Emission spectroscopic monitoring of particle composition, size and transport in laser ablation inductively coupled plasma spectrometry

The spectroscopic line emissions of copper and zinc from atomized particles generated by orthogonal pre-pulse laser ablation of brass and transported from the ablation cell through tubes into an ICP have been simultaneously measured end-on with fast photomultipliers. It was shown that simultaneous line monitoring of major elements provides not only information on the aerosol transport in laser ablation ICP-spectrometry, but also on the ratios of small to single larger particles and their respective elemental compositions and, therefore, on possible elemental fractionation problems. Furthermore, the spectroscopic information can be easily exploited for proper adjustment of the laser fluence in order to minimize the production of large particles, to improve the transport efficiency and to reduce the noise of analytical signals in laser ablation ICP-spectrometry. The present particular experiment on orthogonal pre-pulse laser ablation of brass confirms the recent finding that such kind of double-pulse arrangement produces predominantly ultra-fine particles. Individual brass particles with diameters ≳ 250 nm could be analyzed. They showed large Zn depletions as expected. Finally, strong accumulations of aerosol particles were found in the ablation cell used even at low laser pulse frequencies.