Fast determination of trace metals in edible oils and fats by inductively coupled plasma mass spectrometry and ultrasonic acidic extraction

Abstract

Trace elements play an important role in humans as some are essential for the proper functioning of the body while others may have negative impact in health. Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the determination of nine elements (Cd, Cr, Cu, Fe, Mn, Ni, Ti, V e Zn) in olive oil, soy oil and margarine. Samples were treated with nitric acid solution (10 % v/v) and heated at 50 °C for 30 min. This mixture was placed in an ultrasonic bath for 20 min, in order to obtain quantitative extraction of trace-elements into the acid solution, which was directly aspirated into the ICP-MS to be quantified, using analytical curves constructed with aqueous standards. This simple sample preparation procedure along with an efficient sample introduction strategy (using a Meinhard K3 nebulizer and a twister cyclonic spray chamber) facilitated the overall analytical process. Internal standardization with Rh was used to correct matrix effects and signal fluctuations. Limits of detection in the ng g−1 range were achieved for all elements and were appropriate for the intended application. The method was tested by the analysis of samples before and after fortification with metalo-organic standards and recoveries between 88 and 117% were achieved. The method was found to lead to reliable results using a fast and simple procedure.