Natural Deep Eutectic Solvents: synthesis, characterization, and application for the determination of As, Cd, Cr, Hg, Se, and V in environmental samples using ICP-MS

Abstract

The development of sample preparation methods that enable reductions in the use of reagents and solvents, or their replacement, as well as minimal sample handling, the use of more efficient energy sources, and lower risks to the operator and the environment, are all issues addressed by Green Analytical Chemistry (GAC). The use of organic solvents can have serious environmental impacts, so there is an urgent need to develop new alternatives that offer lower toxicity, low cost, and higher safety to the operator. Natural deep eutectic solvents (NADES) are emerging substances that present advantages such as biodegradability, low toxicity, and simple preparation. Methods for the synthesis of new NADES based on amino acids combined with sugars and organic acids will be developed, using a heating and stirring method, evaporation, as well as synthesis assisted by ultrasound (SAU) or microwave radiation (SAM). Characterizations will be performed using techniques including infrared spectroscopy (IV), thermogravimetry (TG), differential exploratory calorimetry (DSC), and measurements of density and viscosity, in order to evaluate the formation of these NADES. After the synthesis and characterization steps, these new solvents will be applied in different green sample preparation methods: extraction at ambient pressure and temperature, microwave-assisted extraction (MAE), and ultrasound-assisted extraction (UAE). In addition, evaluation will be made of synthesis concomitant with the extraction of analytes by the solid phase matrix dispersion (SPMD) technique, applied to environmental matrices and biological tissues. Determination of the potentially toxic elements As, Cd, Cr, Hg, Se, and V will be performed by inductively coupled plasma mass spectrometry (ICP-MS), including a study of the interferences inherent to this analytical technique. Some of the NADES will be evaluated for their ability to extract emerging contaminants such as brominated flame retardants (BRFs) from domestic and industrial sewage sludge samples, with analysis using gas chromatography coupled to mass spectrometry (GC-MS). (AU)