This paper reports potentiometric determination of oxalic acid in spinach, using PVC-oxalic acid imprinted polymer coated graphite electrode. The intermolecular interactionsbetween oxalic acid and acrylamide functional monomer and the number of moles of functional monomer that interact with one mole of template were studied using computational method based on density functional theory. Oxalic acid specific bulk polymer was obtained by the thermal initiated free radical co-polymerization of acrylamide and ethylene glycol dimethacrylate with oxalic acid as template and acetonitrile as porogen. After extraction of template, the binding parameters of molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) were compared by Langmuir- Freundlich (L-F) adsorption isotherms. After optimization of membrane composition, electrode coated with MIP-PVC membrane in dioctyl phthalate as plasticizer, exhibited super Nernstian response (36.83 0.5 mV decade-1) over a concentration range of 1.0 10-7 to 1.0 10-2 M, with a low detection limit of 1.210-7 M. The sensor showed good selectivity and was successfully applied for determination of oxalic acid in spinach and ground water samples. © 2013 by ESG.