The reaction in organic solvent between atrazine and anti-atrazine antibody modified with 2,4-bis(o-methoxy-polyethylene glycol)-6-chloro-s-triazine was reported. Modification with activated PEG2 (2,4-bis(o-methoxypolyethylene glycol)-6-chloro-s-triazine) was demonstrated to have no influence on the binding affinity of the antibody. Solubility of the antibody modified with activated PEG2 in toluene was 26 μg/mL. PEG modified anti-atrazine antibody immobilized onto Controlled Pore Glass (CPG) was suggested to have affinity towards atrazine in the organic solvent and the possibility of application for the enzyme immunoassay was suggested.