Methacrylamide

The starting monomers were acrylamide, methacrylamide, N-methylacrylamide, and methoxy oligo(ethylene glycol) methacrylate (MOEGM, Mn = 500) from Sigma-Aldrich (Moscow, Russia) and alkoxy(C12–C14) oligo(ethylene glycol) methacrylate (AOEGM) (Figure 1) synthesized following the procedure outlined in [63 (link)]. MOEGM and AOEGM were subsequently purified from an inhibitor by passing through basic alumina. The chain transfer agent CDTPA (4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid) was synthesized following the method described in ref. [64 (link)]. All solvents, including dimethyl sulfoxide, tetrahydrofuran (ACS reagent, ≥99.5%), and acetonitrile (for spectroscopy, ≥99.5%) from Aldrich (Moscow, Russia) were utilized without purification.

All acrylic amine compounds (N-[3-(dimethylamino)-propyl]-methacrylic amide (DMAPMA), methacrylic
acid-2-(dimethylamino)-ethyl ester (DMAEMA), 2-trimethylammoniumethyl
methacrylate chloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride,
(3-acrylamidopropyl)trimethylammonium chloride, 3-(methacryloylamino)
propyl-trimethylammonium chloride, 2-(dimethylamino)ethyl acrylate,
2-aminoethylmethacrylamide hydrochloride, acrylamide, and methacrylamide),
and dimethylformamide (DMF) were purchased from Sigma-Aldrich (St.
Louis, MO, USA). γ-Butyrolactone (GBL) was obtained from Merck
KGaA (Darmstadt, Germany). Polyacrylonitrile (PAN) powder (>99%
acrylonitrile,
homopolymer, M_w = 200 000 g/mol)
was obtained from DOLAN (Kelheim, Germany). All chemicals were used
without further purification.

Citrinin (CIT), 1-hydroxy-2-naphthoic acid, 1,4-dihydroxy-2-naphthoic acid, 2,2-azobis isobutyronitrile (AIBN), trimethylolpropane trimethacrylate (TRIM), methacrylic acid (MAA), and PBS tablets were obtained from Sigma (Steinheim, Germany). Barium chloride, N,N-dimethylaminoethyl methacrylate (DAEM), ethylene glycol dimethacrylate (EGDMA), methacrylamide (MAM), salicylic acid, acetic acid, ammonia (25% aq.), sodium hydroxide solution (1M), orthophosphoric acid, and Tween 20 were purchased from Merck (Darmstadt, Germany). LC-grade acetonitrile and methanol were from VWR (Langenfeld, Germany), acetone was from Honeywell (Seelze, Germany). 2-Naphthoic acid was obtained from Acros Organics (Geel, Belgium), 2-oxocyclohexane carboxylic acid was obtained from Fluorochem (Karlsruhe, Germany), and rhodizonic acid dehydrate (RHO) was obtained from abcr (Karlsruhe, Germany). Ochratoxin A (OTA) was provided by HPC Standards (Borsdorf, Germany) and EASI-EXTRACT^® Citrinin columns were provided by R-Biopharm Rhone Ltd. (Glasgow, UK). Cereal products (wheat flour, pasta, rice, whole grain rice crispies, and oat flakes) were purchased from local markets and did not contain detectable levels of CIT. CIT stock and working solution were prepared according to DIN EN 17203 [38 (link)] and stored in acid-washed amber vials at −20 °C.

All chemicals used throughout this work were purchased from commercial sources and used without further purification. Iron(III) chloride hexahydrate (FeCl₃·6H₂O, Sigma-Aldrich, St. Louis, MO, USA, ≥ 97%) was used as a metal source. Tris(2-pyridylmethyl)amine (TPA, Sigma-Aldrich, St. Louis, MO, USA, 98%), di-(2-picolyl)amine (BMPA, Sigma-Aldrich, St. Louis, MO, USA, 97%), 1,4,8,11-tetraazacyclotetradecane (CYCLAM, Sigma-Aldrich, St. Louis, MO, USA, 98%), nitrilotriacetic acid (NTA, Sigma-Aldrich, St. Louis, MO, USA, 99%), and 3,3′,3″-nitrilotripropionic acid (NTP, Aldrich, Darmstadt, Germany) were used as ligands. The reagents for the molecular imprinting were methacrylamide (98%, Merck, Darmstadt, Germany) as functional monomer, 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT, Merck, Darmstadt, Germany, 98%), N,N-methylenebisacrylamide (MBAA, Merck, Darmstadt, Germany, 99%), and ethylene glycol dimethacrylate (EDMA, Merck, Darmstadt, Germany, 98%) as crosslinking agents (Figure S1) and K₂S₂O₈ (Merck, Darmstadt, Germany, 99%) as a radical initiator.