Copyright © 1998 Elsevier Engineering Information, Inc. All Rights Reserved UNICAMP, Campinas, Brazil

Abstract

A colorimetric method for the quantitative determination of carbon monoxide (CO) by diffuse reflectance is described. The method is based on the reduction by CO of the molybdenum (VI) from the indicator reagent molybdosilicic acid ( H8 Si[Mo2 O7]6 ). This reduction yields a change of color from clear yellow to dark green on a white disk filter paper chart wetted with the reagent indicator solution. The gaseous mixture containing CO is forced to pass through this paper chart propitiating the occurrence of the reaction. The intensity of the color produced, measured by diffuse reflectance, is proportional to the CO concentration present in exhaust gases in the range from 0.02 up to 12% v / v. A LED (650 nm) is used as light source. A two fiber optics system carries the light from the source and to the detection system that is constituted by a photodiode, an amplification circuit and a digital display. The method was applied with success in field measurements for automobiles of the Otto cycle.
 

Index Terms: Photodetectors; Optical sensors; Fiber optic chemical sensors; Portable equipment; Carbon Monoxide.

Journal Air & Waste Managemennt Association
Volume 51 Issue (7)
Pages: 962-965
July 2001 1