A method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine

Abstract

The invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine, which can effectively avoid the loss of sulfur trioxide and remove the interference of trimethylamine on the detection of sulfur trioxide, and has the advantages of simple operation, good linearity, good repeatability and stable solution.

Description

1. Technical field

[0001] The invention belongs to the technical field of drug analysis, and particularly relates to a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. 2. Background technology

[0002] Sulfur trioxide (SO3) easily absorbs moisture, emits strong smoke in the air, and dissolves in water to form sulfuric acid and release a lot of heat. Sulfur trioxide is a strong oxidant, commonly used as an organic oxidant and a sulfation agent. When liquid or gaseous sulfur trioxide is used to directly carry out sulfation reaction on alcohol hydroxyl and phenol hydroxyl, many problems are often involved, such as the formation of polymers and sulfur trioxide treatment. Therefore, sulfur trioxide is usually subjected to sulfation reaction after forming a complex with amines, amides or ethers (Research Progress of Sulfation Reaction of Shifang. Journal of Southeast University (Medical Edition), 2010, Dec; 29(6): 707-710). Complexes of sulfur trioxide and amines are widely used in sulfation reaction.

[0003] Sulfur trioxide trimethylamine is a complex of sulfur trioxide and trimethylamine, with CAS number 17736-86-6, molecular formula C3H9N·O3S, and molecular weight 139.17. Sulfur trioxide trimethylamine plays an important role in the pharmaceutical field due to its mild reaction and stable properties. For example, in the preparation of key intermediates of antithrombotic drug fondaparinux sodium and antibacterial drug avibactam sodium, sulfur trioxide trimethylamine is used as a sulfation agent for hydroxyl groups. The quality of sulfur trioxide trimethylamine plays an important role in the preparation of drug intermediates.

[0004] Sulfur trioxide, as the main active ingredient in the chemical reaction of sulfur trioxide trimethylamine, is the key factor that determines the performance of sulfur trioxide trimethylamine. Therefore, it is very important to control the content of sulfur trioxide in sulfur trioxide trimethylamine.

[0005] At present, no relevant literature or reports on the detection method of sulfur trioxide content in trimethylamine sulfur trioxide have been found. In order to strengthen the quality control of trimethylamine sulfur trioxide, a method for detecting sulfur trioxide content needs to be developed. 3. Summary of the invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for detecting the sulfur trioxide content in sulfur trioxide trimethylamine which is simple to operate, has good linearity, good repeatability and stable solution, so as to meet the existing needs.

[0007] The present invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. The method comprises the following steps:

[0008] (1) Accurately weigh trimethylamine sulfur trioxide and place it in an iodine volumetric flask into which acidic solution has been accurately added. Add water, seal and shake to dissolve.

[0009] (2) Accurately add alkaline solution, shake well, boil, and test with a moistened test paper until the steam is no longer alkaline, cool, and add water;

[0010] (3) Add indicator solution and titrate with acidic titrant until the solution changes color, and correct the titration result with a blank test;

[0011] (4) Calculate the SO3 content in trimethylamine sulfur trioxide according to the following formula;

[0012]

[0013] Where: V1 is the volume of blank consumed acid titration solution (ml);

[0014] V2 is the volume of acidic titration solution consumed by trimethylamine sulfur trioxide (ml);

[0015] F is the ratio of the acid titration solution concentration to its nominal value;

[0016] M is the amount of sulfur trioxide per 1 ml of acidic titration solution;

[0017] W is the sample weight of trimethylamine sulfur trioxide (g).

[0018] In step (1), the acidic solution is hydrochloric acid or sulfuric acid solution; + The molar ratio of the concentration of trimethylamine sulfur trioxide is 0.6 to 4.2:1, preferably 0.6 to 2.8:1.

[0019] In step (2), the alkaline solution is sodium hydroxide or potassium hydroxide solution; the molar ratio of the alkaline solution to trimethylammonium sulfur trioxide is 2.7-18.1:1, preferably 5.5-7.0:1; the detection test paper is pH test paper or red litmus paper; when the alkaline solution is added and boiled, it cannot be evaporated to dryness, and water can be added if necessary.

[0020] In step (3), the indicator solution is methyl red-bromocresol green indicator solution, methyl red indicator solution or bromocresol green indicator solution; the acidic titrant is hydrochloric acid or sulfuric acid titrant, the hydrochloric acid titrant is 0.1 mol / L or 0.2 mol / L, and the sulfuric acid titrant is 0.1 mol / L or 0.05 mol / L; the method for calculating the SO3 content is to detect the amount of alkali in the boiled solution with the acidic titrant, calculate the difference between the titration results of the test solution and the blank solution, that is, the amount of alkali consumed by the sulfuric acid generated by sulfur trioxide, thereby obtaining the amount of sulfur trioxide.

[0021] The present invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. The method comprises the following steps:

[0022] (1) Accurately weigh about 0.1 g of trimethylamine sulfur trioxide and place it in an iodine volumetric flask into which acidic solution has been accurately added. Add water, seal and shake to dissolve.

[0023] (2) Accurately add alkaline solution, shake well, boil, and test with a moistened test paper until the steam is no longer alkaline, cool, and add water;

[0024] (3) Add indicator solution and titrate with acidic titrant until the solution changes color, and correct the titration result with a blank test;

[0025] (4) Calculate the SO3 content in trimethylamine sulfur trioxide according to the following formula;

[0026]

[0027] Where: V1 is the volume of blank consumed acid titration solution (ml);

[0028] V2 is the volume of acidic titration solution consumed by trimethylamine sulfur trioxide (ml);

[0029] F is the ratio of the acid titration solution concentration to its nominal value;

[0030] M is the amount of sulfur trioxide per 1 ml of acidic titration solution;

[0031] W is the sample weight of trimethylamine sulfur trioxide (g).

[0032] in,

[0033] In step (1), the amount of acidic solution added is H + The concentration is 0.5mmol to 3mmol, preferably 0.5mmol to 2mmol; the acidic solution is hydrochloric acid or sulfuric acid solution.

[0034] In step (2), the amount of the alkaline solution added is 2 mmol to 13 mmol, preferably 4 to 5 mmol; the alkaline solution is sodium hydroxide or potassium hydroxide solution; the test paper is pH test paper or red litmus paper; when the alkaline solution is added and boiled, it cannot be evaporated to dryness, and water can be added if necessary.

[0035] In step (3), the indicator solution is methyl red-bromocresol green indicator solution, methyl red indicator solution or bromocresol green indicator solution; the acidic titrant is hydrochloric acid or sulfuric acid titrant, the hydrochloric acid titrant is preferably 0.1 mol / L or 0.2 mol / L, and the sulfuric acid titrant is preferably 0.1 mol / L or 0.05 mol / L; the method for calculating the SO3 content is to detect the amount of alkali in the boiled solution with the acidic titrant, calculate the difference between the titration results of the test solution and the blank solution, that is, the amount of alkali consumed by the sulfuric acid generated by sulfur trioxide, thereby obtaining the amount of sulfur trioxide.

[0036] The present invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. The method comprises the following steps:

[0037] (1) Accurately weigh about 0.1 g of trimethylamine sulfur trioxide and place it in an iodine volumetric flask into which 10 ml of 0.1 mol / L hydrochloric acid solution has been accurately added. Add 20 ml of water, seal the bottle, and shake to dissolve.

[0038] (2) Accurately add 10 ml of 0.5 mol / L sodium hydroxide solution, shake well, boil, and test with a moistened pH paper until the steam is no longer alkaline. Cool and add 50 ml of water.

[0039] (3) Add 5 drops of methyl red-bromocresol green indicator solution and titrate with hydrochloric acid titrant (0.1 mol / L) until the solution changes from green to wine red. Correct the titration result with a blank test and calculate the SO3 content.

[0040] The present invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. The method comprises the following steps:

[0041] (1) Accurately weigh about 0.1 g of trimethylamine sulfur trioxide and place it in an iodine volumetric flask into which 5 ml of 0.1 mol / L hydrochloric acid solution has been accurately added. Add 20 ml of water, seal the bottle, and shake to dissolve.

[0042] (2) Accurately add 8 ml of 0.5 mol / L sodium hydroxide solution, shake well, boil, and test with a moistened pH paper until the steam is no longer alkaline. Cool and add 50 ml of water.

[0043] (3) Add 5 drops of methyl red-bromocresol green indicator solution and titrate with hydrochloric acid titrant (0.1 mol / L) until the solution changes from green to wine red. Correct the titration result with a blank test and calculate the SO3 content.

[0044] The present invention provides a method for determining the content of sulfur trioxide in sulfur trioxide trimethylamine. The method comprises the following steps:

[0045] (1) Accurately weigh about 0.1 g of trimethylamine sulfur trioxide and place it in an iodine volumetric flask into which 10 ml of 0.1 mol / L sulfuric acid solution has been accurately added. Add 20 ml of water, seal the bottle, and shake to dissolve.

[0046] (2) Accurately add 10 ml of 0.5 mol / L potassium hydroxide solution, shake well, boil, and test with a moistened pH paper until the steam is no longer alkaline. Cool and add 50 ml of water.

[0047] (3) Add 5 drops of methyl red indicator solution and titrate with sulfuric acid titrant (0.05 mol / L) until the solution changes from yellow to red. Correct the titration result with a blank test and calculate the SO3 content.

[0048] The beneficial effects of the present invention are:

[0049] (1) Sulfur trioxide trimethylamine has poor solubility in water, but good solubility in hot water and acidic solvents. Dissolving the sample in an acidic solvent can increase the solubility, and it is easy for sulfur trioxide to react with water to form sulfuric acid. In order to prevent sulfur trioxide from overflowing under heating conditions, an acidic solvent is selected for dissolution, which can effectively avoid the loss of sulfur trioxide;

[0050] (2) The boiling point of trimethylamine is about 2.75°C and it is easily soluble in water. Boiling under alkaline conditions can boil out trimethylamine, thus avoiding the interference of trimethylamine in the subsequent acid-base titration;

[0051] (3) Titrate the base with the acid. The difference between the acid and the blank solution is the amount of base consumed by the sulfuric acid produced by sulfur trioxide, thus obtaining the amount of sulfur trioxide.

[0052] (4) The present invention is easy to operate, has good linearity, good repeatability and stable solution.

[0053] In summary, the present invention determines the sulfur trioxide content in sulfur trioxide trimethylamine, can effectively avoid the loss of sulfur trioxide, remove the interference of trimethylamine on sulfur trioxide detection, and has simple operation, good linearity, good repeatability and stable solution. 4. Description of the drawings

[0054] Figure 1 This is the linear result of the determination of sulfur trioxide content in sulfur trioxide trimethylamine in the linear test of Example 7. 5. Specific implementation methods

[0055] Specific embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0056] Reagents

[0057] Preparation of 0.1mol / L hydrochloric acid solution: Take 9ml of hydrochloric acid, add appropriate amount of water to make 1000ml, and shake well.

[0058] Preparation of 0.5mol / L sodium hydroxide solution: Take 20g of sodium hydroxide, dissolve it in water and dilute it to 1000ml, and shake well.

[0059] 0.1mol / L sulfuric acid solution: Take 6.0ml of sulfuric acid and slowly inject it into an appropriate amount of water while stirring. Cool to room temperature, dilute to 1000ml with water and shake well.

[0060] Preparation of hydrochloric acid titration solution (0.1 mol / L): Take 9 ml of hydrochloric acid, add appropriate amount of water to make 1000 ml, and shake well.

[0061] Standardization of hydrochloric acid titration solution (0.1mol / L): Take about 0.15g of standard anhydrous sodium carbonate dried to constant weight at 270-300℃, weigh accurately, add 50ml of water to dissolve, add 10 drops of methyl red-bromocresol green mixed indicator solution, and titrate with this solution until the solution changes from green to purple-red, boil for 2 minutes, cool to room temperature, and continue to titrate until the solution changes from green to dark purple. Each 1ml of hydrochloric acid titration solution (0.1mol / L) is equivalent to 5.30mg of anhydrous sodium carbonate. According to the consumption of this solution and the amount of anhydrous sodium carbonate taken, calculate the concentration of this solution.

[0062] Sulfuric acid titration solution (0.05 mol / L): Take 3.0 ml of sulfuric acid and slowly inject it into an appropriate amount of water while stirring. Cool to room temperature, dilute to 1000 ml with water and shake well.

[0063] Standardization of sulfuric acid titrant (0.05mol / L): Same as the standardization method of hydrochloric acid titrant.

[0064] Preparation of methyl red-bromocresol green indicator solution: Take 20 ml of 0.1% methyl red ethanol solution, add 30 ml of 0.2% bromocresol green ethanol solution, shake well, and you have it.

[0065] Example 1 Determination of sulfur trioxide content

[0066] Take about 0.5g of trimethylamine sulfur trioxide, add 30ml of water, add 10ml of hydrochloric acid to dissolve, and seal. Add 40ml of barium chloride test solution dropwise, a precipitate will precipitate, let it stand for about 30 minutes, then boil it for 2 minutes, let it cool, and let it stand for 4 hours. Filter it with quantitative filter paper, wash it with water until there is no chloride ion in the precipitate (check with silver nitrate test solution). Transfer the precipitate together with the filter paper to a porcelain crucible that has been burned to constant weight at 800℃, ash it, and burn it to constant weight at 800℃. Calculate the sulfur trioxide content in trimethylamine sulfur trioxide according to formula (1).

[0067]

[0068] Where: m2 is the mass of barium sulfate precipitate after ignition (g);

[0069] m1 is the sample weight of trimethylamine sulfur trioxide (g);

[0070] 80.06 is the molecular weight of trimethylamine sulfur trioxide;

[0071] 233.39 is the molecular weight of barium sulfate.

[0072] The sulfur trioxide content in trimethylamine sulfur trioxide was measured to be about 10.5%, which is low. There will be losses during the precipitation and washing process, and the operation is cumbersome and time-consuming. This method is not applicable.

[0073] Example 2 Determination of sulfur trioxide content

[0074] Take about 0.1g of trimethylamine sulfur trioxide, weigh it accurately, put it in an iodine volumetric flask with 10ml of 0.1mol / L hydrochloric acid solution accurately added in advance, seal it, shake it well, accurately add 25ml of 0.1mol / L sodium hydroxide solution to dissolve it, extract it with chloroform 3 times, 10ml each time, discard the organic phase, wash the separatory funnel with water 3 times, 5ml each time, and combine the aqueous phase and the washing liquid. Add 5 drops of methyl red-bromocresol green indicator solution, titrate it with hydrochloric acid titration solution (0.1mol / L) until the solution changes from green to wine red, and correct the titration result with a blank test. Each 1ml of hydrochloric acid titration solution (0.1mol / L) is equivalent to 4.003mg of SO3. Result: The solubility of trimethylamine in water is greater than that in chloroform, and the interference of trimethylamine cannot be removed. There is no difference between the blank titration volume and the sample titration volume, so this method is not applicable.

[0075] Example 3 Determination of sulfur trioxide content

[0076] Take about 0.1g of trimethylamine sulfur trioxide, weigh accurately, put it in an iodine volumetric flask with 10ml of 0.1mol / L hydrochloric acid solution accurately added in advance, add 20ml of water, seal, shake to dissolve, accurately add 10ml of 0.5mol / L sodium hydroxide solution, shake well, boil, use moistened pH test paper to detect until the steam is not alkaline, cool, add 50ml of water, add 5 drops of methyl red-bromocresol green indicator solution, titrate with hydrochloric acid titration solution (0.1mol / L) until the solution changes from green to wine red, and correct the titration result with a blank test. Each 1ml of hydrochloric acid titration solution (0.1mol / L) is equivalent to 4.003mg of SO3. Test two batches of trimethylamine sulfur trioxide samples (source: Aldrich) and calculate the content of sulfur trioxide according to the following formula.

[0077]

[0078] Where: V1 is the volume (ml) of blank consumed hydrochloric acid titration solution (0.1 mol / L);

[0079] V2 is the volume (ml) of hydrochloric acid titration solution (0.1 mol / L) consumed by trimethylamine sulfur trioxide;

[0080] F is the ratio of the concentration value of the hydrochloric acid titrant (0.1 mol / L) to its nominal value;

[0081] M is the amount of sulfur trioxide per 1 ml of hydrochloric acid titration solution (0.1 mol / L), i.e. 4.003 mg;

[0082] W is the sample weight of trimethylamine sulfur trioxide (g).

[0083] The results are shown in Table 1 below.

[0084] Table 1 Results of sulfur trioxide content in sulfur trioxide trimethylamine

[0085]

[0086] The results show that the results obtained by this method have good parallelism and are close to the theoretical content of sulfur trioxide, which is 57.5%.

[0087] Example 4 Determination of sulfur trioxide content

[0088] The method of Example 2 was used to measure the sulfur trioxide content of different batches of trimethylamine sulfur trioxide.

[0089] The results showed that the sulfur trioxide contents in the two test samples of sulfur trioxide trimethylamine from batch MKBK2211V were 56.60% and 56.40% respectively, with an average value of 56.50%.

[0090] Example 5 Determination of sulfur trioxide content

[0091] Take about 0.1g of trimethylamine sulfur trioxide, weigh accurately, put it into an iodine volumetric flask with 5ml of 0.1mol / L hydrochloric acid solution accurately added in advance, add 20ml of water, seal, shake to dissolve, accurately add 8ml of 0.5mol / L sodium hydroxide solution, shake well, boil, test with moistened pH test paper until the steam does not show alkalinity, cool, add 50ml of water, add 5 drops of methyl red-bromocresol green indicator solution, titrate with hydrochloric acid titrant (0.1mol / L) until the solution changes from green to wine red, and correct the titration result with a blank test. Each 1ml of hydrochloric acid titrant (0.1mol / L) is equivalent to 4.003mg of SO3. Calculate the content of sulfur trioxide according to the following formula.

[0092]

[0093] Where: V1 is the volume (ml) of blank consumed hydrochloric acid titration solution (0.1 mol / L);

[0094] V2 is the volume (ml) of hydrochloric acid titration solution (0.1 mol / L) consumed by trimethylamine sulfur trioxide;

[0095] F is the ratio of the concentration value of the hydrochloric acid titrant (0.1 mol / L) to its nominal value;

[0096] M is the amount of sulfur trioxide per 1 ml of hydrochloric acid titration solution (0.1 mol / L), i.e. 4.003 mg;

[0097] W is the sample weight of trimethylamine sulfur trioxide (g).

[0098] The sulfur trioxide trimethylamine sample of batch MKCH1333 was tested and the sulfur trioxide content was found to be 56.83%.

[0099] Example 6 Determination of sulfur trioxide content

[0100] Take about 0.1g of trimethylamine sulfur trioxide, weigh accurately, put it into an iodine volumetric flask with 10ml of 0.1mol / L sulfuric acid solution accurately added in advance, add 20ml of water, seal, shake to dissolve, accurately add 10ml of 0.5mol / L potassium hydroxide solution, shake well, boil, test with wet pH test paper until the steam does not show alkalinity, cool, add 50ml of water, add 5 drops of methyl red indicator solution, titrate with sulfuric acid titration solution (0.05mol / L) until the solution changes from yellow to red, and correct the titration result with a blank test. Each 1ml of sulfuric acid titration solution (0.05mol / L) is equivalent to 4.003mg of SO3. Calculate the content of sulfur trioxide according to the following formula.

[0101]

[0102] Where: V1 is the volume (ml) of the blank consumed sulfuric acid titration solution (0.05 mol / L);

[0103] V2 is the volume (ml) of sulfuric acid titration solution (0.05 mol / L) consumed by trimethylamine sulfur trioxide;

[0104] F is the ratio of the concentration value of sulfuric acid titration solution (0.05 mol / L) to its nominal value;

[0105] M is the amount of sulfur trioxide equivalent to 1 ml of sulfuric acid titration solution (0.05 mol / L), i.e. 4.003 mg;

[0106] W is the sample weight of trimethylamine sulfur trioxide (g).

[0107] The sulfur trioxide trimethylamine sample of batch MKCH1333 was tested and the sulfur trioxide content was found to be 56.21%.

[0108] Example 7 Linearity Test

[0109] Take 0.06g, 0.08g, 0.1g, 0.12g, and 0.14g of trimethylamine sulfur trioxide, weigh them accurately, and place them in iodine volumetric bottles with 10ml of 0.1mol / L hydrochloric acid solution added in advance, add 20ml of water, seal, shake to dissolve, accurately add 10ml of 0.5mol / L sodium hydroxide solution, shake well, boil, and use wet pH test paper to detect until the steam does not show alkalinity, cool, add 50ml of water, add 5 drops of methyl red-bromocresol green indicator solution, and titrate with hydrochloric acid titrant (0.1mol / L) until the solution changes from green to wine red, and correct the titration result with a blank test. Each 1ml of hydrochloric acid titrant (0.1mol / L) is equivalent to 4.003mg of SO3. Plot a curve with the volume of hydrochloric acid titrant (0.1mol / L) actually consumed versus the sample weight, and calculate the regression equation, correlation coefficient, and intercept. The results show that the linearity of sulfur trioxide and trimethylamine is good within the range of 0.0618 to 0.1438 g. The specific results are shown in Table 2. Figure 1 .

[0110] Table 2 Linear results of sulfur trioxide content in sulfur trioxide trimethylamine

[0111] Sample weighing range (g) Linear equations Correlation coefficient intercept(%) 0.0618～0.1438 y=136.14x+0.0428 0.9999 0.31

[0112] Example 8 Repeatability Test

[0113] Take about 0.1g of trimethylamine sulfur trioxide, accurately weigh, a total of 6 portions, respectively, put into iodine volume flasks with 10ml of 0.1mol / L hydrochloric acid solution accurately added in advance, add 20ml of water, seal, shake to dissolve, accurately add 10ml of 0.5mol / L sodium hydroxide solution, shake well, boil, detect with wet pH test paper until the steam does not show alkalinity, cool, add 50ml of water, add 5 drops of methyl red-bromocresol green indicator solution, titrate with hydrochloric acid titration solution (0.1mol / L) until the solution changes from green to wine red, and correct the titration results with blank test, each 1ml of hydrochloric acid titration solution (0.1mol / L) is equivalent to 4.003mg of SO3. Calculate the sulfur trioxide content and calculate the relative standard deviation of the content. The results show that the precision test results of the determination of sulfur trioxide content in trimethylamine sulfur trioxide are good, and the specific results are shown in Table 3.

[0114] Table 3 Results of precision test for determination of sulfur trioxide content in sulfur trioxide trimethylamine

[0115] Serial number 1 2 3 4 5 6 RSD(%) content(%) 56.72 56.38 56.65 56.41 56.53 56.25 0.32

[0116] Example 9 Solution Stability Test

[0117] Take about 0.1g of trimethylamine sulfur trioxide, weigh accurately, a total of 5 portions, respectively, put them into iodine volumetric bottles with 10ml of 0.1mol / L hydrochloric acid solution accurately added in advance, add 20ml of water, seal, shake to dissolve, accurately add 10ml of 0.5mol / L sodium hydroxide solution, shake well, boil, detect with moistened pH test paper until the steam does not show alkalinity, cool, add 50ml of water, and place under natural light at room temperature for 8 hours. Take a portion at 0, 2, 4, 6, and 8 hours, add 5 drops of methyl red-bromocresol green indicator solution, and titrate with hydrochloric acid titration solution (0.1mol / L) until the solution changes from green to wine red, and correct the titration results with a blank test. Each 1ml of hydrochloric acid titration solution (0.1mol / L) is equivalent to 4.003mg of SO3. Calculate the sulfur trioxide content and calculate the change value of the sulfur trioxide content. The results show that the test solution for the determination of sulfur trioxide content in trimethylamine sulfur trioxide is stable within 8 hours under natural light at room temperature. See Table 4 for specific results.

[0118] Table 4 Sulfur trioxide content in trimethylamine sulfur trioxide test solution stability test results

[0119] Time (hours) 0 2 4 6 8 Maximum change value (%) content(%) 56.72 56.36 56.78 56.30 56.71 0.42

Claims

1. A method for determining the content of sulfur trioxide in trimethylamine sulfur trioxide, characterized in that: The following steps are involved: (1) Accurately weigh trimethylammonium sulfur trioxide and place it in an iodine volumetric flask into which an acidic solution has been accurately added, wherein the molar ratio of H+ to trimethylammonium sulfur trioxide in the acidic solution is 0.6-4.2:

1. Add water, seal and shake to dissolve; (2) Accurately add alkaline solution, where the molar ratio of OH- to trimethylamine sulfur trioxide in the alkaline solution is 2.7-18.1:1, shake well, boil, and test with a moistened test paper until the steam is no longer alkaline, cool, and add water; (3) Add indicator solution and titrate with acidic titration solution until the solution changes color. Correct the titration result with a blank test. (4) Calculate the SO3 content in trimethylamine sulfur trioxide according to the following formula; Where: V1 is the volume of blank consumed acid titration solution (ml); V2 is the volume of acidic titration solution consumed by sulfur trioxide and trimethylamine, ml; F is the ratio of the acid titration solution concentration to its nominal value; M is the amount of sulfur trioxide per 1 ml of acidic titration solution; W is the sample weight of trimethylamine sulfur trioxide in g; Wherein, the acidic solution in step (1) is hydrochloric acid or sulfuric acid solution; The alkaline solution in step (2) is a sodium hydroxide solution or a potassium hydroxide solution; the test paper is a pH test paper or a red litmus paper; The acidic titrant in step (3) is hydrochloric acid or sulfuric acid titrant; wherein the concentration of the hydrochloric acid titrant is 0.1 mol / L or 0.2 mol / L; the concentration of the sulfuric acid titrant is 0.1 mol / L or 0.05 mol / L.

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