Search Results

Colorimetric-solid phase extraction (C-SPE) is being developed as a method for in-flight monitoring of spacecraft water quality. C-SPE is based on measuring the change in the diffuse reflectance spectrum of indicator disks following exposure to a water sample. Previous microgravity testing has shown that air bubbles suspended in water samples can cause uncertainty in the volume of liquid passed through the disks, leading to errors in the determination of water quality parameter concentrations. We report here the results of a recent series of C-9 microgravity experiments designed to evaluate manual manipulation as a means to collect bubble-free water samples of specified volumes from water sample bags containing up to 47% air. The effectiveness of manual manipulation was verified by comparing the results from C-SPE analyses of silver(I) and iodine performed in-flight using samples collected and debubbled in microgravity to those performed on-ground using bubble-free samples.

Water quality standards have been completed for space vehicles and habitats for ingestion periods from 1 day to 1000 days. These standards are called spacecraft water exposure guidelines (SWEGs). The National Research Council Committee on Toxicology has worked with the Toxicology Group at the National Aeronautics and Space Administration (NASA) to set and document these standards. Prior to SWEG development, the practice of NASA was to apply the United States Environmental Protection Agency (USEPA) maximum contaminant levels (MCLs) in the interpretation of any potential health effects from water pollutants. This practice had the potential to result in erroneous conclusions because MCLs are intended for lifetime exposures and are set to protect a much more diverse population than is present in the astronaut corps. However, for certain pollutants it was recognized that the stresses of spaceflight may make astronauts more susceptible to adverse effects.

We are developing a drinking water test kit based on colorimetric-solid phase extraction (C-SPE) for use onboard the International Space Station (ISS) and on future Lunar and/or Mars missions. C-SPE involves measuring the change in diffuse reflectance of indicator disks following their exposure to a water sample. We previously demonstrated the effectiveness of C-SPE in measuring iodine in microgravity. This analytical method has now been extended to encompass the measurement of total I (i.e., iodine, iodide, and triiodide). This objective was accomplished by introducing an oxidizing agent to convert iodide and triiodide to iodine, which is then measured using the indicator disks previously developed for iodine. We report here the results of a recent series of C-9 microgravity tests of this method. The results demonstrate that C-SPE technology is poised to meet the total I monitoring requirements of the international space program.