Expert: Eric Brandt - 2/9/2010

Question
QUESTION: Hello, I am a student trying to conduct a science fair experiment. I bought a bottle of 1:3000 25g of pepsin. How would I make a solution of 80 grams per 400 ml of water?

ANSWER: Hi Alli,
You do knot have enough to make this solution. You are trying to make a concentrated solution using a more dilute solution. You will need to evaporate your solution and you do not have enough to make 80 g if you only have 25 g of a more dilute solution.
Thank you for using Allexperts
Sincerely,
Eric Brandt, B.Sc. Pharm

---------- FOLLOW-UP ----------

QUESTION: Woops. I don't know what I was thinking. However, in a science article, I found that the concentration of pepsin in gastric juice is
1.0 mg/ml-1 (sorry,the -1 is an exponent) How would I make a solution, using the pepsin that I bought, with that concentration in like, 100ml?
Thank you very much for your time.

Answer
Hi Alli,
I assume you need 0.1 mg/mL final concentration. For 100 mL you will need 10 mg pepsin. Can you now calculate how much of your stock you will need to make the solution desired?
Thank you for using Allexperts
Sincerely,
Eric Brandt, B.Sc. Pharm