Research And Application Of Separation And Enrichment Technique In Sample Pretreatment

Now analytical instruments have been rapidly developed along with the advancing of science and technology. While sample pretreatment is also a key factor in pharmaceutical analysis, especially for analyzing trace amount analytes in drugs, environmental samples and biological samples. The main function of sample pretreatment is to increase sensitivity and accuracy of the method by extracting, separating, purifying and enriching analyte from complex matrix, and even conducting chemical modification to convert it into measurable form. The traditional sample preparation techniques are usually tedious, tedious, low sensitivity and poor specificity. Thus sample preparation technique has become a great challenge faced by pharmaceutical analyzer. It’s critical to explore a simple, high sensitivity and specificity sample preparation technique.Part one: Ionic liquids as matrix medium for the determination of high-boiling residual substances in Tenofovir simultaneously by static headspace gas chromatographyObjective: Headspace-gas chromatography(HS-GC) is the common way to analyze the volatile compounds. But for the analyte with high boiling point, the sensitivity and specificity are difficult to meet analytical requirement. This is because that traditional headspace solvent in itself is volatile, the formation partial pressure will prevents analyte to enter into the top. Furthermore, the broad chromatographic peak produced by headspace solvent may interfere with analyte. Ionic liquids(ILs) as a new material show many unique physical and chemical properties, such as negligible vapor pressure, excellent thermal stability and high solubility, make them well suitable for HS-GC. Methods: In our study, 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF4) was selected as matrix medium for separating and enriching four high boiling pointsubstances utilized in synthesis of TDF. They are N-methyl-2-pyrrolidone(NMP), N,N-Dimethylformamide(DMF), chloromethyl isopropyl carbonate(CMIC) and toluene. Results: The obtained method was evaluated and validated: the method sensitivity was significantly improved, and the limit of detection was all of the ppm level. Conclusion: The developed method is simple, sensitivity and specificity, providing an alternative for analyzing the high-boiling analyte.Part two: Research and application of new simultaneous derivatization and microextration method in pharmaceutical analysis1 A new simultaneous derivatization and microextraction pretreatment method: application to the determination of Memantine Hydrochloride in environmental samplesObjective: Due to the complex matrix, analyzing trace amount of analytes environmental samples is difficult. Liquid-liquid extraction(LLE) is a classical and common pretreatment technique for clean up and preconcentration. However, these procedures, which require relatively high toxic reagent, are laborious and tedious. For compound with no chromophore, it still needs further derivatization after extraction. The excessive steps lead to an unsatisfactory method’s reliability and precision. Recently, Hollow fiber liquid phase microextration(HF-LPME) provides potentially attractive features in sample pretreatment owing to its high selectivity, efficiency, economic and low consumption of organic solvents. It is suitable for the treatment of environment sample. In this paper, we describe an interesting method, which coupling dervatization with microextraction to one step, for the determination trace levels of MT in environment sample. Method: The hollow fiber was full of cyclohexane and dansyl chloride as acceptor phase and immersed in the alkalinized aqueous samples. Then the system was submitted to stir at 800 rpm for 60 min at 40 ℃ for separating and enriching analyte. Results: It was consisted of derivatization, extraction, clean-up and preconcentration in a signal step, thereby, reducing experimental errors and improving the precision(RSD≤3.8%). During the microextraction,derivatization could facilitate diffusion of the analyte and contribute to a lower LOQ. Moreover, the current method had some other advantages such as excellent clean up ability and requiring negligible toxic organic reagent. Conclusion: The proposed method has a strong potential as a future analytical performance in the analysis of environmental samples.2 A new simultaneous derivatization and microextration method for the determination of memantine hydrochloride in human plasma Objective: Complicated matrices and low analyte concentration have been recognized as an important incentive for carrying out sample clean up and preconcentration before analyzing analyte in biological samples. HF-LPME is an attractive pretreatment technique because that it could not only extract target analyte efficiently but also prevent large molecules from entering into acceptor phase within the fiber, functioning as a protective sheath against matrix. Therefore, it is perfect to be applied to plasma sample. Method: In this paper, both of extraction and derivatization agents were put into the lumen of the hollow fiber. The system was submitted to stirring at 800 rpm for 50 min at 40 ℃. Results: So extraction and derivatization can be achieved simultaneously. Consequently, the experimental errors were reduced and an excellent precision was obtained. Also, derivatization reaction accelerated the mass transfer and thus improved the enrichment ability(LOD=0.1 ng/m L). Conclusion: The proposed method is simple, sensitive and specific, it has a great significance on the analysis of trace levels of analyte in plasma sample.