Raman spectroscopy combined with electrochemical measurement has been proved to be effective in the elucidation of complex voltammetric responses. In the reduction of 2,3,5,6-tetrachloro-1,4-benzoquinone (TCQ), complex voltammograms were observed in the presence of alkaline earth metal ions (M2+) due to ion pair formation. By using thin layer electrochemical Raman (TLER) measurements synchronized with the reduction of TCQ in the presence of Mg2+, it was found that an intermediate ion pair, Mg2+ TCQ(.-), was reduced co an ion pair involving the TCQ dianion, Mg2+ TCQ(2-). In contrast, for the case of Ba2+, the anion radical salt (Ba2+ TCQ(.-))(2) was found to deposit on the electrode surface, which was confirmed through the Raman measurement of the salts of reduced species produced by a flow-electrolysis synthetic method. The electrochemical behavior was dependent on the metal cations, M2+. The intermediate ion pair, M2+ TCQ(.-), may either accept another electron or precipitate on the electrode surface.