Determinación de trazas metálicas en aceites vegetales de España y Marruecos mediante espectroscopía de absorción con cámara de grafito después de la digestión en horno de microondas

Abstract

A simple, rapid analytical method for determining traces of Cd, Cr, Cu, Mn and Pb in in various types of vegetable oils is proposed. Samples are digested in a microwave oven and then analyzed by atomic absorption spectroscopy with electrothermal atomization. The proposed method exhibits good linearity and sensitivity to the five metals, which it can determine with detection limits over the range 0.06-2.15 Ìg/kg. Its precision, as relative standard deviation, ranges from 2.6 to 4.2%. Its accuracy was assessed by using it to analyze a reference material consisting of Used Oil HU-1, which contains certified metal concentrations, and was found to be quite acceptable. The proposed method was applied to the determination of the five metals in virgin olive, olive, sunflower, maize and pomace olive oils from Spain and Morocco. Based on the results, the metal contents varied among oil types and, for olive oil, also with the country of origin; the oil samples from Morocco contained especially high levels of lead.<br><br>En el presente trabajo se propone un método simple y rápido de análisis para la determinación de trazas metálicas (Cd, Cr, Cu, Mn, y Pb) en diferentes tipos de aceites vegetales. El procedimiento consiste en el tratamiento previo de la muestra mediante digestión con horno de microondas y en el análisis mediante espectroscopía de absorción atómica con atomización electrotérmica. El método ofrece una buena linealidad y sensibilidad para los cinco metales determinados, con límites de detección comprendidos entre 0,06- 2,15 μg/kg. La precisión del método expresada como desviación estándar relativa oscila entre 2,6 y 4,2 %. Para el estudio de la exactitud se analizó un aceite de referencia (Used Oil HU-1) con las concentraciones de metales certificadas, obteniéndose unos resultados satisfactorios. La metodología desarrollada se aplicó a la determinación de metales en diferentes tipos de aceite vegetales (oliva virgen, oliva, girasol, maíz y de orujo) de distinta procedencia (España y Marruecos). Los resultados obtenidos han puesto de manifiesto que el contenido de metales depende del aceite analizado, y en el caso del aceite de oliva varía dependiendo del país de procedencia, obteniéndose unos valores elevados para el plomo en las muestras producidas en Marruecos

The origin of aliphatic hydrocarbons in olive oil

“…The presence of these undesirable compounds in olive oil could have different origins, including fraudulent addition, intake by the olive tree from the environment, plant metabolism and incorrect fruit processing. 10 -12 Fraudulent mixtures of virgin olive oil with other lower-quality olive oil and seed oils are well documented, and there is much scientific evidence of olive oil contamination by pesticides, 13 heavy metals, 14 polycyclic aromatic hydrocarbons (PAHs) 15 and mineral oils. 16 -18 The presence of mineral oil in edible oils became particularly relevant after the case of a batch of Ukrainian sunflower oil that was contaminated with a high concentration of mineral oil.…”

“…Fraudulent mixtures of virgin olive oil with other lower‐quality olive oil and seed oils are well documented, and there is much scientific evidence of olive oil contamination by pesticides, heavy metals, polycyclic aromatic hydrocarbons (PAHs) and mineral oils . The presence of mineral oil in edible oils became particularly relevant after the case of a batch of Ukrainian sunflower oil that was contaminated with a high concentration of mineral oil .…”

Determination of copper in liquid and solid insulation for large electrical equipment by ICP-OES. Application to copper contamination assessment in power transformers

“…Many studies underline the difficulties involved in the detection of metals in organic samples, which are mostly ascribed to the viscosity of the sample and to the complexity of the matrix. Brandão et al [14] and Bakkali et al [15], recently used electro-thermal atomic absorption spectrometry (ET-AAS) to detect trace metals in petroleum and in vegetables oil. They overcame the problem using a chemical modifier (Triton-X) and sample pre-treatment by microwave digestion respectively.…”