Browse Publications Technical Papers 2008-01-2201
2008-06-29

Colorimetric-Solid Phase Extraction (C-SPE): In-Flight Methodologies for the Facile Determination of Trace Level Indicators of Water Quality 2008-01-2201

At present, spacecraft water quality is assessed when samples collected on the International Space Station (ISS) are returned to Earth. Several months, however, may pass between sample collection and analysis, potentially compromising sample integrity by risking degradation. For example, iodine and silver, which are the respective biocides used in the U.S. and Russian spacecraft potable water systems, must be held at levels that prevent bacterial growth, while avoiding adverse effects on crew health. A comparable need exists for the detection of many heavy metals, toxic organic compounds, and microorganisms. Lead, cadmium, and nickel have been found, for instance, in the ISS potable water system at amounts that surpass existent requirements. There have been similar occurrences with hazardous organic compounds like formaldehyde and ethylene glycol. Microorganism counts above acceptable limits have also been reported in a few instances. The delays in analyzing potable water suspend implementation of any real-time correction scenarios to an on-board contaminant event. It is, therefore, critical that rapid, on-board methods be developed to monitor trace quantities of several indicators of quality in spacecraft drinking water supplies. To meet some of these needs, our laboratory has developed colorimetric-solid phase extraction (C-SPE). C-SPE is a sorption-spectrophotometric platform that entails the selective extraction and concentration of analytes by a membrane impregnated with a colorimetric reagent, followed by quantification on the membrane surface using a diffuse reflectance spectrophotometer. As such, we have designed and tested C-SPE methods for monitoring iodine, silver, nickel and lead. We have also devised methods to extend C-SPE to determinations of formaldehyde, pH, cadmium, and arsenic. This presentation provides a status report on the development of C-SPE to meet these needs, including results from tests in microgravity simulations via KC-135 and C-9 fights.

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