A straightforward deep eutectic solvent-based extraction for the determination of lead in drill cuttings by graphite furnace atomic absorption spectrometry

An environmentally friendly method was developed using deep eutectic solvent ultrasound-assisted extraction procedure (DES-UAE) for Pb determination in drill cuttings (DC) by graphite furnace atomic absorption spectrometry (GF AAS). In this study, 50 mg of the DC samples in 2.50 g of diluted DES (30% w/w of water) was subjected to UAE at 80 ± 5 °C for 50 min. The extraction parameters, temperature, time, and percentage of water in the DES, were evaluated using a Box–Behnken experimental design. Lead was determined by GF AAS, using Pd as a chemical modifier, 900 °C of pyrolysis, and 2100 °C of atomization temperatures. The results demonstrated that DES composed of choline chloride and oxalic acid (1:1 molar ratio) combined to UAE, showed greater Pb extraction efficiency. The precision (RSD < 3.8), the respective limits of detection and quantification (0.2 and 0.6 µg g⁻¹), were suitable for Pb determination in DC. The method’s accuracy was evaluated through the analysis of certified reference materials and by comparing the results with those obtained by ICP-MS analysis after acid digestion and  no significant difference was observed (at 95% confidence level). The DES-UAE was applied to determine Pb in DC from different depths, with Pb concentration  ranging from 1.14 to 6.13 and 1.64 to 168.4 µg g⁻¹ for samples from onshore and offshore wells, respectively.