Influence of wavelength on fractionation in laser ablation ICP-MS

As laser ablation becomes more ubiquitous for direct solid sampling with in ductively coupled plasma mass spectrometry (ICP-MS), the need to understand and mitigate fractionation (non-stoichiometric generation of vapor species ) becomes critical. The influence of laser-beam wavelength on fractionation is not well established; in general, it is believed that fractionation is reduced as the wavelength becomes shorter. This manuscript presents an inve stigation of fractionation during ablation of NIST glasses and calcite usin g three UV wavelengths (157 nm, 213 nm and 266 nm). Fractionation can be ob served for all wavelengths, depending in each case on the laser-beam irradi ance and the number of laser pulses at each sample-surface location. The tr ansparency of the sample influences the amount of sample ablated (removed) at each wavelength, and the extent of fractionation. Pb/Ca and Pb/U ratios are used as examples to demonstrate the degree of fractionation at the diff erent wavelengths.