Direct Determination of Dy, Sm, Eu, Tm, and Yb in Geological Samples by Slurry Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry

Abstract

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 50 mg of the powdered sample, sediment or soil (≤50 µm) with 0.8 mL of 65% m/v nitric acid, 0.4 mL of 40% m/v hydrofluoric acid and 0.4 mL of 30% v/v hydrogen peroxide in PTFE flasks. The mixture was submitted to an ultrasonic bath for 36 min and then diluted to 14 mL 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 µL of 3.57 mg mL⁻¹ sediment slurry, using 50 µg of NaCl as a physical carrier, and pyrolysis and vaporization temperatures of 1000°C and 2800°C, 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 g⁻¹, respectively. The precision was better than 10%.

Keywords:

• ETV-ICP-MS
• Geological material
• Rare earth elements

Notes

∗Stage of transport to the ICP-MS.