Avaliação de estratégias empregando NADES para o preparo de amostras de peixes visando à determinação de macroelementos por ICP-OES

Abstract

EVALUATION OF STRATEGIES EMPLOYING NADES FOR THE PREPARATION OF FISH SAMPLES AIMING AT THE DETERMINATION OF MACROELEMENTS BY ICP-OES. The sample preparation step is crucial for obtaining consistent results in chemical analyses, since contamination and loss of some analytes can occur in this process. Conventional digestion methods employ strong acids, such as nitric acid, which promote matrix decomposition but are dangerous and generate significant waste. As an alternative to reduce these impacts, this work evaluated the use of green solvents, such as eutectics (DES/NADES). Deep eutectic solvents (DES) are formed by a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD), resulting in a eutectic system with a lower melting point. Natural deep eutectic solvents (NADES) are composed of natural compounds, namely amino acids, organic acids, and sugars, and offer advantages such as lower toxicity, biodegradability, sustainability, and relatively simple preparation. The levels of Ca, K, Mg, Na, and P extracted from fish tissues were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), which exhibits good sensitivity and multi-element capability. Different organic acids (formic, malonic, and oxalic acids) were evaluated as hydrogen bond donors, and choline chloride was used as a hydrogen bond acceptor in a 1:1 ratio. Extraction was performed on fish tissue reference material (MR-agro E3002A) using a thermostatic bath and ultrasound, and the recovery (%) and relative standard deviation (RSD%) of the evaluated analytes were compared. Extractions performed in a thermostatic bath showed recoveries between 68% and 100% compared to the values described in the reference material and a relative standard deviation (RSD) < 18%. Subsequently, the influence of adding water to the composition of the eutectic solvents (1 to 4 mol H2O) was evaluated. Recoveries and relative standard deviations indicated that the NADES composed of choline chloride: formic acid: water (1:1:4) showed the best performance. An experimental design (Doehlert) was carried out to simultaneously optimize the extraction responses of the five analytes, considering extraction time and eutectic solvent volume, and to evaluate the multiple response (MR). The results obtained indicated that the optimized condition, with recoveries of 77–92% and RSD (%) of 0.1–18%, was: 90 min of extraction and 4 mL of NADES. Validation demonstrated adequate reliability of the developed method, and the evaluation using the AGREEprep metric resulted in a score of 0.48. Replacing traditional acid digestion with deep eutectic solvents, especially NADES, as a sample preparation step for fish tissue introduces a more sustainable, less toxic approach with lower waste generation, while maintaining nutrient extraction efficiency, reducing laboratory risks, simplifying preparation, and strengthening alignment with green chemistry practices.