Determination of polycyclic aromatic hydrocarbons in precipitation using solid-phase extraction and column liquid chromatography

Solid-phase extraction (SPE) of polycyclic aromatic hydrocarbons (PAHs) on Sep-Pak C-18 cartridges was studied. Eight 3-6-ring compounds from the 16 EPA priority pollutants were selected for investigation. Factors affecting the recovery of PAHs such as conditioning of the SPE cartridge, addition of organic modifier to the sample, flow-rate of the sample loaded on the cartridge, concentration of PAHs in the sample, drying after sample loading, elution of the analytes from the SPE cartridge with different organic solvents and recovery from spiked rainwater were included. Conditioning time was shortened by omitting the application of a 2-propanol-water mixture, The presence of 25% (v/v) 2-propanol was most appropriate for the enrichment of 3-6-ring aromatic compounds on Sep-Pak C-18. The flow-rate of the sample influenced the efficiency of sample preparation of compounds with a retention volume close to the sample volume. Recoveries did not change significantly in the 20-2200 ng/l concentration range. Drying of the SPE cartridge after sample loading improved recoveries of all PAHs. Elution with dichloromethane and tetrahydrofuran gave the highest recoveries. The detection limit was found to be less than 1 ng/l for several PAHs. The concentrations of PAHs in rainwater were between 3 and 1000 ng/l.