Silica monomeric, determination using

The stationary phases play an important part in Liquid Chromatography using micellar mobile phases. They interact with both the surfactant and with solutes. To study the interactions with surfactants, adsorption isotherms were determined with two ionic surfactants on five stationary phases an unbonded silica and four monomeric bonded ones. It seems that the surfactant adsorption closely approaches the bonded monolayer (4.5 pmol/m2) whatever the bonded stationary phase-polarity or that of the surfactant. The interaction of the stationary phase and solutes of various polarity has been studied by using the K values of the Armstrong model. The KgW value is the partition coefficient of a solute between the... 

Soil microorganisms. Many reports have documented the ability of certain soil microorgEmisms (especially bacteria such as Bacillus siliceous, which is used as a fertilizer in some parts of the Soviet Union (Cooper, 1959)) to depolymerize silica and convert it to the soluble monomeric form (see e.g., Lauwers and Heinen, 1974, and references therein) thus, the presence or absence of these oi anisms can be expected to play an important role in determining the concentration of dissolved silica in soil solutions. 

Collins et al. (1999a) found that Hg2+ sorbed to goethite as an iimer-sphere bidentate complex. Cheah et al. (1998) found that Cu " " sorbed to amorphous silica and Y-AI2O3 as monomeric and monodentate iimer-sphere surface complexes. However, bidentate complexes may also form on Y-AI2O3. Using polarized EXAFS, Dahn et al. (2003) determined that Ni " " sorbed to montmorillonite edge sites as an inner-sphere mononuclear surface complex. Inner-sphere surface complexes were observed with XAS for Cr " " adsorption on manganese (Manceau and Charlet, 1992) and iron oxides (Charlet and Manceau, 1992). 

MPc modified CPFs have been employed by several researchers for the analysis of thiols. Carbon paste electrodes incorporating OMo (OH)Pc catalyzed the oxidation of cysteine with a considerable reduction in overpotential Table 7.2. The oxidation of cysteine was mediated by Mo Pc species. CoPc modified CPMF was used as a sensor for analysis of cysteine and glutathionine in urine using electrophoresis " , with detection limits of 3.1 x 10 and 3.0x10 M, respectively. CoPc modified CPE was employed for the potentiometric oxidation of 2-mercaptobenzimidazole and 2-mercaptobenzothiazole . Low peak potentials of 0.45 V for the former and 0.27 V for the latter were obtained . A detection limit of 5 x 10 M was obtained. CPFs modified with CoPc showed catalytic activity for the determination of thiocarbonyl compounds (thiourea, thioac-etamide, thiobenzamide, and dithiooxamide) " and the oxidation of thioglyconic acid " . The latter occurred via a two step process, which leads to the formation of the dimer of the thiol " . A carbon paste electrode constructed from NiTSPc immobilized on silica gel modified with 1102 catalyzed the oxidation of cysteine " . The immobilization caused the increase in the monomeric form of the catalysts. 

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