Channel dialyzate

Instruments, Inc., Rockville, MD) was added, and the proteins were fractionated using a 10-channel RIEF apparatus. The proteins in each of the 10 fractions were then dialyzed against large volumes of phosphate-buffered saline (PBS, pH 7.4). Immunoelectrophoresis and a radioimmunoassay (RIA) for PCP were used to determine the RIEF fractions with the greatest purity and anti-PCP activity. 

The pump moves the diluted and now segmented sample into a dialyzer. The dialyzer consists of a cellophane sheet compressed between two plastic plates. The plastic plates have superimposed grooved channels through which fluid is pumped. The two fluids in the channels then... 

Finally, the flame photometric methods for determination of sodium and potassium have been adapted to the device. In this case, after the addition of lithium as internal standard, the electrolytes are dialyzed into the recipient stream, which is then pumped into an atomizer-burner of more or less conventional design. A colorimeter has been designed to allow for simultaneous recording of sodium and potassium, utilizing a two-channel recorder as optional equipment. This arrangement would tend to conserve sample. Without the dual recorder, the recorder supplied as part of the basic instrument is used, and the specimens are sampled once for sodium and once for potassium. 

Parallel-plate hemodialyzers using flat membranes, with several compartments in parallel, separated by plastic plates, are now only available from Hospal Co (Crystal and Hemospal models). Blood circulates between two membranes and the dialysate between the other side of membrane and the plastic plate. These parallel-plate dialyzers have a smaller blood-pressure drop than hollow-fiber ones and require less anticoagulants as flat channels are less exposed to thrombus formation than fibers, but they are heavier and bulkier and thus less popular. A recent survey of the state-of-the-art in hemodialyzers is given in [13]. 

Besides these modes, which enable the recording of single channel currents, it is also possible to measure the current flowing through the entire cell. This whole-cell mode is obtained by rupturing the membrane patch in the cell-attached mode (Hamill et al. 1981 Dietzel et al. 1993). This is achieved by applying suction to the interior of the patch-pipette. The whole-cell mode not only allows to record the electrical current, but also to measure the cell potential. Moreover, the cell interior is dialyzed by the electrolyte solution filled into the patch-pipette. 

Plastic microdevices for high-throughput screening with MS detection were also prepared for detection of aflatoxins and barbiturates. These devices incorporated concentration techniques interfaced with electrospray ionization MS (ESI-MS) through capillaries [2], The microfluidic device for aflatoxin detection employed an affinity dialysis technique, in which a poly (vinylidene fluoride) (PVDF) membrane was incorporated in the microchip between two channels. Small molecules were dialyzed from the aflatoxin/antibody complexes, which were then analyzed by MS. A similar device was used for concentrating barbiturate/antibody complexes using an affinity ultrafiltration technique. A barbiturate solution was mixed with antibodies and then flowed into the device, where uncomplexed barbiturates were removed by filtration. The antibody complex was then dissociated and electrokinetically mobilized for MS analysis. In each case, the affinity preconcentration improved the sensitivity by at least one to two orders of magnitude over previously reported detection limits. 

L. Risinger, G. Johansson, Effect of sample viscosity on the behavior of thin-channel flow-through dialyzers in flow-injection analysis, Anal. Chim. Acta 261 (1992) 435. 

Sample preparation Dialyze 400 xL plasma against 175 p,L acceptor solution through a Cuprophane membrane (15 kDa cut-off) at 37° for 10 min, inject 500 xL acceptor solution (including the portion used for dialysis) onto column A at 0.71 mL/min, elute the contents of column A onto column B with mobile phase, remove column A from circuit and condition it with 1 mL acceptor solution, elute column B with mobile phase and monitor the effluent. Flush acceptor channel with 5 mL acceptor solution and plasma channel with 8 mL acceptor solution containing 25 p-g/mL TYiton X-100. (Acceptor solution contained 5.9 g NaCl, 4.1 g sodium acetate, 0.3 g KCl, and 1.65 g sodium citrate in 1 L water, adjusted to pH 7.4 with citric acid.)... 

Sample preparation 500 pL Plasma -l- 125 pL 40 mM decanoic acid in MeCN, mix. Dialyze a 100 pL sample against 20 mM pH 7.0 phosphate buffer using a Gilson Cuprophane membrane (molecular mass cut-off 15 kDa). Continuously pump the buffer through the dialysis cell and through column A at 3 mL/min for 9.6 min, backflush the contents of column A onto column B with the mobile phase, monitor the effluent from column B. (After each injection flush plasma channel with 1 mL 0.05% Triton X-100, with 1 mL 1 mM HCl, and with 2 mL water. After each injection flush buffer channel with 3 mL 20 mM pH 7.0 phosphate buffer and condition column A with 1 mL 20 mM pH 7.0 phosphate buffer.)... 

In order to balance the pressures on the two sides of the channels, the channel with the lower pressure (usually the donor stream) can be connected to a flow restrictor located downstream of the dialyzer. The restrictor is simply a length of thin tubing. Such measures may become necessary when one channel, usually the acceptor stream, is connected with packed reactors which significantly increase the flow impedance. On the other hand, in order to minimize clogging of the membranes, an increase in pressure on the acceptor side may be necessary when samples containing suspended sediments (e.g. urine) are analyzed, possibly with some sacrifice in the dialysis efficiency. 

Mass transfer involving convective transport through a channel and diffusive transport through the channel walls has been previously studied. These studies Involved a single pass of fluid through the channel. The channel wall permeability was assumed constant since the transport through the channel wall was purely diffusive and had no reactive component. A major impetus for these studies was the design of blood dialyzers for use as an artificial kidney. 

Ionic motion leads to the appearance of an ion concentration gradient in the solution at the membrane surfaces. The resultant polarization of concentration is similar to polarization in the electrolytic cell. This polarization is responsible for the low concentration of salt and great strength of the electric field near the membrane in the dialyzate channel. 

Note that the estimation (7.47) is applicable for the dialyzate channel, since in this channel, Q > f-w... 

Once the distribution of ion concentration is found, we can obtain the distribution of potential from (7.38). But we should note first that the total potential drop is a sum of the drop in the dialyzate and concentrate channels and the drop at the membrane. The potential drop at the membrane is analogous to concentration overvoltage at the electrode caused by the difference of ion concentrations at membrane surfaces. For a cation-exchange membrane, the potential drop is equal to... 

Microfluidic Microdialysis Systems Most microfluidic microdialysis systems consist of a two-compartment system with a sample flow channel and perfusion flow channel separated by the microdialysis membrane. A two-compartment cocurrent mass transport model of microdialysis is shown in Fig. 3. For this microdialysis system, molecules inside the sample channel are dialyzed across the membrane into the perfusion flow channel. Again, this system may be modeled by balancing the sample and perfusion convective fluxes with the diffusion of analyte across the membrane. Assuming the overall permeability... 

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