Detection of NOx in Automobile Exhaust

The oxides of nitrogen (NOx) are well-known precursors to ground-level ozone in smoggy areas, and are produced during fuel combustion. A growing body of research suggests that both NOx and ozone pollution exacerbate cardiovascular and pulmonary diseases. We describe here a laboratory project for the general chemistry laboratory which employs UV/vis spectroscopy to indirectly quantify NOx in motor vehicle exhaust using a modified Saltzman method. By quantifying the temporal changes in NOx exhaust levels immediately after engine start-up from cold, the operation of a properly functioning catalytic converter employing reduction catalyst technology may be demonstrated.