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In planning for Exploration missions and developing the required suite of environmental monitors, the difficulty lies in down-selecting a multitude of technology options to a few candidates with exceptional potential. Technology selection criteria include conventional analytical parameters (e.g., range, sensitivity, selectivity), operational factors (degree of automation, portability, required level of crew training, maintenance), logistical factors (size, mass, power, consumables, waste generation) and engineering factors such as complexity and reliability. Other more subtle considerations include crew interfaces, data readout and degree of autonomy from the ground control center. We anticipate that technology demonstrations designed toward these goals will be carried out on the International Space Station, the end result of which is a suite of techniques well positioned for deployment during Exploration missions.

The measurement of ionic contaminants in samples from the potable water system on Space Station Freedom is one of the basic functions of the Crew Health Care System (CHeCS). The U. S. Environmental Protection Agency has identified ion chromatography as the analytical method of choice for measurement of anions and cations in water as described in USEPA method numbers 300.0 and 300.7, respectively. For this reason, ion chromatography was the technology initially identified to perform the ion contaminant monitoring function in the CHeCS Water Quality Subsystem. Subsequently, mass, size, and maintenance restrictions have led to a reevaluation of method options. Capillary electrophoresis (CE) has emerged as one of the more promising alternatives. CE is inherently microgravity compatible and uses an order of magnitude less reagent volume than ion chromatography. The major drawback to CE is its present state of development.