Microfluidic Ion Chromatograph for In-Flight Water Quality Analysis

Although water quality may currently be analyzed on the ground after a flight, long-duration missions will require the capability to perform analyses on-board. If a water purifier fails, contaminants must be detected rapidly and corrective action taken in a timely manner to prevent serious harm to the crew. Many of the possible contaminants which could negatively affect astronaut health are inorganic ions. These ions can be quantified by ion chromatography (IC), although current commercially-available IC's are too large, heavy, and power-intensive to be used on a space mission. These units also require large quantities of caustic chemicals for analysis, which would pose a significant hazard in a microgravity environment. To meet the need for an inorganic water quality analysis device for long-duration missions, Lynntech developed an ion chromatograph tailored for future planned long-duration missions. The entire unit is the size of a shoebox, requires little power, produces anionic and cationic chromatograms simultaneously, and generates the acid and base needed for analysis from benign salt water. Several components were developed specifically for this application over the course of work. A developed microfluidic liquid/gas phase separator performed successfully in microgravity conditions; a syringe pump was developed to provide uniform and repeatable high-pressure flow from a low-power, compact device; and a conductivity detector was designed and implemented with six orders of magnitude in dynamic range, an internal volume of only 0.7 microliters, and an autoranging capability which allows the analysis of both high and low ionic species concentrations in the same sample. The complete system and its measurement capabilities are described in detail.