F16 maxisorp polystyrene microtiter plates

All solutions were prepared using ultrapure water (Milli-Q water purification system, Millipore Inc., Paris, France). Sodium carbonate, sodium hydrogen carbonate, monosodium phosphate, disodium phosphate, sodium chloride, biotinylated goat anti-rabbit IgG secondary antibody, AFM1 from Aspergillus flavus, AFM1-Bovine Serum Albumin conjugate (AFM1-BSA), streptavidin conjugated 40 nm Au nanoparticles from Streptomyces avidinii, polyethylene glycol sorbitan monolaurate (Tween 20) and HPLC-grade acetonitrile were purchased from Sigma-Aldrich (Steinheim, Germany). Bovine serum albumin (BSA) was obtained from Biowest (Nuaillé, France) whereas anti-AFM1 primary rabbit polyclonal antibody was obtained from Agrisera (Vännas, Sweeden). Iridium 1000 mg L -1 stock solution was provided by Merck (Darmstadt, Germany).
Thiourea, 69% w w -1 nitric acid and 35% w w -1 hydrochloric acid were purchased from Panreac (Barcelona, Spain). F16 maxisorp polystyrene microtiter plates were obtained from Thermo-

Primary rabbit polyclonal anti-aflatoxin M 1 (AFM 1 ) antibody (pAb) (purified IgG fraction 1 mg mL -1 ) was obtained from Agrisera (Vännas, Sweden) whereas secondary anti-rabbit IgG (whole molecule) -Biotin antibody produced in goat (secondary Ab) (1 mg mL -1 ) was from Sigma-Aldrich (Steinheim, Germany).
According to the supplier, pAb is highly specific for AFM 1 determination with low cross-reactivity against other aflatoxins (aflatoxin B 1 2%; aflatoxin B 2 , 0.4%; aflatoxin G 1 0.4% and aflatoxin G 2 0.1%).
Aflatoxin M 1 from Aspergillus flavus and AFM 1 -Bovine Serum Albumin conjugate (AFM 1 -BSA) were purchased from Sigma-Aldrich (Steinheim, Germany). Aflatoxins are carcinogenic compounds. So, extracts and solutions should be handled with extreme care. Gloves and other protective clothing were worn as safety precaution during the handling of the analyte. The aflatoxin residues can be destroyed using 5% sodium hypochlorite. For the immunoassays, F16 maxisorp polystyrene microtiter plates were purchased from Thermo-Scientific (Roskilde, Denmark) and used in all immunoassays.