A zinc mixed-ligand microporous metal-organic framework as solid-phase microextraction coating for priority polycyclic aromatic hydrocarbons from water samples

For the first time, a novel triple catenated Zn2+-pillared metal-organic framework (PUM 210) is proposed as solid-phase microextraction coating for the extraction of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) from water samples and their subsequent quantitation via gas chromatography-mass spectrometry. Extraction was optimized by using a central composite face centered design followed by the multicriteria method of the desirability functions. The best conditions for the extraction of the sixteen analytes were found in correspondence to an extraction temperature of 30 °C and an extraction time of 30 min. Method validation allowed to obtain quantitation limits in the 1–7 ng/L range, a repeatability within 16% relative standard deviation (RSD), an intermediate precision within 22% RSD at limits of quantitation, and recovery rates in the 85 (±5) – 117 (±21)% range. As for selectivity, PAHs extraction proved to be feasible also in the presence of high concentration levels of potentially competing compounds like benzene, toluene, ethylbenzene and xylenes with steric hindrance playing a key role in analyte inclusion. Enrichment factors in the 300 (±5) – 14-950 (±150) range were obtained, being the heaviest compounds better extracted with respect to commercial coatings. Finally, the method was applied for the quantitation of PAHs in sixty-nine underground water samples during a monitoring campaign carried out in 2018.