直交表實驗計劃法最適化超臨界流體萃取與固相微萃取分析可疑火場殘跡樣品

Abstract

尋找足可取代現行縱火殘跡樣品前處理方法的新技術是本論文的研究目標，而超臨界流體萃取法及頂空固相微萃取法由於皆有將分析物聚集濃縮的優點，故被選擇作為研究的標的。在超臨界流體萃取的研究中，以一般容易取得之95無鉛汽油、煤油及高級柴油為對象分析物，而於頂空固相微萃取技術的研發上，則再加上去漬油共四種石油系蒸餾物做為萃取的對象。 超臨界流體萃取三種縱火加速劑的研究中，根據對實驗之了解，認為流體的密度、溫度、流速、動態萃取時間與靜態萃取時間應會造成其萃取效率的差異，採用L16（215）直交表實驗計劃法，配合平均回應值之計算與變異數分析之輔助得知對萃取效率有顯著影響之因子，亦獲得初步之較佳萃取條件，該條件並被用來對實際縱火殘跡樣品進行萃取分析，且成功地自樣品中回收微量之縱火加速劑成份。L16（215）直交表實驗計劃法進行之目的在藉由拉大因子的水準間距，了解該實驗因子對實驗結果是否具有顯著影響，而最適化的實驗條件有賴於合理的細分水準間距，因此接著將L16（215）直交表實驗之變異數分析結果中百分比貢獻度大於5%之實驗因子細分成四水準，以L16（45）直交表實驗計劃法，尋找顯著影響因子最適化之萃取條件，最適化的萃取條件經過矽藻土基質樣品與模擬縱火基質樣品之萃取實驗後，從而確認其高萃取回收率及高再現性。 固相微萃取分析四種縱火加速劑的實驗裡，影響因子雖較單純，但吸附纖維的種類、樣品預熱時間、吸附的溫度及吸附的時間等因素亦該於調整實驗條件時列入考量，利用L8（27）及L16（45）直交表實驗計劃法對四種縱火加速劑進行最適化萃取條件的開發，這些研究獲得之最適化萃取條件亦經不同樣品類別之重複分析後確認其再現性，同時在進行過比較實驗後更肯定其萃取效果優於傳統對縱火殘跡樣品預測試之頂空分析法。 本論文的研究結果顯示，直交表實驗計劃法不但節省時間成本與經濟成本，且可系統有效地探尋獲得最佳化的萃取條件，同時無論是超臨界流體萃取亦或頂空固相微萃取之最佳萃取條件，皆證實可將矽藻土中所添加的縱火加速劑或模擬縱火殘跡樣品中的微量縱火加速劑予以萃取回收，甚至是運用在實際採自縱火火場之殘跡證物。故而這兩種方法由於具有高靈敏度與再現性，將可替代傳統上靈敏度或再現性較差的頂空分析法成為縱火殘跡樣品前處理技術之一。

Supercritical fluid extraction (SFE) method and headspace solid-phase microextraction (HS-SPME) were employed in the present studies as effective sample pretreatment techniques of petroleum distillates from fire debris. Three petroleum distillates - 95 unleaded gasoline, kerosene, and premium diesel - were used as target analytes in the SFE study. The three petroleum distillates, in addition to cleaning naphtha, were also chosen as arson accelerants in the HS-SPME study. It is well known that several factors affect the extraction efficiency of SFE, including extraction fluid density, extraction temperature, flow-rate, dynamic extraction time, and static equilibrium time. Thus, two sequential experiments, with a L16 (215) and a L16 (45) orthogonal array design, were conducted to evaluate and optimize primary SFE experimental factors. Similarly, some factors have been known to influence the efficiency of HS-SPME, such as fiber coatings, preincubation time, adsorption time, and adsorption temperature. Consequently, L8 (27) and L16 (45) orthogonal array experimental designs were employed to evaluate and optimize the HS-SPME experimental factors for analyzing the four arson accelerants. Experimental results showed that an orthogonal array experimental design was a cost-effective and timesaving optimization strategy. Furthermore, it offered a systematic and efficient approach to optimize the extraction conditions for arson accelerants. Experimental results also demonstrated that the optimized SFE and HS-SPME conditions not only provided effective extraction conditions for spiked samples, but also successfully recovered residues of petroleum distillates from simulated fire samples or real fire debris. In summary, SFE and HS-SPME are efficient pretreatment methods for analyses of arson suspected fire debris. Their sensitivity and reproducibility are better than the headspace sampling method, which is a traditional sample pretreatment method for fire debris.