“…Additionally, one shoulder peak at 1386 cm À1 was attributed to the aliphatic CeH plane deformations of CH 3 group (Santamaria et al, 2006) and another shoulder peak at 1420 cm À1 was related to the in-plane OH bending mode of carboxylic acid (Smith, 1998). The peak at 1710 cm À1 in the spectra of rich flame soot was assigned to the carbonyl (C¼O) group (Han et al, 2012a ) (Kirchner et al, 2003;Niki et al, 1980;Popovicheva, 2004;Querry et al, 1974;Smith et al, 1989;Zhang et al, 1993) (referred to as sulfate species) were found in the spectra of rich flame soot and lean flame soot, which suggested that sulfate species were generated on soot. Furthermore, because adsorption peaks at~3284 and~1440 cm À1 may be contributed by ammonium ions (Coates, 2000), ammonium ions on lean flame soot generated from fuel containing sulfur were determined with IC.…”