Extraction Study on the Colour Reaction for Vanadium(iv) with the 4-nitrocatechol (nc) – Thiazolyl Blue Tetrazolium (mtt) – Water – Chloroform System

In slightly acidic medium V(IV) forms with 4-nitrocatechol (NC) and 3-(4,5dimethyl-2-thiazol)-2,5-diphenyltetrazolium bromide (Thiazolyl Blue Tetrazolium, MTT) a well extractable into chloroform, intensively colored (ε405=3.5×10 l mol cm) 1:2:2 complex. The optimal conditions for extractive-spectrophotometric determination of V(IV) were found: pH 4.0-4.8, CNC= 2.9×10 mol l, CMTT= 1.6×10 4 mol l, extraction time = 3 min. The Beer’s law was obeyed up to 1.6 μg ml vanadium(IV). The limit of detection (LOD), limit of quantification (LOQ) and Sandell’s sensitivity were calculated to be 0.07 μg ml, 0.23 μg ml and 1.46×10 μg cm, respectively. The effect of diverse ions on the determination of V(IV) was studied. The extraction process was investigated quantitatively and the key constants (the extraction constant KEx, the association constant β, and the distribution constant KD) were determined: Log Kex=12.9, Log β=11.0, Log KD=1.9. The recovery factor was calculated to be R=98.4 %.