Potassium selective quartz crystal microbalance chemical sensors using functionalized copolymer coatings

Quartz crystal microbalance sensors that specifically detect K+ ions have been developed using copolymers based on poly(acrylic acid) and functionalised with crown ethers to provide selectivity. The coatings selectively absorb K+ over other Group I ions such as Li+ and Na+. Sensors have been used in both batch and flow modes with detection limits in the region of 0.1–0.2 ppm for K+(aq) with a linear range extending to over 1000 ppm. The sensors perform at least as well as other recently developed methodologies although further optimisation should significantly improve this performance.