Temporal changes of fractionation index caused by changes in the large size of ablated particles in laser ablation-inductively coupled plasma mass spectrometry.

To elucidate mechanisms of elemental fractionation that are observed in laser ablation-inductively coupled plasma mass spectrometry, the relative intensities of 34 elements, each normalized by a Ca internal standard, were measured every minute during a 10-min laser ablation of an NIST 610 glass standard. Temporal changes in the fractionation index (FI) were obtained by dividing the relative intensity of every minute by that of the first minute. The particles generated by laser ablation were collected on a filter every minute, and they were observed using scanning electron microscopy to investigate changes in the large size of particles. Large variations among the large size of particles were observed using single-site mode and under 1.0 mm defocus conditions. The 34 measured elements were classified into two groups, depending on their observed FI variation. The FI variation was rationalized by elemental behavior due to changes in the large size of ablated particles introduced into the ICP.