Analysis of soil and sediment samples by laser ablation inductively coupled plasma mass spectrometry

The analysis of soil and sediment samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was studied. Solution-based calibration was used for the quantification of trace elements in these samples. In most cases, the measured concentrations were within +/- 20% of the certified values using Ni-60 or Ag-107 as the internal standard. Measurements with Ag were carried out to investigate whether an internal standard could be spiked into soils for quantification purposes. The influence of particle size on the applicability of sample spiking was briefly studied, and it was demonstrated that particle size could significantly influence measurements if only the surface constituents of the particle were ablated. Use of Ca-43 or Ca-44 as an internal standard produced poorer results owing to interferences at these masses. In some cases, such as with Sr, Ba, Y and Rb, the measured concentrations were low by a factor of 2-3. This could be remedied by using one of these elements as an internal standard for the others. The effects of elemental speciation, organic content and particle size were investigated. Elemental speciation and organic content of the soils did not appear to significantly affect the LA-ICP-MS measurements. Particle size, however, was found to influence the precision and sensitivity of the measurements. Samples with smaller particle sizes yielded higher signal levels and better precision.