Copper and Iron Determination with [N,N′-Bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] in Edible Oils Without Digestion

A new method for the determination of copper(II) and iron(III) in liquid edible oils which does not require a digestion step was developed. The suggested method involves extraction of metals with [N,N'-bis(salicylidene)-2,2'-dimethyl-1,3-propanediaminato] (LDM) followed by flame atomic absorption spectrometry measurement. As a first step, metal complexes of copper(II) and iron(III) ions with LDM were investigated spectrophotometrically. After the analytical properties and experimental conditions of the complexation had been determined, these findings were used to determine the extraction period as a second step. Experimental conditions were optimized using a central composite design. Optimum conditions for Cu(II) and Fe(III) extractions from oil were found: the ratios of the volume of Schiff base solution used to the mass of oil (V-LDM/m(oil); mL g(-1)) were 0.76 and 1.19 mL g(-1), the stirring times were 73 and 67 min, and the temperatures were 31 and 28 degrees C, respectively. The developed extraction and determination method was tested on certified reference materials; the recovery percentages were found to be 99.4 +/- 2.8 and 100.2 +/- 5.6 for Cu(II) and Fe(III), respectively. The suggested method was performed on real samples such as olive oil, sunflower oil, corn oil, canola oil and recovery values between 97.2-102.1 for Cu(II) and 94.5-98.6 for Fe(III) were determined. It was concluded that the developed method has some advantages over the common traditional methodincluding rapidity, sensitivity, accuracy, reduced risk and cost.