Development And Application Of Microextraction Tube Injection Technique

Analytical instruments have made significant advance in many areas,however,sample preparation is still the bottleneck in the pursuit of optimal analytical methods,especially in the determination of trace analytes in complex sample matrix.When the sample is directly introduced into the instrument,the complex matrix component not only interferes with the sample analysis,but also affects the life of the instrument.Therefore,it is important to perform sample processing prior to instrumental analysis to reduce matrix interference,enrich for trace analytes,and convert the sample into a form that compatible with the instrument.A complete sample preparation steps typically involve extraction,purification,and preconcentration.Liquid-liquid extraction（LLE）and solid phase extraction（SPE）are the most common methods of sample preparation.For the liquid phase extraction,due to the fact that the extraction solvent cannot be mutually soluble with the sample and the types of commonly used organic solvents are limited,the selection range of extractant is very limited.Solid adsorbents do not have the above problems,and there are a variety of adsorbents to meet the extraction requirements of different analytes.The solid adsorbent based method does not present the above problems,and there are a variety of adsorbents that can meet the extraction requirements of different analytes.As the most widely used pretreatment method,the main advantages of SPE are the high accuracy and good reproducibility.However the operation is still relatively tedious.Nitrogen blowing is usually required to concentrate low-concentration samples,which not only takes time,but also has a low utilization rate of the analyte.In recent years,the miniaturized sample preparation method has become an important development direction of the current sample pretreatment technology because of its remarkable high efficiency and green characteristics.In this work,a novel technique termed as micro-extraction tube injection（METI）has been established for sample pretreatment and then applied to the determination of trace contaminants in milk and environmental water samples.The specific research contents are as follows:1.Some existing miniaturized sample pretreatment technologies in recent years are briefly introduced.2.Poly（BMA-EGDMA）monolithic was synthesized via in-situ polymerization and was used for the construction of METI technology.A preliminary assessment of the enrichment performance of METI has been carried out.The results show that this method has little demand for samples and greatly reduces the demand for organic solvents.Moreover,the routine procedure of concentration（eg.N₂ purging concentration）is no longer required.Thus,METI exhibits obvious advantages in enriching efficiency,organic solvent consumption and time consumption.3.A method of METI hyphenated to gas chromatography for the determination of PCBs in milk sample was established by using poly（BMA-EGDMA）monolith as the extracting media.Under the optimal conditions,the linear ranges of these PCBs are between 0.05,0.2 or 0.5 and 100μg/L depending on the analyte.The detection limits vary from 0.004 to 0.055μg/L and the quantitation limits are within the range from0.014 to 0.184μg/L.It can be seen that this method can provide high sensitivity.4.The poly（NVP-DVB）monolith was used as the extracting media for the establishment of METI-GC/MS for the determination of phenolic compounds in water.Under the optimal conditions,the linear ranges are between 0.2 and 100μg/L for all phenols detected except m-Cresol and 4-CMC（0.5-100μg/L）.The detection limits vary from 0.003 to 0.062μg/L and the quantitation limits are within the range from 0.009 to0.207μg/L.It can be found that the method can be used to extract analytes with different properties by changing the extraction medium.