High Sensitive and Selective Spectrophotometric Method for the Determination of Copper in Industrial, Environmental, Biological and Soil Samples Using 2-Hydroxynaphthaldehydebenzoylhydrazone

A very simple, ultra-sensitive and highly selective spectrophotometric method is presented for the rapid determination of copper at a trace level. 2-hydroxynaphthaldehyde- benzoylhydrazone (HNABH) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of copper (II). HNABH reacts with copper in a slightly acidic (1×10-4-3.5×10^-4 mol L^-1 H2SO4) in 50 % N,N-dimethylformamide (DMF) media with copper (II) to produce a highly absorbent green chelate with a molar ratio 1:1. The reaction is instantaneous and the maximum absorption was obtained at 427 nm and remains stable for 24 h. The average molar absorptivity and Sandell’s sensitivity were found to be 4.35×10^4 L mol^-1 cm^-1 and 5.0 ng cm^-2 of copper (II), respectively. Linear calibration graphs were obtained for 0.01 – 12.0 mg L^-1 of Cu (II). The detection limit and quantification limit of the reaction system were found to be 1 μg L^-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 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) 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 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).