The origin of analytical matrix effects in laser plasma spectroscopy was investigated. We focused on matrix effects in sand/soil mixtures and attempted to explain the increase in the spectral response of trace elements (at constant concentration) with sand percentage. First, it was found that the energy coupled in the plasma, and which can be calculated from the propagation of the laser induced shock wave, indeed characterizes the matrix. A simple experimental setup for such measurements was suggested. Our results indicate that previous explanations of the matrix effects in this system may not be correct. We suggested that the main matrix effects were attributed to the depth of the laser-induced crater, which was correlated to a portion of the laser energy that penetrates into sand particulates and does not cause direct ablation. This explanation holds when no other effects are present (e.g. grain size distribution). The hypothesis was validated by experimental data.
- Laser analysis
- Plasma spectroscopy