## 2 Experimental Section
### Synthesis of templates:  
Fig.1 illustrates the synthesis of template _N_-(2-(3,7,8-trichlorodibenzodioxinyl))-2-methacryloyloxybenzamide (6) for MIP1: details on all steps can be found in ref.1. The synthetic scheme of template (compound (3)) for MIP2 consists of only steps for products (1) to (4) in Fig.1. Figure 1: Synthesis of template N-(2-(3,7,8-trichlorodibenzodioxinyl))-2-metachryloiloxybenzamide) for MIP1, (adapted from [PERSON] et al., 1998). Details of syntheses of precursors (1), (2), (5), (6) are not reported since they were performed and verified as in the original paper [1]. Details of syntheses of (3) and (4) are described because they are directly involved in the new polymerisation scheme. _2.3 Synthesis and characterisation of 2-amino-3,7,8-trichloro-dibenzodioxin (3) and 2-methacryloyloxybenzoic acid (4):_ the main passages, found in both schemes, were the reduction of (2) to (3) and the preparation of (4). The former reaction was realised heating at reflux hydrazine hydrate and Nickel [PERSON] in ethanol and tetrahydrofuran (THF), while (2), dissolved in THF, was added slowly. Afterwards a specified amount of hydrazine hydrate was added, then the mixture was cooled and filtered after the reaction was completed. The filtrate was evaporated to give (3) as a white solid with a high yield (96%). This compound is easily oxidised, thus it must be stored at 4\({}^{\circ}\)C under nitrogen. It was characterised by GC-MS (m/z 301) (Fig.2). (4) was produced starting from salicylic acid and methacrylic anhydride. The anhydride was added to the acid solution in pyridine, cooled in ice. The mixture was stirred overnight and then added to dilute HCl in excess and ice. The product was oily, thus it was extracted with diethyl ether and extracts were dried over MgSO\({}_{4}\) and evaporated. Pure compound was obtained by several crystallization steps from hexane, giving colourless crystals with a 42% yield. Melting point, IR, and \({}^{1}\)H-NMR characterisations were in accordance with literature [18]. In Fig.3 is reported \({}^{1}\)H-NMR spectrum: (CDCl\({}_{3}\)) \(\delta\) (ppm) 7.20-8.20 (m, 4H, aromatic protons), 5.77-6.40 (m, 2H, =C=CH\({}_{2}\)), 2.07 (s, 3H, -CH\({}_{3}\)). _2.4 Polymer synthesis and template removal:_ Polymerisation and template removal schemes for covalent and non-covalent approach are sketched in Figs. 4 and 5, respectively. (7) was synthesised and characterised as in ref.1. Polymerisation was carried out at 65 \({}^{\circ}\)C in presence of azobisisobutyronitrile (AlBN) as radical initiator and divinylbenzene (DVB) as cross-linking monomer in place of more classical ones because of extreme conditions during template removal ([PERSON] et al.,  
Figure 2: MS spectrum of 2-amino-3,7,8-trichloro-dibenzodioxin. 1998). Also template removal was performed as in ref.1. A non imprinted polymer (NIP) was also prepared following the scheme of Fig.4, but using methacrylic acid in place of template. Details on polymers syntheses are reported in Table 1.  
Figure 4: Synthesis of MIP1 and template removal. Figure 3: H-NMR of 2-methacryloyloxybenzoic acid. The polymers were finely grinded in a mortar and employed as such in template removal and re-binding experiments. _2.5 Re-binding experiments on TCDD:_ 10.0 mg of single grinded polymers (MIP1, MIP2, NIP) were weighed into screw cap vials and incubated for 24 h with 1 ml of a 6.96 pM solution of TCDD in anhydrous nonane. After this time contact, solutions were filtered and remained TCDD concentration was determined by APCI-MS. Five standard TCDD solutions (1.39-6.96 pM) were prepared by dilution of the 6.96 pM solution in dry nonane for calibration curve. 50 \(\upmu\)l of each solution was injected monitoring the negative ion at m/z 319.10 (in single ion mode) that resulted the more intense