Science Buddies: "Ask an Expert"

Hello, I am somewhat familiar with the application of the c1v1=c2v2 formula but I am having trouble with a lab question.
In this particular lab I must determine the concentration of two unknown BSA solutions by developing a series of standard solutions. I have been provided with a stock solution of 5mg/mL BSA and must make up to 1mL with the BSA and NaCl (1% W/V) and proceed to add 4mL of Biuret reagent. My question is: does the concentration of the NaCl have to be taken into account or do I just do the formula as if I were adding dH20? For example, one of my test tubes contained 0.5mL of BSA and 0.5mL NaCL; I calculated the final concentration at 2.5mg/ml. (5mg/mL*0.5mL / 1mL (total volume)) Is this approach correct?

Hi, rol17! Yes, you are correct. No matter whether you're adding H2O, NaCl, or any other solution to dilute your BSA (let's call it solution 2), the final concentration of BSA in your mixture depends on the final total volume (volume of BSA solution + solution 2), and is not influenced by the concentration of anything else that may be in your solution 2.