In Situ Mass Spectrometer

An essential component of ecosystems research is characterizing and quantifying the chemical milieu within and around habitats. To date, there is a paucity of chemical sensors that are capable of measuring a wide range of compounds, and be left in situ for longer term investigations. Mass spectrometers are among the instruments that can detect the broadest range of compounds with a single detector, and are capable of high sensitivity and throughput.

Recently, we developed an in situ mass spectrometer (or ISMS) based around a commercially available 24 VDC mass spectrometer that can detect and quantify volatiles up to 200 daltons. It is capable of deployments down to 4500 meters, and has been laboratory-tested to 6000 meters. During a recent expedition in the Gulf of Mexico, the ISMS was deployed 7 times, including three dives to a 2900-meter coral and seep sites in the Gulf of Mexico (see Wankel 2010). More recently, the ISMS was used to interrogate subsurface hydrogen oxidation at hydrothermal vents (see Wankel 2011, Geochemical flux and metabolic activity associated with the hydrothermal subsurface). The ISMS is able to measure parts-per-million concentrations of methane, alkanes hydrogen, oxygen, hydrogen sulfide, carbon monoxide, carbon dioxide, nitrogen, nitrous oxide and many other volatiles. These are of particular interest because they are substrates for microbial and macrofauanal metabolism. The ISMS will soon incorporate a recently developed gas exhaust system that will allow it to operate continuously in situ. It should also be noted that the core components of the ISMS, including the commercially available pump and mass spectrometer, perform best when operated continuously and can be expected to run for 12 to 16 months without servicing (such as lubrication and tuning).