G Ion-Exchange Chromatography

Filtration. Saline matrix removal and analyte preconcentration (e.g., ion-exchange chromatography) or plain dilution with high purity water Filtration. Saline matrix removal and analyte preconcentration (e.g., ion-exchange chromatography) or plain dilution with high purity water. Chromatographic separation... 

In species exchange processes (e.g., ion-exchange chromatography column), conventional adsorption rate models describe mass transfer (or exchange) between phases, assuming the existence of a counterpart species. In contrast, the adsorption models may not be useful in an inert environment (or inactive zone) where adsorption/desorption caimot take place because of lack of counterpart species. 

Bromelain (anti-inflammatory Ananase from pineapple) [37189-34-7] Mr 33 000, [EC 3.4.33.4]. This protease has been purified via the acetone powder, G-75 Sephadex gel filtration and Bio-Rex 70 ion-exchange chromatography and has Aj 20.1 at 280nm. The protease from pineapple hydrolyses benzoyl glycine ethyl ester with a Km (app) of 210mM and kcat of 0.36 sec. [Murachi Methods Enzymol 19 273 1970 Balls et al. nd Eng Chem 33 950 1941.]... 

After a strain improvement and development programme similar to, but more complicated than that of penicillin, the D-a-aminoadipyl side chain containing cephalosporin C was obtained by large scale fermentation. However, cephalosporin C could not be isolated as easily as penicillin G or V. Due to its amphoteric nature it is soluble at any pH in the fermentation broth. Several costly isolation procedures involving ion-exchange chromatography have been developed, as a result of which cephalosporin C is much more expensive than penicillin G. 

Adsorption and ion exchange chromatography are well-known methods of LC. In adsorption, one frequently selects either silica or alumina as stationary phase for separation of nonionic, moderately polar substances (e.g. alcohols, aromatic heterocycles, etc.). This mode works best in the fractionation of classes of compounds and the resolution of isomeric substances (J). Ion exchange, on the other hand, is applicable to the separation of ionic substances. As to be discussed later, this mode has been well developed as a tool for analysis of urine constituents (8). 

Early measurements of " Th were on seawater samples and Th was co-precipitated from 20-30 L of seawater with iron hydroxide (Bhat et al. 1969). This procedure may not recover all of the " Th in the sample, and an alpha emitting Th isotope (e g., °Th or Th) is added as a yield monitor. Following chemical purification of the Th fraction by ion exchange chromatography, the Th is electrodeposited onto platinum or stainless steel planchets. The planchets are then counted in a low background gas-flow beta detector to measure the beta activity and subsequently with a silicon surface barrier detector to determine the alpha activity of the yield monitor. The " Th activity is thus determined as ... 

Measurements of " Th in sediment samples (Aller and Cochran 1976 Cochran and Aller 1979) used much the same approach as outlined above. In this case, the dried sediment sample ( 10 g) was leached with strong mineral acid (HCl) in the presence of a yield monitor (generally Th, an artificial Th isotope resulting from the decay of Th that is produced by neutron capture on Th). Thorium was separated from U and purified by ion exchange chromatography, and electrodeposited onto stainless steel planchets. Counting and determination of " Th activity followed the procedure outlined above. 

Ion-exchange chromatography (lEC) is used mainly for the separation of ions and easily ionized substances (e.g., substances that form ions by pH manipulation or complexation) in which one of the principal contributions to retention is the electrostatic attraction between mobile phase ions, both sa le and eluent, for immobilized ion centers of opposite charge in the stationary phase. The sample ions are separated based on differences in their relative affinity for the stationary phase ion centers compared to that of the mobile phase counterions in a dynamic exchange system, in which sample ions and eluent ions interact with multiple stationary phase ion centers as they pass through the column. Ion-... 

Schmuckler, G., High-performance liquid ion-exchange chromatography /. Liq. Chromatogr., 10, 1887, 1987. 

Houpert, Y., Tarallo, P., and Siest, G., Amino acid analysis by ion-exchange chromatography using a lithium elution gradient. Influence of methanol concentration and sample pH, /. Chromatogr., 115, 33, 1975. 

Murren, C., Stelling, D., and Felstead, G., An improved buffer system for use in single-column gradient-elution ion-exchange chromatography of amino acids, /. Chromatogr., 115, 236, 1975. 

Malmquist, G. and Lundell, N., Characterization of the influence of displacing salts on retention in gradient-elution ion-exchange chromatography of peptides and proteins, J. Chromatogr., 627, 107, 1992. 

Nuryono, Huber, C. G., and Kleboth, K., Ion-exchange chromatography with an oxalic acid-alpha-hydroxyisobutyric acid eluent for the separation and quantitation of rare-earth elements in monazite and xenotime, Chromatograph-ia, 48, 407, 1998. 

Riickert, M., Wohlfarth, M., and Bringmann, G., Characterization of protein mixtures by ion-exchange chromatography coupled on-line to nuclear magnetic resonance spectroscopy, ]. Chromatogr. A, 840, 131, 1999. 

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