1 4 dihydroxy 2 naphthoic acid

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.