17:15 〜 18:45
[HTT16-P14] 酸素/水素リアクションモードICP-MS/MSによるヒ素、セレン分析における希土類元素2価イオン干渉の発生と低減法の探索
キーワード：ICPMS、コリジョン/リアクションセル、ヒ素、セレン
Arsenic (As) and selenium (Se) are categorized to toxic elements. As is a known human carcinogen, and Se toxicity can occur with ingestion of excess selenium, known as selenosis. It is important therefore to monitor As and Se concentrations in the environment. Inductively coupled plasma mass spectrometry (ICP-MS), which is highly sensitive, robust to matrix, and rapid in simultaneous multi-element analysis, is one of the most suitable techniques for the analysis of inorganic elements in the environment. However, the most popular quadrupole ICP-MS instruments cannot separate interferences such as 40Ar35Cl+ and 150Sm++ for 75As+ and 40Ar40Ar+ and 160Gd++ for 80Se+. To overcome this problem, a mass-shift method has been proposed in which As+ and Se+ are converted to AsO+ and SeO+ by ion-molecule reactions with O2 or O2/H2 in the collision/reaction cell (CRC) in a triple quadrupole ICP-MS (ICP-MS/MS). Although this method can almost completely eliminate the main interferences, such as ArCl+ and ArAr+, it may by-produce new interferences, like SmO2++ and GdO2++ in the CRC. To the best of our knowledge, productions of these REEO2++ interferences have not been fully investigated.
In this study, we systematically investigated the degrees of REEO2++ interferences according to the CRC conditions to find optimum conditions for As and Se analysis by reaction-mode ICP-MS/MS using O2 or O2/H2 gas mixtures. Standard solutions containing 10 mg/L of four rare earth elements (Nd, Sm, Gd, and Dy) that may interfere with 75As, 77Se, 78Se, 80Se, and 82Se, respectively, were prepared and introduced into ICP-MS/MS to investigate the relationship between O2 and H2 flow rates and REEO2++ production rate.
As a result, the presence of REEO2++ interferences was confirmed for all As and Se isotopes. As the most severe case on 77Se16O+, a maximum 154Sm16O2++ signal equivalent to about 300 ng/L Se was observed in a 10 ppm Sm solution. With the exception of Gd, the REEO2++ production rate tended to increase significantly with increasing H2 flow rate, suggesting that H2 is likely to be involved in the formation pathway. On the other hand, the presence of H2 slightly increases the production rates of AsO+ and SeO+, which may cause significant interference if the H2 is introduced to CRC in favor of As and Se sensitivity. In this presentation, the optimal conditions for As, Se analysis under high concentration of rare earth elements matrix, and the formation process of REEO2++ will be discussed.
In this study, we systematically investigated the degrees of REEO2++ interferences according to the CRC conditions to find optimum conditions for As and Se analysis by reaction-mode ICP-MS/MS using O2 or O2/H2 gas mixtures. Standard solutions containing 10 mg/L of four rare earth elements (Nd, Sm, Gd, and Dy) that may interfere with 75As, 77Se, 78Se, 80Se, and 82Se, respectively, were prepared and introduced into ICP-MS/MS to investigate the relationship between O2 and H2 flow rates and REEO2++ production rate.
As a result, the presence of REEO2++ interferences was confirmed for all As and Se isotopes. As the most severe case on 77Se16O+, a maximum 154Sm16O2++ signal equivalent to about 300 ng/L Se was observed in a 10 ppm Sm solution. With the exception of Gd, the REEO2++ production rate tended to increase significantly with increasing H2 flow rate, suggesting that H2 is likely to be involved in the formation pathway. On the other hand, the presence of H2 slightly increases the production rates of AsO+ and SeO+, which may cause significant interference if the H2 is introduced to CRC in favor of As and Se sensitivity. In this presentation, the optimal conditions for As, Se analysis under high concentration of rare earth elements matrix, and the formation process of REEO2++ will be discussed.