An integrated optic consisting of buried diffraction gratings and a planar waveguide was developed as an internal reflectance element for broad-band spectroscopic analysis of liquids. Polystyrene or tantalum pentoxide waveguides were deposited over a pair of diffraction gratings etched into the surface of a glass slide. Multiwavelength light was focused through the substrate onto the first grating. Component wavelengths were coupled into the waveguide and spatially dispersed by the second grating after propagating through the waveguide. A silicon photodiode array detector was used to collect the spectral data. Our goal is to produce a compact, rapid spectrometer having no moving parts that can take advantage of fiber optics and fast array detectors in the visible and near-infrared regions for industrial process control. The thin planar waveguide provides enhanced sensitivity to analyze weaker absorptions in the near-infrared.