SPECTROPHOTOMETRY STUDY OF COLOUR REACTION OF VANADIUM(rV) WITH CHROME AZUROL S IN THE PRESENCE OF CATIONIC AND NON-IONIC SURFACTANTS

摘要

The optimum conditions for the formation of complexes of vanadium(IV) with Chrome Azurol S (CAS) in the presence of cationic (benzyldodecyldimethylammonium bromide (ST)) and non-ionic (Triton X-100, Tween 20 and Brij 35) surfactants have been determined. The complexes are formed in weakly acid solution (optimum pH: 4.6, 4.0 and 3.9) and show the absorption maxima at 603, 600 and 598 nm, respectively. The highest sensitivity was obtained for the method based on quaternary system V(IV)-CAS-ST-Triton X-100 due to the higher CAS : V(1V) molar ratio in this complex than in binary and ternary complexes: CAS-V(IV) and CAS-V(I V)-ST. The molar absorptivity of this system is 8.08 x 10~4 L/mol cm. The LOD and LOQ values are: 0.006 and 0.02 p-g/mL, respectively. Beer's law is obeyed in the range: 0.02-0.60 u.g/mL of V. The precision (RSD = 0.51 %) and accuracy (1.9%) are satisfactory. This method has been applied to the determination of vanadium in plant materials.