High-speed, integrated ablation cell and dual concentric injector plasma torch for laser ablation-inductively coupled plasma mass spectrometry

In recent years, laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) has gained increas-ing importance for biological analysis, where ultra-trace imaging at micron resolution is required. However, whilst undoubtedly a valuable research tool, the washout times and sensitivity of current technology have restricted its routine and clinical application. Long periods between sampling points are required to maintain adequate spatial resolution. Additionally, temporal signal dispersion reduces the signal-to-noise ratio, which is a particular concern when analysing discrete samples, such as individual particles or cells. This paper describes a novel, two-volume laser ablation cell and integrated ICP torch designed to minimise aerosol dispersion for fast, efficient sample transport. The holistic design utilises a short, continuous diameter fused silica conduit, which extends from the point of ablation, through the ICP torch, and into the base of the plasma. This arrangement removes the requirement for a dis-persive component for argon addition, and helps to keep the sample on axis with the ICP cone orifice. Hence, deposition of sample on the cones is theoretically reduced with a resulting improvement in the absolute sensitivity (counts per unit mole). The system described here achieved washouts of 1.5, 3.2 and 4.9 ms for NIST 612 glass, at full width half, 10% and 1% maximum respectively, with an 8 to14 fold improvement in absolute sensitivity, compared to a single volume ablation cell. To illustrate the benefits of this performance, the system was applied to a contemporary bio-analytical challenge, specifically the analysis of individual biological cells, demonstrating similar improvements in performance.