A new low-cost portable device uses a smartphone to detect the presence and concentrations of BDE-47 (2,2',4,4'-tetrabromodiphenyl ether), a type of flame retardant and widespread environmental contaminant. The device uses a lab-on-a-chip (LOC) platform to perform microscale enzyme-linked immunosorbent assays (ELISA), a popular lab technique that uses antibodies designed to measure a specific substance in a sample. The LOC platform performed comparably to the standard ELISA laboratory protocol but in much less time and with much smaller sample sizes.