Stoichiometric imprinting relies on the use carefully designed functional monomers and templates that quantitatively associates in an appropriate solvent to form defined monomertemplate complexes. We previously showed that aryl-phosphonates and -phosphates strongly associate (Ka>>1000 M -1 ) with urea monomer 1 in aprotic media to form higher order complexes. Complexation is driven by hydrogen bonding with the urea group of 1 acting as a potent hydrogen bond donor and the phosphate monoanion or dianion as the acceptor leading to cyclic hydrogen bonded structures reflected in enhanced solubility behaviour (Fig. ). The complex stoichiometry is given by the phosphate ionization state with the monoanion and dianion promoting the formation of template:monomer 1:1 and 1:2 complexes respectively. To adapt this system to the ZAP-70 epitopes we first prepared the peptides in Scheme 2a by manual solid-supported synthesis using standard Fmoc chemistry (Table -S2). All peptides were obtained in acceptable yields (≥60 %) and purity (≥95%) based on LC-MS, 1 H-, C-and 31 P-NMR characterization (Fig S2 ) and were transferred to bis-tetrabutylammonium salts prior to imprinting. Preparation of the MIPs followed in large previously reported protocols using 1,3-diarylurea monomer 1 added in a twofold excess with respect to each peptide-phosphate group and with PETA as a hydrophilic crosslinker (Scheme 2b, Table ). Free radical polymerization was conducted with the initiator, monomers and templates dissolved in dry acetonitrile. The polymer monoliths were crushed and sieved to isolate a 25-36 µm particle-size fraction, followed by template removal by acid treatment. This led to a minimum template recovery of ca 90% resulting in a nominal capacity assuming 100% site occupancy of 15 µmol/g (Fig. ). Morphology and structural characterization were thereafter performed by scanning electron microscopy (SEM) (Fig. ), thermal gravimetric analysis (TGA) (Fig. ), and Fourier-transform infrared spectroscopy (FTIR) (Fig. ).