@article{oai:repo.qst.go.jp:00049211,
 author = {Zheng, Jian and Cao, Liguo and Tagami, Keiko and Uchida, Shigeo and 鄭 建 and 田上 恵子 and 内田 滋夫},
 issue = {17},
 journal = {Analytical Chemistry},
 month = {Sep},
 note = {High yield fission products, 135Cs and 137Cs, have entered the environment as a result of anthropogenic nuclear activities. Analytical methods for ultra-trace measurement of 135Cs and 137Cs are required for environmental geochemical and nuclear forensics studies. Here we report a highly sensitive analytical method combining the APEX-Q desolvation sample introduction system with triple-quadrupole inductively coupled plasma-mass spectrometry (AEPX-ICP-MS/MS) for the determination of 135Cs and 135Cs/137Cs isotope ratio at femtogram levels. Using the APEX-ICP-MS/MS system, we introduced only selected ions into the collision/reaction cell to react with N2O, significantly reducing the isobaric interferences (135Ba+ and 137Ba+) and polyatomic interferences (95Mo40Ar+, 97Mo40Ar+, 119Sn16O+, and 121Sb16O+). Compared to the standard instrument setup of ICP-MS/MS, the APEX-ICP-MS/MS enables a 10-fold sensitivity increase. In addition, an effective chemical separation scheme consisting of AMP Cs-selective adsorption and two-stage ion-exchange chromatographic separation was developed to remove major matrix elements and interfering elements from environmental samples (10-40g). This separation method showed high decontamination factors (104-107) for major matrix elements (Al, Ca, K, Mg, Na and Si) and interfering elements (Ba, Mo, Sb and Sn). The high sensitivity of APEX-ICP-MS/MS and the effective removal sample matrix allowed reliable analysis of 135Cs and 137Cs isotopes with extremely low detection limits (0.002 pg mL-1). The accuracy and applicability of the APEX-ICP-MS/MS method was validated by analysis of seven standard reference materials (soils, sediment and plants). For the first time, ultra-trace determination of 135Cs and 135Cs/137Cs isotope ratio at global fallout source environmental samples was achieved with the ICP-MS technique.},
 pages = {8772--8779},
 title = {Triple-quadrupole inductively coupled plasma-mass spectrometry with a high-efficiency sample introduction system for ultra-trace determination of  135Cs and 137Cs in environmental samples at femtogram levels},
 volume = {88},
 year = {2016}
}