SU1728741A1 - Determination of silver by extraction-photometric method - Google Patents

Abstract

This invention relates to analytical chemistry. The purpose of the invention is to increase the sensitivity while simplifying the method by reducing the requirements for the pH value of the extractable solution. To this end, toluene is used to extract the ionic associate of silver with iodide ions and a cyanine dye — 1,1-TeTpaMef and ilenbisindocarbocyanine (TBIC). The concentration of iodide ions and the dye TBIK is 0.08-0.16 and (5-6). M, respectively. Extraction of an associate is carried out from a solution with a pH of 1-11. The molar absorption coefficient of the colored extracts at 566 nm is 2.42 105. The law of Faith is observed in the range of silver concentrations of 0.005-2.5 µg / ml. The method is used to determine silver in films of semiconductor compounds. 6 tab. to C

Description

The invention relates to analytical chemistry, specifically to methods for the extraction-photometric determination of silver, and can be used in the analysis of various silver-containing objects, including semiconductor films.

A known method for the extraction-photometric determination of silver involves the extraction of silver ionic associate (IA) with cyanide ions and the main dye, methylene blue. Ia silver

extracted with dichloroethane, when the acidity of the medium pH 7-8 1.

Potassium cyanide used is a highly toxic substance. The molar absorption coefficient is relatively low — 9.95 U4 at 657 nm.

A known method for the extraction-photometric determination of silver, including its conversion into an ionic associate with iodide ions and brilliant green, and the extraction of AI with an organic solvent. Optimum acidity is 1H. sulfuric acid, and the sensitivity

00

Vj

It is ideal for extracting silver with a mixture of (10: 1) benzene and acetophenone. The value of the molar absorption coefficient in this case is 6.9-10 at 642 nm 2.

The closest to the proposed method is the extraction-photometric determination of silver, including its conversion into an ionic associate with bromide ions and the main dyes of the trifenylmethane series: malachite green, brilliant green, methyl violet and ethyl violet. The most effective reagent is ethyl violet. When toluene is used as an extractant, the silver IA extraction region reaches a maximum value at pH 2. The optimum concentration of bromide ions in the solution is 0.2-0.3 M. Beer's law is observed in the intergrated silver concentration of 0.1-1.0 µg / ml. Silver, strontium, zinc, aluminum, bismuth, chromium (til), manganese (I) iron, cobalt, nickel sulfates, nitrates, chlorides do not interfere with the determination of silver.

The known method has the following disadvantages. The sensitivity of the determination is relatively low, the molar absorption coefficient at 615 nm is 10.33-44, the silver AA is extracted at a narrow pH value (2), which negatively affects the reproducibility of the results.

The aim of the invention is to increase the sensitivity while simplifying the method by reducing the requirements for the pH value of the extractable solution.

To do this, silver is converted into an ionic associate with a halide ion and the main dye, extraction of the associate with toluene and subsequent photometry of the extract, 1,1-tetramethylene bis-indocarbo-cyanine is used as a dye , as the halide - iodide ions in a concentration of 0.08-0.16 M, and the extraction of the ionic associate is carried out at pH 1-11.

The edge of a 1,1-tetra and emtil enbisin docarbocmanin (TBIC) formula is

No

Gt-It

N} Sy.

SA 4lHiH-CH

-ed,

Dye TBIK as a reagent in analytical chemistry is proposed for the first time.

0 5 0

50

five

0 5

0

five

The synthesis and properties of the dye are described in [4].

The maximum detection sensitivity of silver is achieved under the following conditions. The total acidity of the aqueous solution is pH 1-11, the concentration of iodide ions and dye TBIK is 0.08-0.16 and (5-6) M, respectively. Under optimal conditions for the determination of silver, the molar absorption coefficient of the poi extraction with toluene is 2, at 566 nm (Yash). The lower limit of silver detection is 4 µg / ml.

When using other extractants (benzene, xylene, ketones, butyl acetate, amyl acetate, etc.), as well as their mixtures, the sensitivity of the determination of silver decreases.

A comparative sensitivity estimate for the known and proposed methods is given in Table. one.

The equilibrium of the extraction of silver IA is established in 1-1.5 minutes. The color of the extracts is stable for 1-2 hours. The light absorption of the colored extracts follows Beer's law in the range of detectable silver concentrations of 0.005-2.5 µg / ml.

Alkali, alkaline earth metals, aluminum, gallium, zinc, bismuth, manganese, iron, cobalt, nickel, sulfates, chlorides, bromides, nitrates and phosphates do not interfere with the determination of silver by the proposed method.

In tab. 2-4 are examples and experimental data proving the importance of optimal acidity, dye and iodide ion concentrations for maximum sensitivity,

Example 1. In graded test tubes with ground stoppers, 10.79 µg of silver (0.2 ml of M solution of silver nitrate), 0.5 ml of 1 M solution of potassium iodide, 0.5 ml of 0.05 M solution of sulfuric acid, 0, are injected. 5 ml of M solution of dye TBIK and distilled water to a total volume of an aqueous solution of 5 ml. The pH of the resulting solution is 2. The mixture is extracted with 5 ml of toluene for 1 minute. The extracts were separated and after 10 min, the optical density (A) was measured at 566 nm on an SF-18 spectrophotometer in cuvettes with an optical path length of 0.3 cm relative to the control test extract (without silver). From the values of A, the magnitudes of the molar absorption coefficients are calculated. The same experiments were carried out with the addition of dilute solutions of HCl and NaOH to create different pH of water.

solution, the value of which is controlled using a pH meter (in the cell for micro-measurements).

The data presented in Table. 2, from which it follows that the sensitivity of the determination of silver by the proposed method is maximum with the acidity of the solution in the range pl-U1-11. Outside this pH range, the sensitivity of the method is reduced by reducing the optical density values of the extracts.

Example 2. 10.79 µg of silver (0.2 ml of M solution of silver nitrate), 0.5 ml of 1 M solution of potassium iodide and different amounts of M of dye solution of TBIK and distilled water were added to graduated test tubes with ground stoppers to a total volume of 5 ml.

5 ml of toluene are poured in and extracted for 1 minute. The extracts were separated and after 10 min, the optical density was measured at an SF-18 in cuvettes with, 3 cm relative to the control test extract (without silver).

The data presented in Table. 3, from which it follows that the sensitivity of the determination of silver by the proposed method is maximum at an equilibrium concentration of the dye TBIK (5-6) M. At a different concentration of dye, the sensitivity of the determination of silver decreases.

Example 10.79 µg of silver (0.2 ml of a 5-104 M solution of silver nitrate), different amounts of a 1 M solution of potassium iodide, 0.5 ml of the dye TBIK solution and distilled water to a total volume of 5 ml are injected into the test tubes with ground stoppers. . 5 ml of toluene are poured, and then the determination is carried out analogously to example 2.

The data presented in Table. 4, from which it follows that the detection sensitivity of silver is maximum at an equilibrium concentration of iodide ions (based on potassium iodide) equal to 0.08-0.16 M. At a different concentration of iodide ions, the detection sensitivity of silver decreases.

For experimental verification of the proposed method, silver was determined in a solution of its pure salts and semiconductor films.

Example 4. Determination of silver in solutions of its pure salts. 1.08 µg of silver (0.2 ml of M solution of silver nitrate), 0.5 ml of 1 M solution of potassium iodide, 0.5 ml of M solution are injected into the test tubes with ground stoppers.

dye TBIK and distilled water to a total volume of 5 ml. 5 ml of toluene are poured in and extracted for 1 minute. The organic phase is separated and after 10 minutes 5 the optical density is measured on an SF-18 spectrophotometer at 566 nm relative to the control test extract (without silver). The amount of silver is determined by a calibration curve, similarly constructed using standard silver solutions in the range of 0.005-2.5 µg / ml. The data obtained are presented in Table. five.

Example 5. The definition of silver in

5 semiconductor films of AgGaSa.

The base with the film deposited on it is placed on the bottom of a quartz glass with a volume of 50 ml, 2 ml of HM03 (1: 1) and 2-3 drops of bromine are added, and dissolved with heating

0 film. After complete dissolution with teflon tweezers, the base is removed and rinsed with 5 ml of distilled water. The mass of the film is found by the difference in the mass of the base before and after dissolution. The solution is evaporated to dryness and the residue is dissolved in 2.5 ml of 0.1 M sulfuric acid under heating. After cooling, the resulting solution is transferred to a 25 ml volumetric flask and diluted to the mark with distillate. An aliquot (0.5-2.5 ml) of the test solution is taken in a graduated tube with a ground stopper, 0.5 ml of 1 M potassium iodide solution, 0.5 ml of 510 M dye TBIK solution and distilled

5 water to a total volume of 5 ml. 5 ml of toluene are poured in and extracted for 1 minute. Further, the determination of silver is carried out as described in Example 4. The data are presented in Table. 6

Claims (1)

0 formula invented and The method of extraction-photometric determination of silver, which consists in introducing a halogen-ion and a basic dye into the sample solution, until the pH reaches the required value, extracts with toluene and photometrically extracts, in order to increase sensitivity while simplifying the method by reducing the requirements for the pH value of the extractable solution, iodide ion is introduced into the sample solution as a halide-irn up to a concentration of 0.08–0.16 M, 1 1 5 tetramethyl The enbisine-carbocyanine was added to a concentration of (5-6) UM, the pH of the solution was adjusted to a value of 1-11, and the extract was photometrized at a wavelength of 566 nm. Table 1 Note. The concentration of iodide ions - 0.1 M, dye TBIK -, 10.79 µg silver Note: The concentration of iodide ions is 0.1 M, 10, 79 µg silver table 2 Table3 Note: Equilibrium concentration of dye TBIK - 5 M, 10.79 µg silver Determination of silver in solutions of its pure salts T a 6l and c a 5 (n 6, P 0.95: tp 2,571)  n is the number of determinations, c is the average value of the silver content, S is the standard deviation, p is the degree of reliability, tp is the Student coefficient. Determination of silver in semiconductor films AgGaS2 (p 5, P 0.95, tp 2,776) Table- Table