Development of New Detection Schemes Using Colorimetric-Solid Phase Extraction for Formaldehyde and Other Trace Organic Contaminants in Water

摘要

Space exploration by humans requires maintenance of an adequate potable water supply. Biocide levels must therefore be kept within allowable limits to prevent bacterial growth without causing adverse effects on crew health. Likewise, contaminants such as heavy metals and toxic organic compounds must be held at or below acceptable limits. Currently, spacecraft water quality analyses are performed on samples collected on the International Space Station and returned to Earth. Several months, however, can pass between sample collection and analysis, which may compromise sample integrity due to degradation. These delays also inhibit implementation of real-time correction scenarios. There is, therefore, a critical need for rapid, on-board methods for monitoring trace quantities of several analytes in spacecraft drinking water supplies. We have previously described methods for monitoring the biocides iodine (I2) and silver (I), as well as the heavy metals nickel (II) and lead (II), by Colorimetric-Solid Phase Extraction (C-SPE). C-SPE is a sorption-spectrophotometric platform based on the selective extraction of analytes onto a membrane impregnated with a colorimetric reagent, followed by quantification on the membrane surface using a diffuse reflectance spectrophotometer. Building on our previous work, this paper describes recent progress in the development of a C-SPE platform for determining the contaminants formaldehyde and glycol, with detection limits as low as 4.6 ppb. In this method, which is the first to apply CSPE to the determination of organic compounds, the requisite reagents will eventually be immobilized on inert media and packaged in an easy-to-use kit. These reagents are introduced during sample collection, forming a colored product that is exhaustively extracted onto an anion exchange membrane. The analyte concentration is determined on the membrane surface using diffuse reflectance spectroscopy. Details related to the first performance evaluations of this technique will be discussed.