A　glassy　carbon　electrode　was　modified　with　a　composite　consisting　of　ferrocene　imidazolium　salts　and　hydroxy-functionalized　graphene　in　a　Nafion　matrix.　The　electrode　is　shown　to　facilitate　the　reduction　of　oxygen　to　form　the　superoxide　anion　radical.　Atomic　force　microscopy　and　electrochemical　impedance　spectroscopy　were　used　to　characterize　the　electrode.　The　in-situ　production　of　superoxide　anion　was　then　studied　with　an　analogue　of　methyl-Cypridina　luciferin　(also　referred　to　as Vargulin).　As　a　result,　an　electrochemiluminescence　(ECL)　based　assay　was　developed　for　the　improved　determination　of　the　activity　of　the　enzyme　superoxide　dismutase　(SOD).　Under　optimized　conditions,　the　ECL　based　calibration　plot　is　linear　in　the　0.5　to　6.5 U·mL−1　SOD　activity　range,　with　a　0.2 U·mL−1　detection　limit　(at　a　signal-to-noise　ratio　of　3).　[Figure　not　available:　see　fulltext.]　©　2016,　Springer-Verlag　Wien.