Ligandless reversed-phase switchable-hydrophilicity solvent liquid-liquid microextraction combined with flame-atomic absorption spectrometry for the determination of copper in oil samples

A novel ligandless reversed-phase switchable-hydrophilicity solvent liquid-liquid microextraction method is proposed for the determination of copper in oil samples using flame-atomic absorption spectrometry. Optimum extraction conditions were achieved using 500 mu L of triethylamine as the extraction solvent, 750 mu L of 7.5 M nitric acid as a hydrophilicity-switching trigger, 30 mL of the oil sample and 5 min extraction time. Limits of detection and quantitation were found as 6.9 and 23.0 ng mL(-1), respectively. Good linearity was obtained with a coefficient of determination (R-2) value of 0.9998 and a preconcentration factor of 22.7. Intraday and interday precision, expressed as percentage relative standard deviations (%RSD), were less than 4.7 and 9.4%, respectively. Accuracy was checked by addition-recovery studies and percentage recoveries within the range of 85-100% were obtained. The proposed method was successfully applied to determine copper ion in edible oil samples (i.e., sunflower, olive, flaxseed and corn) and baby oil and satisfactory results were achieved.