Science Buddies: "Ask an Expert"

Hi Daven,
For the low concentration test solution described in 9b you also have to add the antifungal agent to be tested. Your preparation of the low concentratin dilution of the drug depends on your preparation for the high concentration drug mix. I have described the key points of making the solution below:

Preparing the high test concentration:

1 part drug per 1000 parts total of solution (in water)- this is what they mean when they say 1000-fold dilution. Since you only need a bit of the original drug (concentrated) you are measuring volume of drug added in units of teaspoons.

Preparing the low test concentration:

1 part high test concentration solution (from above) per 1000 parts of total solution.
While for the high test concentration you were using the concentrated drug, here you are diluting the dilution prepared above further.

I would not worry so much about your results being correct as much as noting whether they were reproducible.

Hope this helps!
Veronica

A simple way to dilute the concentration further would be to dilute it using the method Veronica explained above, then use 1 parts low test concentration per 1000 parts of the total solution. This way you are taking the dilute mixture and diluting it even further.

I hope this helps!
Meg