Study of the formation of vanadium(IV) complexes with some triphenylmethane reagents and cationic surfactants

Abstract

The optimum conditions for the formation of ternary complexes of vanadium(IV) with Eriochrome Cyanine R (ECR), Chrome Azurol S (CAS) and Pyrocatechol Violet (PV) in the presence of zephiramine, cetyltrimethylammonium (CTA) or cetylpyridinium (CP) ions have been determined. The complexes are formed at pH 3.5–5.5 and suitable molar absorptivities are 5–8 × 10⁴ l mol^–1 cm^–1. The higher sensitivites of the methods based on ternary systems are due to the higher R:V(IV) molar ratios in ternary complexes (with cationic surfactants) than in binary complexes. Of the methods studied, that based on the system with ECR and CTA is proposed for the determination of vanadium as it has the highest sensitivity (ε= 7.9 × 10⁴ l mol^–1 cm^–1 at 575 nm). This method has been applied to the determination of vanadium in steel.