紙電噴霧游離結合瞬熱烙鐵熱脫附探針應用於蔬果表面農藥殘留快速檢測

Abstract

食品農藥殘留檢驗常耗工耗時，因此本研究開發了一種創新的快速質譜檢驗方式，可省去傳統萃取濃縮之前處理步驟，應用於蔬果中農藥之檢驗。此方法是基於一種獨創的熱脫附裝置，將不銹鋼接種針與電烙鐵結合，成為快速取樣的探針，直接用接種環被測物刮擦蔬菜、水果等農產品的表面，通過電烙鐵對樣品進行快速熱脫附後，待測農藥可以快速揮發，然後利用紙噴霧裝置產生電噴霧離子和電暈放電的特性，使樣品及待測物農藥解離，進入質譜檢測。 本研究之第一部分先探討電暈放電結合紙電噴霧游離方式之可行性，結果發現對紙張施加介於6.0 kV/cm 與 8.3 kV/cm 之間高電場，確實可觀察得到電噴霧和電暈放電之現象，後續在高於7.0 kV/cm的電場下可以同時產生電噴霧與電暈放電，透過電噴霧以游離極性物質，電暈放電所產生之電漿則可使非極性物質帶電。因此利用質譜儀同時檢測出極性之乙醇、中極性之丙酮、以及非極性之苯的質譜訊號，證明此法適於游離噴霧極性及非極性化合物，可用於替代傳統電灑法與電漿放電獨立系統之游離介面。 第二部分開發結合不銹鋼接種針與瞬熱式電烙鐵之熱脫附裝置，此裝置可在25秒內由室溫升溫至250℃，亦可使含10 ppm 咖啡因的模擬樣品中的咖啡因受熱而脫附，是一種簡便的採樣與脫附系統整合之裝置。配合紙電噴霧之游離方式，可成功於質譜取得液態咖啡因之質譜訊號，顯示以此探針作為熱脫附裝置可應用於樣品直接分析。 第三部分則以標準實驗室收樣之檸檬為材料，透過離子阱質譜儀可同時追蹤多種不同分子量樣本之特性，探討本研究開發的快速熱脫附質譜法，應用於快速蔬果農藥之質譜檢測可行性。並以標準實驗室採用公訂之 QuEChERS 標準檢測流程與 GC-MS/MS 以及 LC-MS/MS 檢測進行驗證。結果發現本研究之快速熱脫附法於離子阱式質譜儀檢出之農藥為克凡派、百利普芬、賽洛寧、亞拖敏、亞滅培以及畢達本。而以台灣標準方法所檢測之農藥殘留及其濃度為克凡派0.225 ppm、百利普芬0.185 ppm、賽洛寧0.110 ppm、亞拖敏0.12 ppm、亞滅培0.31 ppm以及畢達本0.11 ppm。上述結果顯示本研究所開發之快速熱脫附質譜法，於單一次採樣與游離脫附操作中，可在質譜儀同時偵測到蔬果表面之極性及非極性農藥，並且其結果與公告方法是一致的。此結果也證明了本研究中所研發的新式紙電噴霧游離結合瞬熱烙鐵熱脫附探針作為農藥殘留檢驗是具體可行的。 然而本方法的設計是為應用於快速篩選檢驗，無法定量採樣、進樣而進一步得知待測物的實際濃度，在實際應用上仍須搭配其他定量方式。 本研究所開發之技術，具有方便、快速、準確之優點，未來可應用於其他食品安全項目之檢驗，以及醫學檢體、藥物分析、環境科學等其他領域。

Detecting the pesticide residues in food is often described as a labor-intensive and time-consuming event. In this study, we aimed to resolve this issue by developing an innovative method using rapid mass spectrometry. This approach is applicable to pesticides inspection in fruits and vegetables, and is able to eliminate the preliminary treatment step of extraction that is traditionally performed by laboratory. The concept behind this novelty was based on using a thermal desorption device, which connecting a stainless-steel inoculating needle into a commercial instant-heat iron to form a ready-to-use probe for quick sampling. The probe then could be used directly to scrape the surfaces of vegetables, fruits and other agricultural products. When a sample was collected, it was thermally desorbed rapidly by the instant-heat iron enabling the analytes to be quickly volatilized. Moreover, a paper spray device is used to generate electrospray ions and corona discharge, and such characteristics made the analytes in the sample dissociate and enter the mass spectrometry for detection. The first part of this study investigated the feasibility of corona discharge combined with paper electrospray dissociation. The results showed that the phenomenon of electrospray and corona discharge could indeed be observed by applying high electric fields of 6.0 and 8.3 kV/cm to paper. Electrospray and corona discharge could be generated at the same time under the electric field higher than 7.0 kV/cm. Polar analytes are then dissociated by electrospray, and the plasma generated by corona discharge can charge non-polar analytes. As the result, the simultaneously detected mass spectrum signals of polar ethanol, moderately polar acetone, and non-polar benzene could prove that this method is workable for dissociating spraying of polar and non-polar compounds. It could be used to replace the dissociating interface of traditional electrospray method and plasma discharge independent system. The second part of this study was the development of a thermal desorption device, combining a stainless-steel inoculating needle and an instant heat electric soldering iron. This device was heated from room temperature to 250°C in 25 seconds, and could also desorb caffeine in a simulated sample containing 10 ppm caffeine. Desorbed by heat, it was a simple device integrating sampling and desorption systems. Combined with the dissociation method of paper electrospray, the mass spectrometry signal of liquid caffeine was successfully obtained with mass spectrometry. The third part of this study uses lemons collected in a commercial laboratory as materials, and combined rapid thermal desorption method to detect the residues of pesticides. Six pesticides composed of polar acetamiprid, azoxystobin, pyridaben and low polar chlorfenapyr, pyriproxyden, -cyhalothrin were successfully detected in seconds. To verify this novel method, the results were compared with Taiwan official method which uses QuEChERS as pretreatment method and adopts GC-MS/MS and LC-MS/MS as detection instrument. The data showed that the official method detects pesticides at the following concentrations: 0.225 ppm for chlorfenapyr, 0.185 ppm for pyriproxyfen, 0.110 ppm for -cyhalothrin, 0.12 ppm for azoxystrobin, 0.31 ppm for acetamiprid and 0.11 ppm for pyridaben, respectively. The above results were in line with the testing results by using rapid thermal desorption method, and those concluded that the rapid thermal desorption mass spectrometry method developed in this study could simultaneously detect polar and non-polar pesticides on the surface of fruits and vegetables by mass spectrometer in a single sampling and dissociation desorption procedure. This novel thermal desorption probe integrated with the corona-discharged assisted paper-spray mass spectrometry could be applied to other food safety inspection in the future, as well as medical samples, drug analysis, environmental science and various fields.