GFAAS Determination of Lead and Cadmium in Yeast Extract with Separation by Ion Exchange

The sample (1.000 g) of yeast extract was digested with HNO₃ (20 mL). The solution was evaporated to dryness, and the residue was taken up with water (10 mL), and the acidity was adjusted to pH 4.0. D401 ion-exchange resin was used for separation of lead and cadmium from the solution. After rinsing the column with 0.002 5 mol·L^-1 HNO₃ solution (pH 2.6), lead(Ⅱ) and cadmium(Ⅱ) were desorbed from the column with 0.2 mol·L^-1 HNO₃ solution, and the eluate was evaporated to near dryness. Water was added attaining to 10 mL, and contents of lead and cadmium in the solution were determined by GFAAS. Linearity ranges were found between 50 to 350 pg (lead) and 3 to 15 pg (cadmium), with detection limits (3s) of 5.0, 0.3 pg respectively. Three samples were analyzed by this method, and values of recovery found by standard addition method were in the range of 84.0% to 115%, giving values of RSD's (n=8) ranged from 1.8% to 12%.