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Determination of the content of mannitol bulk drug by redox titration, step by step

Mar. 07, 2019

The isomer of mannitol sorbitol, easily with water, is a white transparent solid state, has a sweet taste similar to sucrose, and can be used in the fields of medicine, food, industrial production and the like.

One of the methods for testing the mannitol bulk drug by redox titration, the following is the test procedure.

The content of mannitol in the mannitol bulk drug is determined by redox titration, and the method is only applicable to the mannitol drug substance.

Test principle:

After the mannitol raw material is diluted with water, the taken portion is placed in an iodine bottle. Then add sodium periodate solution, add potassium iodide test solution, and finally titrate the droplet with sodium thiosulfate. Near the end point, add starch indicator solution, continue titration until blue disappears, and correct the titration result with the blank test. The content of mannitol was calculated based on the amount of titrant used.


1. sodium periodate solution; 2. potassium iodide; 3. potassium iodide test solution; 4. sodium thiosulfate titration solution (0.05mol/L); 5. starch indicator solution; 6. dilute sulfuric acid; 7. benchmark dichromate Potassium

Test sample preparation: 1. Sodium iodate solution was prepared by mixing 90 ml of sulfuric acid solution (1→20) with 110 mL of sodium periodate solution (2.3→1000); 2. Potassium iodide test solution taking 16.5 g of potassium iodide, adding water to dissolve into 100mL, the liquid should be used in a new system; 3. Sodium thiosulfate titration solution (0.05mol / L) sodium thiosulfate titration solution (0.1mol / L) diluted with fresh boiling water before use; 4 Starch indicator solution Take 0.5g of soluble starch, add 5mL of water and mix well, slowly pour into 100mL boiling water, continue to boil for 2 minutes with stirring, let cool, pour the supernatant, that is, this liquid should come Using a new system; 5. Dilute sulfuric acid to take 57mL of sulfuric acid, diluted with water to 1000mL.

The steps are as follows:

Weigh accurately about 0.2g of the test sample, place it in a 250mL volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 10mL, place the iodine bottle, add 50mL of sodium periodate solution, and heat it on the water bath. Minute, let cool, add 10mL of potassium iodide test solution, close the plug, place for 5 minutes, titrate with sodium thiosulfate titration solution (0.05mol / L), to the near endpoint, add 1mL of starch indicator solution, continue titration until the blue disappears, The results of the titration were corrected by a blank test. Each 1 mL of sodium thiosulfate titration solution (0.05 mol/L) corresponds to 0.9109 mg of C6H14O6.

Note: “Precision weighing” means that the weight should be accurate to one-thousandth of the weight weighed. “Precision measurement” means that the accuracy of the volume measurement should meet the accuracy requirements of the volumetric pipette in the national standard.

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