Cerium 3 chloride

All reagents and solvents used in this work were of analytical grade from Sigma–Aldrich (Steinheim, Germany). cholesterol oxidase (ChOx), dipotassium hydrogen phosphate, potassium dihydrogen phosphate, cholesterol (CHOL), ascorbic acid (AA), uric acid (UA), salicylic acid (SA), glutathione (GN), glucose (GU), chloroplatinic (IV) acid, creatinine (CN), copper(II) sulfate, hydrogen tetrachloroaurate(III) trihydrate, cerium(III) chloride, o-dianisidine, hydrogen peroxide (30%), glutaraldehyde (25%), cetyltrimethylammonium bromide (CTAB), cysteamine, isopropanol (98%) and Triton X-100 were from Sigma–Aldrich.

Copper(II) sulphate, hydrogen tetrachloroaurate(III) trihydrate, cerium(III) chloride, nickel(II) sulfate, chloroplatinic(IV) acid, palladium(III) chloride, o-dianisidine, 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), catechol, and other reagents and solvents used in this work were purchased from Sigma-Aldrich (Steinheim, Germany). All reagents were of analytical grade and were used without additional purification. All solutions were prepared using ultrapure water. Laccase from Trametes zonatus was purified and characterized as described by us earlier [18 (link),19 (link)].

All reagents were of analytical grade. A fluoride standard solution (Teknolab, Kolbotn, Norway) was used for the experiments. Cerium(III) chloride and sodium perchlorate (to adjust the ionic strength to I = 0.1 M) were purchased from Sigma-Aldrich Ltd (Budapest, Hungary), and dissolved in deionized, double-distilled water purified with a Millipore Milli-Q system (Millipore Inc., Bedford, MA, USA). Measurements were carried out after one-day storage, at room temperature and atmospheric pressure. Elimination of oxygen was realized with argon bubbling and Schlenk technique. The applied concentrations were: 1.0 × 10⁻³ M CeCl₃ and 0–3.16 × 10⁻³ M F⁻. Twelve solutions of various fluoride concentrations were prepared without precipitation. In two further solutions, with 5.26 and 26.3 mM F⁻ concentrations, the appearance of precipitate was detected. The natural pH of the solutions studied was ~4.8 (without application of any buffer).