Mass transfer bidirectional

The antisolvent mode (Table 63.5) is like the traditional recrystallization obtained with classic solvents (e.g., ethanol, acetone, toluene, or cyclohexanone, depending on the nature of applications). The solute of intaest is first dissolved in a classic solvent before the addition of the SC-CO2, which triggers the precipitation since it acts as an antisolvent. In the antisolvent process, in addition to the substances to be micronized and SC-CO2, a third compound is used. This compound is an organic solvent in which the produd of interest solvates straightforwardly and must also have a good compatibility with supercritical fluid as an antisolvent or be perfectly miscible. The principle is based on a bidirectional mass transfer of the solvent to the... 

Den, W., Sompuram, S. R., Sarantopoulos, S., and Sharon, J. (1999) A bidirectional phage display vector for the selection and mass transfer of polyclonal antibody libraries. J. Immunol. Meth. 222, 45-57. 

Dry deposition is generic and very similar process to the mass transfer by scavenging described in Chapter 4.3.7 where the transport axis is vertically downwards and the uptaking object is the fixed earth s surface. The situation, however, is complicated by the possible upward flux of the substance A due to plant and soil emission. Only the net flux is measurable (Foken et al. 1995). The case that downward and upward fluxes (so-called bidirectional trace gas exchanges) are equal Fdry = Fq) is called the compensation point. It only depends on the concentration gradient Ch — Co). Additionally, the net flux can be influenced by a fast gas phase reaction... 

Convection or mass flow of solvent across the gel can be achieved, as in the original method of Southern (1975), by placing absorbing pads or paper towels above the gel which causes the buffer to flow through the gel and transport the proteins to the membrane between the gel and the pads. This method can also be adapted for bidirectional transfer (Reinhart and Malamud, 1982) but the two replicas will not be identical. This method is, except for SDS-containing systems, more efficient, less time-consuming and yields better resolution than the diffusion method. The methods based on convection are given in Table 16.10. 

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