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A newly designed remote probe has been developed for stripping measurements of trace mercury at large sample-instrument distances. Various gold electrodes, stripping modes, and operation conditions have been optimized to meet the requirement of remote monitoring of mercury. The favorable stripping potentiometric response obtained following 0.5-1.0 min deposition, leads to a rapid detection of low ppb mercury concentrations, and offers a fast warning capability. The optimized protocol offers a low detection limit ( of 0.3 mg/L with 5 min deposition) and good precision (RSD of 3.9 % for n ¼ 100). Due to its inherent sensitivity, simplicity, stability, and smaller dimensions the new probe is well suited for in situ monitoring of trace mercury in natural waters.

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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).

The ligand cupferron is used for the simultaneous adsorptive stripping voltammetric measurements of several trace metals. Experimental variables affecting such multielement capability, including the cupferron concentration, adsorption time or metal concentration are explored. Adequate resolution is demonstrated for up to five metals (Fell', U"', Cr"', V", and Bi"'), present at the ppb concentration level. Possible changes in peak heights, associated with competition for the complexing ligand and/or coadsorption effects, are explored. Different concentration ratios of the mixture components can be tolerated. Applicability to groundwater or river-water samples is illustrated.