Development of a direct analysis technique for organic compounds adsorbed on environmental small particles

近年来，内分泌干扰化学品引起了人们的极大关注。由于许多这类物质是疏水性的，蒸气压低，环境中的小颗粒被认为是内分泌干扰物的载体。因此，建立适用于分析吸附在小颗粒上的有机物的技术是非常重要的。飞行时间二次离子质谱（TOF-SIMS）是一种灵敏度较高的表面有机物分析技术。镓聚焦离子束是目前TOF-SIMS中最常用的一次离子束，利用这种聚焦良好的一次离子束，成像分析的横向分辨率可达亚微米级，本文研究了TOF-SIMS在分析吸附在颗粒表面的有机物中的适用性，以评价其作为环境分析工具的价值。邻苯二甲酸二（2-乙基己基）酯、邻苯二甲酸二辛酯和2，2-双（4-羟基苯基）丙烷 关于我们 （双酚A）作为模型化合物。首先，将每种化合物约1个单层吸附在平坦的基底上，而不是颗粒上，并测量质谱。基底是银、覆盖有天然氧化物的硅和石墨。尽管光谱强度在银基底上高得多，但所有基底的碎裂模式相似。两种邻苯二甲酸二烷基酯均在m/z=149处产生最强的碎片峰，这是邻苯二甲酸酯的特征。烷基链产生的碎片峰在光谱中很弱，由于烃污染而难以分配。因此，很难区分邻苯二甲酸酯异构体。双酚A在m/z= 213处出现特征碎片峰。然后，将6.8 μ m的SiO2颗粒浸入稀溶液中，将双酚A或邻苯二甲酸二（2-乙基己基）酯吸附在SiO2颗粒上。将颗粒干燥并铺展在玻璃板上。通过将铟板压到颗粒上来制备TOS-SIMS样品。在50平方微米的面积上以256 x256像素分辨率进行光谱映射。根据二维光谱图数据，得到Si^+（m/z=28）、In^+（m/z=115）、邻苯二甲酸酯碎片离子（m/z=149）和双酚A碎片离子（m/z=213）的图谱。In^+和Si^+显示出互补的图谱。碎片离子的分布与Si^+的分布相同，另一个样品是分别制备的颗粒的混合物，一个吸附了邻苯二甲酸酯，另一个吸附了双酚A，放在铟板上。在混合物样品的视场中，通过比较碎片离子图来区分两种粒子。少

Large attention has been paid recently to endocrine disrupting chemicals. Because many of such substances are hydrophobic and of low vapor pressure, environmental small particles are believed to act as carrier of endocrine disrupters. Therefore, it is very important to establish techniques appropriate to analyze organic species adsorbed on small particles. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is well known as one of the most sensitive analytical techniques applicable for surface organic species. Gallium focused ion beam is now the most popular primary ion beam of TOF-SIMS.By using this finely focused primary ion beam lateral resolution of mapping analysis reaches to sub-micrometer region.The authors examined the applicability of TOF-SIMS to the analysis of organic species adsorbed on individual small particles in order to evaluate the technique as an environmental analytical tool. Di (2-ethylhexyl) phthalate, dioctyl phthalate and 2, 2-bis (4-hydroxyphenyl) propane … More (bisphenol-A) were used as model compounds. All of them are suspected as endocrine disrupters.First, about 1 monolayer of each compound was adsorbed on flat substrates instead of particles, and mass spectra were measured. Substrates were silver, silicon covered with native oxide, and graphite. Although spectral intensity was much higher on silver substrate, fragmentation pattern was similar for all substrates. Both of dialkyl phthalates yielded the most intense fragment peak at m/z=149, which is characteristic of phthalates. Alkyl-chain-originated fragment peaks were weak in the spectra and were difficult to assign because of hydrocarbon contamination. Therefore, distinction of phthalate isomers was difficult. Bisphenol-A showed characteristic fragment peak at m/z=213.Next, di (2-ethylhexyl) phthalate or bisphenol-A was adsorbed on 6.8 micrometer silica particles by dipping the particles into dilute solutions. The particles were dried and spread on a glass plate. By pressing an indium plate onto the particles TOS-SIMS samples were prepared. Spectral mapping was performed over 50 micrometer square area by 256x256 pixel resolution. From the 2-dimensional spectral map data Si^+(m/z=28), In^+(m/z=115), phthalate fragment ion (m/z=149), and bisphenol-A fragment ion (m/z=213) maps were obtained. In^+ and Si^+ showed complementary maps with each other. Fragment ions showed the same distribution as Si^+.Another sample was the mixture of separately prepared particles, one adsorbed phthalate and the other bisphenol-A, on an indium plate. In a view field of the mixture sample two kinds of particles were distinguished from each other by comparing fragment ion maps. Less