## 2 Materials and Methods
### Reagents  
Acetone \(\geq\) 99.8%, dichloromethane \(\geq\) 99.9%, 2-propanol \(\geq\) 99.8%, methanol \(\geq\) 99.9%, sodium hydroxide \(\geq\) 98.0%, sulfuric acid 96-97%, magnesium sulphate anhydrous \(\geq\) 99.5% and NaCl \(\geq\) 99.5% were obtained from Honeywell Riedel-de-Haen, Fisher Scientific Italia, Rodano, MI (Italy). Cyclohexane 99.5% and dichloromethane were obtained from VWR International (Radnor, PA, USA).  
High-purity water (18.2 M\(\Omega\) cm resistivity at 25 \({}^{\circ}\)C), produced by an Elix-Milli Q Academic system (Millipore-Billerica, MA, USA) was used.  
The d-SPE sorbent used was Primary Secondary Amine (PSA) from Agilent Technologies (Santa Clara, CA, USA).  
The 16 PAHs studied, i.e., naphthalene (NaPh), acenaphthylene (AcPY), acenaphthene (AcPh), fluorene (Flu), phenanthrene (Phe), anthracene (Ant), fluoranthene (Flth), pyrene (Pyr), benzo(a)anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbFl), benzo[k]fluoranthene (BkFl), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (Ind), dibenzo[a,h]anthracene (DBA) and benzo[ghi]perylene (BP), were the compounds listed by the United States Environmental Protection Agency (US-EPA) and were purchased from Wellington Laboratories (Guelph, ON, Canada).  
The 14 PCBs studied were purchased from Chemical Research 2000 (Rome, Italy). They were chosen according to the results of the main monitoring campaigns and included 3,3\({}^{\prime}\)-dichloropheniphenyl (PCB 11), 4,4\({}^{\prime}\)-dichlorophenyl (PCB 15), 2,4,4\({}^{\prime}\)-trichlorophenyl (PCB 28), 2,2\({}^{\prime}\),5,5\({}^{\prime}\)-tetrachlorophenyl (PCB 52), 2,2\({}^{\prime}\),4,5,5\({}^{\prime}\)-pentachlorophenyl (PCB 101), 2,2\({}^{\prime}\),3,A,4\({}^{\prime}\),5-hexachlorophenyl (PCB 138), 2,2\({}^{\prime}\),4, 4\({}^{\prime}\),5,5\({}^{\prime}\)-hexachlorophenyl (PCB 153) and 2,2\({}^{\prime}\),3,A,4\({}^{\prime}\),5,5\({}^{\prime}\)-heptachlorophenyl (PCB 180). Furthermore, the following dioxin-like PCBs were included 3,4\({}^{\prime}\),5-tetrachlorophenyl (PCB 81), 2,3\({}^{\prime}\),4\({}^{\prime}\),5-pentachlorophenyl (PCB 118), 2,3\({}^{\prime}\),4\({}^{\prime}\),5-pentachlorophenyl (PCB 118), 2\({}^{\prime}\),3,A,4\({}^{\prime}\),5-pentachlorophenyl (PCB 167), 3\({}^{\prime}\),4\({}^{\prime}\),5,5\({}^{\prime}\)-hexachlorophenyl (PCB 169) and 2,3\({}^{\prime}\),A,4\({}^{\prime}\),5,5\({}^{\prime}\)-heptachlorophenyl (PCB 189)  
Isotope labelled compounds for PAHs (5 mg/L) and for PCBs (2 mg/L), both purchased from Wellington Laboratories, were employed as internal standards and surrogates to obtain calibration curves and to calculate extraction recoveries. The deuterated PAH surrogate solution included the following compounds: benzo[a]anthracene-d12 (Ba-d12), chrysene-d12 (Chr-d12), benzo[b]fluoranthene-d12 (BkFl-d12), benzo[k]fluoranthene-d12 (BkFl-d12), benzo[a]pyrene-d12 (BaP-d12), indeno[1,2,3-cd]pyrene-d12 (Ind-d12), dibenzoanthracene-d14 (DBA-d14), benzoperylene-d12 (BP-d12). The \({}^{13}\)C-PCB surrogate solution included the following congeners: \({}^{13}\)C\({}_{12}\)-PCB28, \({}^{13}\)C\({}_{12}\)-PCB52, \({}^{13}\)C\({}_{12}\)-PCB118, \({}^{13}\)C\({}_{12}\)-PCB153, and \({}^{13}\)C\({}_{12}\)-PCB180. \({}^{2}\)H-anthracene and \({}^{13}\)C\({}_{12}\)-PCB70 were used as internal standards.