Reference electrodes for voltammetry in acetonitrile

✍ Scribed by Robert C. Larson; Reynold T. Iwamoto; Ralph N. Adams

• Publisher: Elsevier Science
• Year: 1961
• Tongue: English
• Weight: 203 KB
• Volume: 25
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(61)80216-x

✦ Synopsis

Over the past few years interest in acetonitrile as a polarographic solvent has produced some extremely fruitful results. These studies have developed some ambiguities with regard to reference electrodes for acetonitrile polarography. Recently when one of the authors attempted to convert the data of several workers to a common reference electrode (aqueous saturated calomel), it became apparent that it was not clear how the individual reference electrodes had been used.

In general, reference electrodes for acetonitrile have been either the ordinary aqueous saturated calomel or the silver ion-silver system used by PLESKOV 1 in potentiometric measurements. PLESKOV measured potentials of various metal-metal ion couples in acetonitrile using a half-cell of AgNOs(o.oI M), CH3CN/Ag as the reference. KOLTHOFF AND COETZEE 2 preferred the aqueous saturated calomel electrode but compared their data to PLESKOV'S reference apparently by measuring the system AgN03(o.oI M), Ag II S.C.E. aq. They reported the silver ion-silver electrode to be +0.29 V vs. S.C.E. aq. However, if it is assumed that their polarographic E1/z for silver ion reduction in o.I M sodium perchlorate medium (0.32 V vs. S.C.E.) can be identified as usual with E ° for silver ion-silver, then EA~ + ~o.ol u~, ~ vs. S.C.E.aq. would be +0.20 V. This appears inconsistent with the value +0.29 V. On the other hand, the E1/~ for silver ion reduction in o.I M tetraethylammonium perchlorate reported by LARSON AND IWAMOTO s (+0.42 V vs. S.C.E.), when converted to EAg + (0.Ol M), Ag gives +0.30 V vs. S.C.E. aq.

PoPov AND GESKE 4 developed a silver-silver chloride electrode where the solubility of silver chloride in acetonitrile was controlled by a fixed concentration of tetramethylammonium chloride. Again the data were converted to PLESKOV'S Ag+(o.oI M)/Ag reference using the value +0.29 V. In more recent acetonitrile work, GESKE 5,6 has used the aqueous saturated calomel as the actual reference electrode.

LARSON AND IWAMOTO, in fundamental studies of solvent effects on metal ion reductions, used the aqueous saturated calomel electrode but did not make conversions to the silver ion-silver system 3. Similarly KUWANA 7, as well as VOORHIES AND FURMAN 8, studied anodic oxidations in acetonitrile using the aqueous saturated calomel.

LUND 9, in pioneering studies of the oxidation of hydrocarbons in acetonitrile, used as a reference electrode what has been tacitly assumed to be the silver ion-silver system of PLESKOV. His reference actually was AgC104(o.i M), NaCl04(o.5 M), Ag.

Since the aqueous saturated calomel does function satisfactorily in acetonitrile