食品中胺基甲酸乙酯分析方法之探討（一）－－內標準品與參考曲線的選擇及樣品中乙醇與葡萄糖對萃取率的影響

Studies on the Methodology of Ethyl Carbamate Analysis in Foods(I)-- Selection of Internal Standards and Reference Curves as Well as the Effects of Ethanol and Glucose on the Extraction

本實驗以0～40%的乙醇及0～20%的葡萄糖水溶液作為模擬樣本，內均含5 mg/1之胺基甲酸乙酯（ethyl carbamate, 簡稱EC）及內標準品（methyl carbamate及n-propyl carbamate, 簡稱MC, PC）。模擬樣品經萃取、純化及濃縮後，以 GC/MS（gas chromatography/mass spectrum）分析，再分別比對標準曲線（standard curve）、檢量線（calibration curve）兩種參考曲線定量，並探討溶液中乙醇及葡萄糖濃度對EC定量的影響。結果顯示以標準曲線定量時，不論以MC或 PC當內標準品，偵測值（MC: 11.45 mg/1, PC: 2.45 mg/1）與實際值（5 mg/1）的誤差都十分顯著。而以檢量線定量時，則以MC或PC當內標準品之偵測值皆與實際值相當（均為5.00 mg/1）。另一方面，乙醇濃度越高，則越不利於EC萃取；而葡萄糖濃度對EC萃取率的影響，則有先昇後降的趨勢，其轉折點所對應的葡萄糖濃度約14～16%（對EC 5 mg/1而言）。推測其原因，可能與溶液的氫鍵力及溶質與EC的分子間作用力有關。故分析食品中EC含量時，必須以檢量線作為參考曲線，而以MC或PC作內標準品皆可，但難以避免因溶液中的溶質干擾定量結果。本實驗結果顯示一般的分析報告或有低估實際EC含量。

In this study, 0~40% ethanol and 0~20% glucose solutions containing 5mg/l ethyl carbamate (EC) as well as internal standards (methyl carbamate, as MC and n-propyl carbamate, as PC) were used as model samples. Standard curves and calibration curves were made by GC/MS analysis after samples were extracted, purified, and concentrated. The effect of solutes on quantiation determination methodology then studied. Results indicated that, no matter MC or PC used as internal standards, the difference between determined values (MC: 11.45 mg/1, PC: 2.45mg/l) and actural values (5.0 mg/1) was significant when standard curve was referred. However, there is no significant difference between those values when calibration curve was adapted. Presence of ethanol and glucose retard the extraction of EC from model samples. The inhibition effect was increased when ethanol concentration increasing but not proportional to glucose concentration. Higher than 14~16% glucose will facilitate the extraction of EC. Intermolecular force between solutes and EC compound might be the cause of this phenomena. Results from this study indicated that current published EC content data might be improperly determined.