16-02-2013, 11:04 AM
VOLTAMMETRY
VOLTAMMETRY.ppt (Size: 1.1 MB / Downloads: 109)
Instrumentation – Three electrodes in solution containing analyte
Working electrode: microelectrode whose potential is varied with time
Reference electrode: potential remains constant (Ag/AgCl electrode or calomel)
Counter electrode: Hg or Pt that completes circuit, conducts e- from signal source through solution to the working electrode
Supporting electrolyte: excess of nonreactive electrolyte (alkali metal) to conduct current
Voltammetric analysis
Analyte selectivity is provided by the applied potential on the working electrode.
Electroactive species in the sample solution are drawn towards the working electrode where a half-cell redox reaction takes place.
Another corresponding half-cell redox reaction will also take place at the counter electrode to complete the electron flow.
The resultant current flowing through the electrochemical cell reflects the activity (i.e. concentration) of the electroactive species involved