The pristine graphene can be easily prepared in isopropanol-water mixture with salts as assistant via liquid-phase exfoliation method. The concentration of graphene dispersion reaches as high as 0.565 mg/mL. The graphene film prepared by drop-casting method shows an excellent electrical conductivity (7.095 x 10(4) S/m). Furthermore, an electrochemical biosensor based on the pristine graphene shows high selectivity and sensitivity for the determination of dopamine. The linear detection range for dopamine is 2.5-1500 mu M with detection limit of 1.5 mu M. This method provides a potential process for preparing high-quality graphene ready-to-use in low-boiling point solvent. (C) 2017 Elsevier Inc. All rights reserved.