Buffer complexes

Al, Fc, Mn Bondasphere 2 3 Injected as 8-ODS acetonitrile 20mm quinolinol acetate buffer complexes Electrochemical spectrophotometric at 390nm PPb [282]... 

Buffering complex for use in detergent formulations - light to medium duty. 

Verify the permeabilization of the cells after SLO treatment. Make sure that none of your buffers complexes Zn. ... 

Total Hg determined by CVAAS after digestion with HNO, for 4 h at 80°C, and reduction with SnCU- For MeHg, 1000 mg was pre-treated by addition of HCI and toluene, back-extraction with thiosulphate, addition of acetate buffer, complexation and on-line oxidation (after HPLC), and reduction with SnCI, separation was by high performance liquid chromatography (HPLC), followed by CVAFS detection (Lab.OS)... 

Phytate. Phytic acid is the phosphoric acid ester of inositol, hexa-hydroxycyclohexane. Every phosphoric acid group contains 2 acidic hydrogens, so that the compound is expected to buffer. Complex formation with a number of cations is known (24) but an aluminum complex has not been reported. 

Anserine, /S-alanyl-L-l-methyUiistidine, a naturally occurring analogue of carno-sine exhibiting numerous biological activities, e.g., pH buffering, complexation of zinc, cobalt and ferrous ions, scavenging of free radical species [E. C. Bate-Smith,/. Phys. 1938, 92,336 E. J. Baran, Biochemistry (Moscow) 2000, 65, 789 A. Guiotto et al., Curr. Medicinal Chem. 2005, 12, 2293]. 

The oligonucleotide-free parent solution of metal salt in buffer (BUFF) will contain aquated metal ions and metal buffer complexes M (BUFF) with the total metal ion concentration [M]tot = [M(aq)] + [M(BUFF)] (Scheme 2,... 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

In Section 8, the material on solubility constants has been doubled to 550 entries. Sections on proton transfer reactions, including some at various temperatures, formation constants of metal complexes with organic and inorganic ligands, buffer solutions of all types, reference electrodes, indicators, and electrode potentials are retained with some revisions. The material on conductances has been revised and expanded, particularly in the table on limiting equivalent ionic conductances. 

Although this treatment of buffers was based on acid-base chemistry, the idea of a buffer is general and can be extended to equilibria involving complexation or redox reactions. For example, the Nernst equation for a solution containing Fe + and Fe + is similar in form to the Henderson-Hasselbalch equation. 

The pH of an NH3/NH4CI buffer (piQ = 9.24) is sufficient to ensure the precipitation of most metals as the hydroxide. The alkaline earths and alkaline metals, however, will not precipitate at this pH. In addition, metal ions that form soluble complexes with NH3, such as Cu +, Zn +, NP+, and Co +, also will not precipitate under these conditions. 

EDTA Must Compete with Other Ligands To maintain a constant pH, we must add a buffering agent. If one of the buffer s components forms a metal-ligand complex with Cd +, then EDTA must compete with the ligand for Cd +. For example, an NH4+/NH3 buffer includes the ligand NH3, which forms several stable Cd +-NH3 complexes. EDTA forms a stronger complex with Cd + and will displace NH3. The presence of NH3, however, decreases the stability of the Cd +-EDTA complex. 

Description of the Method. The operational definition of water hardness is the total concentration of cations in a sample capable of forming insoluble complexes with soap. Although most divalent and trivalent metal ions contribute to hardness, the most important are Ca + and Mg +. Hardness is determined by titrating with EDTA at a buffered pH of 10. Eriochrome Black T or calmagite is used as a visual indicator. Hardness is reported in parts per million CaCOs. 

Why is a small amount of Mg +-EDTA complex added to the buffer ... 

Solutions containing both Le + and AF+ can be selectively analyzed for Le + by buffering to a pH of 2 and titrating with EDTA. The pH of the solution is then raised to 5 and an excess of EDTA added, resulting in the formation of the AF+-EDTA complex. The excess EDTA is back titrated using a standard solution of Le +, providing an indirect analysis for AF+. 

There are several forms of electrophoresis. In slab gel electrophoresis the conducting buffer is retained within a porous gel of agarose or polyacrylamide. Slabs are formed by pouring the gel between two glass plates separated by spacers. Typical thicknesses are 0.25-1 mm. Gel electrophoresis is an important technique in biochemistry, in which it is frequently used for DNA sequencing. Although it is a powerful tool for the qualitative analysis of complex mixtures, it is less useful for quantitative work. 

Procedure. A vitamin B complex tablet Is crushed and placed In a beaker with 20.00 mL of a 50% v/v methanol solution that Is 20 mM In sodium tetraborate and contains 100.0 ppm of o-ethoxybenzamIde. After mixing for 2 min to ensure that the B vitamins are dissolved, a 5.00-mL portion Is passed through a 0.45- xm filter to remove Insoluble binders. An approximately 4-nL sample Is loaded Into a 50- xm Internal diameter capillary column. For CZE the capillary column contains a 20 mM pH 9 sodium tetraborate/sodlum dIhydrogen phosphate buffer. For MEKC the buffer Is also 150 mM In sodium dodecylsulfate. A 40-kV/m electric field Is used to effect both the CZE and MEKC separations. 

Steeping. Sheet, roU, or suitably milled flock pulp is metered into a pulper along with vigorously stirred 18% sodium hydroxide solution at 50°C. The resulting slurry, containing about 5% finely dispersed pulp, passes to a buffer tank from which it is metered to a slurry press that sieves out the swollen fiber and returns the pressings soda for concentration correction and reuse. The cellulose reacts with the soda as a complex alcohol to form the sodium salt or alk-ceU. 

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