Ultrafiltration technique

Evidence for the association of U with humic acids has been documented elsewhere. Dearlove et al. (1991) showed that U concentrated by ultrafiltration techniques from organic-rich groundwater samples were associated with humic colloids. Humic and fulvic acids have been shown to strongly complex U. Lienert et al. (1994) modeled the distribution of U species in the Glatt River and concluded that U-humate complexes become important at pH <6.8. These results reinforce the conclusions in the estuarine studies that U humate and fulvate complexes may account for the association of U with colloids. 

Guo LD, Santschi PH (1996) A critical evaluation of the cross-flow ultrafiltration technique for sampling colloidal organic carbon in seawater. Marine Chem 55 113-127 Guo LD, Wen LS, Tang DG, Santschi PH (2000) Re-examination of cross-flow ultrafiltration for sampling aquatic colloids evidence from molecular probes. Marine Chem 69 75-90 Guo LD, Hunt BJ, Santschi PH (2001) Ultrafiltration behavior of major ions (Na, Ca, Mg, F, Cl, and SO4) in natnral waters. Water Res 35 1500-1508... 

A number of techniques have been used by other authors, and these will be summarized briefly. Wershaw et al4 and Matsuda and Schnitzer have both used the solubility technique. The techniques and interpretation are essentially identical to those used in this research. Means and Wiyajaratne have used an ultrafiltration technique. 

At the dose most commonly employed in the present work (10 mg/kg), 66.6% of phenol red occurred bound as determined by ultrafiltration techniques (8). There were no significant differences in percentage bound at 20 and 40 mg/kg doses whereas there was a slight but significant decrease in the amount of binding by phenol red in the presence of probenecid. 

With the aid of ultrafiltration techniques Lindenbaum and Westfall (15) showed that 92% of the plutonium solution (1.96 x 10 sm) was ultrafilterable in the presence of 3.4 x 10 2m citrate over a pH range of pH 4.0 to 10.0. However, when the citrate concentration was lowered to 1.96 x 10-SM the ultrafilterability was only 77 % for the range pH 4.0 to 8.5 and at pH 11.0 only 5 %. Lindenbaum and Westfall (14) have also demonstrated that citrate could bring about a resolubilisation of the colloid. Equimolar concentrations of Pu(IV) and citrate were adjusted to pH 11.0 and then one hour later the solution was adjusted to either pH 7.8 or pH 4.0. Within... 

This simplified calculation is used to illustrate basic computational techniques. It assumes that all of the Fe(OH)3(aq) is a true solute. The quality of this assumption is a matter of debate as at pH 8, Fe(OH)3(aq), tends to form colloids. Thus, laboratory measurements of ferrihydrite solubility yield results highly dependent on the method by which [Fe(lll)]jQ(gj is isolated. Ultrafiltration techniques that exclude colloids from the [Fe(lll)]jQjgj pool produce very low equilibrium solubility concentrations, on the order of 0.01 nM. This is an important issue because a significant fraction of the iron in seawater is likely colloidal, some of which is inorganic and some organic. In oxic... 

Taylor, S. and Harker, A. (2006) Modification of the ultrafiltration technique to overcome solubility and nonspecificbinding challenges associated with the measurement of plasma protein binding of corticosteroids. Journal of Pharmaceutical and Biomedical Analysis, 41, 299-303. 

The development of these equations has been reported elsewhere (12), and it has also been shown using ultrafiltration techniques that the composition of the monomer is well predicted by the equation (12)... 

The standard free energy is therefore determined by measurement of the mixture CMC holding the micellar composition fixed. This analysis assumes that a is known as a function of temperature and micellar composition and is independent of the electrolyte composition. The heat of micellization cannot be determined from measurement of the temperature dependence of CMCj( without knowledge of the micellar composition and of a. Interpretation of calorimetric data is not possible without information regarding micellar composition. Ultrafiltration techniques designed to measure micellar compositions, take an added importance when considering heats of micellization. 

Rivas, B.L., Del Carmen Aguirre, M. and Pereira, E. (2007a) Cationic water-soluble polymers with the ability to remove arsenate through an ultrafiltration technique. Journal of Applied Polymer Science, 106(1), 89-94. 

Gamble, D.S., M.I. Haniff, and R.H. Zienius (1986a). Solution phase complexing of atrazine by fulvic acid A batch ultrafiltration technique. Anal. Chem., 54 727-731. 

Microdialysis and ultrafiltration techniques are both collection methods. Neither of these two techniques by themselves directly detects analyte within a sample. An early problem with analyte measurements in samples collected with microdialysis... 

Methodological artefacts may arise for a number of reasons, most notably as a result of specific interactions of species with the filter membrane. Therefore the choice of the ultrafiltration system, the properties and influence of the membrane and the operating conditions must be carefully considered before the ultrafiltration technique is applied for the separation of different radionuclide species in environmental samples. 

Leonard, K.S., Harvey, B.R., Woodhead, R.J., Brooks, T. and McCubbin, D. (1994) Assessment of an ultrafiltration technique for the fractionation of radionuclides associated with humic material./. Radioanal. Nucl. Chem. Articles, 181, 309-320. 

Guo, L., and Santschi, P.H. (1996) A critical evaluation of the cross-flow ultrafiltration techniques for sampling colloidal organic carbon in seawater. Mar. Chem. 55, 113-127. 

In order to clarify the solution properties of poly(VAd) in more detail, poly(VAd) was fractionated by ultrafiltration techniques. The observed molar extinction coefficient of poly(VAd) apparently decreases with an increase in the average molecular weight (Table 13). This suggests that the possibility of an inter-... 

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. 

The main advantage of ultrafiltration techniques is that they permit a direct determination of the association constants between colloids and... 

Benoit G. (1995) Evidence of the particle concentration effect for lead and other metals in fresh waters based on ultrafiltration technique analyses. Geochim. Cosmochim. Acta 59(13), 2677-2687. 

Mercury salts have been known for a long time to be toxic to human health. This problem has been stressed during the two past decades, leading various countries to develop research programs aimed to remove mercury salts from industrial waste water. Available methods are either chemical, involving ion exchange resins and various oxidation or reduction processes, or physical, using ultrafiltration techniques, evaporation of solutions or electrochemical treatments. 

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