Abstract: The crown ethers were polymerized onto a 2 mm diameter Pt disc electrode. The monomer solution comprised 0.025 M crown ether and 0.20 M tetrabutylammoniumtetrafluoriborate as supporting electrolyte in acetonitrile. Amperometric measurements were performed with a BAS model MF-1021 flow cell. Static potentiometric and potentiometric FIA measurements were performed with the polymer-modified electrode PTFE block incorporated into a standard BAS thin-layer flow cell with a Ag/AgCl electrode as second electrode. Measurements were performed with an Orion model 601A ionanalyzer. The potentiometric FIA response of all the crown ethers was linear over the range 10 mM to 10 µM. The lowest detection limits were 0.5 µmM for the potentiometric FIA with minimum interference from ascorbic acid, uric acid and acetaminophen. Detection limits for amperometric FIA was 5 µmM but there was significant interference from ascorbic acid, uric acid and acetaminophen.