On-line combining monolith-based in-tube solid phase microextraction and high-performance liquid chromatography- fluorescence detection for the sensitive monitoring of polycyclic aromatic hydrocarbons in complex samples

An automated and sensitive method, consisting of monolith-based in-tube solid-phase microextraction (IT-SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the monitoring of polycyclic aromatic hydrocarbons (PAHs) in water and milk samples. To enrich PAHs, a new poly (9-vinylanthracene-co-ethylene dimethacrylate) monolith was in-situ prepared and used as the adsorbent of IT-SPME. Various parameters affecting the extraction performance were investigated thoroughly. Under the optimal conditions, the synthesized monolith-based IT-SPME could enrich target PAHs effectively through π-π and hydrophobic interactions. Moreover, the developed on-line IT-SPME-HPLC-FLD method displayed satisfactory analytical merits for PAHs. The limits of detection (S/N = 3) for PAHs in water and milk samples were in the ranges of 0.017-0.23 ng/L and 0.10-2.36 ng/L, respectively. The relative standard deviations (RSDs) for intra-day and inter-day precisions with different spiked concentrations were below 9.8% and 11%, respectively. Finally, the proposed method was successfully applied to quantify ultra-trace target PAHs in water and milk samples. Several ng/L level PAHs were detected. Spiked recoveries achieved for water and milk samples were in the ranges of 78.5-118% and 75.5-119%, respectively. The RSDs varied from 0.30% to 10% for all analytes in all samples. In comparison with reported methods for the monitoring of PAHs, the present method exhibits some merits such as high sensitivity, automation of enrichment and determination procedure, low consumptions of sample and organic solvent.