Modified karl fischer reagent for quantitative determination of water content

Abstract

FIELD: chemistry; chemical technology.SUBSTANCE: single-component Karl Fischer reagent composition for the quantitative determination of water is disclosed, containing iodine, sulfur dioxide, wherein the composition additionally contains 3-amino-1,2,4-triazole, polyethylene glycol dimethyl ether, zirconium nanoparticles modified with organic ligands, as well as triphenyl (polyethylene glycol) phosphonium bromide.EFFECT: ensures the absence of precipitation during titration, increased stability of the reagent, as well as its selectivity.1 cl, 4 dwg, 3 tbl, 3 ex

Description

[0001] The invention relates to chemistry and chemical technology, namely to analytical multicomponent compositions aimed at determining the moisture content in various solutions and polymers. This invention can be used in the process of obtaining various substances in the oil and gas, pharmaceutical and polymer fields [G01N31 / 16, G01N25 / 48, C01B17 / 48, C07D233 / 20].

[0002] The most popular method for quantitatively determining moisture content in various solutions is currently the Karl Fischer reagent. However, known Karl Fischer reagents have an unsatisfactory shelf life, limited applicability for various types of solutions, and a suboptimal set of reagents, stimulating further development of this reagent. The classic Karl Fischer reagent composition includes substances such as iodine, sulfur dioxide, methanol, and pyridine. However, pyridine and methanol can be replaced with less toxic components that provide greater solubility of the analyzed sample. The use of imidazoles and methylimidazoles in place of pyridine is known in the art, and diethylene glycol monoethyl ether is also widely used as a solvent.

[0003] A known method (patent SU1511661) for producing a reagent for water determination contains iodine, pyridine, sulfur dioxide, and ethyl cellosolve. The reagent also contains butyl carbitol acetate (19.8-20.6% by weight) to ensure direct analysis of water in oils and lubricants and improve accuracy. The proposed composition is prepared by mixing two solutions (iodine and sulfur dioxide in pyridine). The reagent is then placed in a coulometric cell for further titration. This method requires the addition of an additive to improve oil dissolution. Disadvantages include a lack of variability in the titration process, a narrow range of applicability, and the limited application of pyridine to fats and oils.

[0004] A known method (patent US4647542A) for preparing a water determination reagent composition containing iodine, sulfur dioxide, and ethyl cellosolve, characterized in that pyridine is replaced with an alkaline earth metal salt of ethylene glycol monomethyl ether and similar compounds. This method offers an optimal and environmentally friendly composition for titrating solutions. Disadvantages include: limited applicability of the solution for titrating polymer solutions and low ionic conductivity of the solution for coulometric titration.

[0005] The closest approach to this invention is a method (patent SU1037174, published: August 23, 1983) for preparing a Karl Fischer water determination reagent composition containing iodine, pyridine, sulfur dioxide, methanol, and cellosolve. This method is distinguished by the use of ethyl cellosolve as the cellosolve to enable the determination of water in polymer solutions. This method is more effective for polymers; however, replacing methanol with ethyl cellosolve does not completely eliminate polymer film precipitation upon contact between polymer solutions and the reagent. Another drawback is the presence of highly toxic pyridine.

[0006] The objective of the claimed invention is to optimize the composition of the Karl-Fischer reagent, aimed at eliminating highly toxic and ineffective reagents for polymer analysis, and increasing stability and titer up to 5.

[0007] The technical results of the claimed invention include the absence of precipitation during titration of polymer solutions, increased thermal and chemical stability of the reagent, and its selectivity. Furthermore, the proposed composition is more environmentally friendly to use.

[0008] The specified technical results are achieved due to the fact that a single-component composition of the Karl Fischer reagent for the quantitative determination of water is declared, containing iodine, sulfur dioxide, characterized in that it additionally contains 3-amino-1,2,4-triazole, polyethylene glycol dimethyl ether, zirconium nanoparticles modified with organic ligands, as well as triphenyl (polyethylene glycol) phosphonium bromide, in the following ratio of components, wt.%:

[0009] Iodine 5-10 Sulfur dioxide 5-10 3-amino-1,2,4-triazole 10-25 Polyethylene glycol dimethyl ether 53-78 Zirconium nanoparticles functionalized with carboxyl groups 1-5 Triphenyl(polyethylene glycol)phosphonium bromide 1-5.

[0010] A method for producing a single-component Karl Fischer solution for quantitative determination using a process line employing micromixing systems is also claimed, in which 3-amino-1,2,4-triazole is pre-mixed with polyethyleneglycol dimethyl ether at a temperature of 85°C in a microreactor equipped with a thermostat, the reagents are fed from containers and pumped using syringe pumps; sulfur dioxide is then fed using a cylinder equipped with a flow meter and a regulator into a micromixer equipped with a cryostat, where it is bubbled into the previously obtained mixture at a mixture temperature of 15°C; the resulting solution is pumped with a syringe pump into a micromixer equipped with a thermostat, where it is mixed with iodine, pre-mixed with polyethyleneglycol dimethyl ether in a mixer equipped with a stirrer; the resulting mixture is collected in a product collection container and sealed.

[0011] The invention is explained by diagrams.

[0012] Fig. 1 and 2 show the schemes for preparing the composition in laboratory conditions.

[0013] Fig. 3 and 4 show diagrams of process installations for preparing the composition.

[0014] In the diagrams: 1 – container, 2 – syringe pump, 3 – microreactor, 4 – thermostat, 5 and 10 – micromixer, 6 – cryostat, 7 – cylinder, 8 – flow meter, 9 – regulator, 11 – thermostat, 12 – stirrer, 13 – mixer, 14 – product collection container.

[0015] Implementation of the invention

[0016] A single-component Karl Fischer reagent composition for the quantitative determination of water, characterized in that, in addition to sulfur dioxide and iodine sources, 3-amino-1,2,4-triazole is added to the component composition of the Karl Fischer reagent, which has an activity similar to imidazoles, but higher thermal stability, polyethylene glycol dimethyl ether, which has a higher dissolving power for polymers, as well as the following functional additives in an amount of 1-5% by weight: zirconium nanoparticles modified with organic ligands, which improve the stability of the reagent in polymer matrices, as well as triphenyl (polyethylene glycol) phosphonium bromide, which increases ionic conductivity, which is important for the coulometric method.

[0017] The reagent is prepared using the following ratio of components, wt.%:

[0018] Iodine 5-10 Sulfur dioxide 5-10 3-amino-1,2,4-triazole 10-25 Polyethylene glycol dimethyl ether 53-78 Zirconium nanoparticles functionalized with carboxyl groups 1-5 Triphenyl(polyethylene glycol)phosphonium bromide 1-5

[0019] For the preparation of the proposed one-component composition in laboratory conditions, the solution preparation scheme shown in Fig. 1 is recommended.

[0020] The achievement of the set objectives is determined by the installation in Fig. 3. The technological process is as follows: 3-amino-1,2,4-triazole is pre-mixed with polyethyleneglycol dimethyl ether at a temperature of 85°C in a microreactor 3 equipped with a thermostat 4. The reagents are fed from containers 1 and pumped using syringe pumps 2. Then sulfur dioxide is fed using a cylinder 7 equipped with a flow meter 8 and a regulator 9 into a micromixer 5 equipped with a cryostat 6, where it is bubbled into the previously obtained mixture at a mixture temperature of 15°C. The resulting solution is pumped by a syringe pump into a micromixer 10, equipped with a thermostat 11, where it is mixed with iodine, previously mixed with polyethyleneglycol dimethyl ether in a mixer 13, equipped with a stirrer 12. The resulting mixture is collected in a product collection container 14 and sealed.

[0021] The achievement of the technological result is confirmed by the following examples:

[0022] Example 1.

[0023] Prepare a one-component reagent by saturating the solvent with sulfur dioxide. To do this, take 103 ml of 3-amino-1,2,4-triazole and saturate the solution with 60 g of sulfur dioxide. Then add 40 g of iodine and bring the solution to readiness by adding 625 ml of polyethylene glycol dimethyl ether, as well as other additives.

[0024] Coulometric titration of water contained in a polyacrylonitrile spinning solution sample is performed with the specified composition until a reddish-brown color appears. One drop of water is then added to the polymer from a pre-weighed dropper, after which the dropper is weighed again. The resulting solution is titrated with Karl Fischer's reagent until a reddish-brown color appears. Precipitation does not occur. The titer results are presented in Table 1. The average titer was 1.05.

[0025] Table 1

[0026] Fischer reagent titer determination results

[0027] Measurement number Droplet mass (g) Volume of Fischer reagent used for titration (ml) Fischer reagent titer Average titer value 1 0,0389 38,9 1,00 1,05 2 0,0413 37,55 1,1

[0028] Example 2.

[0029] Prepare a one-component reagent by saturating the solvent with sulfur dioxide. To do this, take 103 ml of 3-amino-1,2,4-triazole and saturate the solution with 60 g of sulfur dioxide. Then add 50 g of iodine and bring the solution to readiness by adding 575 ml of polyethylene glycol dimethyl ether, as well as other additives.

[0030] Coulometric titration of water contained in a polyacrylonitrile spinning solution sample is performed with the specified composition until a reddish-brown color appears. One drop of water is then added to the polymer from a pre-weighed dropper, after which the dropper is weighed again. The resulting solution is titrated with Karl Fischer's reagent until a reddish-brown color appears. Precipitation does not occur. The titer results are presented in Table 2. The average titer was 3.005.

[0031] Table 2

[0032] Fischer reagent titer determination results

[0033] Measurement number Droplet mass (g) Volume of Fischer reagent used for titration (ml) Fischer reagent titer Average titer value 1 0,0263 8,43 3,12 3,005 2 0,0278 9,62 2,89

[0034] Example 3.

[0035] Prepare a one-component reagent by saturating the solvent with sulfur dioxide. To do this, take 103 ml of 3-amino-1,2,4-triazole and saturate the solution with 60 g of sulfur dioxide. Then add 60 g of iodine and bring the solution to readiness by adding 525 ml of polyethyleneglycol dimethyl ether, as well as other additives.

[0036] Coulometric titration of water contained in a polyacrylonitrile spinning solution sample is performed with the specified composition until a reddish-brown color appears. One drop of water is then added to the polymer from a pre-weighed dropper, after which the dropper is weighed again. The resulting solution is titrated with Karl Fischer's reagent until a reddish-brown color appears. Precipitation does not occur. The titer results are presented in Table 3. The average titer was 4.94.

[0037] Table 3

[0038] Fischer reagent titer determination results

[0039] Measurement number Droplet mass (g) Volume of Fischer reagent used for titration (ml) Fischer reagent titer Average titer value 1 0,0158 3,166 4,99 4,94 2 0,0172 3,517 4,89

[0040] Thus, the presented examples 1–3 confirm the achievement of the stated technical results – the absence of precipitation, as well as the production of a stable reagent with various titer values ​​in the stated ranges.

Claims

A single-component Karl Fischer reagent composition for the quantitative determination of water, containing iodine, sulfur dioxide, characterized in that it additionally contains 3-amino-1,2,4-triazole, polyethylene glycol dimethyl ether, zirconium nanoparticles modified with organic ligands, as well as triphenyl (polyethylene glycol) phosphonium bromide in the following ratio of components, wt.%: Iodine 5–10 Sulfur dioxide 5–10 3-amino-1,2,4-triazole 10–25 Polyethylene glycol dimethyl ether 53–78 Zirconium nanoparticles functionalized carboxyl groups 1–5 Triphenyl(polyethylene glycol)phosphonium bromide 1–5

Images