A Simple Spectrophotometric Method for the Determination of Copper in Some Real, Environmental, Biological, Food and Soil Samples Using Salicylaldehyde Benzoyl Hydrazone

Abstract

A very simple, ultra-sensitive, highly selective and non-extractive spectrophotometric method for the determination of trace amounts copper(II) has been developed. Salicylaldehy debenzoyl hydrazone (SAL-BH) has been proposed as a new analytical reagent for the direct non-extractive spectrophotometric determination of copper(II). SAL-BH reacts with copper in a slightly acidic (0.0001-0.005 M H₂SO₄) in 40% 1,4-dioxane media with copper(II) to give a highly absorbent greenish yellow chelate with a molar ratio 1:1(CuII: SAL-BH) The reaction is instantaneous and the maximum absorption was obtained at 404 nm and remains stable for 72 h. The average molar absorptivity and Sandells sensitivity were found to be 1.4×10⁵ L mol^-1 cm^-1 and 5.0 ng cm^-2 of copper(II), respectively. Linear calibration graphs were obtained for 0.01 18 mg L^-1 of CuII. The detection limit and quantification limit of the reaction system were found to be 1 ng mL^-1 and 10 µg L^-1, respectively. A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiocyanate etc.) do not interfere in the determination. The method is highly selective for copper and was successfully used for the determination of copper in several standard reference materials (steels and alloys) as well as in some environmental waters (portable and polluted), biological (human blood and urine), food and soil samples and solutions containing both copper(I) and copper(II) as well as some complex synthetic mixtures. The results of the proposed method for biological and food 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).