串聯微分電移動度粒徑分析系統與單顆粒感應耦合電漿質譜儀分析溶解離子對自來水中鐵和鉛奈米微粒的影響

Abstract

金屬奈米微粒是近年工業製造常用材料，若其流入環境中，可能對生物健康造成危害。金屬奈米微粒的特性與粒徑大小、濃度與化學組成有關。雖然單顆粒感應耦合電漿質譜儀(single particle inductively coupled plasma mass spectrometry, spICP-MS)已被應用在分析金屬奈米微粒，但須假設該奈米微粒為純金屬且為球形，因此，針對環境樣品所得的粒徑分析結果，通常存在偏差。 本研究串聯霧化器(atomizer, ATM)、微分電移動度分析儀(differential mobility analyzer, DMA)和spICP-MS (ATM-DMA-spICP-MS)，並於ATM後結合一高溫爐乾燥避免顆粒聚合作為分析水樣中金屬奈米微粒之方法，因此方法先對金屬奈米微粒選徑後再分析金屬元素，可避免spICP-MS獨立分析時的誤差。但因使用高溫爐，若水樣中存在該金屬離子，則可能在乾燥過程中結晶形成新的奈米微粒，造成分析誤差。為評估離子濃度影響，本研究使用金標準奈米微粒添加金離子進行測試，並嘗試以離心前處處理分離離子和水中原始顆粒再進行分析，以去除離子造成的干擾，並應用該方法分析自來水中鐵和鉛奈米微粒的粒徑和濃度。 於金標準顆粒的分析測試中，添加金離子濃度使訊號半高寬(Full width at half maximum, FWHM)變大，由9.89增大至12.33，並測得較標準微粒粒徑小的金奈米微粒峰值，粒徑範圍約25-35 nm，經離心降低離子濃度後，該峰值明顯下降，顯示高的離子濃度確實會干擾測量結果但可藉由離心前處理去除該干擾。針對自來水樣品的分析，結果顯示該水樣內含有主要粒徑（mode size）為110 nm、濃度為2.74 x 107#/mL的鐵奈米微粒，和有主要粒徑為100 nm、濃度為7.48 x 106 #/mL的鉛奈米微粒，推測這些鐵與鉛奈米微粒可能由氧化鐵、碳酸鉛等管線腐蝕產物構成。 總體而言，ATM-DMA-spICP-MS的串連系統可同時獲得粒徑大小、濃度、和元素等分析資訊，使用離心可減少溶液離子對於分析的干擾。對於日後分析環境水樣中的金屬奈米微粒，此研究提供另一分析方法與參考標準。

Metallic nanoparticles (NPs) are widely used in industrial applications in recent years but their release into the environment raises concerns about potential health risks. The characteristics of metallic NPs, such as size, particle number concentration, and chemical composition, play a crucial role in understanding their behavior and potential impacts. Although single particle inductively coupled plasma mass spectrometry (spICP-MS) has been applied for the analysis of metallic NPs, it assumes that the metallic NPs are all pure metals and spherical in shape, which are not true for most environmental samples and may introduce inherent errors in size analysis. In this study, a method combining an atomizer (ATM), differential mobility analyzer (DMA), and spICP-MS (ATM-DMA-spICP-MS) was utilized for the analysis of metallic NPs in water samples. This method measures NPs size using DMA before elemental analysis using spICP-MS and a high-temperature furnace was employed for drying samples to prevent particle aggregation. However, if metal ions are present in the water samples, they can crystallize and form new NPs in the drying process leading to analytical errors. To evaluate the impact of ion concentration on the determination of size and particle number concentration of NPs, experiments were first conducted by introducing gold ions water samples containing to gold NPs and centrifugation was explored as a pretreatment to separate gold ions from the gold NPs to eliminate the potential interferences. The results showed that the addition of gold ions increased the full width at half maximum (FWHM) of the signals (from 9.89 to 12.33) and a new peak of smaller-sized gold NPs (25-35 nm) appeared, indicating the interferences caused by gold ions. After centrifugation, the interferences can be significantly eliminated, showing that effectiveness of this pretreatment. The method was then applied to analyze the size and particle number concentration of iron and lead NPs in tap water. For the tap water sample collected on the National Taiwan University campus, the results revealed the presence of iron NPs with a mode size of 110 nm and a concentration of 2.74 x 107 #/mL, and lead NPs with a mode size of 100 nm and a concentration of 7.48 x 106 #/mL. These iron and lead NPs were likely iron oxides and lead carbonate derived from corrosion of plumbing materials containing iron and lead in the pipelines. In summary, the hyphenated ATM-DMA-spICP-MS system allows simultaneous analysis of particle size, particle number concentration, and elemental composition. The use of centrifugation reduces interference caused by ions in the analysis. This study provides an alternative method for the analysis of metallic NPs in environmental samples.