need help with basic dilutions!

[pdyogita]

hello all .
I need to have 15 ppm concentration of some solution (100 ppm) when added to 0.1M 150 ml buffer.
I previously added 15 ml of 15 ppm solution in to 150 ml 0.1M phosphate buffer,but then i realised that the original 15 ppm sol.n got diluted to 1.5 ppm when added to buffer.
so how much amount of stock should i add into 150 ml buffer so that my final concentration of 15 ppm remains constant?
I am little bit confused with this.
is it something i can do with V1C1=V2C2?
would really appreciate youe help.

[chromatographer1]

pdyogita

Your solution is 100 ppm.

You want to dilute it with buffer.

Here is a hint.

If you take 1ml of solution and add 9 mL of 0.1M buffer the concentration is 10ppm and you have 10mL of solution but the buffer has a new concentration.

If you take 2mL of solution and add 8mL of 0.1M buffer, the concentration is 20 ppm and you have 10 mL of solution but the buffer has another new concentration.

Now, what will you do with this hint to get 15 ppm?

Rodney George