SU1732242A1 - Method of determination of organophosphorous compounds - Google Patents

Abstract

The invention relates to analytical chemistry, in particular, to methods for determining organophosphorus compounds by oxidizing an analyzed sample with 69-73% by volume with an aqueous solution of sulfuric acid and a 0.006-0.03 M solution of potassium dichromate, taken in an amount not less than 1.1-fold from stoichiometric with respect to the total content of organic substances, during boiling for 10–15 mm, the introduction of a reducing agent and ammonium molybdate, followed by photometry of the colored solution. The determination time was 30 min, relative error + 5%. 2 tab. at

Description

This invention relates to analytical chemistry, and specifically to methods for determining organophosphorus compounds in industrial solutions and wastewater.

A known method for determining organophosphorus compounds by oxidizing an analyzed sample with ammonium persulfate or a mixture of hydrogen peroxide with sulfuric acid, diluted 1: 3, when heated for 6 hours, is treated with distilled water, reducing agent and ammonium molybdate, followed by photometric measurement of the colored solution.

The disadvantages of the method are the low accuracy and duration of the determination.

The closest to the proposed method is the determination of phosphorus-organic compounds by oxidation of the analyzed sample with potassium persulfate and sulfuric acid, diluted in a 1: 2 ratio with heating for 1.5 hours, treated with distilled water, citric acid, reducing agent and ammonium molybdate, followed by photometric measurement colored solution.

The disadvantages of the method are low accuracy (relative error ± 50%) and the duration of the determination (1.5 hours).

The purpose of the invention is to improve the accuracy of the method and reduce the time required to perform the determination.

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The goal is achieved by the fact that in the method of determining organophosphorus compounds, the oxidation of an analyzed sample is carried out with 69-73% by volume with an aqueous solution of sulfuric acid and a 0.006-0.03 M solution of potassium dichromate, taken in an amount not less than 1.1-fold. from stoichiometric with respect to the total content of organic substances at boiling for 10–15 min, the introduction of a reducing agent and ammonium molybdate, followed by photometry of the colored solution.

The results of the experiments to determine TBP (introduced: TBP - 450 µg, oleic acid 340 µg, syntanol DT-7-580 µg,,, 95) are given in Table 1.

The results of experiments on the determination of organophosphorus compounds (conditions of determination: the concentration of sulfuric acid is 73% by volume, the amount of potassium bichromate is 1.5–4.2 — a fold excess of the stoichiometric concentration of potassium bichromate is 0.015–0.025 M;,, 95).

Example 1. In a 50 ml conical flask, 1 ml of an aqueous test solution containing 450 mg / l of tributyl phosphate (TBP), 340 mg / l of oleic acid, 580 mg / l of DT-7 syntanol was added, and 2 ml of 0.5 N was added. . potassium dichromate solution (2.4 times excess from stoichiometric) and 8 ml of concentrated sulfuric acid, which corresponds to 73% by volume of sulfuric acid and 0.015 M potassium dichromate. The flask is attached to a reflux condenser and heated on a hot plate to boil. After 15 minutes, the flask is removed from the hot plate and 0.15 ml of ethanol is poured (to reduce unoxidized chromium VI) and cooled. The solution is transferred to a 100 ml volumetric flask, made up to the mark with distilled water and stirred. I take 10 ml of the solution into a 25 ml volumetric flask, add 5.2 ml of potassium hydroxide solution (300 g / l), 2 ml of 5% ascorbic acid solution, mix and pour 1 ml of the reactive solution (for preparing a flask with a capacity of 500 ml is added with 100 ml of distilled water, 72 ml of concentrated sulfuric acid, 6.3 g of ammonium molybdate, stirred until

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dissolve it, add 0.118 g of antimony trichloride, mix until a clear solution is obtained, bring to the mark with distilled water and mix (the solution is stored in a dark glass bottle). Next, the contents of the flask are made up to the mark with water and mixed. After 10 minutes, the optical density in the cuvette is measured from mm to FEC-56 with a light filter 8 versus the solution of the control experiment. The test solution contains all components except TBP, oleic acid, and synthanol and is carried out through all stages of the analysis. The optical density of the solution is equal to 0.44, which corresponds to the graduation graph built in coordinates: optical density is the PO content, 16.24 µg PO, i.e. 45.5 mcg TBP. The concentration of TBP in the test solution (mg / l) is 45 ,. The average concentration of TBP at 7 parallel determinations is (435117) mg / ls. The relative determination error is 3.3% (Table 2, Example 1).

Example2. In a 50 ml conical flask, add 10 ml of an acetone solution containing 61.5 mg / l of triphenylphosphine (TFF). The flask is immersed in a boiling water bath and heated until acetone is removed. 2 ml of 0.2 N was added to the dry residue. solution

35 potassium bichromate (1, 9-fold excess stoichiometric), 8 ml of concentrated sulfuric acid, which corresponds to 73% by volume of sulfuric acid and 0.006 M potassium dichromate. Further, the determination is carried out analogously to example 1 | The optical density of the solution is 0.57, which corresponds to a calibration curve of 21.75 µg PO, i.e. 60 μg TFF. The concentration of TPP in the analyzed solution (mg / l) is 60. The average value of the concentration of TPP with 7 parallel determinations is (59,012.7) Mg / l. Relative

50 The detection error is 4.1 (Table 2, Example 5).

As can be seen from the examples described, as well as the data given in table 1 (examples 1-11) and table. 2 (examples 1-12), carrying out the decomposition of phosphorus-organic compounds under the conditions: the concentration of sulfuric acid 69-73% by volume, the content of potassium dichromate

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in an amount not less than 1.1 times the stoichiometric ratio with respect to the total content of organic substances (at a concentration of potassium dichromate of 0.006-0.03 M), and boiling the analyzed solution for 10-15 minutes ensures high accuracy of the results of determining various phosphorus compounds.

Beyond the increase or decrease in the content of both sulfuric acid and potassium biochromate in the oxidative decomposition of organophosphorus compounds leads to a decrease in the accuracy of determination.

With an excessive increase in the concentration of sulfuric acid at the indicated values of potassium dichromate, the decrease in the accuracy of determination of phosphorus – organic compounds is due to a spontaneous decrease in the concentration of oxidant due to decomposition of bichromate ions under these conditions (Table 1, examples 14 and 15).

With an extreme decrease in the concentration of sulfuric acid at the indicated values of potassium bichromate, the decrease in the determination accuracy is due to the incomplete oxidation of organophosphorus compounds to phosphate ions (Table 1: 1, example 12). An increase in the heating time of the solution does not allow, under these conditions, to achieve a satisfactory determination accuracy (Table 1, Example 13).

With an extremely low excess of potassium dichromate, for example, 0.9-fold from stoichiometric at the indicated concentrations of sulfuric acid and potassium dichromate in the reaction mixture, quantitative oxidation of organophosphorus compounds is not achieved, which leads to a sharp decrease in the accuracy of their determination (Table 1, Example 16 ).

The incomplete oxidation of organophosphorus compounds explains the decrease in the accuracy of their determination at

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limiting the concentration of potassium dichromate in the reaction mixture, for example, to 0.005 M at the indicated concentrations of sulfuric acid and excess potassium dichromate (Table 1, Example 18).

When the concentration of potassium dichromate in the reaction mixture is extremely high at the indicated concentrations of sulfuric acid and excess bichromate ions, the decrease in the accuracy of determination of organophosphorus compounds is caused by the interfering influence of chromium (III) ions on the photometric determination of phosphate ions (Table 1 , example 17).

Under these conditions, the proposed method allows reliably (relative to 20 ± 5% error) and with a small amount of time (not more than 30 minutes) to determine various phosphorus substances both in the absence and in the presence of organic impurities. The use of the proposed method makes it possible to shorten the analysis time by 6–9 times and improve the accuracy of determining TBP in the presence of other organic compounds rear by 3–16 times as compared with the known method.

invention formula

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Method for determination of organophosphorus compounds by oxidation

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When the sample is analyzed, heating, the introduction of ammonium molybdate and ammonium molybdate followed by photometry of the colored solution, characterized in that, in order to increase the accuracy of the method and shorten the detection time, oxidation is carried out with% aqueous sulfuric acid and 0.006-0.03 M solution of potassium dichromate, recovered in an amount not less than 1.1 times the stoichiometric ratio with respect to the total content of organic substances.

Table 1

Introduced oleic acid 680 nkg. DT-7 syntanol was introduced 290 mkg, oleic acid 170 mcg.

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Claims (1)

The claims are intended to be such that The method for determining organophosphorus. compounds by oxidizing the analyzed sample by heating ·, 'the introduction of a reducing agent and ammonium molybdate followed by photometric measurement of the colored solution, heating and increasing the accuracy of the method and reducing the determination time, the oxidation is carried out with 69 “73 vol.% aqueous solution of sulfuric acid and 0.006– 0.03 M potassium dichromate solution, taken in an amount not less than 1.1-fold of stoichiometric with respect to the total content of organic substances. Table 1 Example The sulfuric acid content in the solution of the decomposition of organophosphorus compounds, obD The ratio of the amount of potassium dichromate introduced to stoichiometric, in relation to the total content of organic substances The concentration of potassium dichromate, M Boiling time, min Found TBP, mcg Error determining D 1 73 1,2 0.008 fifteen 431 + 22 4.2 2 71 1,2 0.008 10 431121 4.2 3 70 1,2 0.008 16 433 ± 19 3.8 4 69 1,2 0.008 10 427 + 25 5.1 5 . 73 1,1 0.007 fifteen 427124 5.1 6 73 2,4 0.015 10 432 + 21 4.0 7 73 4.9 0,030 10 430 + 22 4.4 8 73 4.9 0,030 ' 10 430i23 4.4 9 73 1,1 0.007 12 432 + 20 4.0 10 69 1,1 0.007 fifteen 429 + 24 '4.7 AND 69 4.9 0,030 fifteen 428 + 24 4.9 Outrageous values 12 68 1,2 0.008 fifteen 378 + 80 16 IN 68 1,2 0.008 . thirty . 396 + 60 ' - 12 14 74 ' 1,2 0.008 fifteen 373 + 80 17 fifteen 75 2,4 0.015 fifteen 3511J0 22 16 73 0.9 0.006 fifteen 364190 19 17 * 73 2.7 oz1 fifteen 396159 14 18 ^p 73 1.4 0.005 fifteen 405156 12 19 By the famous - 90 30-164 ’15-82  ~ way V ^ Introduced oleic acid 680 mcg. ** Introduced syntanol DT-7 290 μg, oleic acid 170 μg table 2 Example Determined organophosphorus compound Associated Organic Substances The results of the determination of organophosphorus compounds Name Holchestau » mcg Name Introduced, mcg Found, mcg The relative error of determination,% 1 Tributyl phosphate 450 Sintanol DT-7 ' Oleic acid 580 340 435 + 17 3.3 2 Tributyl phosphate 150 Oleic acid ⁶⁸⁰ 14319 4.7 3 Tributyl phosphate 900 Oleic acid 340 • 868140 3,5 4 Tributyl phosphate 150 Vertolin -? ^: Triethanolamine oleic acid ethylene diamine tetra · ‘ 5000 447.5 500 15748 4.7 acetic acid disodium salt syntanol DT-7 + SINtamtsd 3227.5 75 750 590127 . 4.1 5 Triphenylphosphine 615 • U '·. 6 Triphenylphosphine 148 Oleic acid 680 14218 4.0 7 Rogor 400 Oleic acid 680 384118 4.0 8 Rogor 400 - _ | ^: 385119 3,7 9 Glyphosate 450 • · ’-» ! Ί - '· 464115 3,1 10 Glyphosate 450. Oleic acid . 850 436116 3,1 Continuation of the table. 2 Example Organophosphorus Detectable compound Name Introduced "mcg Associated Organic Substances Name Number, mcg . Results of the determination of organophosphorus compounds Found, mcg Relative determination error,% 1000 - 96Y £ 5O4.0 500 Oleic acid 850 850 481 ± 213.8