工程奈米材料被大量生產並應用於消費品和食品。許多工業處理程序，例如半導體製程中的化學機械平坦化也涉及工程奈米材料的使用。二氧化矽奈米顆粒是最常用的工程奈米材料之一。因此，需要建立一套方法來鑑定水環境中的二氧化矽奈米顆粒的尺寸分佈及質量濃度，以評估二氧化矽奈米顆粒相關產品在其生命週期中釋放到環境的潛在暴露風險。
本研究中，我們比較尺寸排除層析儀串聯感應耦合電漿質譜方法與單顆粒式感應耦合電漿質譜方法用於鑑定水環境介質中之二氧化矽奈米顆粒，結果表明單顆粒式感應耦合電漿質譜方法無法分析50 nm二氧化矽奈米顆粒的尺寸，這要歸因於多元子干擾物的大量訊號(28氮氣)導致奈米顆粒的訊號被隱藏在背景訊號之下。相比之下，尺寸排除層析儀串聯感應耦合電漿質譜方法可以容易的分析到二氧化矽奈米顆粒的尺寸大小。與單顆粒式感應耦合電漿質譜方法不同，顆粒表徵的功能發生在尺寸排除層析儀中。本研究使用多種流洗液，十二烷基硫酸鈉(10 Mm、pH = 11)作為流洗液，可以得到較好的質量回收率；FL-70(2% (v/v)、pH = 11)作為流洗液，則可以得到良好的尺寸分離效果。後續使用十二烷基硫酸鈉作為流洗液，我們成功使用尺寸排除層析儀串聯感應耦合電漿質譜方法與流體動力層析儀串聯感應耦合電漿質譜方法建立奈米金顆粒尺寸(20-100 nm)與停留時間的關係，並使用此關係成功分析二氧化矽奈米顆粒的尺寸(20, 50, 80 nm)。使用尺寸排除層析儀串聯感應耦合電漿質譜方法對於二氧化矽奈米顆粒的質量偵測極限落在0.8 mg/L。最後，我們使用尺寸排除層析儀的方法鑑定科學園區中廢水樣本裡的二氧化矽奈米顆粒，結果表明因為分析矽的背景強度仍然太高而導致無法偵測到矽相關的奈米顆粒。雖然仍需要進行更多的改進，但研究中結果表明，尺寸排除層析儀串聯感應耦合電漿質譜方法用於鑑定水環境介質中之二氧化矽奈米顆粒是有前景的方法。

A large variety of engineered nanomaterials (ENMs) are produced and applied in the manufacturing of consumer and food products. Many industrial processes, such as chemical mechanical planarization (CMP) in semiconductor manufacturing also involves the use of ENMs. Silica nanoparticles (SiO2NPs) are arguably one of the most commonly used ENMs. Therefore, there is a need to establish a method to characterize the size distribution and the mass concentration of SiO2NPs in aqueous environments to evaluate their potential exposure when they are released into the environment during the life cycle of SiO2NPs-enabled products and processes.
In this study, we compared two methods, namely, size exclusion chromatography (SEC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS) and single particle-ICP-MS (spICP-MS), in the characterization of SiO2NPs in aqueous environment. The results of the study show that spICP-MS could not size nanoscale SiO2NPs, such as 50 nm SiO2. This can be attributed to the strong polyatomic interferences (e.g., 28N2+), resulting in strong background that masks the particle events. In comparison, SEC-ICP-MS could readily size SiO2NPs, as the size characterization mainly occurs on the SEC column, a principle distinct from spICP-MS. In this study, we used various eluents, 10 mM sodium dodecyl sulfate (SDS) at pH = 11 as an eluent had better mass recovery; 2% FL-70 at pH = 11 as an eluent had better size separation performance. We used SDS as our subsequent eluent and successfully established the size-retention time relationship (i.e., size calibration curve) using 20-100 nm well-characterized AuNPs with SEC-ICP-MS and hydrodynamic chromatography-ICP-MS (HDC-ICP-MS). The methods were successfully used to characterize SiO2NPs with sizes of 20 nm, 50 nm, and 80 nm. The mass detection of SEC-ICP-MS was currently limited to 0.8 mg/L. Lastly, the SEC-ICP-MS method was used to characterize SiO2NPs in the wastewater sample from a science park. The result indicates no detectable Si NPs, likely limited by the still high Si mass detection limit of the method. While more improvements need to be done, our result indicate that SEC-ICP-MS is a promising method to size SiO2NPs in the aqueous environments.

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