Question

Describe how much of each of the following stock components you would use to make 250mL of a solution with all of the components below (final concentration of each component is shown) (Show work)

a) 1% (w/v) Stock: Dry powder (FW=58.0)

b) 2 micrograms/microliter BSA Stock: 100mg/mL

Answer 1

We need to prepare a 250 mL solution that comprises 1% (w/v) dry powder and 2 ug / uL BSA from a stock of 100 mg BSA per mL.

a. To make a 1% (w/v) dry powder we need to dissolve 1 g of the substance in 100 mL water. To make a 1% (w/v) in a total volume of 250 mL, we need to weigh 250 / 100 = 2.5 g of the substance.

b. A make a 2 ug / uL concentration of BSA in 250 mL, which is also a 2 mg/ mL solution,  we need 2* 250 = 500 mg BSA. Therefore we need 5 mL of the 100 mg/ mL BSA stock.

Therefore, We would weigh 2.5 g of the dry powder, dissolve in about 50 mL water, then add 5 mL of the BSA stock ( 100 mg/ mL) and make up the volume to 250 mL with water to get the desired concentration of 1% dry powder with 2 ug / uL BSA.