Colour Reaction of p-Acetylchlorophosphonazo with Strontium(II) and Analytical Application

Abstract

A simple and sensitive spectrophotometric method for the determination of strontium has been developed using p-acetylchlorophosphonazo (CPApA) as chromogenic agent and optimum reaction conditions along with analytical properties parameters have been established. CPApA with strontium(II) forms a blue complex in CH₃COOH-CH₃COONa buffer solution at pH = 3.5. At maximum absorption wavelength of the complex of 600 nm, absorbance being determined, a good linear relationship is presented over the range 1-20 μg of strontium(II) in 10 mL with a correlation coefficient of 0.9996. Its regression equation is: A = 0.0499C (C: μg/10 mL) + 0.0211. The apparent molar absorption coefficient of the method is e_{660 nm} = 4.45 × 10⁴ L mol^-1 cm^-1 and its detection limit is 0.126 μg/mL. The composition of complex is n_(CPAPA) : n_Sr²⁺ = 2:1 determined respectively by molar ratio method and the equimolar continuous variation method. The method has been successfully applied to the determination of strontium content in KCl and Na₂SO₄ chemical reagents. The results were compared favourably with those obtained by atomic absorption spectrometric method.