以聚焦式微波輔助萃取、乙基化及氣相層析質譜法分析魚肉中甲基汞及無機汞含量   全文下載

Determination of Methyl- and Inorganic Mercury in Fish Using Focused Microwave Digestion Followed by Cu++ Addition, Sodium Tetraethylborate Derivatization, n-Heptane Extraction, and Gas Chromatography-Mass Spectrometry

本研究探討以微波輔助萃取、乙基化及氣相層析質譜法分析魚肉中甲基汞及無機汞含量。將檢體0.5g置微波消化瓶中，加四甲基氫氧化產生溶液5 mL，以聚焦式微波消化器加熱萃取後，以醋酸中和，加入醋酸銅溶液及醋酸緩衝溶液（pH5），再加入四乙基硼酸鈉／氫氧化鉀溶液衍生化，以正庚烷振盪萃取，靜置分層後取上層液以氣相層析質譜儀分析。實驗結果顯示，氣相層析質譜儀分析可於8分鐘內完成分析（不含前處理時間）。最佳微波萃取條件為15-30W加熱3.5分鐘、45W加熱2.5分鐘或60-75W加熱1.5分鐘。添加0.5，1.0及2.0 μg／g甲基汞及無機汞於魚肉中，其回收率分別為92.3-96.1%及93.6-95.5%。其次，分析三種參考物質之甲基汞含量，BCR CRM 464 tuna fish為5.31 ± 0.32μg／g （標示值5.50 ± 0.17μg／g），NRCC DORM-2 dogfish muscle為4.40 ± 0.34μg／g （4.47 ± 0.32μg／g）及DOLT-2 dogfish liver為0.663 ± 0.06 μg／g （0.693 ± 0.053μg／g），顯示本方法適用於魚肉中甲基汞及無機汞含量之分析。

The analytical procedure for analysis of methyl- and inorganic mercury in fish was developed in this study. It involved microwave-assisted digestion with alkaline solution (tetra methyl ammonium hydroxide), addition of Cu++, aqueous-phase derivatization of mercury species with sodium tetraethylborate, and subsequent extraction with n-heptane. The various mercury derivatives were desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by electron impact mass spectrometry. Optimum conditions allowed the sample throughout to be controlled by the instrumental analysis time (about 8 min per sample) but not by the sample preparation step. At the irradiation power of 15-30, 45, and 60-75 W, sample heating times were only 3.5, 2.5, and 1.5 min, respectively. The recoveries of mercury species were 92.3–96.1% and 93.6–95.5% for methyl- and inorganic mercury, respectively. The proposed method was finally validated by the analysis of three biological certified reference materials (BCR CRM 464 tuna fish, NRC DORM-2 dogfish muscle, and NRC DOLT-2 dogfish liver). 本研究探討以微波輔助萃取、乙基化及氣相層析質譜法分析魚肉中甲基汞及無機汞含量。將檢體0.5g置微波消化瓶中，加四甲基氫氧化產生溶液5 mL，以聚焦式微波消化器加熱萃取後，以醋酸中和，加入醋酸銅溶液及醋酸緩衝溶液（pH5），再加入四乙基硼酸鈉／氫氧化鉀溶液衍生化，以正庚烷振盪萃取，靜置分層後取上層液以氣相層析質譜儀分析。實驗結果顯示，氣相層析質譜儀分析可於8分鐘內完成分析（不含前處理時間）。最佳微波萃取條件為15-30W加熱3.5分鐘、45W加熱2.5分鐘或60-75W加熱1.5分鐘。添加0.5，1.0及2.0 μg／g甲基汞及無機汞於魚肉中，其回收率分別為92.3-96.1%及93.6-95.5%。其次，分析三種參考物質之甲基汞含量，BCR CRM 464 tuna fish為5.31 ± 0.32μg／g （標示值5.50 ± 0.17μg／g），NRCC DORM-2 dogfish muscle為4.40 ± 0.34μg／g （4.47 ± 0.32μg／g）及DOLT-2 dogfish liver為0.663 ± 0.06 μg／g （0.693 ± 0.053μg／g），顯示本方法適用於魚肉中甲基汞及無機汞含量之分析。