Working electrode Glassy carbon, Hanging mercury-drop

A Metrohm polarecord E-506 coupled with a Metrohm 663 VA Stand was used. A multimode mercury drop electrode (Metrohm 6.1246.000) which contains a hanging mercury drop electrode (HMDE) was used, which served as the working electrode. The average drop size was 0.52 mm. A glassy carbon was used as the auxiliary electrode and the SCE as a reference electrode. A Metrohm VA 612 Scanner and a rapid X-Y register, Linseis LY 1800, were used to obtain the cyclic voltammograms. All measurements were performed at room temperature. 

This is probably the most sensitive technique for lead, and in very low level work the avoidance of contamination is likely to be a more major problem than the approach of the analytical detection limit. Sensitivity may be improved even further by the use of alternative electrodes (e.g. glassy carbon) in place of the commonly used hanging mercury drop. Advantages of ASV are the possibility of simultaneous determination of four metals (Pb, Cd, Cu, Zn) in one sample, and the freedom from matrix effects as a standard additions technique is always used. 

Figure 7. The automated electrochemical analysis of the low-molecular thiol compounds. The electrochemical measurements were performed with 747 VA Stand instrument connected to 746 VA Trace Analyzer and 695 Autosampler (Metrohm, Switzerland), using a standard cell with three electrodes and a cooled sample holder (4 °C). A hanging mercury drop electrode (HMDE) with a drop area of 0.4 mm was the working electrode. An Ag/AgCl/3M KCl electrode was the reference and a glassy carbon electrode was the auxiliary electrode.

Conventional 3-electrode cells, commercial potentiostats with external feedback IR compensation, and procedures similar to those described previously were used for electrochemical experiments. Working electrodes were a PARC Model 9323 hanging-drop-mercury electrode (HDME, A = 0.019 cm ) or a highly polished glassy carbon disk electrode (GCE, A = 0.071 cm ). A Pt wire served as the counter electrode and the reference was a saturated calomel electrode (SCE). For the HDME, a fresh Hg drop was used for each experiment. A polishing method described previously was used for GCE " and was repeated prior to each voltammetric scan. Area of the GCE was estimated electrochemicaly by using the Randles-Sevcik equation and CV peak for the oxidation of ferrocene in acetonitrile (D = 2.4 X 10 cm s i). Experiments in all CTAB solutions were thermo-statted at 30.0 0.1 C for SDS the temperature was usually 25.0 0.1 C. 

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