Hcl 35 suprapure

Fe(NO₃)₃·9H₂O 96%, Co(NO₃)₂·6H₂O, chitosan, and glacial acetic acid (analytical grade, Sigma-Aldrich Chemie GmbH, Steinheim, Germany) were used in the synthesis of magnetic materials. NaOH pellets, HCl 35% suprapure and NH₄OH 25% (analytical grade) were purchased from Merck KGaA Darmstadt, Germany. Congo Red (CR) 99% (C₃₂H₂₂N₆Na₂O₆S₂) and Methyl Orange (MO) (ACS reagent, dye content 85 %, C₁₄H₁₄N₃NaO₃S, Sigma-Aldrich Chemie GmbH, Steinheim, Germany) and ultrapure water were used for preparing the dye solutions. Ethyl alcohol (95%) and acetone (99%) (Sigma-Aldrich Chemie GmbH, Steinheim, Germany) were used as desorbing agents, while ammonium acetate 99% and acetonitrile 99% (Merck KGaA Darmstadt, Germany) as mobile phase for chromatographic separation and detection were used.

The cobalt ferrite samples were prepared by the use of Fe(NO₃)₃·9H₂O 99%, Co(NO₃)₂·6H₂O and sodium bis-2-ethyl-hexyl sulfosuccinate (analytical grade, Sigma Aldrich, St. Louis, MO, USA). NH₄OH 25% and HCl 35% suprapure (analytical grade, Merck KGaA Germany, Darmstadt, Germany) were used to adjust the solution’s pH. The dye solutions of desired concentrations were obtained from Congo Red (CR) 99% (C₃₂H₂₂N₆Na₂O₆S₂) and Methyl Orange (MO) (ACS reagent, Dye content 85%, C₁₄H₁₄N₃NaO₃S, Sigma Aldrich). Ethyl alcohol (95%) (Sigma Aldrich, St. Louis, MO, USA) was applied as a desorbing agent. Ammonium acetate 99% and acetonitrile 99% (Merck KGaA Germany, Darmstadt, Germany) were utilized as a mobile phase for the dye’s chromatographic separation and detection.