Dialysis micro

The individual membrane filtration processes are defined chiefly by pore size although there is some overlap. The smallest membrane pore size is used in reverse osmosis (0.0005—0.002 microns), followed by nanofiltration (0.001—0.01 microns), ultrafHtration (0.002—0.1 microns), and microfiltration (0.1—1.0 microns). Electro dialysis uses electric current to transport ionic species across a membrane. Micro- and ultrafHtration rely on pore size for material separation, reverse osmosis on pore size and diffusion, and electro dialysis on diffusion. Separation efficiency does not reach 100% for any of these membrane processes. For example, when used to desalinate—soften water for industrial processes, the concentrated salt stream (reject) from reverse osmosis can be 20% of the total flow. These concentrated, yet stiH dilute streams, may require additional treatment or special disposal methods. 

Chemical analysis. Succinoglycan, purified by micro-filtration and dialysis, was hydrolysed in 0.5M sulphuric acid at a concentration of approximately 5mg/ml for 16 hours at 95 C. Sugars and acids were determined by HPLC using Biorad HPX-87 columns. No pretreatment was required for acids analysis - detection was by measurement of UV... 

Rahman S, Zhang J, Engleman EA, Corrigall WA (2004) Neuroadaptive changes in the mesoac-cumbens dopamine system after chronic nicotine self-administration a micro-dialysis study. 

Some investigators apply the sample some distance from the desired starting line and use evaporation to move the sample toward it, thus obtaining in effect a partial dialysis. True dialysis can be achieved with the usual methods, and for micro samples Antweiler (A6) gives a successful technique. A rapid and ingenious method is dilution of the sample with buffer, followed by concentration on an ultrafilter, on which electrophoresis is subsequently performed (unpublished). Better knowledge of the physical conditions of the buffered strip will increase the use of a dialyzing technique in order to obtain better results. 

Yang, Z., Matsumoto, S., Maeda, R., A prototype of ultrasonic micro-degassing device for portable dialysis system, Sensors Actuators A 2002, 95, 274-280. 

Xu, N., Lin, Y., Hofstadler, S.A., Matson, D., Call, C.J., Smith, R.D., A micro-fabricated dialysis device for sample cleanup in electrospray ionization mass spectrometry. Anal. Chem. 1998, 70, 3553-3556. 

Camp et al. (1997) administered a rising dose of amphetamine (1-10 mg/kg over 10 days) to rats and then withdrew the animals for 1-30 days. Using in vivo micro dialysis, they found changes lasting 1 month in norepinephrine concentrations in the hippocampus as well as altered responses to amphetamine challenge. They concluded that amphetamine produces biochemical adaptations that far outlast the acute drug effects and may account for both transient and more persistent discontinuation effects in humans. 

Fig. 4. Scatchard plots for the binding of tilorone hydrochloride to calf thymus DNA (a) Me. lysodeikticus DNA (b) poly (dA-dT) poly (dA-dT) (c) and poly (dG-dC) poly (dG-dC) (d). Each different symbol corresponds to a separate experiment. Thus, each figure represents a set of 4 or 5 separate experiments, r is moles of bound tilorone/base pair concentration and (u) is the concentration of unbound tilorone. Equilibrium dialysis was carried out by a procedure and an apparatus (Dianorm, supplied by Dr. Virus KG, Bonn, Germany) described by Weder et al.61 Dialysing membrane (0.02S mm thick) was sandwiched between two halves of a Teflon (round) macro-cell (dialysable volume = 1 ml). The DNA, or labelled tilorone solutions were introduced by separate micro syringes on either side of the membrane through the side valves. The valves were closed air tight and the macro-cells were fixed into a rotating machine. All equilibrium dialysis studies were carried out at 20°, and at 10 rotations/min. Under these conditions equilibrium was attained in 4-5 hr. After the equilibrium was reached 0.8 ml of the solution from either side of the membrane was withdrawn by microsyringes and the radioactivity was determined using dioxan scintillation fluid...

An alternative to the above method is also largely applied. Dialysis is replaced by a distillation step using a micro distillation column. In the case of total sulphur dioxide, alkaline hydrolysis is replaced by strong acidification and a higher distillation temperature. 

Gel filtration compares very favorably with dialysis through membranes (Kisliuk, 1960). It is rapid and can be performed on either a micro- or a macroscale. The desalting of virus by this procedure has been reported by Matheka and Wittmann (1961). 

One salient example of the need for degassing in the clinical field and of the effectiveness of ultrasound for this purpose is a prototype of ultrasonic micro-degassing device for portable dialysis systems. The bubbles inside these systems reduce the effective exchange surface area, which is extremely important here [104]. 

Polyelectrolyte complexes are very promising materials for preparing semi-permeable membranes of definite permeability and selectivity The methods of preparation and the properties of membranes made of polyelectrolyte complexes based on strong polyelectrolytes, e.g. poly(sodium sterene sulfonate) and poly(vinylbenzyl-trimethyl ammonium chloride) were described These membranes may be applied for reverse osmosis in the desalting of sea-water, for dialysis and ultrafiltration in purifications and concentration of water solutions containing coUoids or micro-and macroparticles ... 

Membranes may be hastily classified according to the driving force at the origin of the transport process (1) a pressure differential leads to micro-, ultra-, nanofiltration, and reverse osmosis (2) a difference of concentration across the membrane leads to diffusion of a species between two solutions (dialysis) and (3) an electric potential difference applied to an ion-exchange membrane (lEM) leads to migration of ions through the membrane (electrodialysis, membrane electrolysis, and... 

Zeppezauer, M., Eklund, H., and Zeppezauer, E. S. Micro diffusion cells for the growth of single protein crystals by means of equilibrium dialysis. Arch. Biochem. Biophys. 126, 564-573 (1968). 

Scheme 1. Setup for simultaneous thermometric and blood-glucose analyser measurements, using a micro-dialysis in-vivo probe on a human volunteer...

In some instances, microdialysis sampling can be coupled on-line with mass spectrometry without prior separation or cleanup with techniques such as GC or LC. Continuous flow fast atom bombardment (cfFAB) has been used for the ionization of microdialysis samples without prior sample preparation. Coupling micro-dialysis directly to mass spectrometry via FAB was more feasible with cfFAB because it provided for a more robust, efficient ionization and prevented source fouling. 

LJ Deterding, K Dix, LT Burka, KB Tomer. On-line coupling of in vivo micro-dialysis with tandem mass spectrometry. Anal Chem 64 2636—2641, 1992. 

Zimmer L, Hembert S, Durand G. Guilloteau D, Bodard S, Besnard JC, et al. Chronic n-3 polyunsaturated fatty acid diet-deficiency acts on dopamine metabolism in the rat frontal cortex a micro-dialysis study. Neurosci Lett 1998 240 177-181. 

In addition to the vapor diffusion method described previously, other techniques such as the batch and micro-batch methods, bulk and micro dialysis, free interface diffusion, liquid bridge, and concentration dialysis have also been developed to produce crystals for x-ray diffraction analysis (see McPherson, 1982 and McPherson, 1999). 

Hydrophobic membranes, e.g., PTFE, permit the efficient removal of volatile analytes from the sample matrix by diffusion though the micropores [257]. As these membranes have a high diffusion efficiency for many gaseous species, selectivity is usually low. For hydrophilic porous membranes, mass transference usually relies on dialysis, provided differences in donor and acceptor stream pressures are low [258] the chemical species originally in the donor stream migrate through the solvent in the interstitial volume of the membrane. Ionic species are therefore efficiently separated from the macromolecules in the sample matrix. Increasing the difference in pressures of both streams favours the micro-filtration process therefore, filtration and dialysis may occur simultaneously [259,260]. 

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