Class-selective immunosorbent for trace-level determination of polycyclic aromatic hydrocarbons in complex sample matrices, used in off-line procedure or on-line coupled with liquid chromatography fluorescence and diode array detections in series

A new immunoaffinity solid-phase extraction (SPE) methodology based on antigen-antibody interactions was evaluated and optimized for the selective extraction of polycyclic aromatic hydrocarbons (PAHs) in various complex environmental matrices. This immunosorbent (IS) consists of anti-pyrene antibodies immobilized on a silica support and is used as a classical SPE sorbent. The cross-reactivity of the antibodies for analytes structurally related with pyrene allows the simultaneous extraction of the priority PAHs included in the European Union and/or U.S. EPA priority lists. In addition, extraction, trace enrichment, and cleanup are achieved in one step due to the selectivity of the antigen-antibody interaction. For aqueous samples, limitation of unwanted adsorption of the PAHs on vessels or tubing due to their high hydrophobicity is obtained by adding acetonitrile in samples before percolation. Losses due to the volatility of the two- or three-ring PAHs are avoided by coupling on-line the extraction using the anti-pyrene IS with LC. From a sample volume of 80 mL, the sensitivity of the fluorescence associated with the selectivity of the IS allows the quantification of individual PAHs in contaminated or surface water below the 0.02 mu g/L level and therefore the fulfillment of the EU regulation for monitoring contaminated surface water used as a source for drinking water. The presence of several PAHs at 0.02 mu g/L could be confirmed by spectral identification using the diode array detector. Off-line extraction procedures were also set up for the extraction of PAHs from complex solid environmental matrices such as sludge or mussel extracts. The whole offline procedure was validated using a sewage sludge reference material containing several PAHs at a concentration varying from 0.5 to 2.2 mg/kg of dry sludge. The high selectivity provided by the antibodies permitted extraction of the PAHs and elimination of the great number of interferents in only one step, so that identification of compounds could be achieved using UV diode array detection.