Detection method of hydroxypropyl methylcellulose quality index

Detection method for the 2% viscosity of hydroxypropyl methylcellulose:

1. This law is applicable to determining the dynamic viscosity of non-Newtonian fluid (solution of platform polymer, suspension, solution of emulsion dispersed liquid or surfactant, etc.).

2. Instruments and appliances

2.1 Rotary viscometer (using NDI-1 type and NDI-4 type as specified in Chinese Pharmacopoeia)

2.2 The constant temperature accuracy of the constant temperature water bath is + 0.1℃

2.3 The thermometer degree is 0.2℃, after periodic verification.

2.4 Frequency meter The viscometer (such as NDJ-1 type, NDI-4 type) must be used aside.accuracy 1%.

3. Operation method Accurately weigh 8.0g of sample, put into a dry, peeled 400mL high foot beaker, add about 100mL of 80-90 degrees Celsius hot water, stir for 10min to disperse evenly, stir and add cold water to a total of 400mL.At the same time, after constantly stirring for about 30min to make a 2% (w / w) solution, put into the refrigerator ice bath to cool to the surface of thin ice, take out and put into the constant temperature tank to keep the center temperature constant temperature to 20 + 01 degrees to detect the viscosity.

3.1 The installation and operation of the instrument shall be carried out according to the operation instructions of the instrument, and the appropriate rotor and rotation speed shall be selected according to the viscosity range of the test product and the provisions of the pharmacopoeia under the text of the variety.

3.2 Adjust the constant temperature water temperature according to the measurement of each drug item.

3.3 Determine the deflection angle (a) in a constant temperature for 30 minutes.Turn off the motor and restart the measurement once again. The difference between the measurement value and the average value shall not exceed 3% of the average taxi, otherwise the third measurement shall be made.

3.4 The average value of the two determinations is calculated according to the formula, that is, the dynamic viscosity of the test product.

4. Record and calculation

4.1 Record the model of the rotary viscosity meter, the rotor number and the rotation speed used, the viscosity meter constant (K value), determine the temperature, and the a value measured each time.

4.2 Computational type

Dynamic viscosity (MPa s) =Ka.

Where K is the viscosity gauge constant a measured by a standard liquid with known viscosity is the deflection angle

Ash detection method:

1. Test product 1.0~2.0g or the specified weight of each variety shall be placed in the crucible with burning to constant weight.

2. Test: put the crucible on the electric furnace, avoid burning, to complete carbonization, no smoke (heated easy foaming test products, should prevent overflow crucible), cool to room temperature, completely gray at 700~800℃, move in the dryer, cool to room temperature, precision weighing, then at 700~800℃ to constant weight, according to the ash weight.

3. Determination results and report

Calculate the percentage content of ash by the following formula.

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