離子溶液在毛細管電泳中的應用

Abstract

離子溶液具有許多優點，如低蒸氣壓、化學性質穩定及熱穩定性好等，應用於毛細管電泳上可與分析物作用提高分離的效率，為一新穎的材料。苯二氮平類的藥物具有安眠、鎮定、抗痙攣以及肌肉鬆弛等作用，鑑於國內濫用的情形日益攀升，目前關於苯二氮平的研究也越來越受到注目。在本實驗中，將離子溶液的應用區分成兩個研究方向，一個是在當離子溶液在毛細管電泳中做為添加劑時，其分離效率與機制的探討，一個則是將離子溶液應用於線上濃縮方法以提高靈敏度，並降低偵測極限。 在第一部分的實驗中，首先利用三種不同陽離子的離子溶液當作修飾劑比較分離效率，同時也固定陽離子種類比較陰離子的影響，由實驗結果證實添加離子溶液確實有助於分離的效果的改善，其中陰離子影響程度大於陽離子，因此我們嘗試只添加陰離子部分的鹽類LiNTf2、LiPF6以及LiOTf測試分析物與陰離子間的作用關係。實驗結果發現在300 mM LiNTf2條件下，7個苯二氮平藥物可在18分鐘內完全分離，除此之外，在比較三種不同陰離子時TfO-、PF6-、Tf2N-造成的影響時，Tf2N-的效果比PF6-與TfO-更佳，文獻中指出Tf2N-為具有強chaotropic effect的陰離子，因此推測陰離子的chaotropic effect對分離有助益，當使用作用越強的chaotropic anion，其分離效率越高。 在第二個實驗中，我們利用兩種離子溶液型態的界面活性劑（C16MIMBr與C16MPYB）做陽離子型的微胞，應用於掃掠式線上濃縮法，偵測低濃度苯二氮平類藥物。實驗中測試了許多掃掠式線上濃縮參數，並將其條件最佳化，如pH、甲醇比例、界面活性劑濃度、緩衝溶液的離子強度以及樣品注射時間等，由這些實驗結果顯示C16MIMBr與C16MPYB均可提高分離效率和增加靈敏度，得到C16MIMBr的放大倍率為31~59倍，C16MPYB則為86~165倍。當使用C16MPYB為微胞時，LOD（S/N=3）為4.68~9.75 ng/mL，最佳條件應用在經過固相萃取的尿液樣品中，也可成功的去除雜質干擾並偵測得到七個樣品的訊號，其回收率在76.6％到88.3％之間，表示離子溶液型態的界面活性劑可成功地應用於掃掠式線上濃縮法上。

Ionic liquids are novel materials that have many advantages such as low vapor pressure, chemical and thermal stability. Using ionic liquids in capillary electrophoresis can improve separation efficiency of interest analytes by the interaction between ionic liquids and analytes. Benzodiazepines are prescribed drugs for hypnotics, minor tranquilizers, anticonvulsants and muscle relaxant. The increasing events in abuse of benzodiazepines make these drugs attract more attentions nowadays in Taiwan. In this study, we divided the applications of ionic liquids into two parts. One part is using ionic liquids as the modifier in running buffer to improve separation efficiency, and according to the experimental results we could understand the separation mechanism between modifiers and analytes. The other is the application of ionic liquids in preconcentration method to enhance the sensitivities and achieve lower detection limits. In the first part, we utilize three different cationic parts of ionic liquids as modifiers to compare the separation efficiency. The influence of anionic parts of ionic liquids was also evaluated. Both of them enhance the separation efficiency. We find out the anionic parts influence the analytical results more than the cationic parts. As the result, attempt to addition of anionic salts, such as LiNTf2, LiPF6, and LiOTf, derives the relationship between anions and analytes. After adding 300 mM LiNTf2, seven benzodiazepines can be completely resolved in 18 min. In addition, the performance of using Tf2N－ which was reported an anion with strong chaotropic effect, is much better than using PF6－ and TfO－ under the same concentration, meaning that the chaotropic effect of anions enhances separation efficiency. We can attribute these results that the more chaotropic anion is, the better resolution we can obtain. In the second part, we take two cationic surfactants, C16MIMBr and C16MPYB, which are reguarded as ionic liquids and used for sweeping-MEKC The optimal separation conditions are rationalized by factors of pH, methanol, surfactant concentration, buffer ionic strength, and injection time. C16MIMBr and C16MPYB illustrate the development of sensitivities and resolutions. Sensitivity enhancement displays 31~59-fold improvement for C16MIMBr and 86~165-fold improvement for C16MPYB compared with normal-MEKC mode. LOD（S/N=3）ranges from 4.68 to 9.75 ng/mL for C16MPYB. After extraction of the urine with SPE cartridge and analyte with optimal conditions, seven benzodiazepines are able to be identified without interference of impurities; recoveries are between 76.6% and 88.3%. As a result, the sweeping-MEKC can be successfully achieved by these ionic liquid typed surfactants.