The powdered samples (0.2 g) were digested by trace metal grade acids (mixture of 9.0 mL concentrated HNO3 and 3.0 mL 40% HF (v/v)) using a Mars microwave digestion system (CEM, USA).
The powdered samples (0.2 g)were digested by trace metal grade acids (mixture of 9.0 mL concentratedHNO3 and 3.0 mL 40% HF (v/v)) using a Mars microwavedigestion system (CEM, USA).