RU2511631C1 - Method of photometric determination of iron (ii) - Google Patents

Abstract

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.

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Description

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

A known method for the photometric determination of iron (II) using aluminone in a binary photometric system, which consists in adding a buffer solution with a certain pH value and the action of an organic aluminone reagent to the test solution (Babko AK, Pilipenko AT, Photometric analysis. General information and equipment. - M.: Chemistry, 1968. - P.283).

The disadvantage of this method is the low sensitivity.

The technical result consists in increasing the sensitivity in the photometric determination of iron (II).

The essence of the invention lies in the fact that in the method for the photometric determination of iron (II), comprising converting it into a complex compound with an organic reagent, in which a solution of iron (II) pH 3 is added 150-200 times the amount of organic reagent, which is used Congo red, 0.2-0.4 ml of a solution of a surfactant in the form of a 0.2% solution of 6-aminocaproic acid, and water up to 10 ml of volume, followed by heating in a water bath at a temperature of 80-98 ° C for 10-15 minutes and further photometric iem.

Surfactant (surfactant) is prepared in the form of a 0.2% solution of 6-aminocaproic acid:

Congo red [4,4'-bis- (1-amino-4-sulfo-2-paphthylazo) biphenyl disodium] organic reagent obtained by the reaction of diazotized benzidine with naphthionic acid [Indicators. Volume 1 / Ed. E. Bishop.- M .: Mir, 1976 .-- 496 p. - S.337]:

, относительно раствора холостого опыта. Линейность градуировочного графика соблюдается в интервале концентраций железа (II) (1,6-5,2)-10^-7 г/мл. Молярный коэффициент светопоглощения комплекса равенExample. Determination of iron (II) with Congo red in the presence of a surfactant. V ml of a 10 ^-4 M solution of iron (II) are placed in test tubes, 2 ml of a buffer solution with a pH of 3, 0.3 ml of a surfactant solution, 1 ml of a 10 ^-2 M Congo red solution, the solution volumes are adjusted to 10 ml of water, heated in a water bath for 10 minutes at a temperature of 80-98 ° C. Photometer on KFK with a wavelength of λ-400 nm and a thickness of the cell $$\ell =0.1\mathrm{from}m$$

, regarding a solution of blank experience. The linearity of the calibration graph is observed in the range of iron (II) concentrations (1.6-5.2) -10 ^-7 g / ml. The molar coefficient of light absorption of the complex is

$$$$

$$E_{MR}=\frac{0.06}{\frac{0.3\cdot {10}^{-\mathrm{four}}}{10}\cdot 0.1}=\mathrm{200,000.}$$

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

1) sharply increases the sensitivity of the determination in comparison with the known method;

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

3) the reaction of the formation of the complex compound proceeds in an aqueous medium, in connection with which there is no need for organic solvents that adversely affect the human body;

4) the resulting complex is stable;

5) good reproducibility of the analysis.

Claims (1)

A method for photometric determination of iron (II), including its conversion into a complex compound with an organic reagent, characterized in that 150-200 times the amount of organic reagent is added to a solution of iron (II) with a pH of 3, using Congo red, 0, 2-0.4 ml of a solution of a surfactant in the form of a 0.2% solution of 6-aminocaproic acid, and water up to 10 ml of volume, followed by heating in a water bath at a temperature of 80-98 ° C for 10-15 minutes and further photometric measurements.