Answer:
You'll need to add 75mL of glucose 20%, 30mL of tris 1M, 6mL of EDTA 0.5M and enough water to make up 300 mL.
Step-by-step explanation:
To prepare the buffer we need to clearly determine the desired final concentrations of each regeant and the final volume, and then we'll see how to reach those concentrations starting from the available (stock) solutions.
Stock solutions:
- 20% glucose
- 1M tris (=1000mM)
- 0.5M EDTA (=500mM)
Final buffer:
- 5% glucose
- 100 mM tris
- 10 mM EDTA
- Water up to 300 mL
To calculate how much of each reagent we need to add to make the buffer we can use the formula C1×V1 = C2×V2 , where C1= concentration of stock solution, V1= volume needed from the stock solution, C2= desired concentration of the reagent in the buffer, V2= volume of buffer we wish to prepare.
*Note that the units of volume/concentration must match, if the initial concentration is in M and the desired concentration is mM, we need to convert either the initial concentration to mM or the final concentration to M.
Glucose
C1×V1 = C2×V2
20% ×V1 = 5% × 300 mL
V1 = 5% × 300 mL / 20%
V1 glucose = 75 mL
Tris
C1×V1 = C2×V2
1000mM × V1 = 100 mM × 300 mL
V1 = 100mM × 300mL / 1000 mM
V1 tris= 30mL
EDTA
C1×V1 = C2×V2
500mM × V1 = 10 mM × 300 mL
V1 = 10mM × 300mL / 500 mM
V1 EDTA= 6 mL
Final answer: you'll need to add 75mL of glucose 20%, 30mL of tris 1M, 6mL of EDTA and enough water to make up 300 mL.