A fast and simple fractionation method was optimized to selectively separate oxy-PAH from polycyclic aromatic hydrocarbons (PAH) and n-alkanes contained in solvent extracted organic matter (SEOM) from atmospheric particles with an aerodynamic diameter a parts per thousand currency sign2.5 mu m (PM2.5). Samples were collected in Mexico City. Multivariate parameters were adjusted on a standard mixture, and on SEOM spiked with pure standard mixture solutions: type and amount of phase; packing densities; type, proportion and amount of solvents, and elution flow rates were tested under several elution schemes. Cyanopropylsilyl-bonded phase material was the selected stationary phase. The separation method was applied to real samples of SEOM (2.6, 5.6 and 8.5 mg) spiked with n-alkanes, PAH and oxy-PAH. n-Alkanes overlapped with PAH due to an excess of n-alkanes in real samples overloading the capacity of the stationary phase. Oxy-PAH was separated totally from n-alkanes and PAH. Mean recoveries +/- A confidence intervals (95 ) for n-alkanes ranged from 53 +/- A 17 (n-tetracontane) to 101 +/- A 11 (n-hexacosane); for PAH from 58 +/- A 5 (phenanthrene) to 85 +/- A 9 (benzo[k]fluoranthene); and for oxy-PAH from 68 +/- A 12 (9,10-dihydrobenzo[a]pyren-7(8H)one) to 108 +/- A 9 (1,2-benzopyrone). This method is an efficient fractionation procedure to be applied to oxy-PAH, PAH and n-alkanes in complex organic mixtures extracted from PM2.5.