Development of an analytical procedure using acid-based hydrophobic deep eutectic solvent for the extraction and preconcentration of heavy metals in sport supplements followed by GFAAS analysis

The excessive use of sports supplements by athletes and the possibility of the presence of toxic metals in these supplements has become a serious concern. Because the accumulation of these metals in body tissues threatens human health in the long term. In the present research work, microwave-assisted extraction (MAE) combined with acid-based deep eutectic solvents (DESs) was developed for the extraction and preconcentration of lead (Pb), cadmium (Cd) and mercury (Hg) in sport supplements. The method was combined with graphite furnace atomic absorption spectroscopy (GFAAS) for sensitive and efficient detection. Acid-based DESs were synthesized from organic acids having 6 to 10 carbon atoms in combination with thymol under appropriate conditions. The synthesized DESs were used as the extraction solvent to extract metal ions from sports supplements. Diethyl dithiophosphoric acid (DDTP) was chosen as the chelating agent due to its acidic properties and high ability to form complexes with the desired metal ions. Some factors affecting the extraction and enrichment were studied, such as DES type, molar ratio of DES components, DES volume, sample solution pH, vortex time, salt addition and interference ions. Under the best conditions, the enrichment factors ranged from 212 to 284, while the preconcentration factors varied between 450 and 610. The calibration curves showed good linearity between 0.05 and 300 μg kg^-1, with detection limits ranging from 0.02 to 0.10 μg kg^-1. RSDs for inter-day and intra-day precision for 1.0 μg L^-1 of Hg and 0.20 μg L^-1 of Cd and Pb were in the range of 2.7-4.4% (<i>n</i> = 7) and 4.5-6.3% (<i>n</i> = 7), respectively. The accuracy of this method was confirmed by obtaining recoveries of spiked real samples. The method was also validated by analyzing two certified reference materials (CRMs).