Determination and In Vitro Bioaccessibility Evaluation of Cu, Fe, Mn, and Zn in Chia (Salvia hispanica L.) Seeds by ICP OES

The objective of this study was to determine the total content and estimate the bioaccessible fraction of Cu, Fe, Mn, and Zn in chia seeds (Salvia hispanica L.) by inductively coupled plasma optical emission spectrometry (ICP OES). For the evaluation of the total content, a method of acid digestion was developed, using a complete factorial design 23, in a digester block with reflux system using cold finger, and the variables chosen were as follows: volume of nitric acid, sulfuric acid, and hydrogen peroxide. Optimization provided the best conditions considering 5.0 mL of HNO3 65% m m−1, 0.5 mL of H2SO4 98% m m−1, and 3.0 mL of H2O2 30% m m−1. The detection limits, in μg g−1, were 0.18 (Cu), 0.22 (Fe), 0.28 (Mn), and 0.37 (Zn). The analyte addition and recovery test were applied to evaluate the accuracy and recovery percentage values ranging from 84 to 114% were obtained, which is considered adequate for quantitative analysis. Precision was expressed as relative standard deviation (% RSD). It was less than or equal to 7.6% (n = 10) for all analytes. The procedure was applied to 10 samples of chia seed commercialized in Salvador (Brazil). The following concentration ranges, in μg g−1, were found: Cu (12–24.2), Fe (53.2–108), Mn (29.8–84.2), and Zn (45.8–77.4). Bioaccessibility was assessed using an in vitro method that takes into account the entire gastrointestinal tract. The following bioaccessible fractions were obtained in percent: Cu (3.6–14), Fe (5.2–5.5), Mn (5.8–29.1), and Zn (< 0.7 μg g−1). The procedure was validated through a mass balance (bioaccessible content + residual fraction compared with the total content), which presented percentages of recovery ranging from 82 to 156%. This new information provides a starting point for more complex evaluations from the nutritional point of view, including the establishment of a recommended daily dietary intake for this frequently consumed seed.