Organic anion concentrations

Table I. Observed Organic Anion Concentrations in Precipitation...

The distribution of highly extractable solutes such as and Pu between the aqueous and organic phases is strongly dependent upon the nitrate anion concentration in the aqueous phase. This salting effect permits extraction or reextraction (stripping) of the solute by controlling the nitric acid concentration in the aqueous phase. The distribution coefficient, D, of the solute is expressed as... 

In the mid-1960s a series of papers by Makosza and Serafinowa (1965, 1966) appeared under the common title Reactions of Organic Anions , in which the catalytic alkylation of phenylacetonitrile and its derivatives carried out in the presence of concentrated NaOH and the catalyst triethylbenzylammonium chloride (TEBA) was described. This was the beginning of phase-transfer catalysis (PTC), and since then thousands of papers haven been published on the subject. 

Precipitation usually occurs when the concentration of a compound in solution exceeds the equilibrium solubility, although slow reaction kinetics may result in supersaturated solutions. For organic wastes in the deep-well environment, precipitation is not generally a significant partitioning process in certain circumstances, however, it may need to be considered. For example, pentach-lorophenol precipitates out of solution when the solution has a pH of <5,35,36 and polychlorophenols form insoluble precipitates in water high in Mg2+ and Ca2+ ions.37 Also, organic anions react with such elements as Ca2+, Fe2+, and Al3+ to form slowly soluble to nearly insoluble compounds. 

There have been several studies that underscore the importance of unbound concentration in cell-based studies of receptor function. In a model study of the effect of plasma protein binding on the renal transport of organic anions using the expression of various organic anion transporters (OATPs) in Xenopus oocytes, the transport of ochratoxin A, methotrexate, and estrone sulfate was found to be strongly inhibited by the addition of human serum albumin to the culture medium [16]. Similarly, the addition of oq-acid glycoprotein was found to reverse the blockade of sodium-ion current by cocaine in a preparation of cardiac myocytes [17]. 

One of the earliest reports on the use of dendrimers in catalysis is the unimolecu-lar decarboxylation of 6-nitro-benzisoxazole-3-carboxylate in the presence of a dendrimer comprising ether dendrons which are functionalized at their periphery with tetra-alkylammonium cations (e.g. 20, Scheme 21) [30]. In aqueous media, the quaternary ammonium groupings promote the reactivity of organic anions which presumably bind in high concentration to the polycationic periphery of the dendrimer. The latter species enhances the rate of the bimolecular hydrolysis of p-nitrophenyl diphenyl phosphate catalyzed by o-iodosobenzoate ion. 

The maximum retention factor (kQ) is related to the log P value and k and k are the retention factors of the cationic and anionic forms, respectively. The pKa values are known, and the retention factor in a given eluent can therefore be predicted in reversed-phase liquid chromatography using an alkyl-bonded silica gel or polystyrene gel column. The separation conditions can be adjusted according to their logP and pKa values by the selection of a suitable organic modifier concentration and the pH of the eluent.3,4... 

DDTC is an organic anion with comparatively big e and variable shape. After adsorption and bonding with mineral electrode, it can be effectively close to the electrode surface so that / becomes small and e becomes big. So its capacitance increases with the DDTC concentration added, amount of adsorption increasing. 

Niemi, M., Schaeffeler, E., Lang, T., et al. (2004) High plasma pravastatin concentrations are associated with single nucleotide polymorphisms and haplotypes of organic anion transporting polypeptide-C (OATP-C, SLCOIBI). Pharmacogenetics. 14, 429-440. 

Solvent extraction results are presented typically in the form of diagrams. This is schematically illustrated in Fig. 4. la for three hypothetical substances. A, B, and C. The distribution ratio is investigated as a function of the concentration of some reactant Z, which may be pH, concentration of extractant in the organic phase (e.g., an organic acid HA, [HA]o,j), the extractant anion concentration in the aqueous phase (e.g., [CT]), salt concentration in the aqueous phase, etc. The... 

The membrane potential of resting cells (resting potential see p. 350) is -0.05 to -0.09 V—i. e., there is an excess negative charge on the inner side of the plasma membrane. The main contributors to the resting potential are the two cations Na"" and K", as well as Cl and organic anions (1). Data on the concentrations of these ions outside and inside animal cells, and permeability coef -cients, are shown in the table (2). 

Any process in which inorganic cations and inorganic/ organic anions combine at concentrations exceeding their respective solubility product(s) to create crystalline or paracrystalhne structures. 

The kidneys are susceptible to toxicity from xenobiotics (Fig. 7.1) because they too have a high blood flow. Cells of the tubular nephron face double-sided exposure, to agents in the blood on the basolateral side and in the Altered urine on the luminal side. Proximal tubule cells are generally the site of nephrotoxicity, since these cells have an abundance of cytochrome P450 and can transport organic anions and cations from the blood into the cells, thereby concentrating these chemicals manyfold. 

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