Phosphoric acid

The reagents used to pretreat and impregnate the raw materials were sulphuric acid (98%) purchased from Merck (Darmstadt, Germany) and phosphoric acid (85%) from Mallinckrodt (Utrecht, The Netherlands). The chemicals and reagents used for preparing metal ion solutions, modifying carbon and detecting Cr(VI) were Ni(II) nitrate hexahydrate (Fluka), lead (II) nitrate (Riedel-deHaën), and potassium dichromate (Merck ), nitric acid (65%, Merck), hydrochloric acid (37%, Mallinckrodt), sodium hydroxide pellets (Merck), iron (III) chloride-6-hydrate (Hamburg Chemicals), calcium (II) hydroxide (GCE), sodium chloride (Merck), 1,5-diphenylcarbazide (Merck) and acetone. All chemicals and reagents were of analytical grade.

Ethanol (96%) was purchased from Altia (Rajamäki, Finland). Chemicals and reagents used in measuring antioxidant capacity were purchased from Sigma Chemical (Sigma Chemical Co., St. Louis, MO, USA). The chemicals used in the characterization of the spruce inner bark and pine heartwood extracts were pyridine, N,O-Bis(trimethylsilyl)trifluoroacetamide and chlorotrimethylsilane, purchased from Sigma–Aldrich (St. Louis, MO, USA). The standards of phenolic compounds and the chemicals used in the assays were obtained from various manufacturers. Catechin, epiCatechin, galloCatechin, epigalloCatechin, caffeic acid, chlorogenic acid, ferulic acid, gallic acid, ellagic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, and sinapic acid were obtained from Sigma Chemical. Procyanidin B2 was from Extrasynthese (Lyon, France). Acetonitrile, methanol, concentrated hydrochloric acid (37–38%), and phosphoric acid (85%) were from J. T. Baker (Mallinckrodt Baker Inc., Utrecht, The Netherlands). Cysteamine and formic acid were from Sigma Chemical (Sigma Chemical Co., St. Louis, MO, USA).

Lipoid S75 (consisting of ~70% of soy phosphatidylcholine, 9% phosphatidylethanolamine and 3% lyso-phosphatidylcholine) was purchased from Lipoid GmbH (Ludwigshafen, Germany). Sodium hyaluronate with low molecular weight (200–400 kDa) and a polydispersity of 1.4 Mw/Mn, was purchased from DSM Nutritional Products AG Branch Pentapharm (Switzerland). Tween 80, glycerol, DPPH radical (2,2-diphenyl-1-picrylhydrazyl), ferric chloride hexahydrate, gallic, chlorogenic, and ascorbic acids, catechin, tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), quercetin, neocuproin, Folin–Ciocalteu’s phenol reagent, 2,4,6-tris(2-pyridyl)-S-triazine (TPTZ) and pyrocatechol violet were purchased from Sigma-Aldrich (Milan, Italy). Potassium hexacyanoferrate (III) was obtained from Merck (Darmstadt, Germany). Anhydrous sodium acetate, copper sulfate pentahydrate and copper chloride dihydrate were obtained from VWR Chemicals BDH^® (Frankfurt, Germany). Cyanidin 3-O-glucoside (≥95%) and delphinidin 3-O-glucoside (≥95%) were purchased from Extrasynthese (Lyon, France). Glacial acetic acid and phosphoric acid (85%) were acquired from J.T. Baker (Mallinckrodt Baker Inc., Utrecht, The Netherlands). All reagents and plastics for cell culture were purchased from Life Technologies Europe (Monza, Italy).