Analytical Sciences

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS): Comparison of Different Internal Standardization Methods Using Laser-induced Plasma (LIP) Emission and LA-ICP-MS Signals

Masaki OHATA, Hiroyuki YASUDA, Yoshimichi NAMAI, and Naoki FURUTA 

Faculty of Science and Engineering, Department of Applied Chemistry, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan

The source of signal variations that governs the analytical performance of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was investigated in this study. In order to specify the source of signal variations of LA-ICP-MS, laser-induced plasma (LIP) Fe emission, LA-ICP-MS Fe⁺ and LA-ICP-MS Ni⁺ signals were used as internal standards for the determination of trace elements in low-alloy steel certified reference materials (BS 50D and JSS 1005-1008). Fe I 373.5 nm emission signals from LIP were measured, while trace element LA-ICP-MS signals were collected. After that, the LIP emission signals, LA-ICP-MS Fe⁺ and LA-ICP-MS Ni⁺ signals were used as internal standards, and the analytical performance was evaluated by the RSDs and the correlation coefficients (r) of the calibration curves. The improvement factors were dependent on the internal standardization methods. Analytical precisions (RSDs) of trace element LA-ICP-MS signals were improved by factors of 1.5 - 3.3 using LIP Fe emission signals as an internal standard. The improvement factors of 2.5 - 5.9 and 4.1 - 17 were obtained by using LA-ICP-MS Fe⁺ and LA-ICP-MS Ni⁺ signals as internal standards, respectively. Better correlation coefficients (r) were also obtained using the LA-ICP-MS signal compensation (0.9985 by LA-ICP-MS Fe⁺ and 0.9996 by LA-ICP-MS Ni⁺) rather than the LIP Fe emission compensation (0.9932). In this paper we compare and discuss the analytical performance achieved by LA-ICP-MS using LIP Fe emission, LA-ICP-MS Fe⁺ and LA-ICP-MS Ni⁺ signals as internal standards.

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