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Abstract
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Heavy metal composition of foods is of interest because of their essential or toxic nature. For example, iron, zinc, copper, chromium, cobalt and manganese are essential, while lead, cadmium, nickel and mercury are toxic at certain levels. Iron and copper are essential for human life at low concentrations, but they can also be toxic at high concentrations [1]. However due to matrix effect and low concentration of metal ions, efficient separation and preconcentration steps are essential prior to analytical measurements [2]. In the present study a miniaturized liquid-phase extraction procedure based on directly suspended droplet microextraction for determination of trace amounts of iron and copper in vegetable, fruit and environmental samples was developed. The method is based on the extraction of the iron and copper complexes with 2-mercaptopyridine n- oxide onto a micro drop of methyl isobutyl ketone (MIBK) as extraction solvent and subsequent flame atomic spectrometric determination. The factors influencing the complex formation and extraction were optimized. Under optimum conditions, enrichment factors of ~ 25 are obtained from only 6.5 mL of aqueous phase for iron and copper respectively. The analytical curves were linear between 30- 800 g L-1 and 20- 1200 g L-1 for iron and copper, respectively. Based on three standard deviation of the blank, the detection limits were 3.76 g L-1 and 1.84 g L-1 for iron and copper respectively.
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