Polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles have received increased attention because some of these compounds have some potential to cause health problems.Especially, particle matters less than 100 nanometers in diameter are thought to pose the greatest health risk because such small particles can reach deeply into the lungs.Therefore, quantification of size-resolved particles is important to determine their toxicity exactly.However, sample amount of size-resolved particles is generally very small (μg level) so that highly sensitive analysis is essential.