Fractionation methods with ultrafiltration

Fractionation Methods. Ultrafiltration and gel filtration are nondestructive methods which, based on limited experience, can be used for fractionation of mineral complexes from digests. In earlier studies mineral absorption on the gel material was a problem. Lonnerdal (30) introduced a method of treating dextran gels with sodium borohydride in order to eliminate the mineral-binding sites on the gel. In preliminary studies we have recovered more than 90 of Ca, Mg, Fe, Zn and P in samples applied to a borohydride-treated gel column (Sephadex G-50, Pharmacia Fine Chemicals, Piscataway, NJ). Recovery of Ca (Table IV) and Mg, Fe and Zn from ultrafiltration was also good. 

Elimination of Cellulases from Xylanases. Classical methods of protein fractionation can be used for to separate cellulases and xylanases on a large scale only when they differ considerably in molecular weight or isoelectric point. The Tricho-derma harzianum enzymes were separated by ultrafiltration because the xylanase was smaller and passed through the membrane into the ultrafiltrate 18). Fractional precipitation with organic solvents is another possibility (7). 

Cylindrical internal reflectance (CIR) techniques have been applied to humic and fulvic acids that were size fractionated by using hollow-fiber ultrafiltration methods with cutoffs of 0.1pm and 100,000, 30,000,... 

Gurley, B.J. Marx, M. Olsen, K. Phenytoin free fraction determination comparison of an improved direct serum injection high-performance liquid chromatographic method to ultrafiltration coupled with fluorescence polarization immunoassay. J.Chromatogr.B, 1995, 670, 358-364... 

Filterable organic phosphorus isolated from several sites in and adjacent to the ENR were analysed by this method, using off-line phosphorus-specific mass spectrometry detection. The organic phosphorus was isolated and concentrated by tangential ultrafiltration and lyophilization to produce concentration factors of —25 and final total organic phosphorus concentrations of —1 mg P/1. Column effluent was collected in 1 ml fractions after ultraviolet detection at 214 nm. The chromatographic fractions, along with a matrix blank and 1 and 10 mg/1... 

In the second method, ultrafiltration, centrifugal force is applied for a few minutes to a sample of the compound in plasma, pushing the unbound fraction through a permeability selective membrane. LC/MS/MS analysis of the ultrafiltrate and retentate is then done. This has the advantage of being faster than dialysis. Methods like 96-well plate have been developed here too. As in HTS, edge effects have been noted with these, and one study comparing such a method with results from individually run samples for a dozen research compounds showed an value of 0.60. ... 

Phosphoribosyl pyrophosphate synthetase (from human erythrocytes, or pigeon or chicken liver) [9015-83-2] Mr 60,000, [EC 2.7.6.1]. Purified 5100-fold by elution from DEAE-cellulose, fractionation with ammonium sulfate, filtration on Sepharose 4B and ultrafiltration. [Fox and Kelley J Biol Chem 246 5739 197h, Flaks Methods Enzymol6 158 1963 Kornberg et al. J Biol Chem 15 389 7955.]... 

Because the chapter is about DOM, detailed information about the role of colloids and the analytical techniques are given elsewhere (e.g., Buffle and Leppard, 1995 Kretzschmar et al., 1999 Frimmel et al., 2007). Different separation techniques, like ultrafiltration, size exclusion chromatography, and flow field-flow fractionation can be coupled with UV-vis absorption and ICP-MS to show the interaction of metals and colloids. Elements like Ni, Cu, Cr, and Co are associated mainly with smaller-size DOM fractions whereas Al, Fe, lanthanides, Sn, and Th are associated with larger-size DOM fractions (Bolea et al., 2006). The laser-induced breakdown detection (LIBD) is a new, sensitive method for the quantification of aquatic colloids of lower-range nanometer size in very low concentration, which cannot be... 

The follow-up section will deal with separation methods based upon (a) molecular size and related to it hydrodynamic volume (size-exclusion chromatography and ultrafiltration), (b) molecular size and related to it molecular diffusivity (field-flow fractionation), and (c) charge/size ratio and related to it molecular polarity (electrophoresis and mass spectrometry). Also reviewed will be hyphenated techniques or those that combine separation by chromatography or electrophoresis with spectral detection. 

Techniques can be classified into two main categories those that detect total metal concentrations and those that detect some operationally defined fraction of the total. Methods which detect total concentrations such as inductively coupled plasma spectrometry, neutron activation analysis, atomic absorption spectrometry and atomic emission spectrometry have no inherent speciation capabilities and must be combined with some other separation technique(s) to allow different species to be detected (approach A in Fig. 8.2). Such separation methods normally fractionate a sample on the basis of size, e.g. filtration/ultrafiltration, gel filtration, or a combination of size and charge, e.g. dialysis, ion exchange and solvent extraction (De Vitre et al., 1987 Badey, 1989b Berggren, 1989 1990 Buffle et al., 1992). In all instances the complexes studied must be relatively inert so that their concentrations are not appreciably modified during the fractionation procedure. 

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