Determination Of Some Organic Pollutants In Samples By Novel Magnetic Adsorbents Coupled With High Performance Liquid Chromatography

Very recently, a new extraction technique called magnetic solid-phase extraction(MSPE) has been developed. MSPE has several advantages in comparison with solid-phase extraction(SPE). The magnetic adsorbents can be readily isolated from the sample solution by an external magnetic field without the need of filtration or additional centrifugation procedures, which makes the phase separation easier and faster. G can form strong hydrophobic and π-stacking interactions with different organic molecules due to its large delocalized π-electron system, so it could serve as a good adsorbent. Three-dimensional graphemes(3D-G) effectively maintain the accessible surface area of the individual G nanosheets, and can achieve fast mass transport kinetics, which is critical for efficient adsorption for some specific analytes. Nanoporous carbon materials(NPC), due to its high pore volume, high specific surface area, good electrical conductivity and thermal conductivity, high chemical stability, interconnected frameworks as well as tunable pore size, have been paid much attention from researchers.In this work, MSPE using novel adsorbents coupled with high performance liquid chromatography(HPLC) was explored for the determination of the neonicotinoid insecticides, endocrine disrupting phenols and phthalate esters in lemon juice, honey peach juice sample, aloe juice sample, peanut milk sample and environmental water sample. The following research works have been carried out:1. A novel three-dimensional graphene magnetic nanomaterial(3D-G-Fe3O4) was prepared and used as an adsorbent for the extraction of four neonicotinoid insecticides(acetamiprid, imidacloprid, thiacloprid and thiamethoxam) from lemon juice samples. Then, high performance liquid chromatography with ultraviolet detection was applied for the determination of the neonicotinoid insecticides desorbed from the 3D-G-Fe3O4 nanomaterial. As a result, the linear concentration range of the method was from 0.3 to 100.0 ng/m L for thiacloprid, from 0.5 to 100.0 ng/m L for imidacloprid and acetamiprid, and from 1.0 to 100.0 ng/m L for thiamethoxam, with the correlation coefficients of 0.9965-0.9985, respectively. The limits of detection of the method based on a signal to noise ratio(S/N) of 3 were between 0.08 and 0.2 ng/m L. The enrichment factors(EFs) obtained was between 67 and 427. The relative standard deviations(n = 6) were in the range from 4.6% to 7.1%, and the recoveries of the method fell in the range of 88.75%-111.60%.2. In order to further evaluate the adsorption capacity of the 3D-G-Fe3O4 on the other environmental pollutants, the prepared 3D-G-Fe3O4 was used as an adsorbent for simultaneous extraction and concentration of three endocrine disrupting phenols(EDPs) including bisphenol A(BPA), 4-tert-butylphenol(t-BP) and 4-tert-octylphenol(t-OP) from bottled honey peach juice sample prior to high performance liquid chromatography-fluorescence detection. In addition, parameters that could affect the extraction efficiencies for the three EDPs were optimized. The results indicated that 3D-G-Fe3O4 adsorbent showed an excellent adsorption capacity for the target analytes. The quantification was achieved by matrix-matched calibration. The calibration curves of the three EDPs in honey peach juice sample showed linearity from 0.05 to 10.0 ng/m L for BPA and from 0.1 to 10.0 ng/m L for t-BP and t-OP, with the correlation coefficients of 0.9966-0.9981. The average spiked recoveries ranged from 88.61% to 108.95%. The limits of detection based on a signal to noise ratio(S/N) of 3 were found to be 0.01-0.025 ng/m L. The developed method has been successfully applied to the extraction of three EDPs in honey peach juice samples, and a satisfactory result was obtained.3. In this work, magnetic nanoporous carbon with high surface area and ordered structure was synthesized using cheap commercial silica gel as template and sucrose as carbon source. The prepared magnetic nanoporous carbon was firstly used as an adsorbent for the extraction of phthalate esters including diethyl phthalate, diallyl phthalate and di-n-propyl-phthalate from lake water and aloe juice samples. Several parameters that could affect the extraction efficiency were optimized. Under the optimum conditions, the limits of detection of the method(S/N=3) was 0.10 ng/m L for water sample and 0.20 ng/m L for aloe juice sample. The linearity was observed over the concentration range of 0.50-150.0 ng/m L and 1.0-200.0 ng/m L for water and aloe juice samples, respectively. The results showed that the magnetic nanoporous carbon has a high adsorption capability toward the target phthalate esters in water and aloe juice samples.4. Magnetic ordered porous carbon(MOPC-ZSM-5) was synthesized using zeolite ZSM-5 as a template and sucrose as a carbon source. It was used as a magnetic solid-phase extraction adsorbent for the extraction of four neonicotinoid insecticides(acetamiprid, imidacloprid, thiacloprid and thiamethoxam) from river water and peanuts milk samples prior to high performance liquid chromatography-ultraviolet detection. The calibration curves for the four neonicotinoid insecticides in water sample showed linearity from 1.0 to 200.0 ng/m L for thiamethoxam, imidacloprid, thiacloprid, and 0.5 to 200.0 ng/m L for acetamiprid. For peanuts milk sample, the linearity was 6.0-1000.0 ng/m L for thiamethoxam, imidacloprid, thiacloprid, and 3.0-1000.0 ng/m L for acetamiprid, respectively. The developed method has been successfully applied to the determination of the four neonicotinoid insecticides in river water and peanut milk samples, and a satisfactory result was obtained.