SU1062600A1 - Method of determination of compounds containing 1,1'-dimethyl-4,4'-dipyridinium cation - Google Patents

Abstract

A METHOD FOR DETERMINING COMPOUNDS CONTAINING CATION 1,1-DIMETHYL-4, 4 -DIPYRIDINIUM by chromatographic separation of the analyzed sample on a thin layer of silica gel. in a solvent mixture followed by treatment of the chromatogram obtained with a chemical reagent characterized in that, in order to increase the selectivity and sensitivity of the process, methanol, 25% ammonia solution and concentrated hydrochloric acid, taken at a volume ratio, are used as a solvent mixture, equal to 30-20: 15-5: 7-3, and as a chemical reagent is used react-. tive Dragendorff. 2. The method according to claim 1, which is intended so that, in order to enable the determination of compounds containing the cation l, l -dimethyl-4, 4-dipyridinium in water O), the sample to be analyzed is previously passed through a column of silica gel, followed by elution with a saturated solution of ammonium chloride.

Description

ABOUT).

The invention is an analytical chemistry, in particular for the determination of herbicides in the environment, and can be used to control the content of 1,1-dimethyl-4,4 cation dipyridium (paraquat-cation) in water. A known method for the determination of compounds containing the cation 1,1-di methyl-4, 4-dipyridinium (paraquatation) by chromatographic separation of the analyzed samples on a thin layer of specifically formed silica gel using as a mobile phase a mixture of n-butanol, water, ethanol at a volume ratio of the components equal to 1: 0.5: 1, followed by treatment of the chromatogram with a 1% solution of nitric silver in 0.5 solution of ammonia i. The disadvantages of the method are the difficulty of preparing a layer of silica gel, the selectivity and sensitivity are not high enough (sensitivity threshold 3 μg). The method to determine compounds containing the cation 1,1-dimethyl-4- is closest to the invention by its technical essence and effect. 4-dipyridyl by chromatographic separation of the sample on a thin layer of silica gel with and using as the mobile phase a mixture of ethanol, concentrated hydrochloric acid, and water with a volume ratio of 6: 1: 3 the subsequent treatment of the chromatographic solution with sodium hydroxide in methanol 2 ,. The disadvantage of this method is that the selectivity and sensitivity of the method are not high enough; the detection limit is 1 µg. The purpose of the invention is to increase the selectivity and sensitivity. The goal is achieved in that according to the method of determining compounds containing the cation 1,1-dimethyl-4,4-dipyridine J by chromatographic separation of the analyzed sample on a thin layer of silica gel in a solvent mixture, followed by processing the resulting chromatogram with a chemical reagent, methanol is used as a solvent mixture. , 25% ammonia solution and concentrated hydrochloric acid, taken at a volume ratio of 30-20: 15-5: 7-3, and Dragendorf reagent C is used as a chemical reagent permit determination of compounds containing a cation of 1,1-dimethyl-4,4-dipyridine in the water sample to be analyzed, previously passed through a column of silica gel followed by elution with a saturated solution of ammonium chloride. The determination of the paraquat cation is carried out as follows. Sorption ton is applied to washed and dried glass plates (13–18 cm), a homogeneous mixture of 14 g of silica gel L, with a particle size of 1–5 µm, 2 g of medical gypsum and 50 ml of water, evenly distributed over the surface of the plate so that the thickness of the silica gel layer is 0.5-0.8 mm. The plates are dried at room temperature and activated at 100-110 ° C for two hours in a drying cabinet, then a start line is plotted on a chromatographic plate, at a distance of 15 mm from the edge, and a microsyringe or micropipette is drawn in the middle of this line 10 µl of the sample solution, and to the right and to the left of the sample spot are applied as separate spots, at a distance of 15 mm from each other, along: 10 µl of standard solutions with different paraquat-cation content (standard spot-witnesses) . The diameter of the deposited spots should not exceed 10 mm, the number of spots is -7 °. The plate is placed in an airtight chromatographic chamber (14-14-20 cm), filled 30 minutes before chromatography (to saturate the chamber with vapor of the mobile phase) mobile phase, representing a mixture of: methanol - 25% aqueous ammonia - concentrated salt on acid (all components of qualification hch7. The amount under the mobile phase in the chamber is chosen so that the plate placed in the chamber is not more than 0, b cm. The plate is eluted In a similar way, the elevation of the front of the mobile phase is 10 cm, the elution time is 20-30 min at room temperature. Then the plate is removed from the chamber, dried in air (5-8 min) and treated with an atomizer with a chromogenic detection reagent (Dragendorff reagent). 8 g of basic bismuth nitrate in 40 ml of water and 10 ml of acetic acid are obtained by dissolving 8 g of potassium iodide dissolved in 20 ml of water into this solution, and diluting 1 ml of the resulting solution to treat the plate. ml of acetic acid and 10 ml of water. A red round paakvat cation (K 0.40to, 05) is conducted on the plate. Quantitative determination is carried out.

or by comparing the intensity of staining of the spot area of the test and standard solution, or by the calibration dependence of the spot area on the amount (in µg) of paraquat cation in it.

Example 1. A 10 µl volumetric flask with a capacity of 10 ml was added with 200 µl of 1.1-dimethyl-4, 4-dipyridinium aqueous solution of 1 mg / ml paraquat cation and the volume of the solution in the flask was made up to the mark with water. The content of paraquat-cation in the resulting solution is 0.02 mg / ml

On the chromatographic plate causes 10 μl of the resulting solution which corresponds to the content in the sample of 0.2 μg of paraquat-cation. Right and to the left of the sample spot are applied as separate spots, at a distance of 15 mm from each other, 10 µl of standard solutions of paraquat-cathine with concentrations of 0.02; 0.05; 0.10 0.50J1.0 mg / ml. The plate is developed in the mobile phase with 25% aqueous ammonia - concentrated hydrochloric acid (25: 10: 5), and then treated from a spray with a detection reagent. A round, clearly marked red paraquat-cation spot (, 40) appears on the plate, the color intensity and the area of which correspond to 0.2 µg of the analyte. From the calibration graph, it is determined that 0.21 µg is contained in the sample. Error of 5% determination.

Example 2. The determination was carried out analogously to example 1, but 1000 µg of an aqueous solution of rhodanide 1,1-dimethyl-4, 4-dipyridine with a paraquat-cation concentration of 1 mg / ml was introduced into the volumetric flask. The content of paraquat cation in the solution is 1000 μg. Found 950 mcg. Definition 5%. 0.45.

Example 3. The determination is carried out analogously to example 1, but 0,0100 technical salts of dipyridinium containing 500 µg (by paraquat cation) sulfate and 1,1-dimethyl-4, 4-dipyridinium thiosulfate are used as samples. Found 480 micrograms of paraquat cation. Error of 4% determination. Rf 0.4.

Example 4. The determination is carried out analogously to example 1, but the ratio of components in the mobile phase methanol — 25% aqueous ammonia — concentrated hydrochloric acid is 30: 5: 5. In this mobile phase, the R value for the paraquat cation is 0.15. Detection limit 0.5 µg. The paraquat-cation band is stretched towards the starting line, blurred. Error determining 10%.

Example 5 The determination is carried out analogously to Example 1, but the ratio of components in the mobile phase of methanol to 25% aqueous ammonia and concentrated hydrochloric acid is 20: 15: 5. The R value for the paraquat cation in this mobile phase is 0.48. The detection limit is 0.25 µg. The paraquat pattern is somewhat flattened towards the starting line. Error 6.7%.

Example 6. The determination is carried out analogously to example .1, but the ratio of components in the mobile phase is 25: 12: 3. The R value for paraquat cation is 0.25. Very deformed, blurred.

Example. The determination is carried out analogously to Example 1, but the ratio of components in the mobile phase is 25: 8: 7. The value of R {paraquat-cation is 0.60. Deformed, blurred.

Example 8. The determination is carried out analogously to Example 1, but the water sample being analyzed contains 50 µg of paraquat cation and 50 µg of diquat cation. The Rj and Rj values for paraquat and diquat cations are 0.40 and 0.50, respectively. 47.5 µg of paraquat cation and 4b, b µg diquat cation were found. 5i. Rj. / R 1.25.

Example 9. The determination is carried out analogously to Example 1, but an ammoniacal solution of silver nitrate is used as the chromogenic reagent. The pattern of paraquatation is weak, indistinct, and appears only after prolonged irradiation in UV light. Quantitative determination of paraquat cation is difficult.

Example 10. The determination is carried out analogously to Example 1, but a solution of caustic soda in methanol is used as the chromogenic reagent. The paraquat-cation spot is weak, diffuse, the minimum detectable amount is 1 µg, the determination error is 10%. In the case of less than 0.2 µg in the water sample, the paraquat cation is pre-concentrated on a silica gel column .

Example 11. A column of size IlO cm was filled to a height of 3 cm with KSK silica gel, fraction 0.25 0.50 mm. For preparation, the columns for the first analysis are sequentially passed through it with 50 ml of acetone and 100 ml of distilled water. To prepare the column for repeated analyzes, it is again washed with acetone (50 ml) and distilled yuda (100 ml), then 2-3 liters of the analyzed water containing 50 µg (0.017-0.025 mg / l paraquat-cation, is passed through column at a rate of 10 ml / min. Then the adsorbed paraquat cation is eluted from the column with a saturated aqueous solution of ammonium chloride (15 ml

The resulting solution was evaporated in a water bath to a volume of 5 ml, 20 µl of this solution was taken and chromatographed as in Example 1. The R value of the paraquat cation 0.45. The amount of paraquat cation, determined in the sample, is equal to 4.7.5 mkg, which corresponds to the content of paraquat cation in the analyzed water at the level of 0.01585-0.0238 mg / l. 5% error,

Example 12 The determination is carried out analogously to Example 11, but water containing 200 µg of paraquat cation is analyzed. Detected

208 µg paraquat cation. Error of 4% determination. .

At p 13. Oprelenie is carried out analogously to example 12, but water containing 40 µg of paraquat cation is analyzed. A non-quantifiable stain was found.

Thus, the proposed method is characterized by increased

separation selectivity oi is 1.25 (example 9), which is 7.7% more than the value characteristic of a known method (about 1.16). The minimum detectable amount of paraquattation is 0.2 μg, while in the known method this value is c. 5 times lower (1 µg. The method allows the determination of the paraquat cation content in aqueous

environmental objects at a concentration level of 0.017 mg / l and above.

Claims (2)

METHOD FOR DETERMINING COMPOUNDS CONTAINING Ι, ΐ’-DI METHYL-4,4'-DIPYRIDINIA COMPOUNDS by chromatographic separation of the analyzed sample on a thin layer of silica gel. in a mixture of solvents, followed by processing the obtained chromatogram with a chemical reagent, characterized in that, in order to increase the selectivity and sensitivity of the method, methanol, 25% ammonia solution and concentrated hydrochloric acid, taken at a volume ratio of 30- 20: 15-5: 7-3, and as a chemical reagent, a re- is used. tiv Dragendorf. 2. The method 'according to p. ^ Characterized in that, in order to enable the determination of compounds containing 1,1'-dimethyl-4,4 * dipyridinium cation in water, the analyzed sample is preliminarily passed through a silica gel column, followed by elution with a saturated solution ammonium chloride. .