以固相微萃取技術分析市售生鮮截切中三鹵甲烷及鹵乙酸含量

Abstract

生鮮截切蔬果產品，是指生鮮蔬菜及水果於採收後，經篩選、清洗及輕度加工，如削皮、切塊等處理，已非蔬果原型態販售之產品。生鮮截切蔬果產品在加工及販售過程中欲避免微生物可能造成的危害，會使用食品用洗潔劑清洗；然而，在此過程中水中或蔬菜水果中的有機和無機物質可能會和洗潔劑反應產生副產物。以最常被加工廠使用的氯系洗潔劑為例(佔比高達百分之七十六)，其所產生之消毒副產物主要為三鹵甲烷和鹵乙酸。 三鹵甲烷中的氯仿及溴二氯甲烷，鹵乙酸中的二氯乙酸、三氯乙酸、二溴乙酸及溴氯乙酸等皆被國際癌症研究署（IARC）評估為2B類物質，亦即為人類的可能致癌物；而國外文獻顯示，市售生鮮截切產品中三鹵甲烷和鹵乙酸皆有顯著的殘留情況。 台灣目前並未針對生鮮截切蔬果中的三鹵甲烷和鹵乙酸等消毒副產物進行規範，另外亦缺乏產品中的殘留濃度等資訊。因此，本研究的目的包括：（一）開發同步偵測三鹵甲烷及鹵乙酸之方法、（二）偵測市售生鮮截切中之三鹵甲烷及鹵乙酸殘留量。 本研究首先改良傳統分析方法中無法同步偵測三鹵甲烷及鹵乙酸的缺點；實驗過程中藉由硫酸二甲酯（dimethyl sulfate）作為衍生試劑，搭配離子對試劑（ion-pairing agent: tetrabutylammonium hydrogen sulfate），使鹵乙酸進行衍生反應，並添加無水硫酸鈉產生鹽析作用，以提升固相微萃取的吸附效率，最後再以氣相層析串聯質譜儀分析待測物。 結果顯示，以Carboxen/Polydimethylsiloxane (CAR/PDMS)纖維在50°C下萃取20分鐘，搭配3.5M之無水硫酸鈉，有最好的效果；達平衡後，纖維於氣相層析質譜儀之250°C進樣口進行2分鐘之熱脫附。而針對11種不同的三鹵甲烷及鹵乙酸之分析建立檢量線，皆顯示具有良好的線性範圍（R > 0.995）以及精確度（相對標準偏差 < 20%）。 本研究自超商、超市、餐廳、夜市和速食店等攤商採集25件不同的生鮮截切產品；而所獲得的樣本中，則包含了92件單一原料。分析結果顯示，三鹵甲烷中以二溴氯甲烷之檢出率最高（16%）、鹵乙酸中則以溴乙酸最高（10%）。在便利商店、速食店及餐廳購入之樣本殘留物質種類較多，而夜市為最少。若以蔬菜及水果種類做劃分，蔬菜較水果易殘留三鹵甲烷及鹵乙酸；其中結球萵苣（美生菜）為最容易殘留消毒副產物之蔬菜。 而利用所測得之殘留濃度進行暴露評估，結果顯示國人透過食用生鮮截切產品 （一天約133.94 g），每天三鹵甲烷及鹵乙酸之最高攝入量分別約為4.72 μg和10.73 μg；若與每天飲用自來水所可能暴露之三鹵甲烷及鹵乙酸相比(皆為14 μg)，本研究顯示透過食用生鮮截切產品所造成之消毒副產物暴露是顯著的。 為了保障民眾之健康，建議未來應進一步討論建立相關規範之必要性，同時也應更全面地評估國人透過攝食暴露消毒副產物之情形。

Disinfectants are used to sanitize fruit and vegetables to produce a product called ready-to-eat (RTE) vegetables. Because of the convenience of RTE vegetables, they are popular with people nowadays. However, the disinfection by-products (DBPs) might form during the disinfection processes. Among the disinfectants, the chlorine-based disinfectants are most commonly used. Hence, DBPs, including trihalomethanes (THMs) and haloacetic acids (HAAs), might be formed via chlorination. It has been reported elsewhere that the amounts of DBPs presented in the RTE vegetables were significant. Moreover, two of the THMs and four of the HAAs have been evaluated by the International Agency for Research on Cancer (IARC) to be possible carcinogens (group 2B) to humans. Nevertheless, there is no legislation available currently regarding the occurrence of DBPs in food in Taiwan. As a result, the aims of this study were: 1) to develop a method that can detect THMs and HAAs concurrently with headspace solid phase microextraction (HS-SPME) coupled with gas chromatography with tandem mass spectrometers (GC/MS-MS); and 2) to determine the THMs and HAAs that might present in the RTE vegetables. In terms of analytical method, traditionally, THMs and HAAs could not be detected simultaneously. Hence, in this study, a method that could analyze THMs and HAAs in situ was first developed. Dimethyl sulfate (DMS) was used as the derivatization reagent and tetrabutylammonium hydrogen sulfate (TBA-HSO4) was used as the ion-pairing agent to improve the derivatization process of HAAs. Salting out effect was also performed with anhydrous sodium sulfate. After the optimization of the parameters, Carboxen/Polydimethylsiloxane (CAR/PDMS) fiber was used to extract the analytes at 50°C for 20 minutes, and the SPME fiber was desorbed at 250°C injection port for 2 minutes. A total of 25 samples, including 92 food items, were collected from convenience stores, supermarkets, restaurants, night markets and fast food restaurants in this study. The results showed that dibromochloromethane (16%) in THMs and bromoacetic acid (10%) in HAAs had the highest detection rates. The convenience stores, fast food restaurants and restaurants had higher variety of residue, while the night markets had the lowest. Moreover, vegetables were more easily to be contaminated by DBPs compared with fruits. For the adults in Taiwan, the maximum daily exposures of THMs and HAAs estimated via the consumptions of RTE vegetables were 4.72 μg and 10.73 μg, respectively. In addition, the exposure of THMs and HAAs through drinking water were estimated to be 14 μg. Hence, in terms of public health, the findings from this study suggest that the exposures of DBPs from RTE vegetables cannot be ignored. To protect people’s health, suggestions were provided to establish guidelines or regulations for the disinfection process of RTE vegetables. Further investigations should also be performed to have more data for the exposure assessments.