蛋類中鉛及銅含量檢驗方法開發   全文下載

The Development of the Method for Iead and Copper in Eggs

蛋類便宜且具有高營養價值，是國人每天易於攝取的飲食之一。在皮蛋加工過程中，會藉由添加氧化鉛及硫酸銅以提升產品的成功率，但卻可能使蛋製品中鉛及銅含量超過法規之限量標準。鉛為毒性化學物質，主要危害人體之神經及消化系統，嚴重者可能導致死亡。銅雖為人體所需之微量元素，但過量攝取會導致肝硬化。本研究將蛋類分別以微波與石墨加熱板消化處理後，以感應耦合電漿質譜儀（inductively coupled plasma mass spectrometer, ICP-MS）分析其鉛及銅的含量，並將兩者結果進行比較。本研究方法為精確稱取樣品（全蛋、蛋黃和蛋白） 0.5g，並添加濃硝酸（70%） 5 mL，分別以微波消化40分鐘及石墨加熱板消化120分鐘後，以ICP-MS分析，質量數以鉛208及銅65定量。微波與石墨加熱板消化前處理之標準曲線的決定係數（R2）皆可達0.999以上，鉛及銅的定量極限分別為0.03及0.25 ppm。於新鮮雞蛋、滷蛋、皮蛋、鹹蛋和鐵蛋的全蛋中分別添加鉛0.03 ppm及銅0.5 ppm，以微波消化前處理之平均回收率為鉛93.2 - 100.3%及銅87.9 - 125.4%。於新鮮雞蛋、滷蛋、皮蛋、鹹蛋和鐵蛋的全蛋中分別添加鉛0.03 ppm及銅0.5 ppm，以石墨加熱板前處理之平均回收率分別為鉛80.5 - 115.8%及銅98.7 - 119.1%。以本研究所建立之方法分析23件市售檢體中，其鉛及銅含量分別為N.D. - 0.03 ppm及N.D. - 3.66 ppm，皆低於我國法規限量標準（鉛0.3 ppm以下；銅5 ppm以下）。此外，5種蛋類中銅含量由小至大，依序為新鮮蛋類、滷蛋、鐵蛋、鹹蛋及皮蛋，且蛋黃之含銅量皆較全蛋與蛋白高。"

Eggs and egg products are highly nutritious and inexpensive foods as an essential part of daily diet in Taiwan. Century egg also known as preserved egg in Chinese preserved food product made by preserving duck, chicken or quail eggs in a mixture of clay, ash, salt, quicklime, and rice hulls for several mouths. Lead (Pb) or copper (Cu) may be added inoder to fasten this process and the amounts may exceed the limits of regulation. Lead is a toxic element, and dangerous to most human organs when exposure exceeds tolerable levels. Copper is a dietary element needed in a very minor quantities for human proper growth. The deficiency of copper may cause anemia, osteoporosis, and depigmentation, while overtake of copper may causes liver cirrhosis. This study investigated the contents of lead and copper in eggs and egg products purchased from Taiwan markets. Samples were prepared by microwave and graphite heating block digestions, followed quantifications were conducted by inductively coupled plasma mass spectrometry (ICP-MS). The sample each (whole egg, egg yolk, and egg albumin) 0.5 g was accurately weighted into a digestion vessel and 5 mL of concentrated nitric acid (70%) was added. Then, the samples was heated by microwave or graphite heating block digestion for 40 and 120 min. Sample solution was analyzed by ICP-MS for lead and copper detected at m/z 208 and 65, respectively. The results showed that the determination coefficients of calibration curves all were above 0.999. The limits of quantitation (LOQs) for lead and copper were 0.03 and 0.25 ppm, respectively. The standard reference material of whole egg power (SRM 1845a) was used for method validation, and the average recovery of copper was 103%. For spiking tests, lead and copper at thelevel of 0.03 ppm and 0.5 ppm, respectively, were added into fresh eggs, marinated eggs, century eggs, salted eggs, and iron-hard preserved eggs. The results of samples prepared by microwave digestion showed the average recoveries of lead and copper were 93.2 - 100.3% and 87.95 - 125.4%, respectively. Samples prepared by graphite heating block digestion showed the average recoveries of lead and copper were 80.5 - 115.8 and 87.9 - 125.4%, respectively. Twenty-three egg samples purchased from markets were analyzed by this method, and the result showed the contents of lead and copper were N.D.-0.03 ppm and 0.28 - 3.66 ppm, respectively, both below the regulation limits in Taiwan (lead 0.3 ppm; copper 5 ppm). The order of the copper contents in the 5 different eggs showed the lowest was fresh eggs, then marinated eggs, iron preserved eggs, salted eggs, and preserved eggs, which was the highest measured. The copper content of egg yolks was found to be higher than those in whole eggs and egg albumins in the five types of eggs studied.