[keetner]

Hello,

How can I calculate the concentration (in μmol/mL) of this question? I was given a solution where the following was added in a test tube:

0.15 mL ATP
0.55 mL water
0.10 mL buffer A
1.70 mL buffer B

The question wants us to determine the concentration of ATP. I was given literature value that ATP = 1mM
The thing I'm confused about is...should I add up the total volume (ATP, water, buffer A, buffer B) which gives me 2.50mL? Or should I not consider the amount of ATP added, leaving me with a value of 2.35mL? Then determine the concentration from there?

______

What I've done so far:
1) 1mmol/L => 0.001mmol/mL => 1μmol/mL

2) 1μmol/mL x 0.015mL (from ATP in the question) = 0.015μmol

3) 0.015μmol/(??)

And the question mark is where I'm stuck.
I think what throws me off is the fact that I'm calculating for something already in the solution. That said, I feel like it would make a lot more sense to use 2.50 and not 2.35...however, I'm not quite sure of the reasoning behind it.

Sorry, I'm a bit rusty on my stoich. Any help would be greatly appreciated!

Thanks in advance!

[keetner]

Nevermind. I think I may have it figured out.