Solvents eluting

Styragel columns can be used in a wide range of organic solvents. Elution protocols have been worked out for all polymers that are soluble in organic... 

Extraction of sample using LSE solvent elution volume reduction... 

Consequences of the Snyder and Soczewinski model are manifold, and their praetieal importance is very signifieant. The most speetaeular conclusions of this model are (1) a possibility to quantify adsorbents ehromatographic activity and (2) a possibility to dehne and quantify chromatographic polarity of solvents (known as the solvents elution strength). These two conclusions could only be drawn on the assumption as to the displacement mechanism of solute retention. An obvious necessity was to quantify the effect of displacement, which resulted in the following relationship for the thermodynamic equilibrium constant of adsorption, K,, in the case of an active chromatographic adsorbent and of the monocomponent eluent ... 

Reverse-phase chromatography may also be used to separate proteins on the basis of differential hydrophobicity. This technique involves applying the protein sample to a highly hydrophobic column to which most proteins will bind. Elution is promoted by decreasing the polarity of the mobile phase. This is normally achieved by the introduction of an organic solvent. Elution conditions are harsh and generally result in denaturation of many proteins. 

The rise in popularity of HPLC is due in large part to its high-performance nature and the advantages offered over the older, noninstrumental open-column method described in Chapter 11. Separation and quantitation procedures that require hours and sometimes days with the open-column method can be completed in a matter of minutes, or even seconds, with HPLC. Modern column technology and gradient solvent elution systems, which will be described, have contributed significantly to this advantage in that extremely complex samples can be resolved with ease in a very short time. 

Water Sample passed though a mixed XAD-4/8 column, solvent eluted and concentrated GC-MS NG 46-70% (distilled water) 9% (tap water) Van Rossum and Webb 1978... 

The primary method of analyzing 1,2-dibromoethane in air is by adsorption on a solid phase (i.e., activated charcoal tube or Tenax adsorbent) followed by thermal or solvent elution for subsequent quantification. GC/ECD and GC/MS are the most commonly used analytical techniques for... 

Oveiiiauser Enhancement caused some downfield shift. The approach needs an assessment of the saturates content which is normally achieved by solvent elution chromatography. 

Occupational air (HDI and oligomers) Air collected/derivatized through tubes with sintered glass (or GFFs) impregnated with 1-(2-methoxyphenyl)piperazine solvent elution reaction with acetic anhydride evaporation HPLC with UV detection 0.31 g/ sample 3.4 g/m (lowest tested—GFFs) 95-107% Sesana et al. 1991 Huynh et al. 1992... 

Drug Matrix Type of SPE Washing solvent Eluting solvent Ref. 

Studies on solid supports have shown that tlie pore size of the silica-based sorbents is of little importance in MSPD, but it should be considered as could vary with the sample. Particle size is of greater importance since particles as small as 3-20 m can lead to extended solvent elution times and plugged MSPD columns. However, 40 m particles with 60 Angstrom pores have been used extensively and successfully. Sorbents that have a blended range of particle size such as 40-100 m work equally well and can be used in most applications (101, 103). These materials also tend to be less expensive. Depending on the application, analysts can also use non-end-capped materials and materials with a range of carbon loading. Different applications may benefit, suffer, or be unaffected by these parameters, but workers should consider them to obtain the best extraction efficiency and the cleanest sample. 

A very efficient thin layer form of circular paper chromatography makes use of a circular glass disc coated with an adsorbent (silica, alumina or cellulose). The apparatus is called a Chromatotron (available from Harrison Research, USA). The disc is rotated by a motor, and the sample followed by the eluting solvent are allowed to drip onto a central position on the plate. As the plate rotates the solvent elutes the mixture, centrifugally, while separating the components in the form of circles radiating from the central point. When elution is complete the revolving circular plate is stopped and the circular bands are scraped off and extracted with a suitable solvent. 

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