A chemically initiated adaptation of the classic [Ru(bipy)(3)](2+)/oxalate electrochemiluminescence coreactant system has revealed the elusive radical intermediates of the light-producing pathway. Oxalyl (HC(2)O(4)˙) and hydroxyformyl (HCO(2)˙) radicals have been captured on a quartz surface and characterised using EPR spectroscopy.