Fabrication Of Magnetic Carbon Nitride Adsorbent And Its Application In Solid-phase Extraction

Objectives For the monitoring of risk components in various complex matrices,the development of convenient and effective pretreatment methods to improve the accuracy and reduce the cost consumption is of great significance and challenge.In this study,magnetic graphitic carbon nitride?g-C₃N₄/Fe₃O₄?composites with good stability and uniformity were first fabricated by a solvothermal strategy.The composites were applied as an effective adsorbent and coupled with high performance liquid chromatography?HPLC?for the analysis of trace hydroxylated polycyclic aromatic hydrocarbons?OHPAHs?in urine samples and estrogen residues in milk powders,respectively.Methods 1 g-C₃N₄/Fe₃O₄ was synthesized via a simple solvothermal reaction and characterized by Fourier transform infrared spectrometer,X-ray diffractometer,scanning electron microscope,vibrating sample magnetometer and surface area and pore size distribution analyzer.2 The prepared g-C₃N₄/Fe₃O₄ was developed as adsorbent for magnetic solid-phase extraction?MSPE?of trace OH-PAHs in urine samples.The factors such as adsorbent amount,adsorption time and eluting solvent and its volume were optimized.The analytical figures of merit were evaluated including linear range,limit of detection,limit of quantification,accuracy,precision,enrichment factor,as well as reusability of the adsorbent.3 The prepared adsorbent was further applied for MSPE of estrogens in milk powders.The effect of extraction parameters such as the adsorbent amount and eluting condition were optimized in detail.The method of g-C₃N₄/Fe₃O₄ based MSPE combined with HPLC was developed for the determination of estrogens in milk powders.Linear range,limit of detection and limit of quantification,accuracy,precision and enrichment factor were evaluated.Results 1 The Fourier transform infrared spectrometer and X-ray diffractometer results confirmed that the representative bands of g-C₃N₄/Fe₃O₄ composites were all attributed to the graphitic carbon nitride and Fe₃O₄,which indicated the successful combination of graphitic carbon nitride and Fe₃O₄.The saturation magnetization value of g-C₃N₄/Fe₃O₄ was 36.4 emu.g-1 and the surface area was found to be 113.7 m2.g-1.The scanning electron microscope images revealed the successful fabrication of graphitic carbon nitride and Fe₃O₄ and the uniform structure of the prepared composites.These properties made gC₃N₄/Fe₃O₄ as a powerful MSPE adsorbent.2 For the selected OH-PAHs,the isolation was achieved within 3 min when performing 4 mg of adsorbent,and acetone with volume of 0.5 m L×2 was selected as eluting solvent.The present method showed a linear range of 0.25-250 ng.m L-1?correlation coefficient r?0.9985?and provided an enrichment factor of 10.The intra-day and inter-day precisions were 1.5%-7.7% and 2.2%-8.7%,respectively.The limits of detection?S/N=3?and limits of quantification?S/N=10?ranged 0.08 ng.m L-1 and 0.25 ng.m L-1 for the analytes,respectively.The recoveries from spiked urine samples varied from 90.1% to 102%.The adsorbent was stable over 10 successive cycles of extraction/desorption of urine samples with variation of extraction efficiency less than 9.8%.3 The extraction of estrogens was achieved by using 15 mg adsorbent with 2 m L×3 of methanol as eluting solvent.Combined with HPLC-variable wavelength detectorfluorescence detector,MSPE with the prepared adsorbent gave the enrichment factors of 22 to 24,the linear ranges of 2.0-200 ?g.kg-1 for 17?-estradiol and 17?-ethinylestradiol,1.5-150 ?g.kg-1 for estrone and 3.0-300 ?g.kg-1 for hexestrol?r=0.9999?.The limits of detection?S/N=3?and limits of quantification?S/N=10?for the estrogens in milk powder samples ranged from 0.5 to 0.9 ?g.kg-1 and 1.5 to 3.0 ?g.kg-1,respectively.The recoveries varied from 86.5% to 97.2%,with the intra-day and inter-day precisions less than 12.3%.Conclusions 1 The g-C₃N₄/Fe₃O₄ composites with good stability were fabricated via facile solvothermal strategy.A method based on MSPE using g-C₃N₄/Fe₃O₄ composites coupled with HPLC-fluorescence detector was developed for the simultaneous determination of three OH-PAHs in urine.The extraction for the analytes by using 4 mg of adsorbent was achieved within 3 min,and provided the enrichment factor of 10.In addition,the method was applied for analysis of urinary OH-PAHs in a simple,fast and effective way.Regarding the good feasibility of the adsorbent,it has great potential in dealing with other nonpolar analytes from biological samples.2 Coupled with HPLC-variable wavelength detector-fluorescence detector,a g-C₃N₄/Fe₃O₄-based MSPE approach was established for the facile and accurate analysis of estrogens in milk powders.The extraction was achieved by performing 15 mg adsorbent within only 2 min.At the same time,the extraction was capable of one-step removal of the fats impurities and gave the enrichment factors of 22-24.The proposed method is convenient and fast,which provides a new approach for the purification and enrichment of polar compounds in food samples.Figure 18;Table 11;Reference 139...