This work extends the concept of in situ electrochemical stripping sensors to environmentally important metals that are not readily accumulated by amalgamation. A renewable-reagent sensor has thus been designed to accommodate the complex formation and adsorptive accumulation steps of adsorptive stripping protocols. Such flow probe relies on the delivery of a ligand solution through a microdialysis sampling tube and transport of the resulting complex to a downstream adsorptive stripping detector. The integrated membrane sampling/adsorptive stripping sensor is characterized, optimized, and tested in connection with the monitoring of trace uranium and nickel using the propyl gallate and dimethylglyoxime chelating agents, respectively. Experimental variables, including the reagent delivery rate and ligand concentration, are explored. The microdialysis sampling step minimizes the interference of surface-active macromolecules and extends the linear dynamic range compared to conventional adsorptive stripping measurements. Detection limits of 1.5 × 10 -8 M nickel and 4.2 × 10 -8 M uranium are obtained following 5-and 20-min adsorption times. A relative standard deviation of 1.7% is obtained for prolonged operations of 20 runs. The applicability to assays of river water and groundwater samples is demonstrated. The renewable-reagent adsorptive stripping sensor holds great promise for remote monitoring of various trace metals (via a judicious selection of the ligand).

Coverage of carbon paste electrodes with poly(1,3-phenylenediamine) (m-PPD) films results in an accelerated oxidation of hydrogen peroxide. Compared to the bare carbon surface, the coated electrode exhibits a substantial (240 mV) lowering of the oxidation potential and a marked enhancement of the current response. Variables affecting the electrocatalytic behavior, including the electropolymerization potential and time, monomer structure, or pH, are explored. Combining this electrocatalytic action of PPD films with their effective permselective/discriminative properties holds great promise for first-generation oxidase-based amperometric biosensors. For example, it leads to a greatly enhanced glucose response while maintaining an effective rejection of coexisting electroactive species.

A renewable‐reagent flow probe has been developed for the remote electrochemical biosensing of enzyme inhibitors. The new submersible device addresses the challenges of continuously replacing the inhibited enzyme and consumed substrate. The internal delivery of microliter enzyme and substrate solutions is coupled to an in situ microdialysis sampling of the toxin, and an amperometric detection of the enzymatically generated product. The new concept is demonstrated for the detection of micromolar concentrations of free cyanide in the presence of the enzyme tyrosinase and its catechol substrate. The optimization of various physical and chemical parameters has resulted in a low detection limit of 2 × 10−6 M cyanide and good precision (RSD = 5%). The new device holds great promise for in situ environmental and industrial monitoring of toxins.