The ferrocenium/ferrocene redox couple (Fc(+)/Fc) and its decamethylated counterpart, decamethylferrocenium/decamethylferrocene (DmFc(+)/DmFc), are important internal standards for potential referencing in electrochemistry in non-aqueous solutions. This study quantifies the difference in the effects of two different solvents on these standards: a typical molecular solvent (acetonitrile) and a typical room-temperature ionic liquid (RTIL), C(2)mim(+)TFSA(-) (where C(2)mim(+) = 1-ethyl-3-methylimidazolium (emim(+)), and TFSA(-) = bis(trifluoromethanesulfonyl)amide (NTf2-)) by using DmFc(+)/DmFc that was found to be a rare alternative couple for the determination of single-ion transfer energies. To this end, the standard molar Gibbs energies of transfer of these redox couples are elucidated with an accuracy of +/- 5mV and a precision of +/- 25mV at 25 +/- 1 degrees C.