Question

caff ppm	Absorbance
2.12	.025
4.24	.0487
6.36	.0762
8.48	.1098
10.6	.1272

blank absorbances readings: .0067 .0058 .0049 .0064 .0056

what is the lowest detectable concentration of Caff in ppm?

Answer 1

"Blank" means all other reagents in the solution same as the Caff solution except for the test substance for which the absorbance is being measured.

"Blank" in other words means no test substance at all in it.

So father the absorbance of Caff solution from the absorbance of blank, the better it cna detected.

So the Caff solution which exhibits absorbance closest possible to the blank (0.0056 - 0.0067) is 2.12 ppm solution which shows 0.025

So 2.12 ppm solution is the one with lowest detectable concentration