Hydrophobic chelates

The major anions and cations in seawater have a significant influence on most analytical protocols used to determine trace metals at low concentrations, so production of reference materials in seawater is absolutely essential. The major ions interfere strongly with metal analysis using graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma mass spectroscopy (ICP-MS) and must be eliminated. Consequently, preconcentration techniques used to lower detection limits must also exclude these elements. Techniques based on solvent extraction of hydrophobic chelates and column preconcentration using Chelex 100 achieve these objectives and have been widely used with GFAAS. 

There is a considerable difference in the antimalarial action of desferrioxamine B (DFO) and the hydrophobic chelators based on ferrichrome analogs. While the former is limited to mature forms in the life cycle of P. falciparum (trophozoites and schizonts), the latter effects to a greater extent early developing stages (ring). Therefore, studies explored... 

Chelating agents that can form insoluble, hydrophobic chelates on the surface of minerals are potential collectors for the selective flotation of minerals.3 4 As early as 1927, Vivian5 reported the use of cupferron, a well-known analytical reagent, as a collector for the flotation of cassiterite (Sn02). Since then, there have been a number of reports on the use of chelating agents in flotation. 

Quantitative determinations of the thicknesses of a multiple - layered sample (for example, two polymer layers in intimate contact) by ATR spectroscopy has been shown to be possible. The attenuation effect on the evanescent wave by the layer in contact with the IRE surface must be taken into account (112). Extension of this idea of a step-type concentration profile for an adsorbed surfactant layer on an IRE surface was made (113). and equations relating the Gibbs surface excess to the absorbance in the infrared spectrum of a sufficiently thin adsorbed surfactant layer were developed. The addition of a thin layer of a viscous hydrocarbon liquid to the IRE surface was investigated as a model of a liquid-liquid interface (114) for studies of metal extraction ( Ni+2, Cu+2) by a hydrophobic chelating agent. The extraction of the metals from an aqueous buffer into the hydrocarbon layer was monitored kinetically by the appearance of bands unique to the complex formed. 

Chelated Metal Ion-Solute. If the metal is first chelated with a relatively hydrophobic chelating agent, solute interactions will increase retention. Cooke et al C25) have developed such a technique using 4-dode-cyldiethylenetriamine and Zn(ll). Not only does this chelated metal greatly increase retention for certain anionic solutes, presumably by an ion pairing interaction, but the relatively rigid conformation of the metal chelate imparts marked selectivities. 

A relatively hydrophobic chelating agent, namely, 4-dodecy-diethylene triamine, has been employed in the presence of Zn (II) ions to achieve the reversed-phase separations of dansyl amino acids, dipeptides, and aromatic carboxylic acids. The metal-derived selectivity results from the formation of outer sphere complexes. The formation of these complexes is rapid, contributing to the high separation efficiencies observed. 

ISEs for li+, K+, Ca " ", and Mg + have been developed on the basis of liquid membranes that contain ionophores these are hydrophobic chelating agents that contain selective binding sites for the ion of interest. While the structures of ionophores used in commercially available devices are often proprietary, examples of well-studied ISE ionophores include 14-crown-4 ether for li+ [20] and valinomycin for K" " [21]. Valinomycin is 5000 times more selective toward K+ over Na" " and 18000 times more selective toward K+ over H+. 

An ion-selective electrode in which a chelating agent is incorporated into a hydrophobic membrane. 

Upon formation of a metal chelate or complex, the next rate-limiting step in delivering iron to the cell is the diffusion of iron complexes through the. soil in response to diffusion gradients. In the vicinity of plant roots, metal chelates and complexes may also move by bulk flow in the transpiration stream as water moves from the soil into the plant. However, depending on their charge characteristics and hydrophobicity, metal chelators and complexes can become adsorbed to clay and organic matter, which may then decrease their mobility and bioavail-... 

The [Co(phen)3]3+ complex is photoactive and a powerful oxidant in its excited state. The ion has no H-bonding groups and hence is considerably more hydrophobic1279 than hexaamine relatives. These properties have proven particularly useful. Aryl and alkyl substituted [Co(phen)3]3+ complexes have received a great deal of attention due to their ability to intercalate within the helical structure of DNA through a combination of electrostatic and hydrophobic forces. The chirality of the tris-chelate complex is crucial in determining the degree of association between the complex and... 

Each step in dendrimer synthesis occurs independent of the other steps therefore, a dendrimer can take on the characteristics defined by the chemical properties of the monomers used to construct it. Dendrimers thus can have almost limitless properties depending on the methods and materials used for their synthesis. Characteristics can include hydrophilic or hydrophobic regions, the presence of functional groups or reactive groups, metal chelating properties, core/shell dissimilarity, electrical conductivity, hemispherical divergence, biospecific affinity, photoactivity, or the dendrimers can be selectively cleavable at particular points within their structure. 

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