b. Calculate the detection limit from the data in the previous problem if the no

Question

b. Calculate the detection limit from the data in the previous problem if the noise (standard deviation) on the blank is 0.0005 absorbance units. Note that the detection limit is expressed in concentration units.

Previous Problem: An analysis was performed by creating a calibration curve with a set of 5 standard solutions. A plot of absorbance (y-axis) vs. concentration (x-axis) gave a slope of 5.22x104 M-1 and an intercept of 0.001. The absorbance of the unknown was 0.087. Calculate the concentration of the unknown. (Answer to this part: concentration = 1.65 x 10^-6 M)

Explanation / Answer

The formula for detection limit is L.O.D = (3 x standard deviation) / slope

We are given slope of 5.22e4 M-1 from the previous part. And standard deviation is 0.0005 absorbance units, given in question.

So, L.O.D will be = [3 x 0.0005]/ 5.22e4 = 2.87e-8 M

Because the unit range is too high, we can write the detecton limit in microM units which is 1microM = 1e-6M

So, 0.0287microM

Hence, detection limit for the data = 0.0287microM or 2.87e-8M.

Have a nice day!! :))

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