RU1778688C - Method for determining tellurium - Google Patents

Abstract

Usage: determination of cadmium in the wastewater of galvanic industries .. used in enterprises of instrument-making and machine-building industries. SUMMARY OF THE INVENTION In the determination of cadmium, the sodium salt of phenylthiosemicarbazone 1,2-naphthoquinone-4-sulfonic acid in the presence of a surface-active substance monoalkylphenyl ether polyethylene glycol (OP-7) is used and the determination is carried out at pH 5-7. 2 tab.

Description

The alleged invention relates to analytical chemistry, in particular to methods for the determination of cadmium and can be used in the chemical control of wastewater in the metallurgical, instrument-making, and engineering industries.

The closest in technical essence and the achieved result to the present invention is a method for the determination of cadmium using thiosemicarbazone 1,2-naphthoquinone-4-sulfonic acid (V. Vajgandand

M. Jaredlc / Chem. Anal. / Warsaw /, 1975, 20, 1125; R.B.Singh. B. S. Garg and R. P. Singh. Analytical application of thicsemlcarbazones and semicarbazones (Talanta 1978, 619-632). The method consists in adding a 1,2-naphthoquinone sulfonic acid thiosemicarbonate solution to a cadmium solution at pH 6-7 to form a colored cadmium thiosemicarbazonate complex and photometric complex at a wavelength of 520 nm. The detection limit is 0.1 µg / ml.

The method has a low sensitivity, a narrow range of pH formation.

The purpose of the proposed method is to increase the sensitivity of determination.

This goal is achieved by treating the analyzed solution with an organic reagent - sodium salt of phenylthiosemicarbazone 1,2-naphthoquinone-4-sulfonic acid (FTSK) in the presence of a non-ionic surfactant - monoalkylphenyl ether polyethylene glycol (OP-7) at pH 5-7 and photometers nii the resulting mixture.

Thus, the distinguishing features of the proposed method are the use of 1,2-naphthoquinone-4-sulfonic acid as an organic reagent, phenylthiosemicarbazone in the presence of OP-7 and determination at pH 5-7.

In the literature, a technical solution with a similar set of features is unknown, therefore, the present invention meets the criteria of novelty and significant differences.

Under laboratory conditions, the determination of cadmium is carried out as follows. AT

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an aliquot of the analyzed solution containing 0.1-0.50 μg / ml (0.25-12.5 μg in 25 ml) of cadmium is added to a 25 ml volumetric flask, an aqueous solution of OP-7, a buffer solution (pH 5) are added. -7), masking agents, a solution of FTSK in dimethylformamide, adjusted to the mark with distilled water and photometric. The range of detectable concentrations for cadmium is 0.01-0.50 µg / ml. The detection limit is mol / L. The molar absorption coefficient of cadmium phenylthiosemicarbazonate is 6.5-104.

The proposed method allows to increase the detection sensitivity by 10 times compared with the prototype.

Example 1. The definition of cadmium by the method of the prototype.

5 ml of acetate buffer solution (pH 6–7), 2.5 m of a 0.002 mol / l dimethylformamide solution of 1,2-naphthoquinone-4-sulfonic acid are poured into 10 ml of the analyzed solution and adjusted to the mark with distilled water (V 25 ml). The solution was mixed well and the absorbance was measured in a glass cuvette with I 1 cm relative to the blank solution. The wavelength is 520 nm. The range of detectable cadmium concentrations is 0.1-1.0 μg / ml.

As can be seen from Example 1, the method for determining cadmium using thiosemicarbazone 1,2-naphthoquinone-4-sulfonic acid is simple, expressed, but it has a low sensitivity.

Example 2. An aliquot of the test solution containing 0.25 μg cadmium was taken into a 25 ml volumetric flask, 5 ml of buffer solution (triethanolamine + hydrochloric acid), pH 6.5 ml of a 10% aqueous solution of sodium tartrate was added , 3 ml of a 0.01 mol / L aqueous solution of OP-7.3 ml of a 15% aqueous solution of thiourea, mix well, then 3.0 ml of a 0.002 mol / L dimethylformamide solution of FTSK is added, adjusted to

Label with distilled water and mix. The optical density of the colored solution was measured on SF-16 at a wavelength of 570 nm relative to a blank solution containing all reagents except cadmium. The thickness of the cuvette is 5 cm. Detection 0.25 µg cadmium, 0% determination error.

As can be seen from Example 2, the sensitivity of the determination of cadmium using FTSK and OP-7 is 0.01 µg / ml.

The procedure for the remaining experiments is similar to that described in Example 2. The results of the determination of cadmium at various pH values are given in Table. 1. As can be seen from the results of table. 1, the optimum pH range for determining cadmium is 5-7. At pH less than 5 and more than 7 results are obtained with an error

definitions of 7% or more.

By the proposed method, tap water with various cadmium additives was analyzed. The results of the determination of cadmium in tap water

are given in table. 2.

Thus, the proposed method for the determination of cadmium can increase the detection sensitivity by 10 times compared with the prototype (detection limit is 0.01 µg / ml).

Claims (1)

SUMMARY OF THE INVENTION A method for determining cadmium, comprising adding a buffer solution to the sample to be analyzed, followed by adding a dimethylformamide solution of thiosemicarbazone derivative naphthoquinone sulfonic acid, and photosensing, wherein, in order to increase the detection sensitivity, masking agents and an aqueous solution of polyethylene glycol monoalkylphenyl ether, as a thiosemicarbazone derivative, are added to the analyzed sample after adding a buffer solution naphthoquinosulfonic acids use the sodium salt of phenylthiosemicarbazone 1,2-naphthoquine o n-4-sulfo acid, and determination is carried out at pH 5-7. Table 1 The results of the determination of camdy using phenylthiosemicarbazone 1,2-naphthoquinone-4-sulfonic acid in tap water (p 3, P 0.95) table 2