元素分析計-同位体比質量分析計(EA-IRMS)によるうなぎ加工品試料の炭素•窒素•酸秦安定同位体比分析の試験所間比較

摘要

現在，日本で流通しているうなぎは,主に国産,台湾産，中国産の養殖うなぎである.消費者の食の安全性への高まりから，国産うなぎへの需要が増加している.うなぎの産地判別技術については，アンギラ種（ヨーロッパうなぎ:Anguilla anguilla)とジャポニ力種(ニホンうなさ：Anguilla japonica)を判別するDNA分析や微量元素組成によるうなぎの産地判別の可能性が報告されている.また，炭素•窒素•酸素同位体比分析を用いた輸入うなぎと国産うなぎの判別の可能性についても報告されている.%In previous studies, stable carbon, nitrogen and oxygen isotope analyses were probably a useful tool for tracing the geographical origin of processed eels. However, the lack of a reliable technique for isotope ratio measurements is significantly regrettable, and should be improved immediately. Here, we present results of an inter-laboratory test on the EA-IRMS determination of stable carbon, nitrogen and oxygen isotopic compositions (δ~(13)C, δ~(15)N and δ~(18)O) in processed eel samples. The processed eel samples were distributed and analyzed by a total of 5 laboratories. The variations of the standard deviations for δ~(13)C (- 18.7 ‰ ± 0.2 ‰) and δ~(15)N (+13.4 ‰ ± 0.3 ‰) among laboratories were not very large compared to the instrument uncertainties. The δ~(18)O values ( +16.5 ‰ ± 3.1‰) in processed eel samples showed a large variation among laboratories. This may have been caused by much the contamination of N_2 to the CO peak on the EA-IRMS chromatogram, and may be improved by using a longer GC column or Purge ＆ trap columns for chromatographic separation.