|Budget Amount *help
¥11,600,000 (Direct Cost : ¥11,600,000)
Fiscal Year 2000 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1999 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1998 : ¥9,600,000 (Direct Cost : ¥9,600,000)
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
(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