Dialysis Techniques

The effect of solution chemistry on the speciation of the organic contaminant 1-naphtol (1-hydroxynaphthalene) and its complexatiom with humic acid is reported by Karthikeyan and Chorover (2000). The complexation of 1-naphtol with humic acid (HA) was studied during seven days of contact, as a function of pH (4 to 11), ionic strength (0.001 and 0.1 M LiCl), and dissolved concentration (DO of 0 and 8 mg L ) using fluorescence, UV absorbance, and equilibrium dialysis techniques. In a LiCl solution, even in the absence of HA, oxidative transformation of 1-naphtol mediated by was observed. In addition, the presence of humic acid in solution, in the absence of DO, was found to promote 1-naphtol oxidation. These reactions are affected by the solution chemistry (pH, ionic strength, and cation composition). 

Fig. 3. Schematic design of a two-vessel arrangement for a scale-up of the dialysis technique...

The stoichiometric measurements were made using a similar dialysis technique. Exactly 50 mg zeolite ( 0.1-0.2 mg) was weighed into a dialysis membrane to which 5 ml 0.01 NaCl (or NaNOs) was pipetted. The mixture was equilibrated with 40 ml of a mixed electrolyte solution of 0.01 total normality, containing sodium and the bivalent cation (Ni, Zn, Co) in various proportions. Each combination requires two identical experiments, involving either a 22Na or a label of the transition element. Equilibrations were made in an end-over-end shaker (5 or 25°C) for one to two weeks. The ion distributions were calculated from the amounts of radioactivity of the initial and the equilibrium solutions for assays of duplicate 5 ml samples. For precision, the total number of counts collected in the 22Na-labeled samples was always about 10 . 

Preservatives such as sodium benzoate, sorbic acid, and methyl and propyl parabens have been used in liquid and semisolid dosage forms. There have been reports that the parabens have been inactivated when used in the presence of various surfactants. This loss of activity was thought to be due to the formation of complexes between the preservative and the surfactant. The interaction between polysorbate (Tween) 80 and the parabens has been demonstrated by a dialysis technique (Ravin and Radebaugh, 1990). It has also been shown that molecular complexes form when the parabens are mixed with polyethylene glycol (PEG) and methylcellulose. The degree of binding was less than that observed with Tween 80. Sorbic acid also interacts with Tweens but does not interact with PEGs. The quaternary ammonium compounds are also bound by Tween 80, which reduces their preservative activity. 

The oil-in-water emulsion method consists Lrst of preparing an aqueous solution of the copolymer. To this a solution of the drug in a water-insoluble volatile solvent (e.g., chloroform is added to form an oil-in-water emulsion) (Jones and Leroux, 1999). The micelle-drug complex forms as the solvent evaporates. The main advantage of the dialysis procedure over this method is that potentially toxic solvents can be avoided. Both dialysis and oil-in-water emulsion methods were compared for the incorporation of DOX in PECb-PBLA micelles (Kwon et al., 1997). The emulsiLcation method was more efLcient with a DOX loading of 12% (w/w) (Kwon et al., 1997) compared with 8% (w/w) for the dialysis technique (Kwon etal., 1995). 

Recently, Weber and co-workers reported on the application of dialysis to the determination of the complexing capacity of fulvic acid for a series of metal cations (19, 20). In the present paper we report a further elaboration on the dialysis technique to allow simultaneous determination of complexing capacity for the humic acid sample, and interaction constants for the metal ion - humic acid complexes, as well as the stoichiometry of the latter. The technique furthermore opens up a possibility for an indirect determination of apparent ionization constants for the humic acids. 

The present paper has demonstrated the versatility of the dialysis technique in studies of interactions between metal ions and humic acid samples. The method allows facile determination of interaction constants, as well as of complexing capacities of the humic acid samples. It is noteworthy that the method described here, without modifications, can be applied to other areas of complex chemistry involving macromolecular ligands. 

The binding data of p-tert-amylphenol to human serum albumin were obtained by the dynamic dialysis technique as follows ... 

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. 

Protein biosynthesis occurs on ribosomes which are small organelles composed of proteins and ribosomal RNA (tRNA). Fluorescence and dialysis techniques have been used to study the interaction of Tb3+ with tRNA. The relative fluorescence was found to be proportional to the amount of bound Tb3+ ion. Intact ribosomes produced similar effects on those of tRNA indicating the primary sphere for lanthanide binding is that of ribosomes. 

Florisil columns are used for the separation of lipids and the target compounds [1, 4, 7]. Zook et al. [9] used a dialysis technique with a polyethylene film for the removal of lipids, followed by gel permeation chromatography (GPC), using S-X3 Bio beads with dichloromethane/n-hexane (50 50, v/v), carbon column chromatography, and florisil columns. De Boer et al. [8] have tried to avoid the use of florisil, because of the extensive pre-treatment and its relative instability. They used GPC, Bio beads S-X3 with dichloromethane/ m-hexane (50 50, v/v) for the separation of lipids and TCPM and TCPMe. The GPC elution was carried out twice and was followed by a silica gel column fractionation to separate TCPM and TCPMe from the PCBs. The recovery of a TCPM spike in a seal blubber extract in this method was 90%. 

It should be emphasized that in this application the methane producers in the isolation of Digester 2, were ideally supported by their natural substrate. The dialysis technique is unique in that it would flush away any waste materials as well as provide all the trace growth factors necessary for the optimum growth of this type of culture, whether or... 

MARS A new therapeutic option that could improve renal function and prolong survival, especially in risk patients to TIPS, can be found in the molecular adsorbent recirculating system (MARS). It represents a cell-free liver dialysis technique and enables the selective removal of albumin-bound substances using an albumin-enriched dialysate fluid. Significant improvements for different biochemical and clinical parameters as well as a 30-day prolongation of survival were reported. (40) (s. p. 385)... 

Donnan dialysis and diffusion dialysis techniques are used [30] to deacidify and concentrate actinide bearing acidic solutions. Near complete deacidification could be achieved from 8 M nitric acid solutions with a high decontamination factor for the actinides. With cation-exchange membranes, the deacidification is accomphshed by the build up of neutralized salt in the feed. With an anion-exchange membrane, the feed acidic solution is deacidrfied free of salt buildup. By superimposing direct osmosis with free deacidiflcation, it was simultaneously possible to concentrate the deacidified actinide solution [30]. 

Marked differences have been found in the properties of isotactic and syndiotactic PMA by studying their binding capacity towards various counterions. Comparative studies of the binding of Cu+ and ]%+ 18) and of a — CO polymethylenebispyridinium bolaform cations 19) to conventional and isotactic PMA have been carried out over a range of degrees of neutralization of the polyacids, by the equilibrium dialysis technique. The results show that Cu+ ions are much more extensively... 

The use of equation (7.21) can be criticised because of the simple manner in which R has been measured and defined, but the equation is useful to estimate effects of changing parameters. When the emulsified system is very complex, containing not one but at least two emulsifying agents (as most do), the determination of the parameters of the equation is a lengthy process, and a direct experimental approach to the determination of free aqueous concentration, such as a dialysis technique, may be the only approach. 

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