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GB/T 20373-2021: Determination of acetyl content in modified starch - Titrimetric method Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB/T 20373: Historical versions
Similar standardsGB/T 20373-2021: Determination of acetyl content in modified starch - Titrimetric method---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT20373-2021GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 67.180.20 CCS X 11 GB/T 20373-2021 Replacing GB/T 20373-2006 Determination of Acetyl Content in Modified Starch - Titrimetric Method ISSUED ON: MAY 21, 2021 IMPLEMENTED ON: DECEMBER 1, 2021 Issued by: State Administration for Market Regulation; Standardization Administration of the People’s Republic of China. Table of ContentsForeword ... 3 1 Scope ... 4 2 Normative References ... 4 3 Terms and Definitions ... 4 4 Principle ... 4 5 Reagents and Materials ... 4 6 Instruments ... 5 7 Methods of Operation ... 5 8 Result Calculation ... 6 9 Precision ... 7 Determination of Acetyl Content in Modified Starch - Titrimetric Method1 ScopeThis 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 ReferencesThe 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 Methods3 Terms and DefinitionsThere are no terms and definitions that need to be defined in this document.4 PrincipleUnder 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 MaterialsUnless 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. 7.3 Sample Titration After the saponification is completed, remove the stopper; use a washing bottle to rinse the stopper and the wall of the conical flask. Inject 0.20 mol/L standard hydrochloric acid titration solution (5.6) into the acid burette (6.3); use it to titrate the specimen, until the pink color vanishes. Record the volume of the consumed standard hydrochloric acid titration solution as V1. 7.4 Blank Test 7.4.1 Non-pregelatinized modified starch: take 25.0 mL sodium hydroxide solution (5.5) as a blank; add 50.0 mL of water and 3 drops of phenolphthalein indicator solution (5.7); shake it well. Inject 0.20 mol/L standard hydrochloric acid titration solution (5.6) into the acid burette (6.3); use it to titrate the blank, until the pink color vanishes. Record the volume of the consumed standard hydrochloric acid titration solution as V0. 7.4.2 Pregelatinized modified starch: take 25.0 mL sodium hydroxide solution (5.5) as a blank; add 5.0 mL of absolute ethanol (5.3), 100.0 mL of water and 3 drops of phenolphthalein indicator solution (5.7); shake it well. Inject 0.20 mol/L standard hydrochloric acid titration solution (5.6) into the acid burette (6.3); use it to titrate the blank, until the pink color vanishes. Record the volume of the consumed standard hydrochloric acid titration solution as V0.8 Result CalculationThe 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); ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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