Renewable copper and silver amalgam film electrodes of prolonged application for the determination of elemental sulfur using stripping voltammetry

New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12 mm(2), both electrodes are characterized by very good surface reproducibility (<= 2%) and long-term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1-2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16 ng L-1 to 4.8 mu g L-1 for Hg(Cu)FE, and up to 6.4 mu g L-1 for Hg(Ag)FE (t(acc)=15 s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and t(acc)=60 s are as low as 14 ng L-1 for Hg(Cu)FE and 4 ng L-1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water.