The application of various immobilized crown ether platinum-modified electrodes as potentiometric and amperometric detectors for flow injection analyses of catechol and catecholamines

Different crown ethers were electrochemically polymerized or adsorbed onto a platinum electrode for the analysis of catechols by either static potentiometric, potentiometric FIA or amperometric FIA. The static potentiometric responses of all the crown ether modified electrodes were linear over about three decades of catechol concentration (10−5−10−8 M). The potentiometric FIA response of all the crown ether modified electrodes exhibited linear responses over four decades of catechol concentration (10−2−10−6 M). The amperometric FIA responses were linear over a 10−2−10−5 M range. Comparing the different techniques; static potentiometric, potentiometric FIA, and amperometric FIA, all had markedly different response slopes for the different crown ethers. Overall, the crown ether modified electrodes, except for an open‐crown ether, displayed excellent response stability for successive injections in both FIA modes. The lowest detection limits were about 0.5 × 10−6 M for the potentiometric FIA with minimal interference from ascorbic acid, uric acid and acetaminophen. For amperometric FIA the detection limits were about 0.5 × 10−5 M, but for ascorbic acid, uric acid, and acetaminophen the interference was significant. Experimental parameters which influence the mechanism of the potentiometric response are discussed.