# Difference between revisions of "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

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