This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 26505, “Deep-Sea Laser Raman—Past, Present, and Future Developments for In-Situ Chemical Analysis and Applications,” by William J. Kirkwood, Monterey Bay Aquarium Research Institute, prepared for the 2016 Offshore Technology Conference Asia, Kuala Lumpur, 22–25 March. The paper has not been peer reviewed.
The deep-ocean Raman in-situ spectrometer (DORISS) instruments were developed for the purposes of identifying compounds and studying in-situ chemical reactions in a nondestructive manner while working with solids, liquids, and gases. The approaches used in the development of three generations of instruments have been successful and have shown that not only is Raman spectroscopy feasible in the deep ocean, but also its results are entirely comparable with spectra taken in terrestrial applications. DORISS has also shown that in-situ measurements are more accurate than returning many samples from the deep sea.
Introduction
The approach taken began with modification of a standard bench-top laboratory unit for use at sea to demonstrate feasibility. The second generation then solved several impediments to improved performance in the deep sea and contributed to the development of additional tools to enhance capabilities. The third generation is now past the design process and in assembly for bench-top testing to bring the fluorescence signal (noise) down to achieve a 19-fold increase in sensitivity. This allows the use of Raman on compounds that have high-order organic compounds such as some oils and makes the detection of carbon dioxide (CO2) much easier. The high-power approach in this system will enable faster operations for subsea mining.
