A Critical Review on Application of Extraction Methods Prior to Spectrometric Determination of Trace-Metals in Oily Matrices

The presence of heavy metals in oily matrices (edible oils or crude-oil and its derivatives) cannot be controlled or prevented as they occur naturally during oil genesis. However, the presence of these metal ions in oils has negative effects, because some metal ions can act as catalyst poisons, refinery corroders and environmental pollutants during refinery processes. Additionally, some metal ions have negative health impacts when consumed by living organisms. Therefore, evaluation of metal extraction methods prior to spectrometric determination is critical for monitoring of metal concentration levels and oil quality assurance purposes. It has to be noted that there are numerous reviews that have been published, which evaluates the use of direct (analysis without sample preparation) and indirect (dry and wet digestion) spectrometric determination of metals in oily matrices. Therefore, the current review focuses on evaluation of extraction methods followed by spectrometric determination of metals published from 2005 to 2020 (16 years). The acquired data shows that extraction induced by emulsion breaking (EIEB) has been the most preferred metal extraction method using Triton X-114 as a surfactant and atomic absorption spectrometer (AAS) as a detection technique.