2021年1月8日

Date: 16:00 – 18:00, Friday, January 8, 2021

日時: 2021年1月8日(金)16:00 – 18:00

講演者: 平田 岳史

Speaker: Takafumi Hirata

Title: Pushing the Limits in Mass Spectrometry

The mass spectrometer utilising an atmospheric pressure plasma as an ion source (ICP-MS) is likely to become a major analytical tool for the trace-elements in various geochemical and biochemical materials. Recent progress in the ICP-MS technique lies in dramatic improvements in precision and accuracy of the analyses through developments of new ion detection techniques such as Daly, SEM, as well as Faraday detectors, having wide dynamic range and high-time resolution ion counting. Moreover, laser ablation sampling technique combined with the ICP-MS technique (LA-ICPMS) is now widely accepted as one of the most sensitive and rapid analytical methods on various solid materials.
The major development in the laser ablation techniquea to come to light in these ten years was the recent application of a femtosecond (fs) lasers for solving various microanalytical problems, and several groups have been independently employing this technology. With the femtosecond lasers coupled with fast-scanning optics (i.e., Galvanometric optics), laser induced sample particles released from different ablation spots or samples can be mixed within the sample cell, and thus, the we can mix the two or more solid samples with various mixing ratios, just like solution samples. This indicates that the various calibration protocols, including internal-standardisation, isotope dilution, or standard addition, can be applied for multi-element determinations directly from solid materials. Furthermore, with the fast-scanning protocol, laser ablation can be conducted from wide area, up to 10 x 10 mm, within short time period (e.g., < 1 s), which results in much better signal-to-noise ratio of the analysis. In fact, the detection limits of the elements for most of the elements are now significantly lower than 1 ng/g (ppb), demonstrating nearly comparable or better than the case of the solution-based ICP-MS. This is also very important for the detection of minor- or trace-isotopes such as 138La, 180Ta, 234U, or 236U in natural or nuclear related-materials. To take a full advantage of our LA-ICPMS technique, we have developed several ion detection protocols for Os and U isotopic analyses (Hirata+, MSSJ, 2020; Hirata+, RSC JAAS, 2020; Yamamoto+, submitted to RSC JAAS). The data obtained here demonstrated clearly that the LA-ICP-MS technique can become a powerful tool to monitor the elemental and isotope ratios from NPs of multiple components (Yamashita+, Spectrochim. Acta, 2020; Yamashita+, RSC JAAS, 2020). To expand the analytical capability of the LA-ICPMS technique, several instrumental developments were carried out in the fiscal year of 2020. However, we should not be too hasty to open the champagne, as there remain many problems to be solved in order to make it a truly routine and mature analytical tool, and experimentation still remains crucial. Faced with this, we are keep working on three major topics in the fiscal year of 2021.

a) Hybrid bio-imaging system using ICP-MS and API-MS
b) Detection of bio-molecules using the inorganic mass spectrometry (i.e., ICP-MS)
c) Elemental and isotopic analysis of NPs from biological and cosmo-chemical materials

With the series of unique mass spectrometers and laser ablation systems, we are going to develop completely new analytical systems aiming at creating a new research fields in both geochemistry and biochemistry. Potential capability of our research group over the traditional geochemistry facility will be highlighted in this talk.

The greatest pleasure in life is doing what people say you cannot do. — Walter Bagehot
J’aime la nourriture italienne.


講演者: 角森 史昭

Speaker: Fumiaki Tsunomori

Title: For Activity Monitoring of Mud Volcanoes by Acoustic Measurement

タイトル: 音響計測による泥火山の活動度モニタリングの実現に向けて  


泥火山の活動度を連続観測するための準備状況について説明する。簡易的な方法で設置した水中マイクによって、泥噴口で破裂する泡の音を約1週間記録した。この音の解析によって、破裂音の特徴・泡の発生頻度を解析しながら、破裂音計測法の問題点を検討した。泥噴口内の音の周波数特性を調べると、静穏時はホワイトノイズまたはピンクノイズ的な周波数特性を持つ弱い音であり、一方、発泡時は0.8kHz付近に特徴的なピークを持つ強い音であった。小さな泡の破裂音を録るための増幅率で固定したままだと、大きな泡の破裂で発生する強い音では計測音圧の限界を超えてしまい、信号を正しく記録できなかった。したがって、大小さまざまな破裂音を記録するためには、高速フィードバック回路による適応型増幅システムが必要であることがわかった。今回の解析では、強い音のデータが飽和していることを前提に、発泡頻度の時間経過を1時間毎に調べた。泡の発生頻度は20Hz程度で、今回の観測期間中大きく変動することはなく、また期間中に地震などのイベントもなかったので地殻活動との関係はまだわからない。COVID-19の影響で現地での計測プロジェクトが進まないので、当面は模擬泥噴口を作って計測システムの高度化を図りながら、災厄が過ぎるのを待つことにする。