Development of a mathematical model for online microextraction by packed sorbent under equilibrium conditions and its application for polycyclic aromatic hydrocarbon determination in water by gas chromatography–mass spectrometry

In this work, partition equilibriums and extraction rates of different polycyclic aromatic hydrocarbons (PAHs) have been calculated by multivariate nonlinear regression from data obtained after microextraction by packed sorbent (MEPS) of 16 PAHs from water samples. The MEPS gas chromatography–mass spectrometry (MEPS–GC–MS) method has been optimized investigating the partitioning parameters for a priori prediction of solute sorption equilibrium, recoveries, pre-concentration effects in aqueous and solvent systems. Finally, real samples from sea, agricultural irrigation wells, streams and tap water were analyzed. Detection (S/N ≥ 3) and quantification (S/N ≥ 10) limits were strictly dependent on the volume of water and methanol used during the extraction process. Under the experimental conditions used, these values range from 0.5 to 2 ng L−1 and from 1.6 to 6.2 ng L−1, respectively. The reasonably good correlation between the logarithm of the partition MEPS–water constants (log Kmeps/water) and the logarithm of the octanol–water partition coefficients (log Kow) (R2 = 0.807) allows a rough estimation of Kow from the measure of Kmeps/water.

► A mathematical model for the calculus of partition constants has been developed.
► A MEPS–GC–MS method has been optimized for PAH determinations.
► A good correlation between Kmeps/water and Kow was found.
► LOD and LOQ ranged from 0.5 to 2 ng L−1 and from 1.6 to 6.2 ng L−1, respectively.
► Analyses of real water samples were performed.