Abstract: A method and device are provided for detecting a target in a biological sample. The target binds to a solid phase substrate. First and second cavities in a plate are filled with an oil. The first and second cavities are in fluid communication with each other. The solid phase substrate is magnetically drawn sequentially from a drop of the biological sample in the first cavity, through the oil, into a drop of the reaction solution in the second cavity. A change in a parameter of the drop of the reaction solution indicates the presence of the target.