Layered Double Hydroxides Based Solid Phase Microextraction And Its Application In Pharmaceutical Analysis

As a novel sample preparation technique,solid phase microextraction(SPME)can effectively decrease matrix interference and realize selective enrichment of target compounds,and has been combined with high performance liquid chromatography(HPLC)for analysis of complex samples such as food,environmental,medical and biological samples.The development of novel extraction sorbents is the important part of SPME.In this work,we aimed to use layer double hydroxides(LDHs)and its functional material as extraction sorbents for developing high efficient and selective SPME methods.After coupling with HPLC,these methods were applied for pharmaceutical analysis.The main contents include two parts:1.In situ immobilization of layered double hydroxides onto cotton fiber and its application in analysis of fluoroquinolones and adsorption of anionic compounds.Cotton fiber is easy to obtain and has high surface area as well as high porosity,so it’s an ideal substrate for SPME.LDHs were modified on cotton fiber through polydopamine method and the modified cotton fiber was filled into micropipette tip as an in-tip SPME device,thus solving problems of high backpressure and limited mass transfer in the filling process.Based on ion exchange interaction,LDHs modified cotton fiber was used for high efficient and selective extraction of fluoroquinolones.An in-tip SPME-HPLC method was developed to extract and determine fluoroquinolones with a low limit of detection of 0.01 ng/m L.The method was applied in the analysis of fluoroquinolone residue in chicken eggs and pork liver with recoveries of 83.36-95.03%.Moreover,LDHs modified cotton fiber was proved to have favourable adsorption performance towards anionic compounds including ketoprofen and Congo red and several adsorption devices were developed for quick and efficient adsorption of anionic compounds.2.Layered double hydroxides supported p-naphtholbenzein on poly(ether ether ketone)jacket for stir bar sorptive extraction of bioactive compounds in Fructus Psoraleae.LDHs were immobilized on the surface of PEEK tube through polydopamine method and then hydrophobic small molecule p-naphtholbenzein(PNB)was immobilized on the surface of silanized LDHs(PNB@LDHs@PEEK).The modification of PNB molecule enhanced the surface hydrophobicity of LDHs and Ni-Al LDHs increased surface area of substrate and immobilization amount of PNB molecule.The modified PEEK was made into a detachable dumbbell-shaped device for stir bar sorptive extraction(SBSE)of three hydrophobic flavonoid compounds in Fructus Psoraleae and good extraction performance was obtained.A SBSE-HPLC method was developed with a low limit of detection of 0.01 ng/m L and applied in the content determination of three flavonoid compounds in Fructus Psoraleae.