The concentration of cadmium in seawater can be determind spectrophotometrically. To six 50.0mL seawater samples, various volumes of a 10.0ppm cadmium solution were added and all were taken through the analytical procedure with the following results:
Amount Cd Added (mL): Absorbance:
0 0.230
10 0.272
25 0.340
40 0.416
60 0.507
75 0.568
Construct a standard addition calibration plot using EXCEL and calculate [Cd] in seawater in ppm (µg)/mL.