Centrifugal microfluidics with integrated sensing microdome optodes for multiion detection

An array of four sensing microdome optodes (potassium, sodium, calcium, and chloride) was incorporated into a centrifugal microfluidics platform to obtain a mullion analysis system. The behavior of each sensing microdome was in good agreement with a theoretical model describing the response. The selectivity of each optode over common interfering ions was established and was used to identify calibrant solutions that can be employed for the simultaneous calibration of all four optodes without significant cross-interference. The microfluidic platform was designed to facilitate both three-point calibration of the optodes and triplicate analysis of a sample within a single run, which increases the accuracy of the determination. The optimized microfluidic system was used to determine simultaneously the concentration of potassium, sodium, calcium, and chloride in aquarium water (with the composition of Lake Tanganyika water) with less than 6% error. The simple process of fabrication of these microdomes and their incorporation into a centrifugal microfluidic platform should facilitate the development of portable ion-sensing analysis systems.