Application of vacuum ultraviolet laser-induced breakdown spectrometry for steel analysis - comparison with spark-optical emission spectrometry figures of merit

Laser induced breakdown spectrometry (LIBS) was evaluated for trace analysis in steel in comparison to spark discharge optical emission spectrometry (spark-OES), including low C, N and S (< 100 ppm) concentrations. The development of an industrial prototype is described, with the ability to be able to use either a spark or a laser source on the same optical mounting to directly compare the performances of both sources. Similar sensitivities between LIBS and spark-OES could be obtained for low alloying elements (Mn, Cr, Ni, Mo, etc., in the range of 0-1200 ppm) as well as for traces of C, N, S, P between 2 and 100 ppm. Limits of detection as low as 5 ppm were measured in a reproducible way for C, P, and S, whereas lower N signal stabilities result in 20 ppm LOD. Compared to a spark source used on the same optical mounting, it should be possible to improve these figures by a factor of 3. The results presented in this work lead us to believe that LIBS should rapidly develop as a steel control tool. and the instrumentation built up will be suitable for on-site process control applications. (C) 2001 Elsevier Science B.V. All rights reserved.