| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 103 === Engineered nanoparticle has widely used in medical products, cosmetics, textiles and food additives. In particular, silver nanoparticle (Ag NP) has become one of the most extensive used nanomaterials in the world. The potential risks of Ag NP were controlled by their fates and transformations once released into the environment. As a result, many emerging analytical techniques have been developed in recent years and used to detect the NPs in the water, including hydrodynamic chromatography (HDC), asymmetric flow field-flow fractionation (AF4) and single particle inductively coupled plasma-mass spectrometry (SP-ICP-MS). However, these techniques have just applied to detect NPs in pure water system so far. Therefore, this study aims to establish a methodology for determining the particle size and concentration of Ag NP in the aquatic environment.
The average particle sizes of two types of commercial Ag NP solutions were 79.9 and 122 nm, respectively. In water samples, the pH values ranged from 6.9 to 8.4 and the conductivities were between 375 and 11200 μS/cm as well as various particles. The stability of Ag NP in different solutions showed that pH did not cause a lot of effects on the aggregation of Ag NPs. However, Ag NPs aggregated obviously in the electrolytic systems. CaCl2 caused a more significant effect than the NaCl since the divalent cations could compress the electrical double layer of Ag NP more easily. Besides, the aggregation and dissolution levels of Ag NP were reduced under low temperatures since the NP-NP collision frequency could be inhibited. Therefore, environmental samples containing NPs should be preserved under a low temperature without pH adjustment.
The result of pretreatment indicated that centrifugation with centrifugal speed of 2000×g for 2 minutes has a better performance for the removal of interferences, thus obtaining a higher recovery of Ag NP than filtration. For the HDC, a good correlation coefficient (R2 >0.99) was achieved with pH 10 water as a mobile phase. The particle size of Ag NP by HDC was consistent with DLS analysis in different water samples. AF4 can also determine the size of Ag NPs well but with low recoveries, which could result from the interactions between Ag NP and working membrane. For the SP-ICP-MS, both particle size and concentrations can be determined with high overall recoveries. The size results from SP-ICP-MS also corresponded to the TEM (p>0.05). Therefore, HDC and SP-ICP-MS were recommended for the environmental samples after the established pretreatment process. Combined the transformation studies of NPs and these analytical methods; the methodology to quantify and qualify the NPs in the aquatic environment was proposed.
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