Two different applications that take advantage of integrated planar waveguides will be shown. The first example is a silicon chips for capillary electrochromatography (CEC), where the fluidic part contains electrically insulated channels with an injection cross and a chromatography column of microfabricated pillars, while the optical part consists of ultraviolet transparent planar waveguides for absorbance detection in the plane of the chip and fiber couplers for easy connection to an external light source and a photodetector. Electrochromatographic separations have been performed using hydrophobic octyl chains (C-8) immobilized onto the pillar sidewalls as a stationary phase. This is the first time capillary electrochromatography has been shown on a chip with integrated waveguides for detection. In another chip, an array of pillars inside a microfluidic column that is designed for electrochromatography is used as an optofluidic filter (1 D photonic crystal) for on-column label-free refractive index detection. Conventional planar waveguides are furthermore integrated for coupling light in and out of the structure.