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Preliminary results on the development of quick, simple analytical method for the low level of lead(II) in water samples are described. The method concentrates lead(II) on a small solid-phase extraction disk, which is then quantified directly on the disk by diffuse reflectance spectroscopy (DRS). This method, termed colorimetric solid-phase extraction (C-SPE), requires only 1–2 min for complete workup and is suitable for use in a wide range of applications, including the microgravity environment on the International Space Station. The procedure first adds an excess of potassium iodide to a 10.0 mL sample at a pH of 3.0–3.5 to produce the anionic PbI42− colored complex, which is exhaustively extracted by the disk that was previously impregnated with cetylpyridinium chloride (CPC). The amount of complex extracted is then determined at 420 nm by a hand-held DRS instrument.

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.

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.

Archived water samples collected on the International Space Station (ISS) and returned to Earth for analysis have, in a few instances, contained trace levels of heavy metals. Building on our previous advances using Colorimetric Solid Phase Extraction (C-SPE) as a biocide monitoring technique [1, 2], we are devising methods for the low level monitoring of nickel(II), lead(II) and other heavy metals. C-SPE is a sorption-spectrophotometric platform based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent that are then quantified on the surface of the membrane using a diffuse reflectance spectrophotometer. Along these lines, we have analyzed nickel(II) via complexation with dimethylglyoxime (DMG) and begun to examine the analysis of lead(II) by its reaction with 2,5-dimercapto-1, 3, 4-thiadiazole (DMTD) and 4-(2-pyridylazo)-resorcinol (PAR).