Ultrasound-Assisted Extraction Applied to Mg, Mn and Zn Determination in Chia Seeds and Flours by F AAS

Abstract

In recent years, consumption of chia seeds and flours has grown because of the numerous health benefits attributed to it. Although, the chia is recognized as an important source of minerals for nutrition, analytical methods for sample preparation and determination of the metals in this food are still scarce. Thus, in an unprecedented way, an ultrasound-assisted extraction method (UAE) was optimized by a factorial design for the determination of Mg, Zn and Mn in chia seeds and flours using a dilute solution of nitric acid (5.0 %, v/v), a time of 30 minutes of sonication, a sample mass of 0.5 g and a sonication frequency of 42 kHz. For the determination of Ca and Fe further optimization studies are still required for the complete extraction of these metal from the matrix. In addition, the UAE methodology presented good accuracy when compared with the wet digestion (values of tcalculated < tcritical and p-values > 0.05), excellent precision (RSD values between 1 and 3.8 %) and linearity (R 2 ≥ 98 %) as well as low detection and quantification limits (LOD between 0.8 and 2 μg g -1 and LOQ between 3 and 6 μg g -1 ). The application of the UAE methodology in routine analyzes in food quality control laboratories is interesting because it presents characteristics such as being environmentally friendly when compared to other methods of sample preparation due to the low consumption of reagents and energy, for offering greater safety to the analyst and for using low-cost instrumentation.