Carbon paste electrode bulk modified with a conducting polymer poly(1,8-diaminonaphthalene): application to lead determination

Carbon paste electrodes modified with conducting polymers for sensitive and selective determination of lead are presented. A novel method for generating a reproducible polymer-coated electrode surface is developed. We prove that 1,8-diaminonaphthalene (1,8-DAN) mixed with a carbon paste electrode leads to a conducting polymer in acidic medium while, in the same medium, this polymer is known to be non-conducting on platinum electrode. The electrode behaviour of poly(1,8-DAN), electropolymerised into carbon paste, was investigated by cyclic voltammetry in the presence of the ferri-ferrocyanide couple. A carbon paste electrode modified with poly(1,8-DAN) was used to determine Pb2+ in aqueous solutions. Pb2+ ions were firstly complexed and then electrochemically deposited by a potential step to -0.9 V. The accumulated lead after reduction was anodically stripped by differential pulse voltammetry. Different parameters, such as pH of the solution, preconcentration time, and electropolymerisation procedures were studied. For a preconcentration time of ten minutes, the calibration graph was linear from 40 to 2070 ng mL(-1) with r(2)=0.998. The detection limit was found to be 30 ng mL(-1), and the relative standard deviation was 6%.