Various metal powders were batch screened as possible on-line reducers for nitropolycyclic aromatic hydrocarbons (NPAHs), in particular 1,3-dinitropyrene (1,3-DNP, 1,8-DNP and 1-nitropyrene (1-NP) and it metabolites. Zinc was found to be an excellent reducer in chemiluminescent compatible mobile phases without any associated disposal problems. Zinc reducer column parameters, namely pH, buffer concentration, packing composition (zinc:glass beads or zinc:silica gel) and column length were all optimized for the HPLC determination system with chemiluminescence detection, named NPAH analyser. The system consisted of three pumps, sample injector, reducer column packed with zinc:glass beads switching valve with a cutting loop, separation column (ODS), chemiluminescence detector and integrator. The mobile phase for the separation column and chemiluminescence reagent solution were respectively acetonitrile:imidazole-HClO44 and acetonitrile containing bis(2,4,6-trichlorophenyl)oxalate and H2O2. When the reducer column was introduced before the separation column, 1,3-, 1,6- 1,8-DNPs and 1-NP in benzene:ethanol extracts from airborne particulates were separately determined with detection limits of 2-50 fmol, respectively, in a 100 microL sample. When the reducer column was introduced just after the separation column, 1-NP, 1-nitrosopyrene and 1-aminopyrene in the incubation mixture of 1-NP and the Salmonella typhimurium YG1021 strain were separately determined with detection limits as low as sub fmol levels. 1,8-DNP and its metabolite were also separately determined in the incubation mixture of 1,8-DNP and the S. typhimurium TA98 strain.