This disclosure concerns methods and apparatus for interferometric spectroscopic measurements of particles with higher signal to noise ratio utilizing an infrared light beam that is split into two beams. At least one beam may be directed through a measurement volume containing a sample including a medium. The two beams may then be recombined and measured by a detector. The phase differential between the two beams may be selected to provide destructive interference when no particle is present in the measurement volume. A sample including medium with a particle is introduced to the measurement volume and the detected change resulting from at least one of resonant mid-infrared absorption, non-resonant mid-infrared absorption, and scattering by the particle may be used to determine a property of the particle. A wide range of properties of particles may be determined, wherein the particles may include living cells.