Thick membrane, solid contact ion selective electrode for the detection of lead at picomolar levels

A new approach for decreasing the lower detection limit of a lead ion selective electrode (ISE) is presented. The ISE is designed using nonfunctionalized porous glassy carbon loaded with ionophore/plasticizer/additive cocktail. This material acts both as the support for the liquid polymeric membrane and as the signal transducer of the ISE. The high purity of the glassy carbon, together with its high conductivity, allows for the development of a thick, low-resistance composite membrane. This sensor element enables the continuous measurement of lead down to picomolar levels, with very small detection limit deterioration due to the lead ion transport within the bulk of the thick membrane.