SCE CI(aq)Hg2Cl2/Hg() Hg2++2e=2Hg( E0=0.24 V VS. SHE Q 25C Saturated KCl Calomel Paste Advantages Disadvantages ·Most Hg g toxIc polarographic. solubility of KCl 6 mm data ref d to temperature From bas www SCE dependent de/dT site http:/www.bi loana 0.67 mV/K(must lytical. com quote temperature)
SCE • Cl- (aq)/Hg2Cl2 /Hg(l) • Hg2 2+ + 2e- = 2Hg(l) • E0 = 0.24 V vs. SHE @ 250C Disadvantages • Hg toxic • solubility of KCl temperature dependent dE/dT = - 0.67 mV/K (must quote temperature) Advantages • Most polarographic data ref’d to SCE From BAS wwwsite: http://www.bioana lytical.com/
Ag/AgCl Ag wire coated with AgCl(), immersed in NaCI or cl solution RE-5B Agt +e=Ag(s) 7. 5 cm Eo=0.22 V vS. ShE@ 25C Advantages Disadvantages chemical processing. solubility of 6 mm industry has KCI/NaCl standardized on this temperature From bas wwv site electrode dependent http://www.bi joana convenient de/dT=_0.73 mV/k LIlytical com · rugged/ durable must quote temperature)
Ag/AgCl • Ag wire coated with AgCl(s), immersed in NaCl or KCl solution • Ag+ + e- = Ag(s) • E 0 = 0.22 V vs. SHE @ 250C Disadvantages • solubility of KCl/NaCl temperature dependent dE/dT = -0.73 mV/K (must quote temperature) Advantages • chemical processing industry has standardized on this electrode • convenient • rugged/durable From BAS wwwsite: http://www.bioana lytical.com/
Ag/Ag °Ag++e=Ag(s) requires use of internal potential standard 7.5ct Advantages Disadvantages ° Most widely used · Potential depends on Easily prepared solvent 6 mm · Works well in all electrolyte LiCI aprotic solvents TBACIO4, TBAPF6 From bas wwv TBABF4 site http://www.bi joana THF CAN, DMSO,. Care must be taken to lytical. com/ DMF minimize junction potentials
Ag+ /Ag • Ag+ + e-= Ag(s) • requires use of internal potential standard Disadvantages • Potential depends on – solvent – electrolyte (LiCl, TBAClO4 , TBAPF6 , TBABF4 • Care must be taken to minimize junction potentials Advantages • Most widely used • Easily prepared • Works well in all aprotic solvents: – THF, CAN, DMSO, DMF From BAS wwwsite: http://www.bioana lytical.com/
Pseudo-References Pt or Ag wire(inert) ·Idea in medium of high resistance, low conductivity, wire will assume reasonably steady, highly reproducible potential (+20 Advantage: no solution contamination Limitation: must use internal potential standard(ferrocene)
Pseudo-References • Pt or Ag wire (inert) • Idea: in medium of high resistance, low conductivity, wire will assume reasonably steady, highly reproducible potential (+ 20 mV) • Advantage: no solution contamination • Limitation: must use internal potential standard (ferrocene)