Standard of HPMC (hydroxypropyl methylcellulose) for capsules

The product 2-hydroxypropyl ether methyl cellulose is a semi-synthetic product and can be manufactured in two ways:

1. Process the cotton linters or wood pulp fibers with caustic soda, and then react the product with methylene chloride and propylene oxide successively, and the refine and pulverize the product.
2. Process a suitable grade of methyl cellulose with sodium hydroxide, and then react the methyl cellulose with propylene under high temperature and high pressure, and purified the product.

The molecular weight ranges from 10,000 to 1,500,000. Hypromellose is divided into four subtypes depending on the content of methoxy and hydroxypropoxy groups, namely, 1828, 2208, 2906, and 2910. Calculating the dried product, the content of each substituted methoxy (-OCH₃) and hydroxypropoxy (-OCH₂CHOHCH₃) should be in accordance with the following table.

Properties

the product is white or off-white fibrous or granular powder; odorless. It is almost insoluble in absolute ethanol, ether or acetone; it swells into a clear or slightly turbid colloidal solution in cold water.

Identification

1. Take 1g of the product, add 100ml of hot water (80 ~ 90 ° C), stir to form a slurry, cool the product in an ice bath, then comes out the viscous liquid. Add 2ml of the liquid in a measure tube, slowly add 1ml of sulfuric acid solution containing 0.035% anthrone, along the tube wall.  Place the tube for 5 minutes, and it will show a blue-green ring at the interface of the two liquids.
2. Take a proper amount of above viscous liquid, pour it into a glass plate, and a tough film is formed after the water evaporated.
3. Take 0.5g of the product, uniformly disperse in boiling water of 50ml, and stir with electromagnetic to form insoluble slurry. Cool down the temperature of the insoluble slurry to 10 °C by stirring with electromagnetic, the comes out a clear or slightly turbid solution. Add 50ml of water, and stir electromagnetically, and heat the solution at the same time, the temperature is raised at a rate of 2~5 ° C per minute, and the temperature shall be not lower than 50 ° C when turbid flocculation is generated.

Viscosity

if the value of the indicated viscosity is smaller than 600mPa·s, measure the viscosity according to method 1, and the viscosity shall be 80% to 120% of the indicated viscosity. If the value of the indicated viscosity is greater than or equal to 600mPa·s, measure the viscosity according to method 2, and the viscosity shall be 75% to 140% of the indicated viscosity.

Take some of the product (calculated in dried product), add water of 90 ° C to make solution of 2.0% (g / g), stir for about 10 minutes, until the particles are completely dissolved. Cool the solution down by putting it in an ice bath, and at the same time, continuously stir to remove bubbles, and if necessary, adjust the weight with cold water, and then we got the measure solution after all foams are removed.

1. Under the temperature of 20 ° C ± 0.1 ° C, measure the kinematic viscosity (v) of the solution with a  ubbelohde viscometer with proper internal diameter (the outflow time should be longer than 200 seconds), and measure the density (ρ) of the solution under the same conditions, and calculate dynamic viscosity (η) = ρv
2. Under the temperature of 20 ° C ± 0.1 ° C, use the appropriate single-column rotary viscometer (Brookfield type LV model) or equivalent viscometer to measure the viscosity according to the following table. after 2 minutes of rotation, read the number, and then stop for 2 minutes. Repeat the experiment for 2 more times, and take the average value of three experiments.

PH

take 1.0g of the product (calculated in dried product), add 50ml of water of 90°C with stirring, and leave it for cooling down. Then add water to dilute the solution to 100ml, and stir until all the product is dissolved completely. PH value should be 5.0 to 8.0.

Insoluble in water

take 1.0g of this product, put it in a beaker, add 100ml of hot water (80 ~ 90 °C) and swell for about 15 minutes, then cool it down in an ice bath. Add 300ml of water (the sample with high viscosity can be add with more water, ensuring that the solution can be filtered.) and fully stirred. Filter the solution with the fused glass the has been dried at 105 ° C to be with a constant weigh. Wash the beaker with water, and add the washing liquor to the above-mentioned crucible, and filter the solution. Dry the crucible at 105 ° C until its weight is constant, and the residual residue should not exceed 5 mg (0.5%).

Loss on drying

take the product and dry it at 105 °C for 2 hours. The weight loss should not exceed 5.0%.

Residue on ignition

take 1.0g of the product, check accordingly, and the residual residue should not exceed 1.5%.

Pb

take 5.0g of the product, and process it by microwave digestion. Use graphite furnace as atomizer, and check according to atomic absorption spectrophotometer method (2015 edition of Chinese Pharmacopoeia General Rule 0406 first method), the content of Pb should not exceed two parts per million.

Arsenic salt

take 1.0g of this product, add 1.0g of calcium hydroxide, mix, and then add water and stir. After drying, carbonize the solution with small fire, then ignite it at 600 °C under it is completely ashed. Leave it for cooling down, and then add 5ml of hydrochloric acid and 23ml of water for dissolution. Check accordingly, and the content of the arsenic salt should meet the requirements (0.0002%).

Methoxy

take the product, and measure methoxy according to the methoxy, ethoxy, hydroxypropoxy measurement. If the capacity method is adopted, take the product, accurately weigh it. Actual methoxy content = measured amount of methoxyl (%) - the amount of hydroxypropoxy (%) * (31/75×0.93).

Hydroxypropoxy

take the product, and measure hydroxypropoxy according to the methoxy, ethoxy, hydroxypropoxy measurement. If the capacity method is adopted, take the product of 0.1g, accurately weigh it, and measure accordingly.  

Storage

sealed.

Marking

indicate the substitution type and indicate the viscosity in mPa·S