Chelation method

Efficiency of Extraction. Selectivity of Extraction. Extraction Systems. Extraction of Uncharged Metal Chelates. Methods of Extraction. Applications of Solvent Extraction. 

More recently, a new chelation method based on the technetium chelator, HYNIC, was developed by Laverman et al. (36). HYNIC is well known for its use in labeling peptides and proteins with high efficiency and excellent stability (37). A-hydroxysuccinimidyl hydrazino nicotinate hydrochloride was conjugated to the free amino group of distearoylpho-sphatidyl-ethanolamine (DSPE) and subsequently incorporated in the lipid bilayer during the liposome preparation. 

Metal-chelating method has also been commonly employed for the regios-elective incorporation of AHB at N-1 of kanamycin class aminoglycoside (Scheme 4.20). Other kanamycin derivatives have been prepared in similar fashion (Figure 4.10). ... 

In a recent article, the metal-chelating method was used to provide a different functional group at the N-1 position (Figure 4.11). ... 

Mobashery and co-workers also reported the synthesis and inhibitory apph-cation of 2 -N02 derivatives of neamine and kanamycin (Scheme 4.28). Using the metal-chelating method, the 2 -NH2 was selectively unmasked and then oxidized into 2 -N02, which will increase the acidity of 2 -H. Upon phosphorylation at the 3 -0H, elimination of phosphate will lead to the formation of a nitroalkene intermediate, 198, that can function as a Michael acceptor and... 

Vlek, P.L.G. Blom,Th.J.M. Beek, J. Lindsay, W.L. (1974) Determination of the solubility product of various iron hydroxides and jaro-site by the chelation method. Soil Sci Soc. Am. Proc. 38 429-432... 

The Guthion solutions were analyzed by measuring absorbances in the infrared region at 645 cm."1 and by the copper chelate method (I, 3). The latter method is the more specific and depends on basic hydrolysis of Guthion followed by formation of a colored Cu2+ chelate with the dimethyl dithiophosphoric acid formed. In instances where the Guthion concentrations were quite low, thin layer chromatographic techniques were employed. 

There are two methods the preformed radiometal-chelate method and the indirect chelator—antibody method. Various antibodies are labelled by the latter, where the bifunctional chelating agent is initially conjugated to a macromolecule, which is then allowed to react with a metal ion, to form a metal-chelate-macromolecule complex. Due to the presence of the chelating agent, the biological properties of the labeled protein may be altered and must be assessed before clinical use. 

Efficiency of extraction. Selectivity of extraction. Extraction systems. Extraction of uncharged metal chelates. Methods of extraction. Applications of solvent extraction. 

Field Test of the Solution-Phase Chelation Method... 

Lewin MJM, Cheret AM (1989) Cell isolation techniques use of enzymes and chelators. Methods Enzymol 171 444 61... 

Treatment of mercury poisoning requires removal from the exposure followed by chelation. New chelation methods that use Ai-acetylpenicillamine, 2,3,-dimercaptopropane-l-sulfonate, or di-mercaptosuccinic acid replaced early uses of British Anti-Lewisite and D-penicillamine (Marsh 1985). British Anti-Lewisite (2,3-di-mercaptopropanol) increases cerebral organic mercury in some cases (Goetz 1985). Ethylenediaminetetraacetic acid does not displace mercury and worsens the renal toxicity of mercury (Goetz 1985). 

Under anaerobic conditions. Mo reacts readily with sulfide ion to form a number of stable thiomolybdate complexes (MoO S4l ) which have been detected by the oxine chelate method (Magyar et al, 1993). A number of insoluble sulfides can be precipitated including M0S2 and M0S3. Very often, the Mo sulfides are co-precipitated with FeS according to the reaction first proposed by Bertine (1972) ... 

Chromium(VI) can be quantitated without coprecipitation by forming a metal chelate. Method 7196A provides a procedure to prepare the diphe-nylcarbazone complex with Cr(VI) in an aqueous matrix. The method is not sensitive in that it is useful for a range of concentrations between 0.5 and 50 mg/L Cr. A more sensitive colorimetric method converts Cr(VI) to Cr(VI) chelate with ammonium pyrrolidine dithiocarbamate (APDC), followed by LLE into methyl isobutyl ketone (MIBK). The molecular structure for APDC is as follows ... 

Benzyl ethers are commonly introduced by the conditions in category (a), section 2.3, Ethers, particularly when perbenzylation is required. The choice of conditions does not affect selectivity greatly (Figure 2.4) [9] except when the copper chelate method is employed. In the latter method dialkoxides (produced from diols with NaH) are deactivated by regioselective complexation of a copper salt so that the free alkoxide reacts preferentially Figure 2.5 illustrates a typical case [10] which should be compared with the variants in Figure 2.4. 

Atomic absorption spectroscopy is a preferred method in clinical chemistry. However, UV/Vis spectrometry by use of chelating methods combined with photometry of chromophores offers simple and fast approaches. Examples are methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS 1990) taking ferrocene for Fe, eliminating interferences by Cu by addition of thiourea. Mg is determined by addition of xylidyl blue, Ca by use of o-cresolphthalein or arsenazo complexes. Interferences by Mg are reduced by addition of 8-hydroxyquinoline. Further chromophores and complexing agents are discussed in subsequent chapters and elsewhere [39]. 

Chelating methods are usually severely interfered by fluoride, EDTA and phosphate. Many of these agents either do not interfere in the iodide method or can be masked with suitable reagents. 

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