ISI 14-2e Determination of Acetyl Content
ISI 14-2e Determination of Acetyl Content 1. Scope The method is applicable to acetylated starch KM Rev. LT 14 Sep 1999 2. Principle Bound acetyl reacts with strong alkali and excess alkali is titrated 3. Apparatus 3.1 Burette 3.2 Conical flask, Erlenmeyer 250 ml with stopper 4. Reagents 4.1 Sodium hydroxide 0.1 N 4.2 Sodium hydroxide 0.45 N 4.3 Hydrochloric acid 0.2 N 4.4 Phenolphthalein: 1 g in 1 l ethanol 90% 5. Procedure Weigh 5 g of sample to the nearest mg. Transfer to conical flask (3.2) and disperse in 50 ml distilled water. Add a few drops of indicator (4.4) and titrate with (4.1) to permanent pink colour. Bound acetyl reaction Add 25.0 ml of NaOH 0.45 N (4.2). Stopper and shake vigorously for ½ hour Use mechanical shaker Titration Flush stopper and neck of flask with a little distilled water and titrate excess alkali with 0.2N HCL to disappearance of pink colour. Blank 25.0 ml 0.45N NaOH (4.2) is titrated as a blank 6. Calculation Calculate acetyl groups by avera