Conifers as environmental biomonitors: A multi-residue method for the concomitant quantification of pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls by LC-MS/MS and GC–MS/MS

International audienceThe conifer is a natural vascular land plant composed of very particular leaves called needles that are able to accumulate, throughout years, a wide range of non-volatile, semi-volatile and volatile compounds of different structure and polarity such as pesticides and persistent organic pollutants. However, the extraction of these compounds from such matrix remains mainly uncommitted. In this paper, a QuEChERS based extraction procedure was developed for the concomitant extraction and analysis of 134 pesticides, 22 polychlorinated biphenyls and 16 polycyclic aromatic hydrocarbons residues from conifer needles. The method included a liquid-liquid extraction using acetonitrile (ACN) followed by a clean-up step using, Primary Secondary Amine (PSA), graphitized carbon black (GCB) and C18 particles, in the presence of salts. The obtained extracts were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for their contamination by non-volatile pesticides. However, volatile pesticides, polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons were subjected to a concentration step using solid-phase microextraction (SPME) prior to their analysis by gas chromatography coupled to tandem mass spectrometry (GC–MS/MS). The method was developed and validated, and the obtained results revealed a recovery rate ranged between 60% and 121% for all the targeted compounds. In addition, the method showed high sensitivity and precision with detection and quantification limits less than 20 ng g−1 for most target compounds and low RSD for both inter and intra-day analysis. Once developed the method was applied on conifer samples collected from 15 different sites in northern Lebanon. The analysis of the collected samples showed a persistence of the different assessed pollutants depending of the characteristics of each site