Imported ceramic bowls are analyzed for toxic heavy metals such as cadmium since
ID: 1066421 • Letter: I
Question
Imported ceramic bowls are analyzed for toxic heavy metals such as cadmium since these metals can be leached from the ceramic by the food in contact with it. The amount of cadmium that can be leached from the bowl is determined by adding an acetic acid solution to the bowl for a 24 hour period, after which the cadmium concentration in the acidic leaching solution is determined. In one experiment, the cadmium concentration in an acidic leaching solution was analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). A series of cadmium standards were prepared from a 100 ppm Cd stock solution. A micropipet was used to deliver 0.10 mL, 0.20 mL, 0.30 mL, 0.40 mL, 0.50 mL, and 0.60 mL of the stock solution to six separate 50.0 mL volumetric flasks. A known, constant amount of a yttrium stock solution was added as an internal standard, resulting in a final concentration of 0.80 ppm Y in each flask. The volumetric flasks were then diluted to the mark. 25.0 mL of the leaching solution was then pipetted into a separate 50.0 mL volumetric flask. The same known, constant amount of the yttrium stock solution was added to the flask containing the leaching solution, again resulting in a final concentration of 0.80 ppm Y. The flask was then diluted to the mark. The intensities of the cadmium and yttrium emissions are shown in the table below for each of the standard solutions and the unknown solution. Calculate the cadmium concentration in the original leaching solution.Explanation / Answer
From the data
concentration od Cd standard in final diluted solution (mg)
0.005
0.01
0.015
0.02
0.025
0.03
So,
concentration of Cd would be,
[Cd] in diluted solution = 0.015 x 39.71/42.24
= 0.0141 x 50/25
= 0.0282 ppm
[Cd] = 0.0282 ppm