Basic modeling approach to optimize elemental imaging by laser ablation ICPMS.
The quality of element image maps generated by laser ablation (LA) ICPMS rastering depends on the measurement conditions (laser fluence, repetition rate, beam diameter, scanning speed, flow rate, and acquisition time). Optimizing these conditions is often a matter of trial and error since the quality criteria for elemental imaging (sensitivity, spatial resolution, noise, and analysis time) are intricately linked. A simple mathematical model, and ensuing software, was developed to simulate the LA-ICPMS output upon virtual rastering of a digital image of a cross-section of a sample. Even though the LA-ICPMS map is not directly correlated with elemental imaging, element distributions are often related to visual features in the sample, allowing optimization of the LA-ICPMS settings for the desired quality criteria (samples without any visual features can not be optimized in this way). The virtual LA-ICPMS rastering software assumes that the ablation cell and tube interface act as a continuous stirred-tank reactor (i.e., exponential washout) and a plug flow reactor (i.e., zero dispersion), respectively, using an inert gas for transport of the aerosol particles. The software also incorporates a random noise generator which simulates the experimentally deduced signal-to-noise ratios as a function of the anticipated concentration and LA-ICPMS settings. The software was successfully validated and demonstrated by comparing the software output of selected patterns created in the emulsion of a black-and-white negative film with the experimental rastering output performed by measurement of (107)Ag in the emulsion.
Triglav
Jure
J
Laboratory for Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia.
van Elteren
Johannes T
JT
Šelih
Vid S
VS