A real-time chemical analysis of rocks at the bottom of the deep-sea Development of a quantitative analytical method: Development of a quantitative analytical method

Takahashi, Tomoko, Thornton, Blair, Sato, Takumi, Ohki, Toshihiko, Ohki, Koichi and Sakka, Tetsuo (2017) A real-time chemical analysis of rocks at the bottom of the deep-sea Development of a quantitative analytical method: Development of a quantitative analytical method. In The Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec). Japan Society of Mechanical Engineers.. (doi:10.1299/jsmermd.2016.1A2-16b2).

Abstract

Long-pulse Laser-Induced Breakdown Spectroscopy (LIBS) is a promising method for an in-situ analysis of chemical compositions of rocks and sediments on the seafloor. We have developed a real-time LIBS device, “Chemicam” and have successfully performed in-situ analysis at the bottom of the deep sea using the device. In order to develop a real-time quantitative analytical method, principal component regression analysis is applied to underwater LIBS measurements. The non-linear effects of plasma temperature fluctuation on the signals are treated as systematic errors in the analysis. The effect of these errors on the analytical performance is evaluated by comparing the conventional PCR, PCR with a temperature segmented database, and calibration-free LIBS. Improvement of accuracy in the proposed PCR model indicates that non-linear systematic effects contribute to fluctuation of underwater plasmas, where temperature-based segmentation can improve the performance of PCR. The results suggest that the proposed method can be applicable to real-time automated quantitative analysis of rocks in the deep sea.

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