Abstract: A simple optical layout for a grazing angle probe mount that allows coupling to a mid-infrared (MIR), laser-based spectrometer is provided. The assembly enables doing reflectance measurements at high incident angles. In the case of optically thin films and deposits on MIR reflective substrates, a double pass effect, accompanied by absorption by the chemicals or biological samples deposited in an Infrared Reflection-Absorption Infrared Spectroscopy (IRRAS) modality is achieved. The optical system includes a probe that allows the passage of MIR light through the same sampling area twice. Initially, the infrared beam produces a spot on the surface, and then the light is returned in back reflection to the sample surface producing a new little slightly larger spot onto the selfsame position.