Search for a Real-Time Measurement of Dimethylsilanediol in the International Space Station Atmosphere using the Air Quality Monitor

The discovery of dimethylsilanediol (DMSD) as a recurring contaminant in the U.S. segment of the International Space Station (ISS) water supply has exhibited the need to accurately determine the levels of this compound in-flight. Currently, the only real-time water quality monitoring systems on the ISS are the total organic carbon analyzer (TOCA) and the colorimetric water quality monitoring kit (CWQMK). These systems both provide important water quality data, but neither can provide compound-specific information for organic contaminants, requiring the use of archival analysis to determine if elevated total organic carbon (TOC) levels are due to a relatively benign compound like DMSD or to other, more toxic compounds. One potential method for indirect monitoring on board the ISS could be the use of the Air Quality Monitor (AQM) to determine if DMSD is present in the atmosphere. However, introducing DMSD samples into the AQM for a determination of analytical parameters has previously proven challenging. Recently, a prototype inlet based on electrothermal vaporization (ETV) was coupled with a ground-based AQM to evaluate its potential for in-flight water quality monitoring. This inlet has allowed us to remove volatile organics from a water matrix and analyze them using the AQM. Based on the parameters determined in this ground-based testing, we have discovered that it may be possible to monitor DMSD in the atmosphere of the ISS with the AQM. This paper will discuss the use of this novel sample inlet to analyze DMSD as well as the methods used to find DMSD in the ISS atmosphere. Additionally, a comparison of atmospheric DMSD data with in-flight TOC data will be presented to determine if changes in atmospheric concentration can be correlated with the periodic TOC increases.