Question

You mixed 600 mL of 5M NaCl and 150 mL of sodium citrate solution and added 250 mL of water to make a 1L stock 20X SSC (standard sodium citrate) buffer. With 40 grams of SDS, sodium dodecyl sulfate you made 800 mL of a 5% SDS solution. ~Calculate how much SDS and SSC you need from the above solutions to make 1 Liter of 0.1X SSC, 0.1% SDS.

Answer 1

Ans. Given,

            Stock [SSC] = 20.0 X

            Stock [SDS] = 5%

            Required [SSC] in final buffer = 0.1X

            Required [SDS] in final buffer = 0.1 %

            Required volume of final volume = 1.0 L

# Calculate required volume of Stock SSC:

Using C1V1 = C2V2            - equation 1

C1= Concentration, and V1= volume of initial solution 1         ; Stock soln.

C2= Concentration, and V2 = Volume of final solution 2         ; Final buffer solution

Putting the values in equation 1-

            20.0X x V1 = 0.1X x 1.0 L

            Or, V1 = (0.1X x 1.0 L) / 20.0X = 0.005 L

Hence, required volume of SSC = 0.005 L = 5.0 mL

# Calculate required volume of Stock SDS:

Using C1V1 = C2V2            - equation 1

Putting the values in equation 1-

            5% x V1 = 0.1% x 1.0 L

            Or, V1 = (0.1% x 1.0 L) / 5.0% = 0.02 L

Hence, required volume of SSC = 0.02 L = 20.0 mL

Preparation of final buffer: To a 1.) L standard volumetric flask, add 5.0 mL of stock SSC and 20.0 mL of stock SDS solution. Make the final volume upto the mark with distilled water. Mix well for uniform concentration. It is the desired final buffer solution.