free energy term to the overall organic compound sorption process due to breaking of watenwater interactions in this layer. 

PCB DESORPTION. PCBs are very soluble in a number of organic solvents. Because acetone is very effective in displacing the water from the pores of the polymer, it will be used in this example of desorption. A fairly strong interaction of acetone with the styrene-divinylbenzene surface can be predicted because acetone and benzene are miscible solvents. Consequently, a small amount of acetone will desorb the PCBs because strong solvent-solute and solvent-polymer interactions override the strong solute-polymer interaction. This desorption, commonly called elution, does not occur during the adsorption process because the matrix water is a poor eluent dictated by its weak interaction with hydrophobic polymers. 

Desorption of the model compounds isolated on the quaternary XAD-4 (QXAD-4) resin column was accomplished by sequential elution with ethyl ether, methanol, ethyl ether, 0.1 N HCl/ether, 0.1 N HCl/methanol, and saturated HCl/methanol. The acidified organic solvents were used for acidic solute removal. 

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