Headspace Ionic Liquid-based Single-drop Microextraction For Analysis Of The Volatile Compounds In Seeds Of Cuminum Cyminum L. And Forsythiae Fructus

Headspace single-drop microextraction (HS-SDME) using ionic liquid (IL) asextraction solvent, followed by a new injection mode of gas chromatography wassuccessfully developed to determine the volatile compounds in solid spices.Hydrodistillation coupled with headspace single-drop microextraction using ionicliquid as the extraction solvent (HD-HS-IL-SDME) and ultrasonic nebulizationextraction coupled with headspace single-drop microextraction using ionic liquid asthe extraction solvent (UNE-HS-IL-SDME) followed by direct GC analysis weredeveloped in this thesis. In these proposed methods, the chromatographic columncannot be contaminated and a clean chromatogram can be obtained. The proposedmethods were environmental-friendly, time-saving and high extraction efficiency.HD-HS-IL-SDME was successfully developed to determine the volatile andsemivolatile compounds in seeds of Cuminum cyminum L.. In the HD-IL-HS-SDME,a50mL round-bottom flask and a5μL microsyringe were used with the needle of themicrosyringe inserted into the headspace of the flask. After reflux for30min(extraction time), IL was pushed out from the microsyringe and suspended from theneedle tip. The microdrop was retracted back into the microsyringe after severalminutes (enrichment time) and the needle was then transferred to the thermaldesorption system. The chromatographic column cannot be contaminated and a cleanchromatogram can be obtained. In order to obtain the most favorable extractionconditions, the extraction parameters of HD-IL-HS-SDME, including the type of ionicliquid, microdrop volume, extraction time, enrichment time, and thermal desorption,were investigated. The RSD values for the retention time of the five components including β-pinene, р-cymene, γ-terpinene, cuminal and cuminalcohol obtained by theproposed method are0.24%,0.31%,0.38%,0.061%, and0.041%respectively, so thatthe reliability of the method was confirmed. The extraction efficiency of the proposedmethod was compared with that of HD. The contents of the constituents in the extractobtained by the proposed method were close to those obtained by HD, which is astandard extraction method. The all content of constituents in the extract obtained was99.8%, and the RSD values for the peak areas of the main components are less than3.5%. The proposed method would extend the application rang of the HS-SDME andwould be useful especially for aromatic plants analysis.It is effective that UNE and HS-IL-SDME are combined to extract the volatilecompounds from Forsythiae Fructus and then determine the analytes by direct GCanalysis. The50mg of sample and5mL of water are used for the dynamic UNEprocedure. The flow rate of purging gas was200mL/min. The IL,[OMIM][PF6], isselected as extraction solvent instead of traditional organic solvent with3μL of thesolvent microdrop volume. After extraction for13min, the target analytes with IL canbe directly transferred and injected into GC injector for thermal desorption and thenentered into GC column. the injection volume was2μL, and thermal desorptiontemperature and time were240℃and5s, respectively. The proposed method wasenvironmental and high effective, compared with hydrodistillation (HD).18differentcompounds were identified by the propose method. The RSD values for the fourmajor components obtained by the proposed method are1.5%,4.1%,2.1%, and4.3%,respectively. The proposed method is beneficial for extracting volatile compoundswhich are sensitive to temperature and a chromatogram without solvent peaks can beobtained. The newly proposed method would extend the application range ofHS-SDME, especially for aromatic Chinese herbal medicine analysis.