Nano3

Glu, AA, DA and UA were purchased from Aladdin Biochemical Technology Ltd. (Shanghai, China). Graphite powder, H₂SO₄ (98%), NaNO₃, HCl (5%), H₂O₂ (30wt%), KMnO₄, ammonium molybdatetetrahydrate (H₂₄Mo₇N₆O₂₄·4H₂O) and thioacetamide (C₂H₅NS) were purchased from the Chengdu Kelong Chemical Reagent Factory (Chengdu, China). Nafion solution (5%) was purchased from Sigma-Aldrich; Merck KGaA (Darmstadt, Germany). PBS (0.2 M; pH=7.4) was prepared with Na₂HPO₄ and NaH₂PO₄. Twice distilled water was used in all of the experiments. All reagents and chemicals were of analytical grade.

CA (>97%) and sorbic acid were purchased from TCI Reagent Co. Ltd. (Shanghai, China). HPLC-grade reagents (acetonitrile, methanol, etc.) were obtained from Shanghai ANPEL Scientific Instrument Co. Ltd. (Shanghai, China). Benzoic acid (99.5%) and sodium azide (99%) were purchased from Aladdin Industrial Corporation (Shanghai, China), and furfuryl alcohol (FFA) (99%) was purchased from the Sigma-Aldrich Company. Acetic acid (99%), isopropanol (99.7%), humic acid, NaOH, H₂SO₄, MgSO₄, ZnSO₄, CuSO₄, Fe₂(SO₄)₃, NaCl, NaNO₃, NaHCO₃ and KH₂PO₄ were obtained from Chengdu Kelong Chemical Reagent Co. Ltd. (Sichuan, China). All reagents were of analytical grade and were used without further purification. Ultrapure water (resistance > 18.2 MΩ) was produced by a water purification system (TKA, Germany).

SMX, tert-butyl alcohol (TBA) and fulvic acid were produced by Aladdin Reagent Company, China. Ferric sulfate and sodium bisulfite were obtained from Sinopharm Chemical Reagent Corporation Ltd., China. Methanol and isopropanol (IPA) were the products of Fisher corporation. H₂SO₄, NaOH, NaCl, NaNO₃, NaHCO₃, Na₂SO₄, Na₂S₂O₃, CuSO₄, Mg(NO₃)₂, Ca(NO₃)₂ were all of analytical grade and purchased from Chengdu Kelong Chemical Reagent Co., Ltd, China. Deionized water was used in all experiments.