Mass SURFER: a low-power underwater mass spectrometer for monitoring dissolved gas, solutes and large organic compounds

The authors are currently developing two low-power, miniature mass spectrometer-based field-sampling systems-a "standard" and CE (capillary electrophoresis)-enhanced version-with an aquatic-based sensor head, vacuum system, pressure case and associated electronics, called Mass SURFER (Mass Spectrometer Using Rotating fields for Exploratory Research). The units incorporate the Rotating Field Mass Spectrometer (RIMS) developed at JPL, and are capable of 2000+ m deployments. Seawater-soluble gas samples are either admitted through an osmotic membrane boundary into a gas-based field ionizer, or the seawater liquid with its load of dissolved gases can be directly injected into a submersible vacuum chamber via a nano-electrospray nozzle (liquid/vacuum interface). The gas-sampler (first type) incorporates a hydrophobic, silicon-coated membrane. The membrane allows dissolved gases to enter the vacuum interface where small aliquots are sampled. The second interface is an on-line capillary nano-electro pray interface (ESI) capable of high-sensitivity mass spectrometry at nanoliter per minute flow rates. Mass SURFER vacuum levels need only be at the milli-torr level for a quality measurement, and the complete system nominally draws <10 watts when active