Preparation Of Stir Bar Sorptive Extraction Based On Monolithic Material For Separation And Analysis

Solid phase micro-extraction (SPME) is an effective sample pretreatment technique which integrates sampling, extraction and concentration into a solvent-free step. Stir bar sorption extraction (SBSE) is a developing type of the SPME. The SBSE can accelerate the mass transfer rate because it stirs itself during extraction. In addition, it has about 50-250 times larger volume of extraction phase than that of fiber-SPME, resulting in corresponding increase in enrichment factor of the target component. Therefore, the SBSE is more suitable for extraction of trace organic compounds. But the commercial SBSE only has one single type of coating for the non-polar or weakly polar compounds, the application scope is limited. Thus, development of more types of SBSE has become a hot topic in current research. Due to the porosity, high permeability and fast mass transfer efficiency, monolithic materials have found important applications in separation, catalysis and other fields. Development of SBSE based on the monolithic materials has attracted the interest of researchers.In this work, a method for rapid determination of malachite green in water was established by using a commercial fiber-SPME, combined with high performance liquid chromatography (HPLC). The SPME operating conditions were optimized including extraction fiber, extraction time, desorption solution composition, desorption time and pH value etc. The method showed a good linear relationship in the concentration range of 0.05²Î¼g·mL^-1, and the linear correlation coefficient was 0.9922. The relative standard deviation was 3.6% and the average recovery was 98.1% -109.6%.To overcome the shortcomings of the commercial fiber-SPME and SBSE, a novel stir bar for sorption extaction based on monolithic material (SBSEM) was prepared by in-situ stepwise polymerization of epoxy resin and diethlene triamine using polyethylene glycol as porogen. It was then used to extract polar compound (malachite green) in the environmental water sample. A method was established by optimizing the experimental conditions such as pH value, stir rate, extraction time, desorption mode and desorption solvent. The method had a good linear relationship in the concentration range of 0.01-5μg·mL^-1 with a correlation coefficient of 0.9998. The SBSE was successfully used to extract polar compounds. The SBSEM was then used to extract Cd ion in the environmental water sample. A method was established by optimizing the experimental conditions such as pH value, stir rate, extraction time and desorption. The method has a good linear relationship in the concentration range of 0.1-50μg·mL^-1, the linear correlation coefficient was 0.9972. The recovery was from 96.8% to 104.2%. The SBSEM was successfully used to extract inorganic ions. Kinetic studies had shown that the SBSEM extracts Cd ion faster than the static extraction. The SBSEM is beneficial for rapid extraction of trace metal ions in solution.Electric field can further enhance the adsorption efficiency of metal ions in solution by accelerating mass transfer. The solid phase micro-extraction rod (SPME rod) was successfully prepared by SBSEM based on the monolithic material. The prepared SPME rod was connected with high voltage power supply as the working electrode. The electric migration was applied to accelerate mass transfer of Cu ion in solution for improving the extraction efficiency. The experimental conditions including the pH value, sorption mode, voltage, adsorption time and desorption condition were investigated and optimized, and a new method for determination of Cu ion in solution was established. The method had a good linear relationship in the concentration range of 0.1-50μg·mL^-1, the linear correlation coefficient was 0.9979. The extraction efficiency of the SPME rod was improved significantly by the applied electric field.In this work, the prepared SBSEM has overcome the shortcomings to some extent of the commercial SBSE. It was successfully applied in the extraction of polar compounds and inorganic heavy metal ions, and achieved satisfactory results. Furthermore, the purpose to enhance the adsorption efficiency of the SPME rod for metal ions was also achieved by applying electric field.