Pharmacopoeia standard for hydroxypropyl methylcellulose
Source and content: This product is 2-hydroxypropyl ether methylcellulose. Hydroxypropyl methylcellulose is divided into four substitution types based on the range of methoxy and hydroxypropyl groups, namely 1828, 2208, 2906, and 2910. According to the calculation of dried products, the content of each substituted methoxy group (- OCH3) and hydroxypropyl group (- OCH2CHOHCH3) should comply with the regulations in the attached table. Character: This product is a white or almost white fibrous or granular powder; Odorless. This product is practically insoluble in anhydrous ethanol, ether, and acetone; Dissolve in cold water to form a clear or slightly turbid colloidal solution. Identification: (1) Take 1g of this product, heat 100mL of water (80-90 ℃), continuously stir, and cool in an ice bath to form a viscous liquid; Take 2 mL and place it in a test tube. Slowly add 1mL of 0.035% anthrone sulfuric acid solution along the tube wall and let it stand for 5 minutes. A blue-green ring appears at the interface between the two liquids. (2) Pour an appropriate amount of viscous liquid under the identification (1) onto a glass plate. After the water evaporates, a harrowing film is formed. Check viscosity: Take 10.0g of this product and calculate it as dry. Add 90 ℃ water to make the total weight of the sample and water 500.0g, and make a 2.0% (g/g) suspension. Stir thoroughly for 10 minutes until the particles are entirely evenly dispersed and wetted. Cool in an ice bath and continue stirring for 40 minutes during the cooling process—centrifuge to remove bubbles. If necessary, add cold water to adjust the weight; Using a single cylinder rotary viscometer (NDJ-1 type can be used for samples with viscosity less than 100Pa · s, NDJ-8S type can be used for models with a thickness greater than or equal to 100Pa · s, or other suitable and qualified viscometers), measure according to the law at 20 ℃± 0.1 ℃ (Appendix VI G, Second Method, Part II, 2010 Pharmacopoeia). For samples with a viscosity less than 600mPa · s, the thickness should be 80% to 120% of the indicated density; If the demonstrated consistency is greater than or equal to 600mPa · s, the viscosity should be 75% to 140% of the stated thickness. If you are looking for high quality, high purity and cost-effective zinc sulfide, or if you require the latest price of zinc sulfide, please feel free to email contact mis-asia.