| 英文摘要 |
The purpose of this project is to establish a DMA-spICP-MS system for continuous analysis of trace metals in ambient particles for at least 6 h. Relevant journal articles and technology workshops were provided in this project as references for future system establishment and application. This project comprised of three main parts. First, we have established and validated a DMA-spICP-MS system. Second, a GED-ICP-MS system was developed and validated. Third, the system was used for real-time analysis in an ambient air environment.
For the DMA-spICP-MS system, we used 30, 50, and 80-nanometer gold particles (AuNPs) to verify DMA. Compared to the TEM and spICP-MS results, the DMA results showed an obvious deviation with particle sizes larger than 70 nm. Based on previous studies, we hypothesized that excess liquid on the surface of the particles might influence the DMA-selected performance. As a result, a furnace was adopted in the system to remove unwanted liquids, which successfully improved the results. As we aimed to collect ambient particles in ICP-MS, the biggest challenge resided in the replacement of air for argon, which acted as the carrier gas in ICP-MS. To solve this problem, a homemade GED device was developed to replace air with argon for the subsequent ICP-MS analysis. In terms of the gas exchange efficiency of the GED, the sample flow (Qa) and sweep flow (Qsweep) were set as 0.2 L/min and 6.0 L/min, respectively. Under these conditions, the gas exchange efficiency was approximately 80%, and the purity of argon reached 96.5% along with the injection of auxiliary gas. For the system evaluation, clean pure argon was used as the blank sample. According to the results, the trace signal of the blank sample was significantly lower than those of other air samples, demonstrating the feasibility and reliability of our system. In addition, to understand the influence of different gas media and their air exchange rate under the detection limit (LOD=3.3×σy-intercept /slope) of GED-ICP-MS, we calibrated the system with zero gas and purified air. The results showed that the air exchange rate had a low influence on the slope of the calibration curve and the LOD. However, for different gas media, it was found that the sensitivity of ICP-MS was strongly affected by the matrix (the slope had a difference of approximately 1-2 times), which should be cautioned and addressed. Finally, the results of the continuous analysis of GED-ICP-MS for 6 h showed that, except for Fe and Al, the concentrations of all the other metals were similar to those in previous related studies.
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