THE USE OF SONOTRODES FOR ELECTROANALYSIS - SONO-ASV DETECTION OF LEAD IN AQUEOUS-SOLUTION

Sonotrodes were made by implanting a working electrode into the tip of an ultrasonic horn. These were investigated For the use in ultrasound assisted anodic stripping voltammetry (ASV) of Pb2+ and Cu2+ in aqueo us solutions to which Hg2+ was added to permit the formation of lead/c opper amalgam in a plating step. Insonation not only allows this preco ncentration step to tahr place under conditions of unusually high mass transport bur also causes enrichment of the trace metals in the form of intermetallic compounds leading to sharp,tripping responses. The ef fect of increasing insonation time on the oxidation peak sizes, shapes and positions was studied. Comparison was made with the voltammetry o f Pb2+ and Cu2+ observed at platinum electrodes in the absence of Hg w here broad signals for both were seen. The nature of the deposition of mercury on platinum electrodes was studied by both voltammetry and at omic force microscopy (AFM). The growth of mercury droplets with time under `silent' platinum sonotrodes the ratio of Hg2+ to Pb2+ in the co deposition was examined along with the total amount of charge deposite d for a range of Pb2+ concentrations. Sharp anodic stripping responses were obtained down to a Pb2+ concentration level of 2 mu gL(-1) makin g sono-ASV a potentially valuable technique for the detection of Pb2in solution. In contrast glassy carbon sonotrodes were found to be uns atisfactory since the adhesion of mercury under insonation was poor.