Published on July 15, 2014
BUFFER : Its preparation & application in dosage forms: BUFFER : Its preparation & application in dosage forms Uddipta Ghosh dastidar 7 th Sem. B.Pharm Roll 25 G.N.I.P.S.T. BUFFER : Let’s define: BUFFER : Let’s define Compounds or mixture of compounds, that by their presence in a solution, resist changes in pH , upon addition of small quantity of acid or base…. Why are buffers needed ?: Why are buffers needed ? Modifying solubility : Inorg. salts of Fe, phosphate, borate and amines & alkaloids….. Soluble in acid media, but ppt. in alkaline Modifying colour: Colors of cherry & raspberry syrups is red at acid pH but pale yellow at basic Contd . PowerPoint Presentation: Modifying stability: At basic pH Vit C & penicillin are unstable Na thiosulfate , Na polysulfide liberate S At acidic pH , Nitrites turn brown , forming N-oxides Salts of cabonate & sulfite liberate CO 2 & SO 2 PowerPoint Presentation: Modifying activity : Activity if Methenamine buffered with NaH 2 PO 4 Na hypochlorite kept in low pH Modifying patient comfort: Lesser the pH diff. lesser the irritation Discussing dosage forms individually: Discussing dosage forms individually Tablets To control pH in the drug particle microenvironment In case of acidic drugs to reduce gastric irritation Common buffering agents : Na-bicarbonate, Mg-carbonate, Na-citrate Ophthalmic preparation pH of lacrimal fluid =7.4 It can buffer within a range of 3.5 – 8.5. Buffers used with regard to dessociation , pemeation , solubility & irritability Common buffering agents : Borate, phosphate & carbonate Discussing dosage forms individually: Discussing dosage forms individually Parenterals Blood pH = 7.4 If Parenterals are of pH >9 or pH <3......... Tissue necrosis But LVP don’t need buffers. Commonly used buffers for SVP: Acetate, citrate, phosphate & glutamate Topicals Mainly used for maintaining their stability during storage. Commonly used buffers: Citric acids & its salts, phosphoric acids & its salts Steps to prepare a Buffer: Steps to prepare a Buffer Take a standard pharmacopoea See through the index & go to “Buffer” Note the composition & follow the procedure Phosphate buffer 6.8 (IP 2007) : Phosphate buffer 6.8 (IP 2007) Dissolve 28.8g disodium hydrogen phosphate and 11.45g potassium dihydrogen phosphate in sufficient water to produce 1000ml. All crystalline reagents should be dried at 110-120 0 C , 1hr before. Water must be CO 2 free PowerPoint Presentation: OOPS !!! IT’S NOT THERE IN THE LITERATURE DON’T WORRY Prepare a buffer solun. of pH of 5 & capacity of 0.02: Prepare a buffer solun . of pH of 5 & capacity of 0.02 Choose a weak acid whose pK a is close to reqd. pH. Here acetic acid has pK a = 4.76 The ratio of salt & acid conc. Is derived from PowerPoint Presentation: Buffer capacity equation. After preparation….: After preparation…. Store in alkali-free glass containers. Use within 3 months of preparation. References : References Physical Pharmacy .. 4 th edition [Lippincott Williams & Wilkins: Indian edition] Alfred Martin Indian Pharmacopoea 2007 Pharmaceutical Chemistry- Inorganic G.R.Chatwal PowerPoint Presentation: Thank You PowerPoint Presentation: All undesirable mistakes and inconveniences are deeply regretted…..