Multi-parametric polymer-based potentiometric analytical microsystem for future manned space missions

The construction and evaluation of a Cyclic Olefin Copolymer (COC)-based continuous flow potentiometric microanalyzer to simultaneously monitor potassium, chloride and nitrate ions in samples from an on-board water recycling process expected to be installed in future manned space missions is presented. The main goals accomplished in this work address the specific required characteristics for a miniaturized on-line monitoring system to control water quality in such missions. To begin with, the integration of three ion-selective electrodes (ISEs) and a reference electrode in a compact microfluidic platform that incorporates a simple automatic autocalibration process allows obtaining information about the concentration of the three ions with optimal analytical response characteristics, but moreover with low reagents consumption and therefore with few waste generation, which is critical for this specific application. By a simple signal processing (signal removal) the chloride ion interference on the nitrate electrode response can be eliminated. Furthermore, all fluidics management is performed by computer-controlled microvalves and micropumps, so no manual intervention of the crew is necessary. The analytical features provided by the microsystem after the optimization process were a linear range from 6.3 to 630 mg L-1 and a detection limit of 0.51 mg L-1 for the potassium electrode, a linear range from 10 to 1000 mg L-1 and a detection limit of 1.58 mg L-1 for the chloride electrode and a linear range from 10 to 1000 mg L-1 and a detection limit of 3.37 mg L-1 for the nitrate electrode with a reproducibility (RSD) of 4%, 2% and 3% respectively. Sample throughput was 12 h(-1) with a reagent consumptions lower than 2 mL per analysis. (C) 2017 Elsevier B.V. All rights reserved.