Development of an underwater mass-spectrometry system for in situ chemicalanalysis

Progress in the design, construction and packaging of small portable mass s pectrometers for operation on autonomous underwater vehicles (AUVs) is desc ribed. Our first deployable version consists of a membrane introduction int erface coupled with a linear quadrupole mass filter for in situ detection a nd quantification of dissolved gases and volatile organic compounds. We pre sent laboratory results which demonstrate that sub-parts-per-billion detect ion limits have been achieved for toluene. The mass-spectrometer system is compatible with AUV constraints and operates on 24 V dc, consuming of the o rder of 100 W of power. Technical challenges of performing underwater mass spectrometry are addressed, in particular sample introduction from the wate r column and the maintenance of a vacuum system. Initial operation will be in shallow water of 30 m depth or less. Alternative versions of interfaces and mass spectrometers are also discussed. We anticipate that providing the capability of performing in situ underwater mass-spectrometric analysis wi ll have a significant impact in the areas of marine science and environment al monitoring.