An improved method for determination of lanthanoids in environmental samples by inductively coupled plasma mass spectrometry with high matrix introduction system

The capability of ICP-MS equipped with the high matrix introduction system (HMI) for accurate analysis of lanthanoids in environmental samples was investigated. Compared to the conventional operation, the amounts of oxide and hydroxide molecular species formed in the plasma were reduced by up to 5 times. The relative yields of oxides did not exceed 0.02% for BaO+ species and were as low as 0.3% for lanthanoids with the highest oxide-formation rates (LaO+, CeO+, PrO+ and NdO+). Hydroxide formation was less than 0.02% when HMI system was used. In addition, two digestion procedures were evaluated by the analysis of standard reference materials (SRMs) of different matrices. The digestion efficiency and limits of detection (LOD) were improved when samples were digested with a mixture of HNO3/H2O2/HCl/HF, and HF was removed by evaporation in presence of concentrated HCl. Using this procedure and HMI-ICP-MS analysis, LOD ranged from 0.1 μg kg−1 to 6 μg kg−1. Recoveries ranged from 85 to 115% for La to Ho and from 75 to 85% for the other lanthanoids. Relative standard deviations for replicate analysis of SRMs were less than 10%.

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► High matrix introduction system decreased spectral interferences.
► Oxides and hydroxide yields were less than 0.5% and IDLs below 8 ng L−1.
► Evaporation of excess HF in presence of HCl improved dissolution of lanthanoids.
► Recoveries of lanthanoids after digestion with HNO3/H2O2/HCl/HF were 76–115%.
► The obtained limits of detection ranged from 0.1 to 6 μg kg−1.