The present application relates to microfluidic devices and related technologies, and to chemical processes using such devices. More specifically, the application discloses a fully automated synthesis of radioactive compounds for imaging, such as by positron emission tomography (PET), in a fast, efficient and compact manner. In particular, this application describe an automated, stand-alone, microfluidic instrument for the multi-step chemical synthesis of radiopharmaceuticals, such as probes for PET and a method of using such instruments.