A magnetically separable Fe3O4@Diaion HP-2MG composite was prepared using the coprecipitation method and the resulting magnetic Fe3O4@Diaion HP-2MG composites were used for the separation and preconcentration of trace amounts of dopamine. For the detection stage, square wave voltammetry on a disposable graphene-screen-printed carbon electrode was successfully used for the determination of dopamine. The graphene-screen-printed carbon electrode exhibited excellent electroanalytical performance for dopamine. The linear concentration range was from 0.8 to 80 mu M and a detection limit of 50nM for dopamine was obtained. In combination with the magnetic solid-phase extraction method, the sensor response was linearly proportional to the concentration of dopamine in the range of 0.01-6.0 mu M with a correlation coefficient of approximately 0.9992. The detection limit of the sensor was found to be 5.0nM by square wave voltammetry. The combined methodology was successfully applied to determine dopamine in urine samples with good recoveries ranging from 95 to 98%.