A Simple Spectrophotometric Method for the Determination of Trace Level of Cadmium in Real, Environmental, Biological, Tobacco, Fertilizer and Soil Samples Using 2, 3, 4, 5, 7 Pentahydroxyflavone

Abstract

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of cadmium using 2/, 3, 4/, 5, 7- pentahydroxyflavone (morin) has been developed. Morin reacts in a slightly acidic (0.000001-0.000012M H2SO4) in 50% ethanolic solution with cadmium to give a deep greenish- yellow chelate which has an absorption maximum at 422 nm. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption co-efficient and Sandell’s sensitivity were found to be 4.09 × 106 L mol-1cm-1 and 4.0 ng cm-2 of cadmium, respectively. Linear calibration graphs were obtained for 0.01 - 25 mg L-1 of cadmium with a correlation co-efficient value 0.9996 for Cd-morin complex. The stoichiometric composition of the chelate is 1:2 (Cd:morin). The detection limit and quantification limit of the reaction system were found 1µg L-1 and 10µg L-1, respectively. A large excess of over 50 cations, anions and complexing agents (like, chloride, tartrate, azide, citrate, EDTA, SCN- etc.) do not interfere in the determination. The developed method was successfully used in the determination of cadmium in several Standard Reference Materials (alloys and steels) as well as in some environmental waters (inland and surface), biological samples (human blood, urine and hair), tobacco, fertilizer, soil samples and complex synthetic mixtures. The results of the proposed method for biological samples were comparable with AAS and were found to be in good agreement. The method has high precision and accuracy (s = ±0.01 for 0.5 mg L-1).