Application of Semi Automated Pipette-Tip Solid-Phase Microextraction Technology Based on Chitosan Modified Magnetic Graphene Oxide in Rapid Determination of Trace Lead in Environmental Water

By modifying graphene oxide (GO) with chitosan (CS) and Fe₃O₄ using glutaraldehyde as the crosslinking agent, the composite of Fe₃O₄-GO/CS (adsorbent) was prepared. The 20 mg of Fe₃O₄-GO/CS was filled into a 200 μL-micro gun head, and a small amount of glass wool was filled into both ends, with a magnet around the gun head. Then the gun head was connected with a 12 mL-plastic syringe, and 1 mL of water was taken by the plastic syringe to rinse impurities that might be adsorbed on the surface of Fe₃O₄-GO/CS. Environmental water samples were passed through a 0.22 μm filter membrane, and the acidity of the filtrate was adjusted to pH 6.0. Then 10 mL of water sample was taken by the plastic syringe, which was fixed on the infusion pump. The water sample was passed through the gun head at flow rate of 0.8 mL·min⁻¹. Then 1 mL of 0.010 mol·L⁻¹ hydrochloric acid solution (eluent) was taken for elution of lead adsorbed on Fe₃O₄-GO/CS at flow rate of 0.5 mL·min⁻¹. The eluate was collected and determined by inductively coupled plasma mass spectrometry. It was shown that the equilibrium adsorption capacity of Fe₃O₄-GO/CS (which could be reused 50 times) to lead was 126 mg·g⁻¹, and the adsorption process followed the Langmuir isotherm model. Linear relationship between values of the mass concentration and response value of lead was kept in the range of 0.01-10.00 μg·L⁻¹, with detection limit of 0.005 μg·L⁻¹. Test for the spiked recovery at 3 concentration levels was conducted on actual water samples, giving recoveries in the range of 84.7%-105%, and RSDs (n=5) of the determined values ranged from 0.90% to 3.9%.