A probe for a system for determining the chemical signature of a pharmaceutical compound. The probe comprises: a housing; an inlet in the housing adapted to be connected to a transmitting optical fiber; a scanning aperture in the housing; a receiving outlet in the housing adapted to be connected to a receiving optical fiber; at least one transmission reflector positioned in the housing to receive laser light from the transmitting optical fiber and reflect the laser light through the detection outlet to a pharmaceutical vial containing a pharmaceutical compound positioned outside the housing, and at least one receiving reflector positioned in the housing to receive light reflected by the pharmaceutical compound and reflect the light to the receiving outlet. This configuration can enable rapid and accurate scanning of a pharmaceutical contained in a vial positioned adjacent the detection outlet.