A method of particle detection includes optically trapping a single particle having an averaged linear dimension of between 0.10 microns and 50 microns in a focal region optical trap formed from a trap visible to near-infrared wavelength. The trap is proximal to a substrate having a discontinuous metal coating so as to exploit a surface plasmon resonance generated electric field caused by irradiation of the metal coating. The single particle is then exposed to an interrogation wavelength to yield scattering spectrum relating to the particle. A particle identification digital database containing scattering spectra from a variety of different single particles that vary in spectral features facilitates identification of unknown spectra. A microfluidic cell is detailed to facilitate the automated scanning of numerous particles from a sample.