Spectrophotometric determination of microquantities of Carbidopa using the Carbidopa-iron(III)-phenylfluorone ternary complex in micellar medium

Summary

A new analytical method for the spectrophotometric determination of Carbidopa (CBDA), either in pure form or in tablets is described. The method is based on a ternary complex formation between CBDA, iron(III) and phenylfluorone (Phfl) in the presence of Tween 20 as a surfactant. At the optimum pH 9.55, the ternary complex shows an absorption maximum at λ=636 nm, with an apparent molar absorptivity of 1.098×10⁵ l mol⁻¹ cm⁻¹ and a Sandell's sensitivity of 2.22 ng cm⁻². The solution of the ternary complex obeys Beer's law in the concentration range of 0.1–3.0 ppm of CBDA. The correlation coefficient was found to be r=0.9999. Results obtained by application of the proposed method and the B.P. 1988 official one were in good agreement and a statistical comparison by means of the Student's t-test as well as by the variance ratio F-test shows no significant difference between the two analytical methods.