SU923271A1 - Method for detecting chloroorganic pesticides in water - Google Patents

Description

A metric method for the determination of chlorine-containing organic pesticides in water by preliminarily converting chlorine atoms bound in an organic molecule to chlorindones by boiling an organic extract of pesticides with metallic sodium 3J. For example, an analyzed water sample is agitated with isooctay for 3 hours. The extract obtained is diluted with isobutyl alcohol and boiled with metallic sodium for 2 hours. The solution is diluted with water and acidified with nitric acid. The aqueous phase obtained after separation is mixed with a solution of gum arabic in nitric acid and then a solution of silver nitrate; irradiated for 15 minutes with ultraviolet lamina and absorbance at I 600 nm relative to an aqueous solution containing NaNOs, HNOs, gum arabic and AgNOa. The calibration curve is based on reference solutions, for example hexachlorocyclohexane, in amounts corresponding to a chlorine content of 50 to 500 µg.

The disadvantages of this method, first of all, include the significant duration of the analysis, the use of a large number of chemical reagents, which increases the likelihood of impurities with them that distort the analysis. The application of this method requires the use of high-purity, expensive reagents.

Multi-stage is also one of the significant drawbacks of this method, since at each stage there are losses of the analyte. All of the above does not allow for satisfactory reproducibility of the analysis results.

The aim of the invention is to reduce the time of analysis of organochlorine pesticides in water while maintaining the high sensitivity of the method.

The goal is achieved by implementing a method for determining organochlorine pesticides in water by decomposing an analyte in a sample and determining the resulting chloride ions by treating with an inorganic compound followed by measuring the luminescence spectrum of the solution obtained, whose distinctive feature is the decomposition of the analyte with UV light with 1,254 nm 60-90 seconds; using bismuth sulphate as an inorganic compound; lumin spectrum recording stsentsii I obtained solution at 445 nm in liquid nitrogen. The initial solution of the reagent for chlorine ion — bismuth sulphate — is prepared by dissolving, when heated, an exact weighed portion of bismuth oxide (P1) (rare) in 9 M sulfuric acid. The resulting solution of bismuth sulphate has a concentration of 10 mg.

The conducted studies show that in the solution of sulfuric acid at the temperature of liquid nitrogen in the presence of chloride ion, intense blue luminescence of bismuth chloride is observed,

the spectrum of which is a wide, structureless band with a maximum in the 445 nm region. The analytical signal of the chloride ion decreases with an increase in the sulfur titration. In order to understand the concentration of acid in a solution of bismuth sulfate (P1), serial dilution of the initial reagentite solution with water is used to a working concentration of 10 μg.

The luminescence intensity of bismuth chloride in its luminescence spectrum is shown below.

As a result of this dilution, the concentration of sulfuric acid in the analyzed solution is 0.01 M, which corresponds to the concentration region of the acid in which the highest luminescence intensity of bismuth chloride is observed. The dependence of the luminescence intensity of bismuth chloride on the concentration of sulfuric acid (I 445 nm) is given below.

To build a calibration curve for chlorine ion, sodium chloride solutions are used. Working solutions of chloride and dopes are prepared by successive dilution with water of the initial solution, obtained by dissolving an exact weight of sodium chloride (pure) in water. The standard deviation of the blank experiment, calculated from the results of 40 parallel measurements, is 0.4. Chlorine ion detection limit calculated by 3H-critoigo corresponds to.

Study the luminescence of bismuth chloride complexes in the presence of bromine, iodine and fluorine ions. So the definition of chloride ion by the proposed method does not interfere with the following weight amounts of halides: 20-fold bromide ion. 200kpatnoe iopid-ion and 1000-fold fluoride dcM. tab. one).

The proposed method is used to determine the content in model aqueous solutions of the following chlorine-free insecticides and pestinigts: DDT, hexachlorocyclohexane (HCCH), fosalone, dicotex. Structural formulas and molecules Determination of fluoride, bromide, iodide ions

in the determination of chloride ions (HsSOi 0.01 M; K them 445;, 95)

In tab. Figure 2 shows the dependence of the percentage of chlorine-containing molecules in the form of chlorine-containing ions in the solution on the time of irradiation with 0.5 ml of an aqueous solution of these substances (irradiation with a SVD-120 mercury-quartz lamp, 230 V, 1.4 a from a distance of 5 cm) .

Example. 1 ml of a working solution of bismuth sulphate with a concentration of 100 µg is introduced into a 10 ml volumetric flask.

The specific weights of these compounds are presented in table. 2. Pre-study the effect of the duration of irradiation of the solutions of these substances on the amounts of chlorine ions produced thereby. In these experiments, the concentration of organo-cotton substances is. The optimal time of irradiation of the analyzed sample is 60-90 s, which corresponds to the maximum

the content of chlorine ions formed in the solution. The results of the pre, put in table. 2

On the number of chlorine atoms transferred to the chloride-ion from an organic molecule,

can be judged by the intensity of the measured luminescence. In tab. 2 shows the percentage ratio of the number of chlorine atoms transferred to the chloride ion from the organic substance molecule to the total chlorine content in this molecule. As follows from the table. 2, in the rez ptaty irradiation for the optimum time for a given compound, chloride ions are formed in the solution in quantities proportional to the content of chlorine atoms in the aromatic core of the molecule.

Table 1

The flask is made up to the mark with the solution to be analyzed. An aliquot portion (0.5 ml) of the carefully transferred prepared solution is transferred to a quartz crucible and irradiated from a distance of 50 mm with the full light of a SVD-120 mercury-quartz lamp (230 V, 1.4 a) for 60-90 seconds. The crucible with the solution is then frozen with liquid nitrogen and the luminescence intensity is measured at a wavelength of 445 nm. The luminescence is excited by the light of the DRSh-250 mercury quartz lamp passing through the UFS-1 light filter.

As an idle experiment, allowing it, taking into account the initial content of chlorine ions in the solution, using the analyzed solution of organochlorine substances, and without irradiating the solution with a mercury welding lamp, measuring the intensity of the luminescence at the temperature of liquid nitrogen of the chloride complexes introduced into the solution of bismuth sulphate (III ).

Thus, the proposed method allows the determination of the above chlorine-containing compounds, their organic substances, with the detection limits indicated in Table 2. 2

The advantages of the proposed method in the first place include the high express analysis. For the analysis of one solution in total complexity, it takes 5 minutes. Perform one analysis

requires a small volume of water sample (up to 10 ml). The use of only one reagent (a weakly acid solution of bismuth sulphate) is also an advantage of the described procedure (see Table 3).

The entire course of the determination is carried out in just two stages: the radiation of a mercury-quartz lamp and the measurement of the luminescence intensity of the frozen solution. In addition, the proposed method allows the determination of organochlorine substances directly in aqueous solutions and does not require the use of any organic solvents.

The value of the proposed method also lies in the fact that carrying out the analysis of chlorine in pesticides allows determining, in addition to the actual chlorine-containing substances, also the extensive soil of phosphorus-containing insecticides, the molecules of which include chlorine atoms directly related to the aromatic core molecule.

9

The above allows to relate the proposed method as an express and sensational characteristic of the prototype method and the proposed method.

Specifications

Preliminary conditioning with extraction followed by reextraction is required.

Isooctane Isobutanol Metallic sodium Nitric acid Water

Gum arabic silver nitrate

Claims (3)

1. Hancock W., Laws E. A. “The Determination of Traces of Benzene Hexachloride in Water and Sewege Effluents, Analyst, 80, 665 (1955). 2. Rosen A. A., Middleton F. M. “Chlorinated Insecticides in Surface Waters. Anal. Chemistry, 31, 1729 (1959). 3. Leyte B. Determination of organic contamination of drinking, natural and waste waters. M., “Himi, 1975, p. 163-171.