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Formation and extraction of niobium(V) complex with xylenol orange in presence of 4-pyridone derivative

Xylenol orange (XO) is a suitable reagent for spectrophotometric determination of niobium in a weakly acidic medium. The present study shows that the addition of 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) influences the complex formation as well as the spectroscopic properties of this colored system. To prevent the formation of niobium(V) hydrolysed species in water tartaric acid was used for preparing niobium stock solution. The red-violet colored complex formed by heating between niobium(V) and xylenol orange (XO) in presence of HX at pH = 3 has a maximum absorption at 565 nm. The complex can be extracted by chloroform solution of tetraphenylphosphonium (TPP) chloride. The optimum reaction conditions and other parameters for complex formation have been evaluated. The mechanism of extraction is probably based on the formation of the associated ion pair between the tetraphenylphosphonium cation and mixed Nb(V)-XO-HX anion. The extracted complex in chloroform showed maximum absorbance at 585 nm with the corresponding molar absorption coefficient 3.72 x 104 L mol– 1 cm– 1, and obeys Beer’ s law in the range 3 x 10-6 – 3 x 10-5 mol L-1.

Niobium ; Xylenol orange ; 4-pyridone derivative ; Spectrophotometry ; Extraction ; Complexes

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