Pipette-tip SPE based on Graphene/ZnCr LDH for Pb(II) analysis in hair samples followed by GFAAS

In this work, a nanocomposite of ZnCr layered double hydroxide (ZnCr LDH) and graphene oxide (GO) was successfully assembled. An efficient pipette-tip solid-phase extraction (PT-SPE) based on GO/ZnCr LDH followed by GFAAS analysis was used for to preconcentrate Pb(II) in hair samples. Hair samples were treated using acid digestion to make the solid samples suitable for performing the PT-SPE procedure and decrease the interactions between Pb(II) ions and the sample matrix. The sorbent was characterized by FT-IR, SEM, TEM, EDX, elemental mapping, and XRD. Effective extraction parameters were thoroughly investigated. Under the best conditions, the calibration plot was linear within the range of 0.5-15 ng mL^-1 (R² = 0.991). Preconcentration factor (PF) of 10 and absolute recovery (%) of 100% were obtained. LOD and LOQ were found to be 0.1 μg g^-1 and 0.5 μg g^-1, respectively. The intra-day and inter-day precisions (n = 3) at the concentrations of 2.0 and 10 ng mL^-1 were less than 6.8% and 12.5%, respectively. Finally, the method efficiency was investigated for the analysis of Pb(II) in hair samples, and good relative recoveries (RR%) were obtained within the range of 92%-104%.