Method of photometric determination of iron (ii)

FIELD: chemistry.

SUBSTANCE: invention relates to field of analytical chemistry, namely to photocolorimetric method of analysis, and can be used for determination of iron (II) content in extract of spruce needles, containing iron (II) in very low concentration. Method includes its transfer into complex compound with organic reagent, with addition of 150-200-fold amount of organic reagent to solution of iron (II) with pH 3, as reagent used is Congo red, 0.2-0.4 ml solution of surface-active substance in form of 0.2% solution of 6-aminocapronic acid, and water to 10 ml with further heating on water bath at temperature 80-98°C for 10-15 min.

EFFECT: increased analysis sensitivity.

1 ex

 

The invention relates to the field of analytical chemistry, namely, the photometric method of analysis, and can be used for the determination of iron (II) in solutions of pure salts containing iron (II) in very low concentration.

The known method photometric determination of iron (II) using aluminon in binary photometric system, which consists in adding to the analyzed solution buffer solution with a specific pH and organic reagent aluminon (Babko, A., Pilipenko A.T. Photometric analysis. General information and equipment. - M.: Chemistry, 1968. - S).

The disadvantage of this method is its low sensitivity.

The technical result is to increase the sensitivity in the photometric determination of iron (II).

The invention consists in that in the method photometric determination of iron (II), including converting it into a complex compound with an organic reagent, which to a solution of iron (II) pH 3 add 150-200-fold amount of organic reagent, which is used as Congo red, 0.2-0.4 ml of a solution of surfactant in a 0.2%solution of 6-aminocaproic acid, and water to 10 ml volume followed by heating on a water bath at a temperature of about 80 to 98°C for 10-15 mi and further photometry.

Surface-active substance (surfactant) prepared in a 0.2%solution of 6-aminocaproic acid:

Congo red [disodium salt of 4,4'-bis-(1-amino-4-sulfo-2-partiesa)biphenyl] organic reagent, obtained by the interaction of diazotized benzidine nationway acid [Indicators. Volume 1 / edited by E. Bishop.- M.: Mir, 1976. - 496 S. - S]:

Example. Determination of Fe (II) with Congo red in the presence of surfactants. In test tubes placed in V ml of 10-4M solution of iron (II), 2 ml of buffer solution with a pH equal to 3, 0.3 ml of the surfactant solution, 1 ml of 10-2M solution of Congo red, bring the volume of solution to 10 ml of water, heated on a water bath for 10 minutes at a temperature of about 80 to 98°C. Photometrate on CPK with wavelength λ is 400 nm and the thickness of the celll=0,1with amregarding the solution of the blank experience. The linearity of the calibration curve is observed in the concentration range of iron (II) (1,6-5,2)-10-7g/ml Molar absorption coefficient of the complex is equal to

EMR=0,060,310 -4100,1=200000.

The advantages of the proposed method for the photometric determination of iron (II) with Congo red in the presence of surfactants the following:

1) dramatically increases the detection sensitivity in comparison with the known method;

2) a complex of a metal ion with Congo red does not precipitate;

3) the reaction of formation of complex compound is in an aqueous environment, and therefore there is no need for organic solvents, adversely affecting the human body;

4) formed complex sustainable;

5) good reproducibility of the analysis.

The way photometric determination of iron (II), including converting it into a complex compound with an organic reagent, characterized in that the solution of iron (II) with pH 3 add 150-200-fold amount of organic reagent, which is used as Congo red, 0.2-0.4 ml of a solution of surfactant in a 0.2%solution of 6-aminocaproic acid, and water to 10 ml volume followed by heating on a water bath at a temperature of about 80 to 98°C for 10-15 min and further photometry.



 

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