Colorimetric Assays Of Foods And Drugs Based On Gold Nanoparticles

Gold nanoparticles(Au NPs) exhibit unique optical, electrochemical and catalytic properties strongly depending upon their size and shape. For example, after gold nanoparticles interact with some organic functional groups by hydrogen bonding, van- der Waals and chemical covalent bond, the feature peaks that represent recognition particles in UV-vis spctra can change, which achieve the purpose of identification and detection. Based on the optical properties of gold nanoparticles, in this article, the gold nanoparticles aggregation colorimetric method was applied for the detection of nicotinamide in pills and thiourea in food,meanwhile,any organic solvents was not used in sample pretreatment, thus, the method achieved the simple,rapid, sensitive and green determination for nicotinamide and thiourea. This article will be divided into three chapters. Its content is as follow:Chapter 1: Introduction. The chapter reviewed the history of gold nanoparticles, and summarized its preparation, properties and applications. Based on molecular recognition properties of gold nanoparticles, gold nanoparticles can bond with amino(-NH2) and thiol group(-SH), etc., so that the feature peaks in UV-vis spctra will change, so as to achieve the purpose of identification and detection. In view of this, in this paper, the gold nanoparticles aggregated colorimetric method was applied for the detection of the substances in drugs and foods, for achieving the rapid, sensitive and green detection as the research vision and ideas.Chapter 2: Based on the crosslinking mechanism of gold nanoparticles combinating with amino(-NH2), the paper established the gold nanoparticle aggregation colorimetric method for the determination of nicotinamide. This chapter investigated the influence of the p H value of the buffer solution, the reaction temperature and the reaction time on the interaction of gold nanoparticles with nicotinamide, which derived the optimal experimental conditions as follows: p H = 4.0; the reaction temperature 10 ℃; reaction time 60 min. Meanwhile, under the optimal conditions, the influence of some interfering substances on the interaction of gold nanoparticles with nicotinamide was investigated. Under the optimal conditions, the linearity of the target analyte between 2.5 ~ 5.5 mg/L was good, and the linear regression equation was Y = 0.32289X-0.6013, R2 was 0.996. This method had been successfully applied to the determination of nicotinamide in nicotinamide tablets. The recoveries of real samples and spiked samples were between 68.8-88.3%, and the relative standard deviations were between 0.8-2.2%. In the whole experiment, any volatile and toxic solvents were no used, and the operations and the instruments were simple, so this method exhibits the features of simple, convenient and environmently friendly.Chapter 3:Based on the non-crosslinking mechanism of gold nanoparticles combinating with thiol group(-SH), the paper established the gold nanoparticle aggregation colorimetric method for the determination of thiourea in drinks. This chapter investigated the influence of the p H value of the buffer solution, the reaction temperature and the reaction time on the interaction of gold nanoparticles with thiourea, which derived the optimal experimental conditions as follows: p H = 3.0; the reaction temperature 10 ℃; reaction time 3 min. Meanwhile, under the optimal conditions, the influence of some interfering substances on the interaction of gold nanoparticles with thiourea was investigated. Under the optimal conditions, we obtained the linear range of the target analyte between 0.02-0.16 mg/L, the linear regression equation Y = 0.32289X-0.6013, R2 0.996 and the limit of detection(LOD) 1.18 μg/L(n=11). Under the optimal conditions, two kinds drinks were determined and no thiourea was detected. The recoveries of spiked samples were between 80.0~103.6%, and the relative standard deviations were between 2.3-8.6%. This method exhibits the features of simple operations, simple instruments, high sensitivity and being environmently friendly. Therefore, this method has certain feasibility and promising applications.