Fentanyl and fentanyl analogs are playing an increasing role in the opioid health crisis that is sweeping America. These synthetic opioids are much more potent and lethal than morphine or heroin and must be treated with extreme caution. Many of these substances are entering the country through International Mail Facilities (IMFs) and Express Courier Hubs (ECHs) in the form of counterfeit prescription drugs and bulk powders, resulting in a critical need for field-deployable techniques that...