Question

are measuring the concentration of Fe2 in a sample by measuring the absorbance of its complex with ferroxine. Your sample, measured in a 1.00-cm pathlength cuvette, has an absorbance of 0.208 while the reagent blank in the same cuvette has an absorbance of 0.046. What would be the absorbance reading of these two solutions if measured in a cuvette with 8.00 cm pathlength?

Answer 1

A = cl

where, A is absorbance, is molar absorptivity, c is concentration and l is path length.

For a given sample with same concentration and absorptivity, Absorbance is directly proportional to path length.

For blank reagent, absorbance in a 1.00-cm pathlength cuvette is 0.046. Its absorbance at 8.00 cm is:

solving above equation, we get:

A = 0.368

Hence, absorbance of blank reagent in a cuvette with 8.00 cm pathlength is 0.368.

For the sample, absorbance in a 1.00-cm pathlength cuvette is 0.208. Its absorbance at 8.00 cm is:

or, A = 1.664

Hence, absorbance of the sample in a cuvette with 8.00 cm pathlength is 1.664.