Hydrophobic deep eutectic solvent-based vortex-assisted dispersive liquid-liquid microextraction with UV-visible spectrophotometry for copper determination in waste printed circuit boards

Nearly all electronic devices utilise Printed Circuit Boards (PCBs), which contribute significantly to the generation of electronic waste (e-waste). They are rich in metal content, with copper being present in higher percentages. In this work, a simple, efficient and environment-friendly pre-concentration technique was developed, using hydrophobic deep eutectic solvent as an extractant in vortex-assisted dispersive liquid-liquid microextraction. This pre-concentration technique is coupled with spectrophotometry for the determination of copper in PCBs. The complexing agent, sodium diethyl di-thiocarbamate (DDTC), and copper formed a complex in the 2-3 pH range. The Cu-DDTC complex was vortexed for 1 min at 2800 rpm to extract in hydrophobic DES. The sediment was analysed using a UV-Visible spectrophotometer at lambda max 435 nm. The optimisation parameters, including pH, extraction solvent selection and its volume, concentration and volume of chelating agent, interference of forein ios, etc., have been assessed. Analytical figures of merit such as limit of detection (1.98 mu g/L), limit of quantification (5.9 mu g/L), relative standard deviation (3.4%) and enrichment factor (10) have been obtained under optimal experimental conditions. The method was validated by a certified copper solution and applied successfully to determine copper in waste PCBs of personal computers.