Round robin tests on laser ablation and quantitative analysis by LIBS
Résumé
Referring to the “Seven ages of an analytical method” proposed by Laitinen in 19731, LIBS may be presently considered at the threshold of the sixth one, when the number of applications of the technique has significantly increased, and the need of standardization is simultaneously growing. While the preferred scope of LIBS applications is onsite, online or in situ analysis, the diversity of experimental configurations required to address such issues is somewhat contradictory with a standardization approach. An alternative way to make LIBS progress to become a fully mature analytical technique could be the determination of reference performances of different instruments or experimental setups for a given analytical case. Such an approach would have several advantages: 1) Newcomers, both researchers and industrials, could better evaluate if the technique could meet their needs; 2) It would be a solid basis to which enhancement approaches could be compared (e.g. hyphenated techniques, microwave assisted LIBS, etc.); 3) It could help to define good experimental configurations and analytical practices that could be of general interest for any application. For that purpose, two round robin tests have been organized since 2012 within the French LIBS community. The first one involved five laboratories and was focused on the characterization of laser ablation of iron. Very consistent results on the craters volume were obtained, but no correlation was found between the repeatability of laser ablation and that of the LIBS signal. The second one was devoted to quantitative analysis of glass samples. Eleven teams contributed to the work. In spite of the dispersion in the experimental setups and protocols, the results obtained on unknowns showed an acceptable bias, whereas the measurement uncertainty was much more variable among the participants. Overall, the results of those two preliminary round robin tests show that a good reproducibility level is reachable between independent LIBS measurements and, in this sense, are very encouraging for the future.