RU2760530C1 - Method for determination of residual amounts of fenoxycarb in soil by high-performance liquid chromatography - Google Patents

Abstract

FIELD: chemical analysis.

SUBSTANCE: invention relates to a method for determining the residual amounts of fenoxycarb in the soil by high-performance liquid chromatography, including sample preparation: extraction from the soil, subsequent purification of the extract in a system of immiscible solvents: hexane, saturated sodium chloride solution, aqueous sodium bicarbonate solution and directly quantitative determination of fenoxycarb in the soil by high-performance liquid chromatography, and at the extraction stage the less toxic carbon tetrachloride is used as a solvent, and at the stage of purification of the extract, a corrugated filter was used.

EFFECT: extension of the range of methods for determining chemical substances in soil.

1 cl, 2 ex, 3 tbl, 4 dwg

Description

The invention relates to agriculture and can be used to determine the mass concentration of phenoxycarb in soil by high performance liquid chromatography (HPLC).

Fenoxycarb is a white crystalline powder, melting point 53-54 ° C, boiling point 100 ° C, decomposition temperature 248 ° C. Vapor pressure at 25 ° C: 8.67 × 10 ^-4 MPa. Partition coefficient n-octanol / water: K _ow log P = -4.07. Solubility (g / l) at 25 ° C: acetone - 770, ethanol - 510, ethyl acetate - 500, toluene - 630, hexane - 5.3, n-octanol -130, water - 0.008. The substance is stable in the light and does not hydrolyze in aqueous solutions at pH 3-9. Fenoxycarb is an insecticide related to the growth regulators of juvenile insects with a contact-intestinal effect. It is used against lepidoptera pests in cotton, vineyards, fruit trees and ornamental crops. It is used in Russia to combat apple and plum moths, bunch moths on pome and stone fruit crops and grapes by one to three spraying during the growing season with a consumption rate of 0.4-0.6 kg / ha. According to GN 1.2.3539-18, the approximate permissible concentration of phenoxycarb in soil (APC) is 0.003 mg / kg.

TLC (thin layer chromatography), GC (gas chromatography), CE / MS (capillary electrophoresis with an MS detector), HPLC (high performance liquid chromatography) are used to quantify the content of pesticides in the objects of study. Quantification is used to monitor the concentration of pesticides in soil, water sources, rivers, air and food. Some countries have introduced legal control over the permissible levels of pesticides in the environment.

There is a known method for the determination of phenoxycarb in soil by gas-liquid chromatography or thin-layer chromatography (VMU 6176-91 Temporary guidelines for the determination of phenoxycarb (Insegara, VDG) in plant material, water and soil by chromatographic methods). The method is based on the extraction of phenoxycarb from the test object with acetone or chloroform and subsequent determination by the method of reaction gas-liquid chromatography in the form of an acyl derivative (Murashko S.V., Shcherbakova I.P., VNIIGINTOKS, Kiev). The disadvantage of this method is that the chloroform used is a highly toxic substance, class 6 of the UN list. I. GOST 20015-88 Chloroform. Technical conditions. The use of acetone provides for special requirements; an equipped room is required for storage. Acetone is narcotic and highly flammable. Class 3 of the UN list. All work with acetone should be carried out using supply and exhaust ventilation away from fire and sources of sparking. When sampling, conducting analysis and handling in the process of transport and production operations with acetone, personal protective equipment is used in accordance with the norms for the issuance of special clothing, special shoes and other protective equipment, approved in the prescribed manner. GOST 2768-84 Technical acetone. Technical conditions.

A known method of measuring the concentrations of phenoxycarb in the atmospheric air of populated areas by capillary gas-liquid chromatography MUK 4.1.3461-17 (FBUN "Federal Scientific Center for Hygiene named after F.F. Erisman" Rospotrebnadzor N.E. Fedorov, O.E. N. Sobolev). To measure indicators, a chromatograph (GLC) with a mass-selective detector (MSD) is used. The determined range of mass concentration of phenoxycarb is 0.0004-0.004 mg / m ³ . The concentration of the substance from the air is carried out on sampling tubes filled with a porous polymer sorbent, extraction from the tubes is carried out with acetone. The lower limit of measurement in the analyzed sample volume is 0.01 ng. Average tube recovery: 92.5%. The disadvantage of this method is the use of acetone, which is classified as harmful (hazard class 4).

A known method for the determination of 25 combined pesticides (neonicotinoids, imidazole derivatives, urea derivatives, sim-triazines, triazoles, carbamates, organophosphorus compounds, pyrethroids) in water, vegetables and fruits in the concentration range of 0.005-10 mg / l (mg / kg) by HPLC with diode detection matrix at 220 Nm. The determination is carried out according to the "QuEChERS" method (fast, simple, cheap, effective, durable and safe). The investigated vegetables and fruits were ground using a mixer. A weighed portion of a crushed sample weighing 10.0 g was added to a centrifuge tube with a capacity of 50 ml, 10 ml of acetonitrile was added, the tube was closed and the tube was vigorously shaken for one minute. Then the following salts were added: 4.0 g of anhydrous magnesium sulfate, 1.0 g of sodium chloride, 1.0 g of sodium citrate trisubstituted double hydrate and 0.5 g of sodium citrate disubstituted sesquihydrate. Then the mixture was shaken for one minute (to avoid the formation of lumps) and centrifuged for 5 min at 3000 rpm, 4 ml of the upper part of the extract was taken and transferred to a centrifuge tube (15 ml), which contained a mixture of Bondesil-PSA sorbent (0 , 5 g) and magnesium sulfate (0.5 g). The tube was vigorously shaken for 30 s and centrifuged for 5 min at 3000 rpm, then the extract was taken and passed through the chromatograph. The disadvantage of this method is inaccurate analysis, poor sample cleaning.

The closest to the claimed method is the method for determining the residual amounts of phenoxycarb in apples, plums and grapes by the method of high-performance liquid chromatography MUK 4.1.2272-07 (Talalakina T.N., scientific researcher; Makeev AM, head of laboratory, Candidate of Biological Sciences . Research Institute of Phytopathology). The technique is based on the determination of phenoxycarb using high performance liquid chromatography (HPLC) with an ultraviolet detector. Control of phenoxycarb in samples of apples, plums, berries and grape juice is carried out according to the substance content after its extraction from juice with hexane, from apples, plums and berries with methanol, purification of the extract by redistribution in a system of immiscible solvents, as well as on a column with silica gel and a Diapak C8 concentrating cartridge ... The disadvantages of this method include the use of a potent poisonous substance - methanol (GOST 2222-95 Methanol technical. Specifications). This is an especially hazardous flammable liquid. Flash point 6 ° C, flash point 13 ° C. When working with the product, loading and unloading operations, the requirements of electrostatic intrinsic safety in accordance with GOST 12.1.018 must be observed. Production and laboratory premises in which work with methanol is carried out must be equipped with supply and exhaust ventilation and local ventilation that meet the requirements of GOST 12.4.021, ensuring the air condition of the working area in accordance with the requirements of GOST 12.1.005.

The technical result of the proposed invention is to improve the accuracy of the phenoxycarb indicator in determining its microamounts in the soil by means of high performance liquid chromatography, while the method improves the safety of workers in toxicological laboratories.

The technical result is achieved by replacing, at the stage of solvent extraction, potent toxic methanol, acetone or chloroform with a less toxic solvent - carbon tetrachloride, the use of which shows complete separation of peaks, high accuracy of the result. At the stage of filtration of the soil extract, instead of a Buchner funnel (GOST 0147), a corrugated filter was used, which retains soil particles on its surface. Standard deviation 4.8%, confidence interval mean at n = 5 and d = 0.95 ± 4.95%.

The proposed method can be used to control the quality of the soil of perennial plantations (apple, plum, grapes). The control of the content of phenoxycarb in the soil is carried out by the content of the substance after its extraction from the soil with carbon tetrachloride, followed by purification of the extract in a system of immiscible solvents, on a column with silica gel and a Diapak C8 concentrating cartridge. Quantification is carried out by the absolute calibration method using the ClarityChrom software.

The method was carried out as follows. At the first stage, an extraction solvent was selected to determine the residual amounts of phenoxycarb in the soil. The following solvents were taken for testing: carbon tetrachloride, hexane, ethyl acetate, methanol for the standard version. Fenoxycarb was added to the soil in an amount of 10 mg / kg. Further, a study was carried out to determine the concentration after extraction and purification of the sample. The arithmetic mean of three parallel measurements was taken for the results (table 1).

From the data obtained, it can be seen that methanol and carbon tetrachloride have the highest extractable capacity. Since methanol is a potent poisonous substance, the following studies were carried out with carbon tetrachloride.

When preparing samples and performing measurements, the following conditions were observed: ambient air temperature (23 ± 5) ° С; atmospheric pressure (97 ± 10) kPa; relative air humidity not more than 80% at 25 ° С; AC frequency (50 ± 0.4) Hz; mains voltage (220 ± 22). To carry out the determination, the following reagents and materials were required: Fenoxycarb, an analytical standard with an active ingredient content of 99.5% (Syngenta, Switzerland), for analysis prepare 2 standard solutions of the basic 1 mg / kg and working 10 μg / ml, acetonitrile for chromatography, reagent grade (TU 2634-002-54260861-2013), bidistilled or deionized water (GOST 6709-72), n-Hexane, reagent grade (TU 6-09-3375-78), orthophosphoric acid, reagent grade, 85% (GOST 6552 -80), carbon tetrachloride (carbon tetrachloride), reagent grade (GOST 20288-74), sodium sulfate, anhydrous, reagent grade (GOST 4166-76), sodium chloride, reagent grade (GOST 4233-77), sodium bicarbonate, reagent grade (GOST 83- 79), ethyl ester of acetic acid, h (GOST 22300-76).

Fenoxycarb was introduced into a weighed portion (20 g) of soil with specified concentrations, placed in a homogenizer glass with a capacity of 500 cm ³ , added 100 cm ^{3 of} carbon tetrachloride and homogenized for 5 minutes at 8000 rpm. The homogenate was filtered through a pleated paper filter into a 250 cm ³ flask. The filter cake was washed with 50 cm ^{3 of} carbon tetrachloride. The extract and the washing liquid were transferred into a beaker, stirred, the volume of the solution was measured, and 1/4 of it (equivalent to 5 g of the sample) was transferred into a round bottom flask with a capacity of 100 cm ³ .

The selected aliquots were evaporated at a temperature of 40 ° C on a rotary vacuum evaporator until the aqueous extract residue was 1–2 cm ³ . Further purification of the phenoxycarb extract is carried out in a system of immiscible solvents: hexane + saturated sodium chloride solution + 0.5% aqueous solution of sodium bicarbonate.

^{15 cm 3 of} deionized water, 25 cm ^{3 of a} saturated solution of sodium chloride were added to the aqueous residue of the extract, stirred and transferred into a separating funnel with a capacity of 100 cm ³ . ^{30 cm 3 of} hexane was introduced into the funnel, vigorously shaken several times at intervals of half a minute; before each successive shaking, the pressure in the separatory funnel was relieved. After separation of the phases, the upper organic layer was collected in a separating funnel with a capacity of 250 cm ³ , and the lower aqueous phase was extracted twice more using 25 cm ^{3 of} hexane. The hexane fractions were combined, 40 cm ^{3 of a} 0.5% aqueous solution of sodium bicarbonate was added to the funnel, and the contents were vigorously shaken for 2 minutes. After phase separation, the lower aqueous layer was discarded, and the hexane fraction was re-treated with 30 cm ^{3 of a} 0.5% aqueous solution of sodium bicarbonate with shaking. After phase separation, the hexane fraction was filtered through a layer of anhydrous sodium sulfate into a round-bottom flask with a capacity of 100 cm ³ and then evaporated to dryness on a rotary vacuum evaporator at a temperature of 30 ° C.

The dry residues in a round-bottomed flask were dissolved in 2.4 cm ^{3 of} hexane, placed in an ultrasonic bath for 1 min, 0.6 cm ^{3 of} ethyl acetate was added, stirred, and again placed in an ultrasonic bath for 1 min. The solution was applied to a column containing a layer of glass wool, a suspension of 5 g of silica gel of I degree of activity in 20 cm ^{3 of} hexane and a layer of anhydrous sodium. The flask was washed with 5 cm ^{3 of a} mixture of hexane-ethyl acetate (8: 2, by volume), which was also applied to the column. The column was washed with 15 cm ^{3 of a} mixture of hexane-ethyl acetate (8: 2, by volume) at a rate of 1-2 drops per second, the eluate was discarded. Fenoxycarb was eluted from the column with 45 cm ^{3 of a} mixture of hexane-ethyl acetate (7: 3, by volume), the eluate was collected directly into a round-bottom flask with a capacity of 100 cm ³ . The solution was evaporated to dryness on a rotary vacuum evaporator at a temperature of 30 ° C.

The dry residue in a round-bottom flask was dissolved in 1.2 cm ^{3 of} acetonitrile, placed in an ultrasonic bath for 1 min., 1.8 cm ^{3 of} deionized water was added, stirred, and again placed in an ultrasonic bath for 1 min. The solution was applied to a Diapak C8 concentrating cartridge, and the eluate was discarded. The column was washed with 2 cm ^{3 of a} mixture of acetonitrile-water (1: 1, by volume), the eluate was discarded. Fenoxycarb was washed from a cartridge with 5 cm ^{3 of} acetonitrile, the eluate was collected directly into a round-bottom flask. The solution was evaporated to dryness at a temperature not exceeding 40 ° C. The remainder in the flask was dissolved in 1 cm ^{3 of the} mobile phase, placed in an ultrasonic bath for 1 min, and analyzed for the content of phenoxycarb.

The determination of the residual amounts of phenoxycarb in the soil was determined by high performance liquid chromatography (HPLC), using a liquid chromatograph with an ultraviolet detector (Knauer, Germany), with a steel column 15 cm long, 4 mm inner diameter, containing Diaspheres 110-С18 as a stationary phase , grain size 5 microns. Column temperature: 22-25 ° С, operating wavelength: 230 nm, sensitivity: 0.005 units. absorption on the scale. Injected sample volume: 20 mm ³ , linear detection range 1-10 ng, mobile phase: acetonitrile-0.005 M H ₃ PO ₄ (65:35, by volume), eluent flow rate: 0.8 cm ³ / min, retention time fenoxycarb: 4-5 minutes.

Examples of specific applications

Example 1. Under laboratory conditions, phenoxycarb was introduced into soil samples weighing 20 g at dosages: 1, 2, 5 and 10 mg / kg. The quantitative parameters of phenoxycarb were determined after its extraction from soil with methanol. At the next stage of filtration of the extract, a Buchner funnel was used. The extract was purified in a system of immiscible solvents, on a column with silica gel and a Diapak C8 concentrating cartridge. Data processing was carried out using the ClarityChrom program.

The arithmetic mean of three parallel measurements was taken as the results. As a result of the analyzes carried out, it was revealed that the maximum percentage of extraction of phenoxycarb by means of methanol was noted with the introduction of a concentration of 1 and 10 mg / kg and amounted to 97.9-99.1%, which is reflected in figures 1 and 2.

Example 2. Under laboratory conditions, phenoxycarb was introduced into different soil samples weighing 20 g at dosages: 1, 2, 5, 7 and 10 mg / kg. Carbon tetrachloride was used as a solvent. At the stage of filtration of the extract, a paper corrugated filter was used. Further sample preparation was carried out analogously to example 1.

Data processing was carried out analogously to example 1. The percentage of phenoxycarb recovery in the study, where carbon tetrachloride, which is less toxic than methanol, was used as a solvent turned out to be close to the results of a study where methanol was used as a solvent, which is reflected in Figures 3 and 4.

Claims (1)

A method for determining residual amounts of phenoxycarb in soil by high performance liquid chromatography, including sample preparation: its extraction from soil, subsequent purification of the extract in a system of immiscible solvents, hexane, saturated sodium chloride solution, aqueous solution of sodium bicarbonate and directly quantitative determination of phenoxycarb in soil by high performance liquid chromatography, characterized in that at the stage of extraction, less toxic carbon tetrachloride is used as a solvent, and at the stage of purification of the extract, a corrugated filter is used.

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