We report synthesis, characterization and covalent fabrication of graphene nanosheets (GR) at gold (Au) electrode. The synthesized GR nanosheets were characterized by FTIR, UV-vis spectroscopy, XRD and FESEM techniques. The GR nanosheets were functionalized to produce GR–Ph–COOH. In another step, Au electrode was modified by cysteamine to form Au–S–CH₂–CH₂–NH₂. The COOH groups of GR–Ph–COOH were covalently attached to amine groups of Au–S–CH₂–CH₂–NH₂ through carbodiimide linkage using EDC and NHS as coupling agents. The GR–Cyst–Au interface was used for electrochemical determination of resorcinol (RS), an endocrine disruptor in solubilized ionic liquid (IL) ([C₄mim][Cl]) system over a concentration range from 0.3 to 45.2 µM with a detection limit (LOD) of 0.02 µM. The faster electron transfer kinetics of RS in [C₄mim][Cl] system were attributed to synergetic effects of large surface area, high conductivity, charge transporting abilities of GR and high intrinsic conductivity of [C₄mim][Cl] system. The GR–Cyst–Au interface was applied for determination of RS in the Garnier hair color cream as a real sample. Computational quantum approach i.e. COSMO-RS model was used to study trend of interactions in ternary mixture of water, RS and solubilized system for proposed RS sensor.