Synergistic extraction and spectrophotometric determination of copper(II) using 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol: Analysis of alloys, pharmaceuticals and biological samples

A simple and selective spectrophotometric method was developed for the determination of copper(II) with 1-(2′,4′-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2′,4′-dinitro APTPT] as a chromogenic reagent. The procedure was based on the synergistic extraction of copper(II) with 2′,4′-dinitro APTPT in the presence of 0.5 mol L−1 pyridine to give green colored ternary complex of a molar ratio 1:2:2 (M:L:Py) in the pH range 8.7–10.5. It exhibits a maximum absorption of colored complex at 445 nm and 645 nm in chloroform against the reagent blank. Beer's law was followed in the concentration range 10–80 μg mL−1 of copper(II) and optimum range of 20–70 μg mL−1 the metal as evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of copper(II)–2′,4′-dinitro APTPT–pyridine complex in chloroform are 0.87 × 103 L mol−1 cm−1 and 0.072 μg cm−2, respectively. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The proposed method is rapid, reproducible and successfully applied for the determination of copper(II) in binary and synthetic mixtures, alloys, pharmaceutical formulations, environmental and fertilizer samples. Comparison of the results with those obtained using an atomic absorption spectrophotometer also tested the validity of the method.

(A) Absorption spectra of 2′,4′-dinitro APTPT vs. chloroform blank. (B) Absorption spectra of Cu(II)–2′,4′-dinitro APTPT–pyridine complex vs. 2′,4′-dinitro APTPT blank: Cu(II) = 30 μg mL−1; 2′,4′-dinitro APTPT = 5.0 mL of 0.01 mol L−1; pyridine = 5.0 mL of 0.5 mol L−1; pH = 9.5; shaking time = 15 min.Figure optionsDownload as PowerPoint slideResearch highlights
► Synergistic extraction and spectrophotometric determination of copper(II).
► Pyridine as an auxiliary synergent.
► The proposed method is very simple, selective and permits higher tolerance limit with foreign ions.
► The results were in good agreements with atomic absorption spectrometry.