固相萃取 (Solid Phase Extraction，簡稱 SPE) ，此項技術近年來被廣泛地應用在揮發性、半揮發性及不揮發性物質之分析應用，包括食品、香味、環境、毒物、藥物、天然物及法醫鑑識等相關領域，這種方法可解決許多分析上樣品前處理的問題。固相微萃取的操作方式可分為二大步驟: (1) 吸附樣品，(2) 脫附樣品及後續樣品的分析。在樣品吸附部份，待測物藉由”擴散”作用從基質 (Matrix) 到達靜相表面，被靜相表面的特殊材質所吸附，經”脫附”後待測物直接進入 HPLC 或 GC 進行分析。而固相萃取材料的發展與探討，更是固相萃取方法的重點所在。
本研究以管制的麻醉性藥品 Ketamine 做為重要指標， Ketamine 在近年來已成為藥物濫用的指標性藥物之一；實驗中所合成的固相萃取材料會利用甲基丙烯酸 (MAA; Methacrylic acid) 做為功能性單體(functional monomer) ；利用乙二醇二甲基丙烯酸 (EGDMA; ethyleneglycoldimethacrylate) 以及三羥甲基丙烷三甲基丙烯酸 (TRIM; Trimethylolpropane trimethacrylate) 做為交聯劑(cross-linker) ；使用偶氮二異丁腈 (AIBN; azobisiso butyronitrile) 做為起始劑(iniator) ；並使用孔洞劑(porogen) 二甲基甲醯胺 (DMF; Dimethylformide) 來製備材料，在不同環境下對 Ketamine 的吸附效果，並進一步使用 HPLC 偵測 Ketamine 之訊號；最後會於日常隨手可購得的飲料中添加 Ketamine 來測試所製備出的材料對偵測效果的可行性。
由本實驗測得每毫克的固相萃取材料於不同濃度 Ketamine 溶液中，其吸附效果會隨著Ketamine濃度的增加而提升；而在汽水樣品中Poly(MAA-co-TRIM) 對 Ketamine之吸附效果比Poly(MAA-co-EGDMA) 來的較佳，每毫克Poly(MAA-co-TRIM) 於添加100 μM Ketamine 有60%的吸附效果。 Solid phase extraction (SPE) is the most widely used sample preparation technique for purifying complex samples before their analysis by liquid chromatography (LC) or gas chromatography (GC). In SPE, analytes are partitioned between a solid phase and a liquid phase and the sorbent usually is chosen to have a greater affinity for the analytes than for the sample matrix. Most SPE sorbents are based on silica that has been bonded to a specific functional group. In recent years, there has been a renewed growth in SPE, primarily driven by the introduction of newer packing materials based upon specialized polymer technology that overcomes some of the disadvantages of silica-based materials.
In this study, SPE sorbents with high adsorption capacity for ketamine have been synthesized. MAA and EGDMA or TRIM were chosen as functional and cross linking monomers and determined by the ratio of 1:5. The pore properties of these materials are controlled by the percentage of monomers in the polymerization mixture. The rigid was found to increase with the monomer content of the monolith.
Poly(MAA-co-EGDMA) and Poly(MAA-co-TRIM) both effectively extracted ketamine from purified water. The effect of pH on adsorption of ketamine on poly(MAA-co-TRIM) from phosphate buffer has been investigated by measuring adsorbed amounts of ketamine in the pH range of 2–12. The adsorbed amount increases largely with increasing pH from 4.0 to 8.0. When the pH was increased to 8, the adsorption of the ketamine on poly(MAA-co-TRIM) reached a maximum and remained almost constant until pH 12.
The effect of initial ketamine concentration was determined by contacting 1.0 mg sorbent with 0.5 mL of ketamine solutions (100–5000μM). The maximum adsorption loading, under the studied experimental conditions, found to be about 290 mg/g for poly(MAA-co-TRIM) and 200 mg/g for poly(MAA-co-EGDMA) .
Three different types of desorbing solvents were used to remove the adsorbed ketamine from the sorbents. When mobile phase was used as the desorbing solvent, only about 30-40% of the adsorbed ketamine was desorbed, whereas the value increased to 60-84% when methanol/acetic acid (9/1, v/v) was used for the extraction of ketamine from the polymer.
The experimental results show that poly(MAA-co-TRIM) and poly(MAA -co-EGDMA) has high adsorption capacity and rapid adsorption/desorption kinetics for ketamine.
