Objective
- Prep 1 mL fiber samples for analysis
- Make 500 mL of 10 mM Tris buffer, pH 9
- Make 500 mL of 10 mM phosphate buffer, pH 7
Procedure
To Prep 1 mL fiber samples
- We centrifuge our samples and removed the supernatant
- We left the tubes open so that rest of the water can evaporate
To prepare a 500 mL of 10 mM Tris buffer at pH 9
- Make a 500mL solution of 10mM Tris Buffer, pH 9
- Weigh 0.06057g of Tris powder. Actual amount weighed: 0.0629g
- In a 500mL volumetric flask, add approximately 300mL of water, and a stirring pill
- Add the weighed powder
- Fill up to the 500mL mark using a pipette
- Place on stirring plate, and let it stir for a few minutes
- Measure conductivity and pH
- If first pH reading is not 9, add HCl until wanted pH is measured
To prepare a 500 mL of 10 mM phosphate buffer at pH 7
- sodium phosphate monobasic, MM = 137.99 g/mol
- potassium phosphate dibasic: 174.18 g/mol
- Need 0.0005mol of each to make the solution.
- Weigh 0.398g of sodium phosphate monobasic. Actual amount weighed: 0.40053g
- Weigh 0.368g of potassium phosphate dibasic. Actual amount weighed: 0.36682g
- In a 500mL volumetric flask, add approximately 300mL of water, and a stirring pill.
- Add both the sodium phosphate monobasic, and the potassium phosphate dibasic.
- Fill up to the 500mL mark using a pipette.
- Place on stirring plate, and let it stir for a few minutes.
- Measure conductivity and pH.
- 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.
Calculations:
Wanted concentration: 10mM = (10-3)M = 10(-3) mol/L
Wanted volume: 500mL = 0.5L
Number of moles: (10-3 mol/L)/2 = (5-4) mol
Amount of solute needed: MM of solute·(5*10-4) mol = amount that should be weighed
Results
The final pH and conductivity reading for the tris buffer was 9.01 and 293 μS/cm.
The final pH and conductivity reading for the phosphate buffer was 6.89 and 14.63 μS/cm.
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