Dropping mercury electrode assembly

Fig. 10. Typical dropping mercury electrode assembly. A, Mercury reservoir B, Tygon tubing C, Pt wire connection to mercury D, capillary E, reference electrode F, counter electrode.

Figure 6.13 Cell for voltammetry and amperometric titrations (a) dropping-mercury electrode assembly (b) cell with provision to flush the salt bridge.

MEK peroxide can be analyzed by polaro-graphic method using a dropping mercury electrode assembly and a saturated calomel electrode (Floyd and Stockinger 1958). 

The apparatus is assembled and electrical connections are duly completed with dropping mercury electrode (C) as cathode and saturated calomel half-cell as anode,... 

Figure 14.1 Classical standtube and mercury reservoir assembly for use with dropping mercury electrodes.

The polarographic cell assembly comprising cell base and cover with a dropping mercury electrode as the cathode, a platinum wire auxiliary electrode as the anode and a saturated calomel reference electrode making solution contact via a liquid junction bridge. The mercury column is kept at a constant height, to have a natural drop time of about 4 s. The instrumental conditions for the differential pulse technique were 0.5 s drop time, -10 mV/S scan rate, 50 mV modulation amplitude. 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

Figure 5.25 Hanging-mercury-drop electrode (a) electrode-cell assembly with scoop to transfer mercury drops from DME to the electrode (b, c) details of construction for amalgamated platinum electrode to which mercury drops are attached.

---