Question

How do you calculate the concentration (ppm) if you have:
the amount of total solution (60 ml)
the amount of sample that is added to the solution (15 uL)
the density (0.904 g/mL)

Answer 1

Sorry I took so long.
I guess I didn't explain what I wanted very well. ppm comes in three flavors; i.e., w/w, w/v, and v/v. You have volume and volume so you can get ppm v/v from your numbers. Since you give the density I assume you want w/v; you want to convert the 15 uL to a weight(Mass).
So you have 15 uL (0.015 mL) with a density of 0.904 g/mL.
mass = volume x density = 0.015 mL x 0.904 g/mL = 0.0136 g per 60 mL.
ppm in w/v is g/1,000,000 mL so we convert 0.0136 g/60 mL this way.
0.0136 g x (1,000,000/60) = 227 ppm. Another way, which I find simpler is you have 15 uL/60 mL which is 0.015 mL and time density is 0.0136 g or 13.6 mg/60 mL or 13.6/60 = 0.227 mg/mL or 227 mg/L and since 1 ppm is 1 mg/L that is 227 ppm. Two definitions to keep in mind are
1 ppm = 1 mg/L or 1 ug/mL. Then I just convert whatever I have to mg/L and that's the ppm.

Answer 2

Thanks a lot! this make so much sense!!