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Specification of the test : Pb/Cd in 0.1 M HClWorking Electrode : Mercury drop (HMDE)Reference Electrode : Ag // AgClAuxiliary Electrode : PtAbstractThe Potentiostatic Universal Differential Pulse method can be used to detectCadmium and Lead at ppm level. A Hanging Mercury Drop Electrode (HMDE) is usedin combination with a differential pulse measurement. This combination correspondsto a “stripping analysis”. During electrolysis at a set potential, Pb 2+ and Cd 2+ arereduced and amalgamated on the hanging mercury drop. The determination is thenperformed by potential scanning in the anodic direction. The amalgamated metalsare stripped back into the solution in their ionic form. The resulting stripping current isproportional to the concentration of the metal ions in solution.Sample* Reagents(1) Supporting Electrolyte: 1M HCl.(2) 1000 mg/l Pb(II) stock solution.(3) 1000 mg/l Cd(II) stock solution.(4) 100 mg/l Pb(II) -10 mg/l Cd(II) standard solution.* Standard solution preparationAdd 10.0 ml 1000 mg/l Pb(II) solution,1.0 ml 1000 mg/l Cd(II) solution and10.0 ml of 1M HCl Suprapur in the same flask. Dilute to 100 ml with deionized water.Always use reagent grade chemicals for reagent preparation.* Apparatus- MDE150 Polarographic Stand- VoltaLab 80 (PGZ402 & VoltaMaster 4)See chapter 6.4.* Electrodes- TR020 Reference Electrode- TM010 Platinum Electrode- MDE/CAP 70 µm CapillarySettings - ExperimentalThe “Run External Unit” method is used to control the MDE in order to organise thepurge, the blanketing, the stirring and the mercury drop itself.VoltaLab 21/06/10/40/50/80 165Section 6, Chapter 5: HMDE (MDE150)