本研究開發了一套有效且直接的方法檢測市售蔬菜中的五種對-羥基苯甲酸酯類的防腐劑(alkyl 4-hydroxybenzoate, 簡稱parabens)。運用新開發的雙重震盪輔助基質固相分散萃取法(double- vortex-assisted matrix solid-phase dispersion, 簡稱DVA-MSPD)，搭配超高效液相層析串聯質譜儀(UHPLC-QTOF-MS)中的負離子電灑法(ESI)模式進行檢測。DVA-MSPD能快速的萃取出待測物，省去使用研缽研磨或固相萃取法(SPE)中管柱沖提的過程。本研究是先進行實驗設計 Multilevel categoric design 實驗因子的篩選，再利用 Box-Behnken design 優化各因子的數值。 本實驗方法DVA-MSPD最佳化條件為：取 0.2 g 蔬菜粉末與 0.2 g C18吸附劑，以震盪機震盪 1 分鐘使之均勻分散，省去研缽的使用，於15 mL離心管中加入 8 mL 萃取劑甲醇並震盪 5 分鐘，此過程取代了以往使用的SPE管柱，再以 3000 rpm 離心 15 分鐘。取上層清液，吹氮濃縮至乾，並以 200 µL 的甲醇和超純水 (1:1) 回溶，最後進樣 2 µL 到UHPLC-ESI-QTOF-MS 進行檢測。 使用DVA-MSPD方法，五種 parabens的定量極限介於 1.0-2.0 ng/g (乾重)；在6個濃度水準下的標準檢量線，呈現良好的線性關係，其決定係數 R2 值都在 0.9961 以上；在 Intra-day 與 Inter-day 的萃取回收率介於 85 到 108 % ，相對標準差 (RSD)介於4 % 至 17 % ，表示此方法有良好的準確度與精密度。在五種市售蔬菜樣品中都有檢測到 methyl 4-hydroxybenzoate (MeP) 不同濃度的殘留，殘留的濃度介於 23.6-68.5 ng/g (乾重)。 ;In this study, an efficient and straightforward method was developed to determine the presence of five paraben preservatives (alkyl 4-hydroxybenzoate) in marketed vegetables. The target analytes were rapidly extracted from the vegetable samples using a novel double- vortex-assisted matrix solid-phase dispersion (DVA-MSPD) technique, without the use of mortar/pestle and SPE-column elution procedures. The analytes were then detected by an ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS), which operated in the negative electrospray ionization (ESI) mode. The DVA-MSPD factors were screened by means of a multilevel categorical design, and then optimized by Box-Behnken Design plus with response surface methodology. The optimal conditions of DVA-MSPD were: powdered vegetable sample 0.2 g was dispersed with 0.2 g of C18 adsorbent by vortex- homogenized for 1 min (mortar/pestle-free). The blend was transferred to a 15 mL centrifuge tube, and 8 mL of methanol (as an extractant) was added, and the content was thoroughly vortex-extracted for 5 min (SPE-column-free). Then for 15 min, the phase was separated by centri- fugation at 3000 rpm. The supernatant was evaporated to dryness, and the residue was re-dissolved in a 200 L of methanol：DI water (1:1). The final extract 2 L was then subjected to UHPLC-QToF-MS analysis. The limits of quantification (LOQs) of the developed method varied from 1.0 to 2.2 ng/g (dry weight). Excellent linearities (coefficient of determination (R2) greater than 0.9961) were found for each target analyte in the six-level calibration standard curves. Good precisions were obtained for both intra- and inter-day analysis, and ranged from 4 to 17%. Satisfactory average spiked recovery ranged from 85 to 108%. Optimal DVA-MSPD procedure combined with highly sensitive UHPLC-QTOF- MS was successfully applied for the rapid determination of selected parabens in vegetable samples. Methyl 4-hydroxybenzoate was the major parabens detected in selected vegetable samples, and the concentrations ranged from 23.6 to 68.5 ng/g (dry weight).
