title: Colorimetric detection of melamine during the formation of gold nanoparticles.
abstract: A sensitive and simple colorimetric method for determination of melamine was reported based on the seedless production of gold nanoparticles (Au-NPs). Au-NPs were synthesized by using pyrocatechol-3,5-disodiumsulfonate (PD) as reducer without adding nanoparticles seeds and stabilizing agent. PD can form intramolecular hydrogen-bonding in solution by adjacent sulfurnate and α-phenolic hydroxyl group, resulting in its weak reducing capacity and thus the synthesis of Au-NPs was slow. While in the presence of melamine, PD reacted with melamine through hydrogen-bonding. Therefore, the intramolecular hydrogen-bonding of PD was interrupted by melamine, and the α-phenolic hydroxyl group was free to reduce Au(3+), hence, the synthesis of Au-NPs was accelerated. Especially, the presence of melamine led to a shift in the surface plasmon bond and a color change of Au-NPs from green to yellow. Results showed that the absorbance ratio (A(436)/A(600)) was linear with the logarithm of melamine concentration in the range of 4.8×10(-9) to 1.6×10(-6) M with a correlation coefficient of 0.9949. The detection limit (3σ) obtained by UV-vis spectrum was 6.4×10(-10) M (i.e., 0.08 ppb). The proposed method was applied successfully to the determination of melamine in pretreated liquid milk products, and the recoveries were from 93% to 107%.
authors.affiliation: College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, 19A YuQuan Road, Beijing 100049, China.
authors.forename: Zhijiao
authors.initials: Z
authors.lastname: Wu
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: Xue
authors.forename: Qian
authors.initials: Q
authors.lastname: Cao
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.forename: Yujian
authors.initials: Y
authors.lastname: He
authors.forename: Xiangjun
authors.initials: X
authors.lastname: Li
authors.forename: Zhuobin
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000818:Animals; D002417:Cattle; D003124:Colorimetry / Q000295:instrumentation*; D005504:Food Analysis / Q000295:instrumentation*; D005506:Food Contamination / Q000032:analysis*; D006046:Gold / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation; D014227:Triazines / Q000032:analysis*
chemical_list: D014227:Triazines; D006046:Gold; C011907:melamine