Spectrometric determination of copper in edible oil based on the extraction with N, N′-bis(5-methoxy-salicylidene)-2-hydroxy-1,3-propanediamine

Abstract

A new method for the determination of copper in edible oils was suggested. The proposed method is based on the extraction of copper with N,N'-bis(5-methoxy-salicylidene)-2-hydroxy-1,3-propanediamine (5MSHP) followed by flame atomic absorption spectrometry measurement. Firstly, copper complex with 5MSHP was investigated spectrophotometrically. After the analytical properties of the complexation had been defined, optimization of the extraction conditions of copper from oils was performed using a central composite design. Optimal conditions for the extraction of copper with 5MSHP were found to be 26.7 degrees C, 1.3 mL g(-1), 5.6 min for the temperature, the ratio of the volume of used Schiff base solution to the amount of oil, and the stirring time, respectively. The proposed method has been validated by using oil based metal standard, obtaining satisfactory results. The limit of detection (LOD) and the relative standard deviation of the method were found to be 0.06 mu g g(-1) and 2.31% respectively. The method has been successfully applied to the analysis of various oil samples, and the accuracy was assessed by an alternative determination procedure by ICP OES. The concentrations of copper in olive, sunflower, corn and hazelnut oils were found to be 0.41 +/- 0.03, 0.31 +/- 0.03, 0.29 +/- 0.04, 0.28 +/- 0.01 mu g g(-1) in the present work, respectively.