RU2164214C1 - Method of determining ultra amounts of iodine - Google Patents

Abstract

FIELD: analytic chemistry, more particularly analyses of biological liquids and environment objects. SUBSTANCE: 10 ml of urine containing iodide ions are diluted with biidistilled water (1:3), are passed through sorbent-filled column 1 drop of 1% orange methyl solution, 1 or 2 drops of sulfuric acid (1: 10) and 3 to 5 drops of bromine water are added to 10 ml of filtrate. Mixture is heated, boiled for 5 minutes, stirred and cooled, 0.5 ml of 5% Kl solution are 3 drops of 0.5% starch solution are added to mixture and titrated with 0.0001 M sodium thiosulfate solution till discoloration occurs. Amount of iodine in sample is calculated according to formula X= 84.6·V wherein 84.6 is constant, V is amount (ml) of 0.0001 M solution of sodium thiosulfate solution used for titration purposes. Amount of iodine found is 10.14 mcg per 100 ml. Error of determination is 1.4%. Invention makes it possible to determine ultramicro amountes of iodine with insignificant error. EFFECT: more efficient determination method. 1 ex

Description

 The invention relates to analytical chemistry, namely to titrimetric methods of analysis, and can be used to determine the ultramicroquantities of iodine in biological fluids, such as blood, urine, saliva and in environmental objects, water, soil, etc.

A known kinetic method for determining the ultramicroquantities of iodide ions in biological material and environmental objects (A.S. N 916381, MKI ³ C 01 B 7/13; G 01 N 31/10, publ. 30.03.82, bull. N 12 ) The ultramicroquantities of iodides are determined by their catalytic effect on the oxidation reaction of malachite green chloramine B in the presence of acetone at PH 5.78 + 0.3, with the induction period of the oxidation reaction determined by the change in the redox potential of the system.

 Disadvantages: a large error in the method for determining iodide ion.

 The invention is aimed at solving the problem: reducing the error in determining the ultramicroquantities of iodine in biological fluids and environmental objects.

This problem is achieved by passing the diluted sample through a column filled with a sorbent, adding 1-2 drops of sulfuric acid 1:10 and 3-5 drops of bromine water to the filtrate. To a boiled, mixed and cooled mixture add 0.5 ml of 5% potassium iodide solution and 3 drops of 0.5% starch; the mixture is titrated with a 0.0001 M sodium thiosulfate solution. The amount of iodine is calculated by the formula
X = 84.6 V
where 84.6 is a constant;
V is the number of ml of 0.0001 M sodium thiosulfate solution, which went to the titration.

 Distinctive features of the method are the use of a column with a sorbent to separate iodide ion from a bioliquid or other medium, the transfer of iodide ion first into iodate by adding sulfuric acid and bromine water, and then adding potassium iodide to elemental iodine, which is determined by titration of sodium with thiosulfate in the presence of starch.

 The method is as follows: the analyzed sample, for example urine, is diluted with water 1: 3, passed through a column with a sorbent and 1 drop of 1% methyl orange solution, 1-2 drops of sulfuric acid 1:10 are added to 10 ml of the filtrate. During the reaction, a red coloration should result. Then 3-5 drops of bromine water are added and a yellow color is obtained. The solution is heated, boiled for 5 minutes, stirred and cooled rapidly. Then add 0.5 ml of a 5% potassium iodide solution, 3 drops of a 0.5% starch solution and titrate with a 0.0001 M sodium thiosulfate solution until discoloration.

The amount of iodine in the sample is calculated by the formula
X = 84.6 V
where 84.6 is a constant;
V is the number of ml of 0.0001 M sodium thiosulfate solution, which went to the titration.

 Example 1 (urine): 10 ml of urine containing 10 μg of iodide ion in 100 ml, diluted with 1: 3 bidistilled water, passed through a sorbent column and 1 drop of 1% methyl orange solution, 1-2 drops added to 10 ml of the filtrate sulfuric acid 1: 10, 3-5 drops of bromine water, heated, boiled for 5 minutes, stirred and quickly cooled. Then add 0.5 ml of a 5% potassium iodide solution, 3 drops of a 0.5% potassium iodide solution, 3 drops of a 0.5% starch solution and titrate with a 0.0001 M sodium thiosulfate solution until discoloration. The found amount of iodide in this case is 9.65 μg /%. The error of determination is 3.5%.

 Example 2 (water): 10 ml of the analyzed sample containing 5 μg of iodide ion in 100 ml, diluted with 1: 3 bidistilled water, passed through a sorbent column and 1 drop of 0.1% methyl orange solution, 1 is added to 10 ml of the filtrate -2 drops of sulfuric acid 1:10, 3-5 drops of bromine water, heated, boiled for 5 minutes, stirred and quickly cooled. Then add 0.5 ml of 5% potassium iodide solution, 3 drops of 0.5% starch and titrate with a 0.0001 M sodium thiosulfate solution until discoloration. The found amount of iodide in this case is 10.14 μg /%. The error of determination is 1.4%.

 The proposed method is superior in error to the known methods of determination and allows to determine the ultramicroquantities of iodine (0.003 μg / ml) in biological fluids and other environmental objects.

Claims (1)

A method for determining ultramicroquantities of iodine, characterized in that the diluted sample is 1: 3 in water, passed through a sorbent column, and 1 drop of 1% methyl orange solution, 1-2 drops of sulfuric acid 1:10, 3-5 drops of bromic acid are added to 10 ml of the filtrate water, the mixture is heated, boiled for 5 minutes, stirred, cooled, 0.5 ml of a 5% potassium iodide solution, 3 drops of a 0.5% starch solution are added, titrated with a 0.0001 M sodium thiosulfate solution until discolored, and the amount of iodine in the sample is calculated by the formula
X = 84.6 x V,
where 84.6 is a constant;
V is the number of ml of 0.0001 M sodium thiosulfate solution, which went to the titration.