User:Allison K. Alix/Notebook/CHEM-581/2013/02/06

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Objective -Begin PVA microsphere preparation Procedure 1) Prepare 20mM phosphate buffer (pH=7.4) Dissolve 1.256 g disodium phosphate and 1.337 g monosodium phosphate in ~900mL water. Add sodium hydroxide to obtain pH of 7.4 (~100mL) 2) Dissolve 0.5 g PVOH (MW= 89,000-98,000 g/mol) in 3mL phosphate buffer. Heat @ 100°C for 15 minutes with stirring. 3) Add 2μL R6G in 2mL phosphate buffer to the PVOH/buffer mixture. Be sure to mix thoroughly. 4) Add 100mL Mineral Oil (CVS, 99.9%) to a homogenizer and subsequently add the PVOH mixture. Homogenize for ~5minutes to form a w/o emulsion 5) Pour final w/o emulsion into a beaker and place in a freezer at -20°C for 20 hours. Remove and allow thawing for 4 hours. Repeat this cycle for a total of three cycles. Calculations Preparation of 20mM phosphate buffer, pH = 7.4 [Base] = monosodium phosphate, 119.98 g/mol [Acid] = disodium phosphate, 141.96 g/mol pH = pKa + log ([Base]/[Acid]) 7.4 = 7.3 + log ([Base]/[Acid]) ([Base]/[Acid]) = 1.2589 [Acid] + [Base] = 20mM [Base] = 20mM - [Acid] (20mM - [Acid])/[Acid] = 1.2589 [disodium phosphate] = 8.85mM [monosodium phosphate] = 11.14mM 8.85mmol x 141.96g/mol x 1mol/1000mmol = 1.256g disodium phosphate 11.14mmol x 119.98g/mol x 1mol/1000mmol = 1.337g monosodium phosphate References http://www.sciencedirect.com/science/article/pii/S0168365998000893