Attenuation of doubly charged ion interferences on arsenic and selenium by ICP-MS under low kinetic energy collision cell conditions with hydrogen cell gas

• Published in: Journal of analytical atomic spectrometry 2021-02, Vol.36 (2), p.294-32
• Main Author: Sugiyama, Naoki
• Format: Article
• Language: English
• Subjects: Arsenic; Attenuation; Collision dynamics; Cross-sections; Energy; Helium; Inductively coupled plasma mass spectrometry; Ions; Kinetic energy; Mathematical analysis; Matrix methods; Physical properties; Quadrupoles; Rare earth elements; Selenium; Trace elements
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/d0ja00301h

Most spectral interferences that arise in ICP-MS are caused by matrix or plasma-based ion overlaps on an analyte ion. These interferences can be effectively controlled using collision/reaction cell (CRC) technology operating in helium (He) collision cell mode, improving the data quality of trace elements in a variety of matrices. However, spectral interferences caused by doubly charged ions (M ++ ), such as rare-earth element (REE ++ ) ion interferences on arsenic (As) and selenium (Se), are difficult to resolve using single quadrupole ICP-MS operating in He collision cell mode. Therefore, a new method was investigated using hydrogen (H 2 ) as a collision cell gas and kinetic energy discrimination (KED) to separate the ions. For KED to be successful there needs to be a difference in the collisional cross-section of the analyte ion and interfering ion. The collisional cross-section of a doubly charged ion is greater with H 2 molecules than He (the traditional ICP-MS collision cell gas) due to the higher polarizability of H 2 . Utilizing these physical characteristics, the reduction of M ++ interferences by KED was investigated both theoretically and experimentally. The developed low kinetic energy H 2 collision cell method correctly measured 1 μg L −1 of As and Se in the presence of 0.5 mg L −1 each of 16 REEs. No mathematical interference correction equations were needed. A conventional He collision cell method provided a false positive result for As and Se of more than 10 μg L −1 . A collision cell with hydrogen gas in place of the widely used helium attenuates not only polyatomic ion interference but also doubly charged ion interference by using KED.