Development of a dispersive liquid–liquid microextraction method for preconcentration and determination of copper in water and vegetables

ABSTRACT

Accurate and reliable determination of copper in vegetables and water is often difficult because of low copper concentrations and matrix effects. A new dispersive liquid–liquid microextraction method has been developed for preconcentration of trace amounts of copper as a prior step to its determination by flame atomic absorption spectrometry. In this method, carbon tetrachloride was used as the extraction solvent and 1-(2-pyridylazo)-2-naphthol (PAN) was used as the chelating agent. The factors: type and volume of extraction solvent, volume of PAN, pH of sample solution, extraction time, and salting out effect influencing extraction efficiency of copper ions were optimized. Under optimal conditions, the calibration curve was linear in the range of 1.0–500 ng · mL⁻¹ of copper with an R² = 0.999. Detection limit (3S_b) was 0.3 ng · mL⁻¹ in original solution and the relative standard deviation for eight replicate determinations of 0.1 μg · mL⁻¹ copper was ± 1.8%. Copper is aggregated in edible parts of leafy vegetables. Metals analysis on vegetables is essential for the protection of human health and to comply with regulatory controls. Speed and ease of operation, and cost and timesaving are advantages of this method.

KEYWORDS:

• Detection limit
• flame atomic absorption
• 1-(2-pyridylazo)-2-naphthol

Additional information

Funding

The authors thank the Azad Ahwaz University Research Council for financial support of this work.