Question

You are given stocks of 4 M NaCl, 40% Glucose, and 1M Tris-HCl (pH 8.5). You need to make 400 ml of a buffer containing 0.5 M NaCl, 8% Glucose and 50 mM Tris-HCl (pH 8.5). How would you make the buffer?

Answer 1

Answer:

50mL of 4M NaCl, 80mL of 40% glucose, 20mL of 1M Tris-HCl (pH 8.5) and 250mL of water.

Explanation:

To make 400mL containing 0.5M NaCl you need to add:

4M / 0.5M = 8 (dilution 1/8). 400mL / 8 = 50 mL of 4M NaCl.

Glucose 8% you need to add:

40% / 8% = 5 (dilution 1/5). 400mL / 5 = 80 mL of 40% glucose

Buffer 50mM you need to add:

1000mM / 50mM = 20 (dilution 1/20). 400mL / 20 = 20mL of 1M Tris-HCl (pH 8.5)

The resting volume: 400mL - 50mL of 4M NaCl - 80mL of 40% glucose - 20mL of 1M Tris-HCl (pH 8.5) = 250 mL must be completed with water.

Thus, to make the solution you need: 50mL of 4M NaCl, 80mL of 40% glucose, 20mL of 1M Tris-HCl (pH 8.5) and 250mL of water.

I hope it helps!