Development and Validation of a Multi-residue Method for the Determination of Pesticides in Chios Mastic Gum by QuEChERS and Liquid Chromatography–Tandem Mass Spectrometry A. K. Psoma & I. N. Pasias & A. A. Bletsou & N. S. Thomaidis Received: 27 March 2014 /Accepted: 26 June 2014 # Springer Science+Business Media New York 2014 Abstract A simple, rapid, and sensitive method was de- veloped for the simultaneous determination of 21 pesti- cides from different chemical classes (organophosphorus, triazines, carbamates, and anilinopyrimidine pesticides) in Chios mastic gum (Pistacia lentiscus L. var. Chia). Quick, easy, cheap, effective, rugged, and safe (QuEChERS) tech- nique was used for the extraction of the target analytes; the mastic gum samples were initially extracted with acetoni- trile (ACN), and then, the extracts were purified by disper- sive solid-phase extraction using primary secondary amine (PSA) and C18 as sorbents. The determination of pesti- cides in the final extract was carried out by liquid chroma- tography coupled with tandem mass spectrometry with electrospray ionization (LC-ESI-MS/MS). The method was validated for linearity, accuracy, precision (repeatabil- ity and inter-laboratory reproducibility), limits of detection and quantification, and the matrix effect factor. Recoveries of the pesticides fortified at 5, 50, and 500 ng g -1 ranged from 49.7 % (quinalphos) to 127 % (pirimiphos-ethyl) and reproducibility (RSD R , n =2×3) ranged from 4.4 % (propham) to 20 % (pirimiphos-methyl, propham, and triazophos). The detection limits of the method were 0.8 (mecarbam, pyrazophos) to 23 ng g -1 (parathion-ethyl). The uncertainty of the method was also calculated based on the Eurachem/Citac Guidelines, and the contribution of each independent parameter was investigated. Keywords Chios mastic gum . Pesticides . LC–MS/MS . QuEChERS . Dispersive solid-phase extraction . Uncertainty Introduction Mastic gum is the resin obtained as an exudate from the trunk and branches of Pistacia lentiscus L. var. Chia, an evergreen shrub belonging to the family Anacardiaceae and uniquely cultivated in the southern island of Chios, Greece. Mastic gum has been used for more than 2,500 years in traditional Greek medicine (Paraschos et al. 2012). It is used as a seasoning in Mediterranean cuisine, as a flavoring in food products and beverages, and in the production of chewing gum and in perfumery (Lemonakis et al. 2011). Recently, modern scien- tific researches have proved its numerous diverse pharmaceu- tical and biomedical properties (Dimas et al. 2012). Mastic has in vitro antibacterial and antifungal activity (Magiatis et al. 1999), is effective against Helicobacter pylori in vitro and in vivo (Paraschos et al. 2007) also at Crohn’ s disease (Kaliora et al. 2007) and colon (Balan et al. 2007) or prostate cancer (He et al. 2006). Mastic also protects against functional dyspepsia (Dabos et al. 2010a and in some cases eradicates H. pylori in humans (Dabos et al. 2010b). Chios mastic gum is nowadays used extensively as a constituent of herbal drugs or functional foods (Lemonakis et al. 2011). More than 1,000 substances are considered to be used for pest control; however, it is one of the most extensively regu- lated chemical groups regardless the large number of pesti- cides (Tomlin 2003). Organophosphorus (OP) and carbamate (CB) pesticides are among the most common and most toxic insecticides used today, not only for crop protection but also for industrial or home purposes. They are widely used as A. K. Psoma : I. N. Pasias : A. A. Bletsou : N. S. Thomaidis (*) Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, 15771 Athens, Greece e-mail: ntho@chem.uoa.gr Food Anal. Methods DOI 10.1007/s12161-014-9930-7