Browse Publications Technical Papers 2003-01-2406
2003-07-07

Rapid Determination of Biocide Concentrations Using Colorimetric Solid Phase Extraction (C-SPE): Results from Microgravity Testing 2003-01-2406

A sorption-spectrophotometric platform for the concentration and subsequent quantification of biocides in spacecraft drinking water is described. This methodology, termed Colorimetric Solid Phase Extraction (C-SPE), is based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent. Quantification of the extracted analytes is accomplished by interrogating the surface of the membrane with a commercially available diffuse reflectance spectrophotometer. Ground-based experiments have shown that C-SPE is a viable means to determine biocide concentrations in the range commonly found in water samples from the Space Shuttle and the International Space Station (ISS). This paper details efforts to advance C-SPE closer to space flight qualification and ISS implementation, starting with the modification of the ground based biocide detection platform to simplify operation in a microgravity environment. The modified platform was used during KC-135 reduced gravity flights for the rapid, low level determinations of molecular iodine (I2) and silver ion (Ag (I)), the biocides used by NASA and the Russian Space Agency, respectively. Iodine is determined as the yellow iodine-poly(vinylpyrrolidone) (PVP) complex and Ag (I) is quantified as the pink silver-5 (p-dimethylaminobenzylidene) rhodanine (DMABR) complex. The results from these flight tests, along with the application of C-SPE to the determination of total iodine in a water sample by employing a pre-extraction Oxone treatment are discussed, along with issues requisite for operational improvements.

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