Showing papers on "Buffer solution published in 1968"

Protein Bindings. I. Binding of 2-(4'-Hydroxyphenylazo) benzoic Acid to Bovine Serum Albumin

Abstract: Binding of anionic dye 2-(4'-hydroxyphenylazo) benzoic acid (HABA) to bovine serum albumin at pH 7.4 was studied spectrophotometrically. The relationship between albuminbound ratio of HABA and concentration of the unbound dye was expressed by a modified Langmuir-type equation involving a repulsing interaction. The binding becomes more difficult with the increasing bonds. The binding constant and the number of binding sites on albumin were evaluated in 0.05 M phosphate buffer solution and in 0.15 M tris. buffer solution at 25°and 37°.

Determination of hydrofluoric acid in inhibited red fuming nitric acid

Abstract: A simple method has been devised for directly measuring fluoride-ion concentrations in inhibited red fuming nitric acid, which is commonly used in propellents. The technique involves the use of a newly developed fluoride-sensitive electrode, and the concentrations are determined by measuring the potential developed between this electrode and a reference electrode. A special procedure, involving a buffer solution, was devised for weighing the inhibited nitric acid before neutralisation, dilution and measurement. The results are more accurate than those obtainable by the commonly used, and more complex, indirect methods. For the particular instance of inhibited red fuming nitric acid, the technique also proved superior to another proposed direct method in that it is effective with samples as small as 1 g.

Ligands containing elements of Group VIB. Part II. The silver complexes of substituted phenylselenoacetic acids

Abstract: The stability constants of the neutral and protonated silver complexes of 20 substituted phenylselenoacetic acids of general formula R·C6H4·Se·CH2·CO2H have been measured at 20° in a sodium acetate–acetic acid buffer solution of µ= 0·10M(0·20M for the protonated complexes), using a silver–silver chloride indicator electrode. For comparison the silver complex of phenoxyacetic acid has been found to have the value log K1= 0·58. Comparison of these results with those for the analogous sulphur complexes shows selenium to be decidedly more class (b) or ‘soft’ than sulphur. Trends in the stability constants of the complexes are considered in terms of the Hammett σ-functions for the substituents, and the slopes (ρ) of graphs of log K values against σ-values are used to consider the extent of dπ-bonding present in the complexes. It is concluded that dπ-bonding may be present but can only play a relatively minor role in the stability trends found.

A.c. polarographic determination of lanthanum(iii), nickel(ii), calcium(ii), and magnesium (ii) by using diethylenetriaminepentaacetic acid as a titrant.

Abstract: The a.c. polarographic determination of lanthanum(III), nickel(II), calcium (II), and magnesium(II) with diethylenetriaminepentaacetic acid was studied by using a dropping mercury electrode and a hanging mercury drop electrode as indicator electrodes. Lanthanum(III) and nickel(II) in an acetate buffer solution and calcium(II) and magnesium(II) in an ammonia buffer solution could be titrated with diethylenetriaminepentaacetic acid in the concentration range from 5×10−5 to 1×10−3 M by measuring the height of the a.c. polarographic wave of diethylenetriaminepentaacetic acid after the end point. The effect of the presence of calcium-(II) ions on the a.c. polarographic determination of lanthanum(III) in an acetate buffer solution of pH 4.0 was also examined and discussed thermodynamically.

Spectrophotometric determination of small amounts of sulfur in heavy oil.

Abstract: A simple spectrophotometric method for the determination of a small amount of sulfur in heavy oil has been proposed. An amount of heavy oil is diluted with toluene, and 10 μl of the diluted solution is transfered through a microsyringe onto a filter paper strip on a platinum wire. The paper is burned in an oxygen flask, and sulfur dioxide formed is absorbed in a definite amount of an aqueous solution of mercuric nitrate and potassium bromide. An aliquot of this solution is transfered into a brown separatory funnel, and is shaken with a buffer solution (pH 7), benzene and an ethanol solution of diphenyl-carbazone. Sulfur in heavy oil can be thus determined with satisfactory results by measuring the absorbancy of the benzene phase at 562 mμ, refereing to the calibration curve prepared beforehand.

Spectrophotometric determination of salicylamide in pharmaceutical preparations

Abstract: Salicylamide (I) reacts with dimethyl-p-phenylenediamine, and K3Fe (CN)6 in an alkaline medium (phosphate buffer : pH 8.0) to give green coloration (indophenol dye). This chromogen produced is extractable with chloroform, the extract showing an absorption maximum at 650mμ.A new spectrophotometric method, based on this color reaction, has been established to the determination of (I) in pharmaceutical preparations.Influences of 47 compounds were examined. The interferences from acetaminophene, ethoxybenzamide, salicylate, phenylephrine hydrochloride, sulpyrine, ascorbic acid, etc. are eliminated by the extraction with chloroform in an acidic medium. The recommended procedure is as follows. Sample {containing 100mg of (I)} is taken in a separatory funnel. To it are added 10ml of water and 10ml of 0.1 N HCl, and it is extracted 4 times with 30ml portions of chloroform. The extracts are combined and evaporated on a water bath. The residue is dissolved in 50ml of ethanol, and is made up exactly to 100ml with water. A 10ml aliquot is taken into another 100ml volumetric flask, and is made up to 100ml with ethanol. Ten ml of this solution is taken into another 100ml volumetric flask and prepared in the similar way.A 2 ml aliquot is transfered into a 30ml glass-stop-pered test tube. Five milliliters of buffer solution (phosphate buffer : pH 8.0), 2ml of 0.05% dimethyl-p-phenylenediamine solution and 1 ml of 1% K3Fe(CN)6 solution are added. After 5 min., the solution is shaken with 10ml of chloroform. The separated chloroform layer is dried with 2 g of Na2SO4, and is filtered. The absorbance is measured at 650mμ (ET) against chloroform. At the same time the absorbance of standard solution (ES) is determined, and the amount of (I) is calculated by ET/ES.