Question

To make 10X gel electrophoresis running buffer, 30.0 g Tris base, 144.0 g glycine, and 10.0 g SDS must be dissolved into 1000 mL water. The working stock is a 1X concentration.

a. What is the concentration in % w/v of each of the 3 reagents in the 10X stock?

b. Describe how you would make 1 L of a 1X working stock solution.

c. If 50 mL of the 1X working stock are used to run a gel, how many grams of each of the 3 reagents are in the 1X solution?

Answer 1

a) the mass of water taken = Volume / Density = 1000mL / 1g/mL = 1000grams

the mass of tris base = 30grams

Mass of glycine = 144 grams

Mass of SDS for 10X = 10grams

total mass of solution = 1000 + 30 + 144 + 10 = 1184 grams

We may assume that the density of solution = 1g/ mL

so total volume of solution = 1184 mL

a) %w / Volume = mass of solute X 100 / total volume of solution

(i) Tris base (%w/v) = 30 X 100 / 1184 = 2.534%

(ii) Glycine (%w/v) = 144 x 100 / 1184 = 12.16 %

(iii) SDS (%w/v) = 10 X 100 / 1184 = 0.845%

b) For 1X working solution we will take 1/10th amount of Tris base, glycine and SDS in the same volume of water

So we will take 3 g Tris base . 14.4 gram of glycine and 1 gram of SDS in 1L of solution to preapre 1X stock

Or we can take 10mL of 10X stock solution and make up the solution to 1L by adding 990mL of water to it

It will give 1X working stock solution

c) Volume of 1X working stock taken = 50mL

As we know that 1184mL of 10X stock solution contains 30gram of tris base

So amount of tris base in 1000mL = 30 X 1000 / 1184 = 25.34 grams

so amount of tris base in 10mL = 0.2534 grams = amount of tris base in 1X stock solution

(ii) similarly the amount of glycine in 1X stock solution = 144 X 10 / 1184 = 1.22 grams

(iii) the amount of SDS in the 1X stock solution = 10 X 10 / 1184 = 0.0845 grams