Determination of Heavy Metal Pb in Vegetables with Gold Nanoparticles

Aurichlorohydric acid, H［AuCl4］ was reduced by sodium borohydride to give gold nanoparticles (AuNP′s). An appropriate amount of the AuNP′s was added to a mixed solution of H［AuCl4］-K2CO3 and reacted with mixed solution of gallic acid (GA)-NaCl to give AuNP′s functionalized with gallic acid (abbrv. as GA-AuNP′s). It was shown that GA on the surface of AuNP′s can react with Pb(Ⅱ) ion to form a complex, leading to bathochromic shift of absorption maximum of localized surface plasma resonance (LSPR), and that linear relationship between values of lgcPb(Ⅱ) and magnitude of the bathochromic shift (λ) was kept in the range of 2.7×10-8 to 5.1×10-6mol·L-1 of Pb(Ⅱ), with detection limit (3S/N) of 1×10-9mol·L-1. Based on these facts, by using GA-AuNP′s, a spectrophotometric method for determination of traces of Pb(Ⅱ) in vegetables was proposed. An eggplant sample was analyzed by this method, and recovery was tested by standard addition method, giving results of recovery in the range of 93.1% to 111% with values of RSD′s (n=6) less than 2%.