In an exemplary embodiment, the apparatus includes an electromagnetic radiation source, an optical analyzer, and a fiber optic bundle. The fiber optic bundle has an excitation fiber in optical communication with the electromagnetic radiation source and a plurality of emission fibers in optical communication with the optical analyzer. The optical analyzer can have multiple channels, including a fluorescence-emission channel in optical communication with the emission fibers. Optionally, the fiber optic bundle can further contain at least one reflection fiber in optical communication with an absorbance/reflectance channel. In addition to detecting Fries product in formed polycarbonate materials, the method and apparatus can also be utilized to directly determine the concentration of a target species in parallel polycarbonate reactor systems.