Microfluidic analysis of fentanyl-laced heroin samples by surface-enhanced Raman spectroscopy in a hydrophobic medium
nanoparticles, designed to be stable in mixtures of octanol and ethanol. The sample is then loaded into an SU8/glass microfluidic device that is compatible with non-aqueous solutions. The SERS-active nanoparticles are aggregated by dielectrophoresis using microelectrodes embedded in the microfluidic channels, and the nanoparticle aggregates are interrogated using Raman spectroscopy. Using this method, we were able to reliably detect fentanyl from samples with as low as 1 : 10 000 (mol/mol) fentanyl-to-heroin ratio, improving the limits of detection of fentanyl-laced heroin samples by two orders of magnitude over current techniques. The described system could also be useful in chemical detection where rapid and robust preconcentration of trace hydrophobic analytes, and rapid SERS detection in non-aqueous solvents is indicated.