The influence of ablation carrier gasses Ar, He and Ne on the particle size distribution and transport efficiencies of laser ablation-induced aerosols:: implications for LA-ICP-MS

The influence of ablation cell carrier gasses He, Ne and Ar on the particle size distribution generated and subsequently transported during the laser ablation process of silicate glasses was investigated using 266 and 193 nm wavelengths for ablation. The particle size distributions was determined for the NIST 600 series glasses and synthetic quartz glass using an optical particle counter within the size range of 0.1 to >2 mum. The results illustrate that the ablation carrier gas strongly influences the particle size distribution for lambda = 193 nm while this effect is far less pronounced for ablations using lambda = 266 nm. The experiments also show that 266 nm produces to a larger degree primary particles which are not largely influenced by the ablation carrier gas environment while 193 nm produces a larger amount of vapour during impact of the laser beam which subsequently condenses to form larger aggregates. These results verify and give the reason for the large increase in sensitivity obtainable by inductively coupled plasma mass spectrometry (ICP-MS) when using helium together with 193 nm ablation systems while only a minor increase will be observable when using 266 nm under similar conditions. Furthermore the influences of the laser energy density, on the particle size distribution as well as values for the transport efficiency were investigated. (C) 2002 Elsevier Science B.V. All rights reserved.