SU592757A1 - Method of determining iron - Google Patents

Description

The invention relates to methods of chemical analysis, in particular to photo methods (metric determination; metals, and can be used to determine the iron content in solutions of metal salts, for example nickel, cobalt.

Photometric methods for the determination of iron (II) are known, for example, phenanthroline, dipyridyl. The determination of iron (II) is carried out by complexing the iron with the listed reagents or their derivatives and measuring the optical density of the resulting colored compounds 1. The methods are characterized by insufficient sensitivity.

More sensitive methods are those in which the determination of iron is carried out by the formation of colored complex compounds with more sensitive dye reagents: Mie: 4- (2-pyridylazo) resorcin, rhodamine B and C and others, or combinations of complex formation and extraction of the resulting colored compounds with various solvents. However, these methods do not allow the determination of iron (II) content without prior making (Interfering ions, which is caused either by the low selectivity of the reagents or by the color of the metals themselves (Ni, Co, Cs, Cr), and therefore, they take time-consuming

on maokirovaniya, and to achieve extraction equilibrium.

A highly sensitive method of photometric determination of iron (II) using 4 -; (2- (Pyridilazo) -resorcinol) is known, which consists in the formation in the alkaline medium of pH 9.0-10.5 colored compounds of iron (II) complexes with reagent and quaternary aiM- monopic bases extracted with chloroform 2. The method is highly sensitive: the molar repayment coefficient is 4.5 Berah law is fulfilled at the concentration of iron in the extract O-1.5 µg / ml. However, this method of determination of iron is impossible when sharing large amounts of such.-metals,; nickel, cobalt, due to the low selectivity of 4- (2-pyridylazo) -resorcinol, and time is required as pa masking the bleaching elements (heating for 30 min with a solution of complexone III in borate buffer), and to achieve extraction equilibrium in the system (the time of 1 phase contact is 10 minutes. In addition, the determination is carried out under strictly defined conditions regarding pH, complex formation time and temperature.

The closest to the invention of the technical essence and the achieved result

It has a photometric method for determining iron (II) using a redox reaction with colored camllix and forming molybdenum blue 3. However, this method does not allow to determine small amounts of iron (II) in the presence of large amounts of such 1 metal salts as cobalt , nickel and others forming colored compounds in the region of the light spectrum of the spectrum (Molybdenum blue (520 nm)), for example, for an aqueous solution of cobalt sulfate, the maximum light absorption is 510 nm. Overlapping spectra reduces Sensitivity determination of iron (II).

The aim of the invention is to increase the sensitivity, selectivity of the method for determining iron (II) and accelerating the analysis.

The goal is achieved by the fact that the process is conducted by the redox reaction of iron (II) with colored chlorine associates, antimony (V) complexes and basic Dyes, such as crystal violet (CF5B1b) in organic solvents, which allowed determination in the presence of gram solvents. quantities of nickel, cobalt and other metals.

In order to accelerate the reaction, WCE, complexing properties of complexing agents, for example ethylenediaminetetraacetate (EDTA), are used, the process is carried out at a pH of 4.6-8.4.

By using colored associates, a high sensitivity is achieved (method: the molar extinction coefficient is 5.7 times. Bera is performed at an iron concentration of 0-1.25.

KpOiMe addition, the proposed method of determination is conducted in a wide range of pH 4.60 - 8.40, and does not require the masking of the present metal ions.

To determine the iron in the solution. X salts of nvkel or 1 cobalt, a few (milliliters of acetic acetate buffer (pH about 6.0) are added to the separatory funnel, grams of nickel or cobalt salts containing iron (II) are added, for example 0.6 µg / ml, 20 ml of the benzene solution of the colored associate (| KF5B1b) I 10 mol1l, an excess amount of EDTA (0.05 mol) is introduced in a ratio of 1K to the introduced concentration of 1 metal ions, the volume of the aqueous phase is adjusted to

20 ml is immediately shaken for 1 minute, sufficient to achieve equilibrium in the system. After filtration through the filter paper, the organic phase is photometricized with O3 (K-56iM (light filter No. 8,

cuvette / 2 cm) relative to benzene.

Iron content is determined by cal. curve built. under the same conditions. The relative error of determination does not exceed 5%.

The proposed method of photometric determination of iron (II) provides, in comparison with the existing methods, the following advantages: high selectivity, as a result of using the oxidizing properties of colored associates and reducing ones, iron (II); acceleration of the analysis, which is achieved by introducing into the EDTA system, which causes a sharp increase in the reducing properties of iron (II) and increases the reaction rate. The method is simple and Zdoben in performance and in order of sensitivity is not inferior to the previously proposed.

Formula of invention

The method for the determination of iron (II) in solutions of cobalt and nickel salts, based on the redox reaction of iron with a colored associate m followed by photometry, that is, in order to increase the sensitivity, selectivity and acceleration of the analysis, iron (II) reactivity is carried out with chloro1Co dyed associates. Antimony and

basic dyes, for example, crystal violet, in the presence of sodium ethylenediamine-tetrata at pH 4.6-8.4.

Sources of information taken at the examination:

1. Marchenko 3. Photometric definition of elements. M., “Peace, 1-971.

2.J. “Anal. Chem., 44, 1091, 1972.

3.Zaki V.M., Khalil S. S. “Microchem. J.