Question

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd2+ content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 °C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 99.31 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0 mL of 0.1 M HCl to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.0 mL volumetric flasks, each containing 5.00 mL aliquots of the sample solution. Varying amounts of a 97.0 ppb (μg/L) Cd2+ standard were added to each of the flasks, which were then brought to volume with 0.1 M HCl. The Cd2+ content of the solutions was then analyzed using GFAAS, resulting in the absorbance data given in the table.

Sample Volume (mL)	Cd2+ Standard Volume (mL)	Absorbance
5.00	0.00	0.080
5.00	2.50	0.119
5.00	5.00	0.163
5.00	7.50	0.200
5.00	10.00	0.241

Determine the amount of Cd2+ per gram of dry clam. Express your final result as milligrams of Cd2+ per gram of dry clam.

Answer 1