HPLC-ICPMSを用いたSpecies-unspecific及び Species-specific同位体希釈分析法による セレンィースト標準物質中のセレノメチォニンの定量

摘要

Determination of selenomethionine (SeMet) in a selenium-enriched yeast standard material (SELM-1, National Research Council of Canada, NRC) was carried out, and extraction methods were investigated. SeMet in SELM-1 was determined by using a hyphenated instrument of HPLC, and an inductively coupled plasma-three dimensional quadrupole mass spectrometer (HPLC-ICP3DQMS), and two different isotope dilution analysis methods (species-unspecific IDA and species-specific IDA). Two different IDA methods were evaluated by comparing the analytical results. It was confirmed that enzymatic hydrolysis with using Lipase Ⅶ (Sigma Chemicals, St, Luis, MO, USA) and Protease, Type ⅪⅤ (Sigma Chemicals, St, Luis, MO, USA) for 24 hours was appropriate for the extraction of SeMet. Our analytical values of SeMet for species-unspecific IDA (3040 土 77 μg g~(-1)) and species-specific IDA (3154 ± 82 μg g~(-1))showed agreements with the certified value (3448 土146 μg g~(-1)) within 4σ and 2σ，respectively. It is concluded that species-specific IDA should be used when a stable isotope enriched compound could be synthesized.%セレンィースト標準物質（SELM-1, National Research Council of Canada製）中のセレノメチォニン(SeMet)の定量を行い，抽出手法の検討を行った.また高速液体クロマトグラフィーをオンラインで接続した誘導結合プラズマ三次元四重極質量分析計（HPLC-ICP3DQMS)を用いたspecies-unspecific及びspecies-specificな同位体希釈分析法（isotope dilution analysis, IDA)によりSELM-1中のSeMetの定量を行った.そして，結果を比較することで2種類のIDAの評価を行った.SeMetの抽出には，Lipase Type VII (Sigma Chemicals. St, Luis, MO, USA)及びProtease Type XIV (Sigma Chemicals, St. Luis, MO, USA)を用いて24時間酵素分解を行う方法が，適していることが確認された.ただし，前処理操作中にSeMetの分解が確認された.SELM-1中のSeMetの測定値は，species-unspecific IDA が3040 ± 77 μg g~(-1), species-specific IDAが3154 ±82μg g~(-1)であり，保証値（3448 ±146μg g~(-1))とそれぞれ4σ, 2σ以内で一致したことから，安定同位体を濃縮した化合物が合成できる場合はspecies-specific IDAを用いる方がよいと結論づけた.