Evaluation of liquid- and solid-contact, Pb2+-selective polymer-membrane electrodes for soil analysis

Pb2+-selective electrodes (ISEs) have been developed for the analysis of soil. Recent advances have extended the previous achievable limits of detection of ion-selective electrodes (ISEs) to submicromolar levels, opening up possibilities for new applications in environmental analysis. The simple construction of ISE's, their low cost and low power demand, coupled with improved detection limits make the electrodes well suited for environmental analysis. In this paper, the development and use of both liquid- and solid-contact ISEs for the detection of Pb2+ in a range of soil samples from abandoned mining sites is described. Solid-contact electrodes were made using poly(3-octylthipophene) as the internal mixed conductor layer. In addition, three techniques for the extraction of analyte from soil were studied in order to optimize the extraction of metal ions using techniques and solvents compatible with portable devices. Soil Pb2+ levels between 30 and 29,100 mg/kg were measured with the ISEs and were shown to be in good agreement with reference AAS measurements. Issues arising from the current definition and interpretation of ISE detection limits are also discussed.