Emprego de solvente eutético profundo natural (NADES) no desenvolvimento de método verde para determinação elementar em amostras de café solúvel

Abstract

The contamination of coffee beans, used in the production of instant coffee, with potentially toxic elements may pose risks to human health, making their monitoring necessary. Natural deep eutectic solvents (NADESs) represent a sustainable alternative for application in coffee sample preparation with the purpose of elemental determination, due to their low toxicity, biodegradability, and simple preparation. In this context, the present work aimed to develop an ultrasound-assisted extraction method using a natural deep eutectic solvent (NADES-UAE) for the determination of Fe, Mn, and Zn in instant coffee samples by flame atomic absorption spectrometry (FAAS). The experimental conditions for both NADES preparation and the NADES-UAE method were optimized, and the extraction was carried out using 0.3 g of coffee, 5.0 mL of NADES, and 35 minutes of sonication. The method achieved limits of detection of 0.26, 0.55, and 3.38 μg g⁻¹ for Zn, Mn, and Fe, respectively. The accuracy of the method was evaluated using a certified reference material of green coffee, yielding agreement between 92.4% and 112.3%. Spike and recovery tests were carried out on instant coffee samples, and the recovery values ranged from 86% to 125%. Repeatability and intermediate precision tests were performed, yielding relative standard deviations ranging from 3.0% (Mn) to 5.7% (Fe), and from 4.4% (Fe) to 10.2% (Zn), respectively, indicating good precision of the method. The proposed method was effectively applied to ten instant coffee samples, which exhibited concentrations ranging from 2.14 μg g⁻¹ (Mn) to 60.44 μg g⁻¹ (Fe). The developed method represents a simple, rapid, and sustainable alternative for the preparation of instant coffee samples, aligned with the principles of green analytical chemistry (GAC) and green sample preparation (GSP), achieving AGREE and AGREEprep scores of 0.71 and 0.75, respectively.