Gradient flow-injection amperometry based on induced retention by the detector coating

A novel approach for enhancing the selectivity of amperometric flow-injection systems is described. This strategy relies on the use of coated electrodes to induce longer residence times for the target analyte (within the detector) compared to the interfering species. Selective measurements of the analyte are thus performed on the tailing edge of its peak, after passage of the interfering species from the detector. Surface coatings with different permeability properties, including charge-exclusion Nafion or hydrophobic lipid and alkanethiol films are thus used to retain and selectively detect counterionic or nonpolar analytes, after the elution of co-ionic and polar interferences, respectively, from the detector.