The measurement of Nitrite in natural water in a miniaturized and standardized way is still needed for the water quality measurement. Here a microfluidic approach of the miniaturization of the colorimetric Griess assay for the quantitative measurement of Nitrite is presented. The chip is designed for the measurement range of 0.1μM to 50μM the nitrite concentration range in seawater. The absorption cell was integrated in the microfluidic chip. The coupling to the optical system is done by optical fibers. As a light source a laser diode with the wavelength of 520nm was used. The usage of the fiber coupling allows the usage of sophisticated optical setup while the chip itself stays a cheap PMMA part. The design of the system and the first measurements are presented.