| In the analysis of complex samples(biological,food,environmental),sample preparation plays a crucial role in the overall analytical process.An appropriate sample pretreatment ensures an adequate sensitivity by enriching the trace or ultra-trace target analytes to detectable limits,and simultaneously increases the selectivity of the method by removing potential interferences present in the matrix of the sample.In this thesis,magnetic molybdenum disulfide-based nanomaterials were fabricated as selective adsorbents,and new methods for the determination of trace components in complex matrices(food and biological samples)by magnetic solid-phase extraction combined with ultra-high-performance liquid chromatography-mass spectrometry was established.(1)A novel magnetic adsorbent,three-dimensional magnetic graphene-like molybdenum disulfide composites(AL-MoS2@Fe3O4)using ultrasonic-assisted alkali lignin exfoliating in an aqueous medium and simple hydrothermal method,has been successfully synthesized.AL-MoS2@Fe3O4 composites were used as MSPE sorbent to enrich and separate eight triazine and ten sulfonylurea herbicides from environmental water and corn samples for the first time.The extraction performance of the AL-MoS2@Fe3O4 in MSPE procedure was investigated.Coupling with ultra-high-performance liquid chromatography-multistage mass spectrometry(UHPLC-MSn),a rapid,convenient,and efficient method for simultaneously concentration,separation and quantification of eighteen target herbicides at trace levels in environmental water and corn samples using AL-MoS2@Fe304 as sorbents was established.The limit of detection(LOD)range of the proposed method was 0.020-0.17 ?g·L-1 in com samples,and the recoveries in spiked corn samples were from 64.7%to 103.8%with the relative standard deviations(RSDs)less than 7.6%.(2)The adsorption performances of simetryn,methoprotryne and cyclosulfamuron on AL-MoS2@Fe3O4 nanomaterials were further studied.Effects of pH values,initial concentration of three herbicides,contact time and temperature on the adsorption process were explored.The results indicated that the adsorption agreed well with the Langmuir isotherm with the maximum adsorption capacity of AL-MoS2@Fe3O4 for simetryn,methoprotryne and cyclosulfamuron were 19.96 mg·g-1,21.74 mg·g-1 and 27.86 mg·g-1 respectively,when the pH value was 4.0.And the adsorption process followed a pseudo-second-order model.Meanwhile,it was spontaneous and endothermic.In addition,AL-MoS2@Fe3O4 adsorbents were still able to maintain stable adsorption performance after repeated adsorption-desorption of 10 times.Consequently,magnetic molybdenum disulfide-based nanomaterials as a novel type of MSPE sorbent in sample pretreatment technology have attractive application prospects for the separation and preconcentration of trace or ultra trace pesticide residues in complex samples.(3)Global characterization and in-depth understanding of phosphoproteome based on mass spectrometry(MS)desperately needs a highly efficient affinity probe during sample preparation.A magnetic metal oxide affinity probe material with ferroferric oxide nanoparticles coated on the surface of graphene/molybdenum disulfide composites and functionalized with zirconium dioxide probe(mag-MoS2/G-ZrO2)was initially designed and synthesized,which exhibited high sensitivity,selectivity and excellent regenerability in the capture of endogenous phosphopeptides.The mag-MoS2/G-ZrO2 materials demonstrated low limit of detection(10 fmol·mL-1),along with an extremely good specificity to enrichment phosphopeptides from a tryptic digest of the mixture of a phosphorylated protein ?-casein and a nonphosphorylated protein BSA with molar ratios of P-casein/BSA up to 1:200.It was also successfully applied for enrichment of phosphopeptides from non-fat milk and 8 phosphopeptides could be detected.Moreover,this material could keep a stable enrichment effects while reused 8 times.All above results demonstrated that the combination strategy of ZrO2 probe,MoS2/graphene scaffold and Fe3O4 with high magnetic susceptibility had broad application prospects for the phosphopeptides capture.(4)A novel magnetic metal oxide affinity probe material(mag-MoS2/G-TiO2)was prepared by loading titanium dioxide probe based on the magnetic MoSa/graphene scaffold.The obtained mag-MoS2/G-TiO2 composite nanomaterials showed low limit of detection(1 fmol·mL-1)and largely-satisfactory selectivity(?-casein:BSA=1:500)for phosphopeptides capturing from ?-casein.Besides,11 phosphopeptides could be easily detected in the tryptic digest of non-fat milk.The mag-MoS2/G-TiO2 composite nanomaterials displayed a character of high selectively,high sensitivity and exceptional great efficiently enrichment for phosphopeptides in view of the above-mentioned facts.Accordingly,our work is promising for phosphopeptides enrichment and identification especially in complicated biological sample preparation,which also opens a new perspective in the design of multifunctional affinity probe for the separation and enrichment of phosphopeptides in phosphorylated proteomics. |
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