DIRECT DETERMINATION OF Dy, Sm, Eu, Tm, AND Yb IN GEOLOGICAL SAMPLES BY SLURRY ELECTROTHERMAL VAPORIZATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

摘要

Slurry sample introduction with electrothermal vaporization (ETV) has been applied to inductively coupled plasma mass spectrometry (ICP-MS) for the direct determination of Dy, Sm, Eu, Tm, and Yb in geological samples. The slurries were prepared by mixing 50mg of the powdered sample, sediment or soil (-50 lm) with 0.8mL of 65% m/v nitric acid, 0.4mL of 40% m/v hydrofluoric acid and 0.4mL of 30% v/v hydrogen peroxide in PTFE flasks. The mixture was submitted to an ultrasonic bath for 36min and then diluted to 14mL with water. The best compromise conditions for the furnace temperature program, the nebulizer gas flow rate, the RF power, and the amount of NaCl used as carrier were determined. By introducing 20 lL of 3.57mg mL1 sediment slurry, using 50 lg of NaCl as a physical carrier, and pyrolysis and vaporization temperatures of 1000C and 2800C, respectively, the obtained values for four geological reference materials were well within the certified range, using external calibration with aqueous solutions. Under the optimum operating conditions, the detection limits for 164Dy, 152Sm, 153Eu, 169Tm e, 174Yb were of 200, 30, 20, 10, and 10 pg g1, respectively. The precision was better than 10%.