Characterization, construction, and deployment of a prototype In Situ Mass Spectrometer (ISMS)
Project Manager: Ken Johnson
Lead Scientists: Peter Girgius, Gernot Friederich
Lead Engineer: Jon Erickson
Quadrupole mass spectrometers are instruments that can measure a wide range of gaseous compounds, including many of interest to MBARI scientists, such as carbon dioxide, methane, oxygen, sulfides, and others. There is ongoing interest in adapting this technology for use in oceanography, but the difficulties of sustaining the necessary vacuum while allowing in only dissolved gasses has posed a formidable challenge. To our knowledge, the instruments currently available at other institutions are limited in their application (incapable of working deeper than 200 meters) or are still in the developmental stages.
MBARI efforts during the last year resulted in the design and construction of a membrane inlet system that provides the requisite reliability and sensitivity. The membrane will withstand 6000 psi (pounds-per-square-inch, analogous to 4000 meters depth) for a period of hours. We have yet to test the inlet to failure. A safety shut-off system is being developed to protect the instrument at pressure. We have used this inlet with the quadrupole mass spectrometer to detect and measure a suite of dissolved gasses in both oceanic and hydrothermal vent seawater at 4000 psi, while at sea.