Borate adsorption

Ghromate adsorption by iron oxides is suppressed by a large excess of carbonate or silicate species. Gompetition between silicate and borate adsorption on ferrihydrite was reported by McPhail et ak (1972). Low levels of sulphate suppress uptake of phthalic and chelidimic acids by goethite (Ali Dzombak, 1996 a). 

Diphenylcarbazide as adsorption indicator, 358 as colorimetric reagent, 687 Diphenylthiocarbazone see Dithizone Direct reading emission spectrometer 775 Dispensers (liquid) 84 Displacement titrations 278 borate ion with a strong acid, 278 carbonate ion with a strong acid, 278 choice of indicators for, 279, 280 Dissociation (ionisation) constant 23, 31 calculations involving, 34 D. of for a complex ion, (v) 602 for an indicator, (s) 718 of polyprotic acids, 33 values for acids and bases in water, (T) 832 true or thermodynamic, 23 Distribution coefficient 162, 195 and per cent extraction, 165 Distribution ratio 162 Dithiol 693, 695, 697 Dithizone 171, 178... 

Van den Berg [131] used this technique to determine nanomolar levels of nitrate in seawater. Samples of seawater from the Menai Straits were filtered and nitrite present reacted with sulfanilamide and naphthyl-amine at pH 2.5. The pH was then adjusted to 8.4 with borate buffer, the solution de-aerated, and then subjected to absorptive cathodic stripping voltammetry. The concentration of dye was linearly related to the height of the reduction peak in the range 0.3-200 nM nitrate. The optimal concentrations of sulfanilamide and naphthyl-amine were 2 mM and 0.1 mM, respectively, at pH 2.5. The standard deviation of a determination of 4 nM nitrite was 2%. The detection was 0.3 nM for an adsorption time of 60 sec. The sensitivity of the method in seawater was the same as in fresh water. 

The four layer model (Bowden et ah, 1980 Bousse and Meindle, 1986) also locates different adsorbing ions in different planes. It has been used to model adsorption of phosphate, citrate and selenite (Bowden et ah, 1980) and borate (Bloesch et al., 1987) on goethite and competitive adsorption of Ca and Cd on ferrihydrite (Cowan et al., 1991). 

CZE-ELD, with a Au microelectrode at —0.6 V vs. SSCE and a Pt wire as auxiliary electrode, using sodium borate buffer and dodecyltrimethylanunonium bromide for dynamic coating of the capillary internal surface, can be applied for separation and determination of ultra-trace amounts of many oxidizing substances. Thus, the concentration of peroxodisulfate (S208 ) and peroxomonosulfate (S05 ) ions in pickling baths can be monitored by this method. The faster emergence of the heavier peroxodisulfate ion is attributed to different adsorption of the two analyte ions by the capillary coating . ... 

CZE separation of sugar isomers in a PMMA chip was enhanced by using a phosphate-based, rather than a borate-based buffer. The resolution enhancement may be caused by a rapid carbohydrate-phosphate complex formation process, as compared to a slow carbohydrate-borate complex formation process. To reduce adsorption of the labeled sugar isomers to the PMMA surface, 0.5% methylcel-lulose (viscosity of 2% aqueous solution at 20°C, 4000 cP) was added to the run buffer [560],... 

Efficient borate ion adsorption on saccharide-functionalized MCM-41 materials.135... 

Figure 7-11. Purification ot staphylococcal nuclease by affinity adsorption chromatography on a nuclease-specific agarose column (0.8 x 5 cm). The column was equilibrated with 50mM borate buffer, pH 8.0, containing lOmAf CaClj. Approximately 50 mg of partially purified material containing about 8 mg nuclease was applied in 3.2 ml of the same buffer. After 50 ml of buffer had passed through the column, O.IM acetic acid was added to elute the enzyme. 8.2 mg nuclease and all the original activity was recovered. The flow rate was about 70 ml/hour. [From P. Cuatrecasas, M. Wilchek, and C. B. Anfinsen, Proc. Natl. Acad. Sci. US, 61 636 (1968).]...

In a detailed study of the zone-electrophoretic behavior of amylosac-charides on paper using a borate buffer (pH 10), Foster, Newton-Heam and Stacey showed that, whilst the amylopectin (blue value, 0.18) underwent appreciable migration toward the anode with but little adsorption of the polysaccharide in the path of movement, the pattern of movement of amylose (blue value, 1.35) depended on the amoimt of the polysaccharide put on the paper. Thus, a sufficiently small amount was adsorbed at the origin, but, with larger amounts, migration toward the anode occurred. A mixture of amylose and amylopectin was easily resolved, whereas, with... 

A micellar electrokinetic chromatographic method allows the separation of optically isomeric diltiazem hydrochloride using bile salts as chiral surfactants. The chiral separation of diltiazem hydrochloride from several analogs is achieved at ambient temperature using 0.05M sodium taurodeoxycholate in a 0.02M aqueous phosphate-borate buffer solution of pH 7.0. Separation is performed using a fused-silica capillary tube (650 mm x 50 mm I.D.) and a voltage up to +25 kV. Detection is achieved on-column using UV adsorption at 210 nm (31). 

The adsorption of diethyl ether or tetrahydrofurane decreases for shortly heated glasses in comparison to non-heated ones and increases for longer heated CPG (e.g. see Fig. 14). This can be attributed to the described processes occuring on the CPG surface during its thermal treatment (dehydroxylation of Si-OH groups, creation of B-OH groups, increase of surface boron and sodium concentration, borate cluster formation). Each of these processes differently influences the adsorption properties of CPG. The adsorption properties of silica gel treated thermally in the same conditions (above 400°C) significantly decrease as the result of surface dehydroxylation. 

Adsorption of borate on two types of commercial activated carbons (from deionized water and its mixtures with natural waters) resulted in uptake maximum at pH about 8 [9], Nearly linear decrease in uptake of chromate by a commercial sample from 50% to 10% over the pH range 2-10 (no supporting electrolyte added) was reported [7], In contrast Dobrowolski [5] reported uptake curves of chromate with a maximum at pH about 3 for three de-ashed and modified activated carbons. These two types of adsorption behavior are common in specific adsorption of weak acids on inorganic materials (cf Table 4,2). Activated carbon was found to be an efficient adsorbent of iodides from synthetic clay water at pH as high as 8.5 [10],... 

Borate uptake peaks at pH 7 5 Langmuir type adsorption isotherm of silicate fpH not specified). 

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