Comparison of adsorbents for on-line solid-phase extraction of polycyclic aromatic hydrocarbons before liquid chromatography with UV detection

On-line solid-phase extraction (SPE) coupled with reversed-phase liquid chromatography and UV detection at 254 nm has been used for the determination of trace-level polycyclic aromatic hydrocarbons (PAH) in soil extracts. Five commercially available adsorbents (C-8, C-18, PLRP-S, PRP-1, and Bond-Elut Env) were evaluated. Results showed that recovery of the PAH decreased with increasing molecular weight, because of their poorer solubility. Recovery of high-molecular-weight PAH was significantly improved by addition of 10% (v/v) acetonitrile to the sample before loading of the SPE adsorbent. PAH recovery ranged from 64.0 to 108% when a 50 mL sample spiked with 1 muq L-1 was applied to these adsorbents. Determination of PAH was possible with detection limits below 0.05 mug L-1, which corresponds to 0.2 mug kg(-1) soil. The method was successfully used to determine PAH in soil extracts.