A portable fiber-optic chemical device for the quantitative determination of carbon monoxide from automobile exhaust emissions

A colorimetric method for the quantitative determination of CO by diffuse r eflectance is described. This method is based on the reduction by CO of Mo (VI) from the indicator reagent molybdosilicic acid (H8Si[Mo2O7](6)). The r eduction yielded a change of color from clear yellow to dark green on white disk filter chart paper wetted with reagent indicator solution. The gaseou s mixture containing CO was forced to pass through this chart paper, initia ting the reaction. The intensity of the color produced, measured by diffuse reflectance, was proportional to the CO concentration present in exhaust g ases in the range from 0.02 to 12% volume/volume (v/v). A 650-nm light-emit ting diode was used as a light source. A two-fiber-optic system carried the light from the source to the detection system, which was composed of a pho todiode, an amplification circuit, and a digital display. The method was ap plied with success in field measurements for automobiles in the Otto cycle. In a previous paper, this method was used for the quantitative determinati on of exhaust emissions from diesel-fueled vehicles.