Determination of cadmium in sediments by atomic absorption spectrophotometry with a carbon tube atomizer

Sediment sample (1 g) was treated with Chester and Hughes's method (1967). Cadmium in sediments was leached into a mixed solution of 1 M hydroxylamine hydrochloride and 25% (v/v) acetic acid. The residue was then dissolved in nitric acid and, after drying up, diluted to 100 ml with 0.01 m HCl solution. Various coexisting elements in the solutions thus obtained interfered with the determination of cadmium by atomic absorption spectrophotometry with a carbon tube atomizer. Among the elements tested i.e., Na, K, Mg, Ca, Fe, Al, Si, Mn, Zn and Cu, 200 ppm of magnesium, 200 ppm of iron and 8 ppm of zinc in the solution decreased the absorbance of cadmium by 44%, 28% and 20%, respectively. Mock solutions containing 10 ppb of cadmium and 10 foreign ions as chloride were treated in a similar way, and both calibration and standard addition methods were tested. Because of interference of coexisting elements, the calibration method is not recommened. The standard addition method should be used after diluting the solution to one tenth. With this method cadmium concentrations in the sediments of the Hiro Bay in Hiroshima ranged (0.56 -- 2.36) ppm. The relative standard deviation for a sample containing 1.0 ppb of cadmium was 4.0%. (author)