茶葉中過氯酸鹽之檢驗研究   全文下載

Investigation on the Test Method for Perchlorate in Tea

過氯酸鹽為一新型環境污染物，攝入後會引起甲狀腺功能失調，影響胎兒及嬰幼兒大腦發育，對孕婦及胎兒健康影響最為顯著。茶葉種植過程中接觸灌溉用水、肥料及土壤等均可能造成過氯酸鹽殘留，為歐盟關切的議題之一，105年2月亦有相關外媒輿情報導，故建立茶葉中過氯酸鹽之檢驗方法有迫切需要。本研究於茶葉樣品加入過氯酸鹽同位素內部標準品後，先以去離子水混勻，再以含1%甲酸之甲醇溶液萃取，經離心後取濾液稀釋，以液相層析串聯質譜儀（liquid chromatograph-tandemmass spectrometer, LC/MS/MS）配合多重反應偵測（multiple reaction monitoring, MRM）模式進行分析，並以綠茶空白檢體添加標準品製作之檢量線進行定量。確效試驗係於綠茶樣品中添加過氯酸鹽0.2及0.4 mg/kg，執行5重複添加回收試驗，平均回收率分別為78.0及99.0%，變異係數分別為5.8及6.6%，定量極限（limit of quantification, LOQ）為0.1 mg/kg，低於歐盟暫定之限量標準（0.75 mg/kg）。以建立之方法針對20件東南亞進口茶葉及5件台灣本土茶葉進行檢測，檢驗結果：進口茶葉部分，1件越南綠茶檢出0.2 ppm，1件越南紅茶檢出4.77 ppm，其餘18件未檢出；本土茶葉部分，1件烏龍茶及1件綠茶粉分別檢出0.68及0.83 ppm，其餘3件未檢出。本研究方法具良好的準確度及重複性，已公開為建議檢驗方法供各界參考使用。"

Perchlorate is a new environmental pollutant and can cause thyroid dysfunction. It occurs as a contaminant arising from the irrigation water, fertilizers and soil during tea tree cultivation. Recently, residue perchlorate in tea reported by foreign media in Feb 2016 led to great concern to the European Union and caught our attention to develop a test method of perchlorate in tea. In this study, the tea sample was added with an internal standard and then dissolved in deionized water. The sample solution was extracted with methanol containing 1% formic acid and centrifuged. The filtrate was further diluted before analysis by a liquid chromatograph-tandem mass spectrometer (LC/MS/MS) in multiple reaction monitoring (MRM) mode. The calibration curve was established by adding standard to the blank green tea sample. The green tea samples spiked with 0.2 and 0.4 mg/kg perchlorate standards were used for the recovery tests. The average recoveries were 78.0 and 99.0%, respectively. The coefficients of variation were 5.8 and 6.6%, respectively. The limit of quantification (LOQ) of this method was 0.1 mg/ kg, which was lower than the EU limit of perchlorate (0.75 mg/kg) as a reference for intra-union trade. Twenty imported tea samples from Southeast Asia and 5 Taiwan local tea samples were evaluated by the developed method. The results showed that the concentrations of perchlorate in one Vietnamese green tea and one Vietnamese black tea were 0.2 and 4.77 ppm, respectively; and those in the remaining 18 samples from Southeast Asia perchlorate was not detected. One oolong tea and one green tea powder were found to contain 0.68 and 0.83 ppm of perchlorate, respectively; and those in the remaining 3 Taiwanese samples perchlorate was not detected. The method showed good accuracy and reproducibility. A full version of the method was published and made available to the public.