Sarah Mackin runs a cotton swab around the inside of a tiny plastic baggie that appears to be empty. She spreads whatever residue the swab picked up onto a test strip that resembles a Band-Aid, then slides the strip into a buzzing machine about the size of a boxed, take-home pie. Then she waits, hoping for information that she can share with Boston's community of opioid users.
Mackin is using an MX908, a mass spectrometer initially marketed as a counterterrorism tool. The machine can help military teams looking for traces from biological or chemical weapons, or hazardous material specialists trying to identify materials used in spills or explosions. But now the MX908 has been commandeered in the fight against fentanyl, one of Boston's — and the nation's — top killers.