Ammonium acetate

Acetonitrile, acetone, ethyl acetate, hexane, isopropyl alcohol, methanol, formic acid, and ammonium acetate were acquired from Loba Chemie, India. Betanidin 5-β-D-glucopyranoside standard with percent purity ≥ 95% was used (Wuhan ChemFaces Biochemical Co., Ltd, China). Sodium formate and 2, 2-difluoroethoxy phosphazene were used (Fisher Scientific, USA). Distilled and deionized water, as well as cleaned-up samples (before HPLC analysis), were filtered through a 25 mm and 0.45 mm nylon syringe filter (Millipore, USA). The analytical grade of each chemical or reagent purchased allowed for usage without further purification.

All reagents were of analytical grade. Methanol LC grade and glacial acetic acid were purchased from Merck (Darmstadt, Germany) and Fisher Chemical, respectively. Ammonium acetate (Loba Chemie PVT L.T.D, 96% purity, 0.01 mol L⁻¹), concentrated hydrochloric acid (Panreac Quimica, 37%), and sodium hydroxide (Fisher Chemical, purity ≥ 99%, 1 mol L⁻¹) were used. Certified standard solutions of BA and SA were obtained from Fluka (purity ≥ 99%). Standard stock solutions of 1 g L⁻¹ of both acids were prepared in methanol/ultrapure water (40:60, v/v). Standard mixtures, ranging from 1 to 45 µg mL⁻¹, were prepared by appropriate dilution of the stock solution with acetate buffer/methanol (60:40, v/v) [34 (link)]. The buffer solution (pH = 4.6) was prepared by mixing Ammonium acetate and acetic acid in appropriate proportions. Silica-based sorbent with octadecyl functional group was acquired from Applied Separations Company, Allentown, PA, USA (3 mL; 500 mg, with a particle size of 40 μm and an average porosity of 60 A°), and multiwalled carbon nanotubes (MWCNT) were purchased from Sigma-Aldrich (France). MWCNT were 5–9 µm in length and 110–170 nm external diameter. Activated carbon (AC) was purchased from Sigma (20–60 mesh, product number C3014).

Ferrous sulfate heptahydrate (FeSO₄·7H₂O, > 99%) and sodium borohydride (NaBH₄, > 98%) were purchased from Merck (Darmstadt, Germany). Ethanol, acetic acid (H₃COOH), and sodium hydroxide (NaOH) were obtained from Fisher Scientific Co. (Springfield, NJ), while ammonium acetate was purchased from Loba Chemie, India. Reagent grade chitosan (low molecular weight) and MB dye (basic blue 9, C₁₆H₁₈CIN₃S) were purchased from Sigma Aldrich. Deionized water of 18.2 MΩ cm⁻¹ resistivity, purified by Milli-Q, Germany, was used in all the experiments.