ICP-AES Determination of Molybdenum and Copper in Molybdenum Ores with Acid Dissolution of Sample in Closed Vessel

The ground and dried molybdenum ore sample (0.1 g) was digested with HCl, HNO3 and HF in a closed PTFE digestion vessel by heating for 3 h on a hot plate at medium temperature. One mL of HClO4 was added and fumed to near dryness. The residue was taken up with 5 mL of 6 mol·L-1 HCl and diluted to 50 mL with water in a volumetric flask after adding 5.0 mL of 10 mg·L-1 Rh(Ⅲ) solution as internal standard (using its spectral line of 343.489 nm). The spectral lines of 202.030 nm and 327.396 nm were selected as analytical spectral lines for Mo and Cu respectively. Detection limits (3s) found for the 2 elements were 3.8, 7.1 μg·g-1 respectively. Precision of the method was tested, giving values of RSD′s (n=12) in the ranges of 1.3%-3.2% (for Mo) and of 2.4%-4.6% (for Cu). Three CRM′s of molybdenum ores were analyzed by the present method, values of Mo and Cu found were in consistency with the certified values.