Hollow Fiber Flow Field Flow Fractionation Coupled With ICP-MS For Analysis Of Gold Nanoparticles In Environmental Water

Nanoparticles?NPs?have roused great attention and are widely used in various fields due to their unique physical and chemical properties.With the rapid increase of their production and application,more and more NPs are released into the environment,posing potential threat to ecological environment and human health.It has been demonstrated that the toxicological effects of NPs are closely related to their composition,size,concentration and coating.For accurate assessment on their environmental toxicology and health risks,it's necessary to obtain the information of the composition,content,size,and coating of these NPs.Inductively coupled plasma mass spectrometry?ICP-MS?is a high sensitive detection technique for trace elements analysis.While,the analysis of metal-containing NPs by ICP-MS is still a challenge,since NPs can't be distinguished from the corresponding metal ions,NPs with different sizes and coatings can't be distinguished,or the concentration of NPs is extremely low with the presence of complex sample matrix.In order to solve these problems,it's a feasible solution to choose appropriate separation techniques or sample pretreatment techniques before ICP-MS detection.Field flow fractionation?FFF?is a chromatographic technique which has no stationary phase and can maintain the original morphology of analytes,enabling high resolution separation of analytes with size ranging from 1 nm to 100?m.Hollow fiber flow field flow fractionation?HF5?employs a disposable hollow fiber?HF?as the separation channel,which has the advantages of low cost,low consumption of sample and mobile phase.Metal ions and matrix components can flow into the waste liquid through the pores of membrane without interfering with the analysis of NPs.In addition,the flow rate in the HF is low and compatible with sample introduction into ICP.Magnetic solid phase extraction?MSPE?is a simple and efficient sample pretreatment technique with high enrichment factors and good clean-up ability.The problem of high dilution factor of sample in FFF can be improved by coupling MSPE with FFF.While relevant research work are still very scarce.The aim of this dissertation is to couple HF5 with ICP-MS for NPs analysis,to establish a method based on HF5-ICP-MS to analyze trace Au NPs in environmental water,and investigate the factors affecting the size variation of Au NPs;and to develop a method based on MSPE-?HF5?-ICP-MS for analysis of trace Au NPs in environmental water.The main contents are described as follows:?1?High resolution separation of 3,13 and 30 nm Au NPs was achieved by using30 kDa polyacrylonitrile?PAN?membrane as the separation channel and optimizing the experimental conditions such as the mobile phase concentration,crossflow rate,and focusing time.Polystyrene nanoparticles?PS NPs?were introduced into the optimized HF5 system with Ultraviolet/Visible?UV/Vis?detection.The standard curve was constructed for calibrating the sizes of Au NPs by plotting the particle sizes against the retention time values of PS NPs.A method based on HF5-ICP-MS was developed for separation,characterization and quantification of Au NPs with different sizes and investigating the effects of the ionic strength,humic acid?HA?and other factors in environmental water on the size variation of Au NPs.Compared with commonly used characterization techniques for NPs?e.g.,transmission electron microscopy,dynamic light scattering?,the method of HF5-ICP-MS has the advantages of simple operation and high precision,which is more suitable for the analysis/characterization of NPs at extremely low concentration level??g/L?.?2?3-aminopropyltriethoxysilane?APTES?modified magnetic sorbents Fe₃O₄@SiO₂@APTES was prepared,and the adsorption of Au NPs and gold ions on Fe₃O₄@SiO₂@APTES were investigated.The results showed that Au NPs were adsorbed quantitatively within a wide pH range?2-11?,and cysteamine could be used for the complete desorption of the adsorbed AuNPs from Fe₃O₄@SiO₂@APTES.Based on it,a method based on MSPE-ICP-MS was developed for the analysis of trace Au NPs in environmental water samples,and the adsorption and desorption conditions were optimized.Under the optimized conditions,the limit of detection of 1.38 ng/L with enrichment factor of 100 fold was obtained for Au NPs.The proposed method was employed for trace Au NPs analysis in real water samples.The recoveries of 90.4-92.5%were obtained in tap water sample,while low recoveries were obtained for lake water samples,probably due to the relatively high content of organic substance in the water matrix.MSPE was then coupled with HF5-UV/Vis for the characterization of Au NPs before and after extraction.The peak width of Au NPs after extraction increased,and the signal peak corresponding to uneven small particles disappeared.It's speculated that the thickness of the electrical double layer between Au NPs and HF is changed by the cysteamine solution,causing the agglomeration of Au NPs.