Preparation of Oxine Modified Functional Magnetic Particles and Its Application to Voltammetry Determination of Trace Amount of Lead in Water Sample

Magnetic Fe₃O₄ particles were prepared and modified by its reaction with 3-aminopropyl-triethoxysilane (APS) in ethanol medium and with 10% (volume fraction) of glutarldehyde solution in aqueous medium in succession to form aldehyde groups on the surface of Fe₃O₄ particles. And in its further reaction with 8-hydroxyquinoline (Ox) in phosphate buffer medium of pH 6.8, thus the Ox modified functional magnetic particles of Fe₃O₄ (abbrev as Fe₃O₄/Ox) was obtained. It was shown that Fe₃O₄/Ox particles have strong complexing action towards Pb²⁺ ion. On this basis, magnetic Fe₃O₄/Ox particles were applied to the preconcentration and separation of trace amounts of Pb²⁺ from water sample for the anodic stripping voltammetric determination. In the analysis, 50.0 mL of water sample were transferred to a small beaker and 1.5 mL of suspension of Fe₃O₄/Ox particles in pH 6.8 phosphate buffer solution were added and stirred for 20 min. The magnetic particles were settled at the bottom of the beaker by the action of a magnet at outside of the beaker, and the supernatant was separated and discarded. 1 mL of 1 mol·L^-1 HCl solution was added to the magnetic particles to dissolve Pb²⁺ from its oxine-complex adsorbed on the surface of the particles. The solution was diluted to 5.0 mL with water and analyzed by voltammetry. GCE was used as working electrode, Ag/AgCl was used as reference electrode and Pt-electrode as counter electrode. Pb²⁺ ion the solution was first electrodeposited at the cathode for 50 s, and then defermined by anodic stripping voltammetry. Stardard curve was prepared with standard lead solution. Linear relationship between values of derivate of oxidation current found and the respective mass concentrations of lead was obtained within 0.50 mg·L^-1. Value of detection limit (3S/N) found was 0.7 μg·L^-1. Six samples of enviromental water were analyzed by this method, giving results in consistency with the known values. RSDs (n=5) found were in the range of 0.48%-3.5%. Recovery was tested by the standard addition method, giving values of recovery ranged from 91.0%-138%.