Cellulose-based polymers methylcellulose

This class of cellulose derivatives includes hydroxypropylmethylcellulose or HPMC, hydroxyethylcellulose (58), methylcellulose, HPC, and ethylcellulose. As mentioned earlier, most cellulose-based polymers except for PVP, have lower surface tension values in the range of 40-50 mN/m, thus similar adhesive and film-forming qualities will be seen. 

Imran, M., El-Fahmy, S., Revol-Junelles, A.M., Desobry, S. 2010a. Cellulose derivative based active coatings Effects of nisin and plasticizer on physico-chemical and antimicrobial properties of hydroxypropyl methylcellulose films. Carbohydrate Polymers, 81 219-225. 

The key consideration in the analysis of any sustained release dosage form as previously discussed (see Sections II.A, II.B, II.C.l, and II.C.2rg) is to determine what solvent or solvent system will be most appropriate to assure the dissolution of the drug and its excipients to make it amenable to HPLC analysis. Aqueous solubility of weak acids and bases is governed by the pfCa of the compound and the pFI of the medium. In an acidic or low pFI medium, weak acids will be unionized and will be more soluble in organic solvents. The reverse is the case for basic compounds as previously discussed in Section II.B. Because the formulation of sustained release dosage forms tend to rely on the use of insoluble plastics (i.e., methyl acrylate-methyl methacrylate, polyvinyl chloride, and polyethylene), hydrophilic polymers (i.e., methylcellulose, hydroxypropyl-methylcellulose, sodium carboxymethyl cellulose, and carbopol 934), and fatty compounds (i.e., waxes such carnauba wax and glyceryl tristearate), similar hydro-organic solvents and sample preparation steps that have been discussed for tablets and capsules can also used for their analysis by HPLC (see Sections II.A, II.B, II.C.l, and II.C.2). 

P. are viscous liquids, which are either strongly alkaline, aqueous solutions that contain - methyl-cellulose or acrylic polymers as thickener or are solvent-based (e. g., methylene chloride) and neutral. The latter are thickened by ->methylcellulose of high DS, - hydroxyethylcellulose, - hydroyx-propylcellulose and their mixed ethers (- cellulose ethers). Some contain - ethylcellulose. 

The polymerization takes place in the monomer droplets, which are stabilized in the aqueous phase by water-soluble polymers derived from RR, e.g., cellulose ethers, such as ->methylcellulose, ->car-boxymethyl cellulose, and - hydroxyethyl cellulose. - Starch and ->-sodium alginate are also used. There are some other additives of minor importance that are based on RR ... 

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