An analytical chemist was directed to collect razor clams from a heavily-contami
ID: 1068315 • Letter: A
Question
An analytical chemist was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for cadmium (Cd^2+) content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 degree C overnight and ground them in a scientific blender for preparing homogenized dry samples. A representative sample was taken from the homogenized dry material and dissolved in 100.00 mL of 0.1 t to create a sample solution. Using the method of standard additions the chemist prepared five standard solutions in 100.00-mL volumetric flasks, each containing 5.00-mL aliquots of the sample solution. Varying amounts of a 92.0 ppb (mu g/L) cadmium standard were added to each of the flasks, which were then brought to volume with 0.1 M HCI The solutions were Then examined for their Cd^2+ content using GFAAS and the following graph was obtained.Explanation / Answer
Cd analysis
Calculate concentration of Cd standard in dilute solution
with 2.5 ml Cd std added to make 100 ml total volume
final concentration of Cd std in solution = 92 ppb x 2.5 ml/100 ml
= 2.3 ppb
let Cx be the concentration of Cd in unknown 5 ml solution.
Cx/(Cx + 2.3) = 0.08/0.119
0.119Cx = 0.08Cx + 0.184
Cx = 0.184/0.039
= 4.72 ppb in 5 ml sample
So, in 100 ml original soltuion
concentration of Cd = 4.72 x 100/5