Separation chamber device membranes

Zahoransky et al. described an improved Fl-FFF channel which assures a uniform cross-flow in the whole channel [476]. This is achieved by a division of the hollow compartment under the membrane supporting frit into three separate chambers with an independent pressure control. By means of special spring-loaded clamping devices, the spacer and membrane change is reported to be simple, thus making the whole experimental handling with this new channel convenient. 

At present, experimental studies on the dissolved/solid interactions in such complex systems seem to be more promising. One approach is with a a six-chamber device, where the individual components are separated by membranes, which still permit phase interactions via solute transport of the elements (Calmano et al., 1988) in this way, exchange reactions and biological uptake can be studied for individual phases under the influence of pH, redox, ionic strength, solid and solute concentration, and other parameters ... 

The laboratory system used in these studies was developed from the experience on sediment/algae interactions with a modified two-chambered device (Ahlf et al., 1986). The system is made of a central chamber connected with 6 external chambers and separated by membranes of 0.45 pm pore diameter (Figure 5-4). The volume of the central chamber is litres and each of the external chambers contains 250 ml. Either solution or suspension can be inserted into the central chamber in each... 

As a new option, for the bioconversion of poorly soluble substrates the classical EMR-concept can be extended to an Emulsion Membrane Reactor , comprising a separate chamber for emulsification (with a hydrophilic ultrafiltration membrane), an EMR-Ioop with a normal ultrafiltration module, and a circulation pump. This approach has been successfully demonstrated for the enzymatic reduction of poorly soluble ketones [107]. Using this device, e.g., for the enantioselective reduction of 2-octanone to (S)-2-octanol (e.e. >99.5%) with a carbonyl reductase from Candida parapsilosis under NADH-regeneration with FDH/for-mate, the total turnover number was increased by a factor 9 as compared with the classical EMR. 

Some systems use reagents or antibodies that have been immobilized in a reaction coil or chamber to repetitively carry out a chemical reaction or a separation of art analyte contained in ahquots of successive specimens. Other systems use enzymes immobhized on membranes that are coupled to sensing electrodes. The reaction products are then measured by the sensing device. Only a buffer is required as a diluent and wash solution, and thus the membrane has an extended life of approximately several months. Some... 

Rubinsky s group presented the first microfluidic device to electroporate a cell (Davalos et al., 2000 Huang and Rubinsky, 1999). Their devices consisted of three silicon chips bonded together to form two chambers, separated by a 1 pm thick silicon nitride membrane with a 2—10 pm diameter hole. Because silicon nitride is nonconductive, any electrical current flowing from the top chamber to the bottom chamber must pass through this microhole. A cell suspension was introduced into the top chamber, followed by the immobilization of one cell in the hole by lowering the pressure in the bottom chamber. 

A micropump or active microvalve is said to use external actuators when the component responsible for opening or closing the valve or moving the fluid is added to the device after fabrication. Examples would be a separate miniature solenoid valve used to pressurize or depressurize air chambers in a pneumatic actuator or piezoelectric patches glued to a micromachined silicon or glass membrane. 

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