(HPMC)Determination of the hydroxypropyl methyl group

Method name:

determination of hydroxyproxyproxycellulose-hydroxypropoxygroup.

Scope of application:

This method determines the content of hydroxypropimoxyl in cellulose.

Method principle:

This method is applicable to hydroxypropioncellulose.

Sample preparation:

1.Sodium hydroxide drip solution (0.02 mol/L):

  • Preparation: Take 5.6mL of clarified sodium hydroxide saturated solution. And add newly boiling cold water to make 1000mL.
  • Calibration: Take about 6g of reference potassium hydrogen phthalate dried from 105℃ to constant weight, add 50mL of newly boiling cold water to dissolve as much as possible. Add 2 drops of phenolphthalein indicator liquid and titrate this, near the end point. Every 1mL of sodium hydroxide titer (1 mol/L) is equivalent to 20.42mg of potassium hydrogen phthalate.
  • Storage: put in polyethylene plastic bottle, sealed storage; 2 holes in the plug, one glass tube, 1 tube connected with sodium lime tube, 1 tube for the liquid use.

2.Phenolphthalein indicator fluid: One g of phenolphthalein was taken and 100mL of ethanol was added to dissolve.

3.Sodium thiosulfate titration solution (0.02 mol/L):
  • Preparation: Take 26g of sodium thiosulfate and 0.20g of anhydrous sodium carbonate, add new boiling cold water to dissolve into 1000mL, shake well, and place for 1 month before filtering.
  • Calibration: take about 0.15g of reference potassium dichromate at 120℃ dry and constant weight. Accurately determine, put iodine bottle, add water 50mL, dissolve potassium iodide 2.0g, gently shake. Dilute 40mL of sulfuric acid, shake, place in the dark for 10 minutes, add water 250mL to dilute, add 3mL. Titrate to blue disappearance and bright green, and correct by blank test.Each 1mL of sodium thiosulfate (0.1 mol/L) is equivalent to 4.903g of potassium dichromate. According to the consumption of the liquid and the amount of potassium dichromate.

4.Starch indicator liquid:

Take 0.5g of soluble starch, stir with 5mL of water well, slowly pour into 100mL of boiling water, stir with the add, continue to boil for 2 minutes, cool, pour out the supernatant. This liquid should be made in temporary use.

Operation steps:

take 0.1g of this product, precision weighing, put in the distilled bottle D, add 30% (g / g) cadmium trichloride solution of 10mL.Install water in the steam generator tube B to the joint and connect the distillation unit. Tittrated with sodium thiosulfate (0.02 mol/L), Note the consumed volume V2 (mL). Record the volumes Va and Vb (mL) of the consumed sodium hydroxide titration (0.02 mol/L) and sodium thiosulfate titration (0.02 mol/L), respectively.


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