# Question #12905

Feb 14, 2017

I'm not sure what you did, but I don’t think it was correct.

#### Explanation:

First, you prepared a standard curve, in which you plotted the absorbances of known concentrations of the drug.

I presume you got a graph something like this.

You use this plot to determine the concentration of your unknown.

Then you diluted your unknown sample by a factor of 1000 (?).

You measured its absorbance and got a value of 0.247.

From the regression equation, $y = 0.045 x + 0.0273$, you get

$x = \frac{y - 0.0273}{0.045} = \frac{0.247 - 0.0273}{0.045} = \frac{0.2197}{0.045} = 4.88$

The concentration of the drug in your diluted sample was 4.88 µg/mL.

Thus, the concentration in your original sample was 4.88 mg/mL or 48.8 mg/10 mL.