Laboratory Evaluation of Laser-Induced Breakdown Spectroscopy (LIBS) as a new in situ Chemical Sensing Technique for the Deep Ocean

Anna P.M. Michel, Ph.D., 2007
Alan Chave, Advisor

Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for in situ chemical sensing, and is a promising technique for field measurements in extreme environments. In this work, laboratory experiments validate the LIBS technique in a simulated deep ocean environment to pressures up to 2.76 x 107 Pa. A key focus of this work is the validation that select elements important for understanding hydrothermal vent fluid chemistry (Na, Ca, Mn, Mg, K, and Li) are detectable using LIBS. A data processing scheme that accurately deals with the extreme nature of laser-induced plasma formation was developed that allows for statistically accurate comparisons of spectra. The use of both single and double pulse LIBS for high pressure bulk aqueous solutions is explored and the system parameters needed for the detection of the key analytes are optimized. Using both single and double pulse LIBS, the limits of detection were found to be higher than expected as a result of the spectrometer used in this experimentation. However, the results of this validation show that LIBS possesses the characteristics to be a viable chemical sensing method for in situ analyte detection in high pressure environments like the deep ocean.