Sodium hydrogen carbonate

Sodium hydroxide (NaOH), sodium carbonate (Na₂CO₃), and acetone were obtained from J.T.Baker (Deventer, Holland). ABTS radical (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), Folin-Ciocalteau phenol reagent 1N, gallic acid, sodium nitrite (NaNO₂), formic acid (HPLC grade), potassium persulfate (K₂S₂O₈) and ethanol p.a. (99.5%) were purchased from Sigma-Aldrich (Steinheim, Germany). Sodium hydrogen carbonate (reagent grade; 99.7%) and methanol (reagent grade; 99.9%) were purchased from Scharlau (Barcelona, Spain). Deionized water was obtained from Millipore (Bedfore, MA, USA).

Sodium hypochlorite (NaClO, 14%), sodium hydrogen phosphate (NaH₂PO₄), sodium chloride (NaCl), calcium chloride dihydrate (CaCl₂∙2H₂O), magnesium sulfate heptahydrate (MgSO₄∙7H₂O), sodium hydrogen carbonate (NaHCO₃), potassium nitrate (KNO₃), sodium nitrate (NaNO₃), calcium carbonate (CaCO₃), magnesium chloride hexahydrate (MgCl₂∙6H₂O), potassium sulfate (K₂SO₄), sodium sulfate (Na₂SO₄), calcium sulfate dihydrate (CaSO₄∙2H₂O), boric acid (H₃BO₃, 0.5%), hydrogen peroxide (H₂O₂, 30%), and chloride acid (HCl, 0.1 M) were purchased from Scharlab S.L., Barcelona, Spain. The ultrapure water (Milli-Q) used in the experiments was obtained from Millipore, Molsheim, France, equipment (conductivity less than 0.055 µS cm⁻¹).
Polyvinyl chloride (PVC, Mw 112,000 g mol⁻¹) was supplied by ATOCHEM, Madrid, Spain. Tetrahydrofuran (THF) was purchased from Scharlab S.L. Amberlite^® IRA-402 (Cl⁻ form, total exchange capacity ≥ 1.0 mol L⁻¹) was supplied by Merck Life Science, Darmstadt, Germany, S.L.U.

Iron(III) chloride hexahydrate 98%, iron(II) chloride tetrahydrate 99%, tetraethylortosilicate (TEOS), 98%,hexadecyltrimethylammonium bromide (CTAB), 2-hydroxybenzoic acid, triphenyl phosphite (TPP), tetrabutylammonium bromide (TBAB), 2-aminothiophenol, sodium hydroxide (NaOH), pyridine, 3-isocyanatopropyltriethoxysilane (ICTES), 3-iodopropyltrimethoxysilane (IPTMS), magnesium sulfate, and the nitrate salts of metal cations for fluorescence measurements, that is, Na⁺, K⁺, Ag⁺, Ca²⁺, Mg²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Hg²⁺, Pb²⁺, and Al³⁺, were purchased from Sigma Aldrich (Tres Cantos, Spain) and were used as received. Iron(III) nitrate nonahydrate, extra pure sodium acetate anhydrous, sodium hydrogen carbonate, ascorbic acid, and ethylene glycol were purchased from Scharlau (Móstoles, Spain) and were used as received, without further purification. Triethylamine (Et₃N) redistilled 99% was purchased from Fluka (Tres Cantos, Spain) and was used as supplied. Organic solvents such as THF and acetone were purchased from Carlo Erba (Sabadell, Spain) and were distilled and dried over appropriate drying agents. Ethanol was purchased from VWR (Barcelona, Spain) and Milli-Q (Merck-Millipore, Barlington, MA, USA) quality water was used in the experiments.