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Colorimetric Solid Phase Extraction (CSPE): Using Color to Monitor Spacecraft Water QualityIn August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS). The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was launched as a Station Development Test Objective (SDTO) experiment to evaluate the suitability of CSPE technology for routine use monitoring water quality on the ISS. CSPE is a sorption-spectrophotometric technique that combines colorimetric reagents, solid-phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water samples. In CSPE, a known volume of sample is metered through a membrane disk that has been impregnated with an analyte-specific colorimetric reagent and any additives required to optimize the formation of the analyte-reagent complex. As the sample flows through the membrane disk, the target analyte is selectively extracted, concentrated, and complexed. Formation of the analyte-reagent complex causes a detectable change in the color of the membrane disk that is proportional to the amount of analyte present in the sample. The analyte is then quantified by measuring the color of the membrane disk surface using a hand-held diffuse reflectance spectrophotometer (DRS). The CWQMK provides the capability to measure the ionic silver (Ag +) and molecular iodine (I2) in water samples on-orbit. These analytes were selected for the evaluation of CSPE technology because they are the biocides used in the potable water storage and distribution systems on the ISS. Biocides are added to the potable water systems on spacecraft to inhibit microbial growth. On the United States (US) segment of the ISS molecular iodine serves as the biocide, while the Russian space agency utilizes silver as a biocide in their systems. In both cases, the biocides must be maintained at a level sufficient to control bacterial growth, but low enough to avoid any negative effects on crew health. For example, the presence of high levels of iodine in water can cause taste and odor issues that result in decreased water consumption by the crew. There are also concerns about potential impacts on thyroid function following exposure to high levels of iodine. With silver, there is a risk of developing argyria, an irreversible blue-gray discoloration of the skin, associated with long term consumption of water containing high concentrations of silver. The need to ensure that safe, effective levels of biocide are maintained in the potable water systems on the ISS provides a perfect platform for evaluating the suitability of CSPE technology for in-flight water quality monitoring. This paper provides an overview of CSPE technology and details on the silver and iodine methods used in the CWQMK. It also reports results obtained during in-flight analyses performed with the CWQMK and briefly discusses other potential applications for CSPE technology in both the spacecraft and terrestrial environments.
Document ID
20100017254
Document Type
Conference Paper
Authors
Gazda, Daniel B. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Nolan, Daniel J. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Rutz, Jeffrey A. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Schultz, John R. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Siperko, Lorraine M. (Utah Univ. Salt Lake City, UT, United States)
Porter, Marc D. (Utah Univ. Salt Lake City, UT, United States)
Lipert, Robert J. (Iowa State Univ. Ames, IA, United States)
Flint, Stephanie M. (NASA Johnson Space Center Houston, TX, United States)
McCoy, J. Torin (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2010
Subject Category
Man/System Technology and Life Support
Report/Patent Number
JSC-CN-20566
Meeting Information
Inter-Society Color Council Meeting 2010(Princeton, NJ)
Distribution Limits
Public
Copyright
Other