Microextraction by packed sorbent coupled with gas chromatography–mass spectrometry: A comparison between “draw-eject” and “extract-discard” methods under equilibrium conditions for the determination of polycyclic aromatic hydrocarbons in water

tIn this work, two different extraction procedures for the analysis of different polycyclic aromatic hydro-carbons (PAHs) in water by microextraction by packed sorbent (MEPS) have been compared in terms ofsensitivity, reliability and time of analysis. The first method, called “draw-eject”, consists of a sequenceof cycles of aspirations and injections in the same vial; the second one, called “extract-discard”, consistsof a similar cycle sequence, but the aspired sample in this case is discarded into waste. The relevant par-tition equilibriums and extraction rates have been calculated by multivariate regression from the dataobtained after MEPS gas chromatography–mass spectrometry (MEPS-GC–MS) analysis of 16 PAHs fromwater samples. Partitioning parameters for a priori prediction of solute sorption equilibrium, recover-ies and preconcentration effects in aqueous and solvent systems have been calculated and comparedfor the two extraction procedures. Finally, real samples from sea, agricultural irrigation wells, streamsand tap water were analyzed. Detection (S/N ≥ 3) and quantification (S/N ≥ 10) limits were calculated forthe extraction processes. Under the experimental conditions used for the “draw-eject” procedure, thesevalues were in the range 0.5–2 ng L−1and 1.6–6.2 ng L−1, while for the “extract-discard” procedure theyranged from 0.2 to 0.8 ng L−1and from 0.8 to 2.0 ng L−1, respectively.