Spectrophotometric Determination of V(V) Using TTC and NTC

Reagents from Merck (Schnelldorf, Germany), Fluka (Buchs, Switzerland), and Loba Feinchemie (Fischamend, Austria) were used without additional purification as aqueous solutions. The standard solution of V(V) was prepared from NH₄VO₃ (Merck, puriss. p. a.) at a concentration of 2.0 × 10⁻⁴ mol L⁻¹. Solutions of TTC (Loba Feinchemie, p.a.) and NTC (Fluka, for microbiology) were stored in dark flasks; c_TTC = 3 × 10⁻³ mol L⁻¹ and c_NTC = 2 × 10⁻³ mol L⁻¹. The azo dye HTAR (Merck) was dissolved in the presence of KOH [22 (link),57 (link),62 (link)]; c_HTAR = 2 × 10⁻³ mol L⁻¹. A series of buffer solutions (pH 3.3–7.4) were made by mixing 2 mol L⁻¹ solutions of acetic acid and ammonia. Chloroform was purified by distillation and used repeatedly according to safety regulations. Distilled water was used in all experiments.