GB/T 20373-2021Determination of acetyl content in modified starch—Titrimetric method (English PDF)

1 Scope

This Standard specifies the determination of acetyl content in modified starch through the titrimetric method. This Standard is applicable to modified starch that contains acetyl.

2 Normative References

The content of the following documents constitutes indispensable clauses of this document through normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document.

GB/T 601 Chemical Reagent - Preparations of Standard Volumetric Solutions

GB/T 603 Chemical Reagent - Preparations of Reagent Solutions for Use in Test Methods

GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods

3 Terms and Definitions

There are no terms and definitions that need to be defined in this document.

4 Principle

Under alkaline conditions (pH 8.5 or higher), modified starch containing acetyl is saponified by excess alkali. Use a standard hydrochloric acid titration solution to titrate the remaining alkali. Through conversion, calculate the acetyl content.

5 Reagents and Materials

Unless it is otherwise specified, the used reagents shall be analytically pure. The water used for tests shall comply with the requirements of Grade-2 water specified in GB/T 6682.

Use 0.10 mol/L sodium hydroxide solution (5.4) to titrate the specimen solution (7.1.1 or 7.1.2) to slightly red, then, add 25.0 mL of 0.45 mol/L sodium hydroxide solution (5.5); thoroughly shake it and put on the stopper. Under room-temperature conditions, on a mechanical oscillator, oscillate it for 30 min, or on a magnetic stirrer (6.2), stir it for 60 min to perform saponification.

7 Methods of Operation

8 Result Calculation

The mass fraction w0 of acetyl shall be calculated in accordance with Formula (1):

Where, V0---the volume of the standard hydrochloric acid titration solution consumed by the blank, expressed in (mL);

V1---the volume of the standard hydrochloric acid titration solution consumed by the sample, expressed in (mL); c---the accurate concentration of the standard hydrochloric acid titration solution, expressed in (mol/L);