Development of a simple field test for vehicle exhaust to detect illicit use of dyed diesel fuel

► A need exists to identify the use of dyed (tax-free) fuel by analyzing vehicle exhaust. ► Azo dyes produce alkyl aryl amines under simulated combustion conditions. ► A simple micro-analytical spot test was developed to detect aryl amines in exhaust. ► Test based on reaction with 4-(dimethylamino)benzaldehyde showed the most promise. ► Developed test could distinguish between engines burning dyed or non-dyed fuel.