Evaluation of Electrospray Ionization-Ion Mobility Spectrometry for Real-time Water Monitoring on the ISS

摘要

Current water quality monitors aboard the International Space Station (ISS) are specialized and provide limited data. The Colorimetric Water Quality Monitor Kit (CWQMK) and the Total Organic Carbon Analyzer (TOCA) are used to measure biocide concentrations and the total organic carbon load, respectively. While each of these instruments provides important analytical information, they lack the ability to fully characterize the organic and inorganic compounds present in the ISS water systems. Identification of individual compounds requires the return of ISS archival samples that are analyzed in ground laboratories. A survey of the other environmental monitoring hardware used on the ISS reveals that air quality monitors have advanced further toward the end goal of providing real-time, compound-specific information that can be used by the crew. As many of the organic compounds on the target lists for air and water quality monitoring are identical, evaluating the current air quality monitoring technologies is a logical first step toward development of a water quality platform that can characterize the organic load in spacecraft water systems. The initial phase of this effort is focused on ion mobility spectrometry (IMS). IMS technology was previously used in the ISS Volatile Organic Analyzer (VOA), and it is employed for numerous terrestrial applications, such as the detection of a variety of large analytes in aqueous solution. It also is widely field-deployed by the Department of Homeland Security for explosives detection. Our approach couples IMS with electrospray ionization (ESI) to ionize and detect target analytes in water samples. In this paper we discuss the initial performance of the ESI-IMS instrument with an emphasis on detection of analytes typically found in archival water samples from the ISS. We also include results from focused experiments performed with dimethylsilanediol, a recently discovered environmental contaminant that is problematic for the Water Processing Assembly.