Use of Constrained Mixture Design in the Optimization of a Method Based on Extraction Induced by Emulsion Breaking for the Determination of Ca, Mg, Mn, Fe and Zn from Palm Oil by Flame Atomic Absorption Spectrometry

In this study, it was developed a method for Ca, Mg, Mn, Fe and Zn determination in palm oil samples by flame atomic absorption spectrometry (FAAS) after ultrasound-assisted emulsification and extraction induced by emulsion breaking (EIEB). Optimization of the method was carried out by a constrained mixture design. The developed method has presented limits of detection (LOD) between 0.012 and 0.057 mg L-1, limits of quantification (LOQ) between 0.039 and 0.19 mg L-1 and precision was expressed as repeatability (%RSD, n = 10) between 1.8 and 3.2% for the five studied metals. Method accuracy was assessed by the application of recovery tests (87 to 113%) and by comparison of concentration values with the dry ashing method, showing good agreement with the standard method. The developed methodology allows operational simplicity, multi-sample treatment, and low cost when compared with some methods based on decomposition. It was applied in palm oil samples collected in the Bahia State (Brazil). The concentrations (in mg L-1) found in the samples were: 3.93-13.9 Ca, 0.37-2.26 Mg, > LOQ-0.32 Mn, 1.77-8.57 Fe and 0.38-2.54 Zn.