Ferrous chloride tetrahydrate

Ferric chloride hexahydrate (FeCl₃.6H₂O) and ferrous chloride tetrahydrate (FeCl₂.4H₂O) were purchased from Xilong Scientific Co. Ltd., China. Citric acid monohydrate (C₆H₈O₇•H₂O, ACS grade, 99–102%) and sodium hydroxide (NaOH) (98%) were purchased from Neolab and Loba Chemie Ltd., India, respectively. Potassium dihydrogen phosphate (KH₂PO₄), glutaraldehyde (GA), and Cetyltrimethylammonium bromide (CTAB) were obtained from Sigma-Aldrich Co., MO, USA. Potato starch with amylopectin to amylose weight ratio of 77/23 was supplied from AVI Chem™, Mumbai, India. Glycerol (98% purity) was supplied from CDH® Ltd., India. All the chemicals and reagents were analytical grade.

Graphite was purchased from Merck Sigma-Aldrich China. Ferric chloride hexahydrate (FeCl₃·6H₂O) and ferrous chloride tetrahydrate (FeCl₂·4H₂O) were both obtained from Xilong Scientific Co., Ltd. 3-Aminopropyltriethoxysilane (APTES) as silane coupling agent was purchased from Nanjing Chemical Reagent Co., Ltd. In addition, sodium hydroxide, hydrochloric acid, methanol, toluene, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), acetic acid, HI acid, sulfuric acid, hydrogen peroxide, sodium nitrate and potassium permanganate were procured from Sinopharm Chemical Reagent Co., Ltd.

Ferric chloride hexahydrate (FeCl₃·6H₂O) and benzene-1,3,5-tricarboxylic acid (H₃BTC) were purchased from Sigma Aldrich (St. Louis, MO, US). Ferrous chloride tetrahydrate (FeCl₂·4H₂O) was obtained from Xi Long Chemical Co., Ltd. (Guangdong, China). Methylacrylic acid (MAA), tetraethyl orthosilicate (TEOS), and thiophene were supplied by Aladdin Industrial Corporation (Shanghai, China). Ammonia solution (25%, w/w) was purchased from Macklin Biochemical Co., Ltd. (Shanghai, China). Analytical grade ethanol and trichloromethane were provided by Beijing Chemical Works (Beijing, China). LC grade acetonitrile (ACN) and hexane were acquired from Fisher Scientific (Pittsburgh, USA). DMP (99.5% purity), DEP (99.5% purity), DBP (99.4% purity), BBP (98.4% purity), DEHP (99.6% purity), and DnOP (99.5% purity) were supplied by Dr Ehrenstorfer GmbH (Augsburg, Germany).
The standard stock solutions (1.0 mg mL⁻¹) of the tested PAEs were prepared by reconstituting the appropriate amount of each tested analyte in ACN and stored at 4 °C in dark. Working solutions were prepared daily by appropriate dilution with ACN. To minimize the risk of xenobiotic phthalate contamination, all solvents were examined for the presence of phthalates before use.