Hydrogen peroxide

Graphite powder was purchased from Graphene Supermarket (Ronkonkoma, NY, United States). Sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), potassium permanganate (K₂MnO₄), hydrochloric acid (HCl), and hydrogen peroxide were purchased from PanReac AppliChem (Chicago, IL, United States). 3-[(2-amino ethyl) dithio] propionic acid·HCl (AEDP), NH₂-PEG₁₂-Propionic acid (PEG), N-[3-(dimethylamino)-propyl]-N′-ethyl carbodiimide hydrochloride (EDC), N-hydroxy-sulfosuccinimide (NHS), dimethyl-formamide (DMF), phosphate-buffered saline (PBS), 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), Rhodamine B, Propidium iodide, and Triton X-100 were purchased from Sigma-Aldrich (St. Louis, MO, United States). Buforin II (BUF-II: TRSSRAGLQFPVGRVHRLLRK) was synthesized by GL Biochem (Shanghai, China). High-glucose Dulbecco’s modified Eagle medium (DMEM) was purchased from Gibco (Amarillo, TX, United States). Fetal bovine serum (FBS) was purchased from BioWest (Riverside, MO, United States). Lysotracker Green DND-26 and Hoechst 33,342 were purchased from Thermo Fisher (Waltham, MA, United States). Vero cells (ATCC^® CCL-81) and THP-1 cells (ATCC^® TIB-202) were used for the cytotoxicity and cell internalization assays.

Paracetamol (98% purity), from now on PCT, and Sulfamethazine (99% purity), from now on SMT, were purchased from Sigma-Aldrich, while hydrogen peroxide (33% w/v) was purchased from Panreac. The catalyst, added as heptahydrate ferrous sulphate (FeSO₄∙7 H₂O), was provided by Merck. Sulfuric acid (95%) used to adjust the pH was provided by Fisher. H₂O₂ was determined following the ammonium metavanadate (NH₄VO₃ 98.5%) which was obtained from Fisher. Distilled water (DW) was used as water matrix in most of the experiments while the assays carried out to assess water matrix effect were done in natural water (NW).

All solutions were prepared using ultrapure water of resistance 18 MΩ cm^-1 (produced using a Milli-Q purification system, Millipore Corp., Bedford, MA). Stock standard solutions of the elements (1000 mg L^-1) were of ultrapure grade: ICP Multi element standard solution IV certiPUR for B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Sr and Zn; and ICP standard certiPUR for Hg and Se were both purchased from Merck (Poole, U.K.). As, Mo, Sb and U standards were obtained from Panreac (Barcelona, Spain).
In the SAD preparation method, the samples were digestion in nitric acid (69%, Hiperpur-Panreac, Barcelona, Spain) and hydrogen peroxide (33% w/v, Panreac, Barcelona, Spain). In the AKD preparation method, the samples were digested in a mixture of ammonia (NH₄OH, 25%, Merck, Darmstadt, Germany), Triton X100 (Panreac, Barcelona, Spain), anhydrous 1-butanol (Panreac, Barcelona, Spain) and EDTA (Panreac, Barcelona, Spain). The certified reference material (NIST SRM-1598a inorganic constituents in animal serum) used to validate ICP-MS measurements was obtained from the National Institute for Standards and Technology, NIST (Gaithersburg, MD, USA).
Polypropylene tubes used for preparation of samples and standards were soaked in 10% Hiperpur HNO₃ for at least 24 h and rinsed with deionised water and dried before use. The sample tubes were tested and found to be free of trace elements.

Lipase B from Candida antarctica (CAL-B) solution was purchased from Novozymes (Copenhagen, Denmark). Copper (II) sulfate pentahydrate [Cu₂SO₄ 5H₂O] and hydrogen peroxide (33%) were from Panreac (Barcelona, Spain). Sodium bicarbonate, sodium phosphate, sodium borohydride, Bisphenol A (BPA), benzoquinone, and hydroquinone were purchased from Sigma-Aldrich (St. Louis, MO, USA). HPLC grade acetonitrile was purchased from Scharlab (Barcelona, Spain).

Sodium hypochlorite (10%), hydrogen peroxide (30%), sulfuric acid (50%), phosphoric acid (25%), hydrochloric acid (25%), ultra-pure ethanol (96%) and glacial acetic acid (99.5%) were purchased from PanReac AppliChem (Barcelona, Spain). Graphite flakes (99%), pepsin, N-[3-(dimethylamino)-propyl]-N’-ethylcarbodiimide hydrochloride (EDC) (98%), N-hydroxysuccinimide (NHS) (98%), ascorbic acid (99%), sodium chloride (99%), triton X-100, potassium permanganate (99%) and formaldehyde (36%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Dulbecco’s modified eagle’s medium (DMEM) and fetal bovine serum (FBS) were obtained from Biowest (Nuaillé, France). Penicillin/streptomycin (P/S) was purchased from Lonza (Basel, Switzerland). Hoechst 33342, Alexa Fluor 594 Phalloidin, LDH and alamar blue assay kits were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Vero (ATCC^® CCL-81), HaCat (ATCC^® CCL-2404) and HFF-1 (ATCC^® SCRC-1041) cells were obtained from ATCC (St. Cloud, MN, USA).

Hydrogen peroxide (H₂O₂, 30% w/v), ferrous sulfate heptahydrate (FeSO₄.7H₂O, 99.0% purity), sodium sulfite (Na₂SO₃, 98.0% purity), sodium hydroxide (NaOH, 99.0% purity), sulfuric acid (H₂SO₄, 97–98% purity) and nitric acid (HNO₃, 65% purity) were purchased from Panreac. Pure liquid toluene (99% purity) (chemical formula C₇H₈, molar mass = 92.14 g mol⁻¹) and di-sodium hydrogen phosphate anhydrous (99% purity) were purchased from VWR Chemicals.
A commercial activated carbon, Norit GAC 1240 AF, was used as the initial material to prepare all modified activated carbons and AC-Fe catalysts. Melamine (C₃H₆N₆, ≥ 99% purity) and iron (III) nitrate nonahydrate (FeH₁₈N₃O₁₈, 99% purity) were obtained from Fluka.