# User:M Jaffe/Notebook/Maxis Protease Lab 471/2015/09/16

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## Objective

Make our own phosphate buffer and tris buffer solutions at their specific pHs.

## Procedure

Following the basic guidelines stated in Dr. Hartings' lab notebook

• Phosphate Buffer, pH 7
1. Make a 500mL solution of 10mM Phosphate buffer, pH 7.
2. Use:
1. sodium phosphate monobasic, MM = 137.99 g/mol
2. potassium phosphate dibasic: 174.18 g/mol
3. Need 0.0005mol of each to make the solution.
4. Weigh 0.398g of sodium phosphate monobasic. Actual amount weighed: 0.40053g
5. Weigh 0.368g of potassium phosphate dibasic. Actual amount weighed: 0.36682g
6. In a 500mL volumetric flask, add approximately 300mL of water, and a stirring pill.
7. Add both the sodium phosphate monobasic, and the potassium phosphate dibasic.
8. Fill up to the 500mL mark using a pipette.
9. Place on stirring plate, and let it stir for a few minutes.
10. Measure conductivity and pH.
11. If first pH reading is not very close to 7, or 7, add either potassium phosphate dibasic or sodium phosphate monobasic to reach the desired pH.
• Tris Buffer, pH 9
1. Make a 500mL solution of 10mM Tris Buffer, pH 9
2. Weigh 0.06057g of Tris powder. Actual amount weighed: 0.0629g.
3. In a 500mL volumetric flask, add approximately 300mL of water, and a stirring pill.
5. Fill up to the 500mL mark using a pipette.
6. Place on stirring plate, and let it stir for a few minutes.
7. Measure conductivity and pH.
8. If first pH reading is not 9, add HCl until wanted pH is measured.

Calculations:

```  Wanted concentration: 10mM = 10^-3M = 10^-3mol/L
Wanted volume: 500mL = 0.5L
Number of moles: (10^-3mol/L)/2 = 5*10^-4 mol
Amount of solute needed: MM of soluteĀ·(5*10^-4 mol)=amount that must be weighed
```

## Description

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## Data

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## Notes

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