The influence of UV light irradiation on the metal ion open-circuit accumulation process is determined using a glassy carbon modified electrode with poly(2,2'-(ethan-1,2-diylbis((2-(azulen-2-ylamino)-2-oxoethyl)azandiyl))diacetic acid (polyL). A correlation analysis between the semiconductive properties of polyL film and sensing properties is performed. Photo-assisted metal ion open circuit accumulation led to the simultaneous detection of Cu(II) and Hg(II) which allowed a detection limit of 0.4 nM and 0.7 nM for Cu(II) and Hg(II), respectively.