Fast Determination of Trace Elemental Sulfur Residue in Rare Earth Sulfide Samples by Inductively Coupled Plasma Optical Emission Spectrometry

A new method for the fast determination of elemental sulfur (ES) in rare earth sulfide samples was developed, using ultrasonic wave-assisted solvent extraction and oxygen flask combustion (OFC), followed by analysis with inductively coupled plasma optical emission spectrometry (ICP-OES). Toluene was used as the solvent to separate ES from the rare earth sulfide matrix by ultrasonic wave-assisted solvent extraction. All factors that played key roles in both the extraction and OFC methods were systematically investigated. It was found that after ultrasonic extraction with 10 mL toluene for 2 min, the complete extraction of ES in 15 g could be realized, while for the OFC method, 100 mu L of the extraction solvent solution combusted in a 500 mL flask with 10 mL of the mixed solution (9.6 mL H2O + 0.2 mL H2O2 + 0.2 mL EINO3) as the absorbent was enough for the complete transformation of ES under atmospheric pressure. After method optimization, the sample treatment time was less than 40 min, and the LOD of 1.00 mu g g(-1) and the RSD (n=6) of 4.55% were achieved. To verify accuracy, the method was evaluated by a spike test and conducted in four real samples, the recoveries rate ranged from 96% to 100%, which proved that the method was accurate and reliable.