High Density Functionalized Silica And Cotton Fiber And Their Application In Enrichment Of Trace Components In Real Samples

Solid phase extraction (SPE) is an important method of sample pretreatment. Nowadays, most of the functionalized ligand modifications on the surface of material are prepared via the traditional methods of directly bonding. The binding capacities of the resulting one-to-one modification materials are not satisfactory due to the limited binding sites, thus affect the adsorption perfomance. Therefore, significant effort is still being made to develop new methods for preparation of one-to-multiple modification materials with high capacities. To solve this issue, we synthesized a novel mixed-mode adsorbent by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main scaffold due to their plentiful functional groups, amino groups and benzene rings. The suitability of dispersive solid-phase (d-SPE) extraction of chlorophenols in environmental water samples was demonstrated. The effect is limited after all for increasing the density of active sites just by introducing ligands with multiple functional groups. In order to increase the density of ligands, three sorts of adsorbents were prepared via dendrimer-modification and branched polymer-modification based on silica and cotton fiber, which were utilized for selective enrichment and determination of trace nucleosides in human urine. The dissertation includes the following five chapters.1. Fabrication of a novel hydrophobic/ion-exchange mixed-mode adsorbent for the dispersive solid phase extraction of chlorophenols from environmental water samples:A novel mixed-mode adsorbent was prepared by functionalizing silica with tris(2-aminoethyl)amine and 3-phenoxybenzaldehyde as the main mixed-mode scaffold due to the presence of the plentiful amino groups and benzene rings in their molecules. The adsorption mechanism was probed with acidic, natural and basic compouds, and the mixed hydrophobic and ion-exchange interactions were found to be responsible for the adsorption of analytes. The suitability of dispersive solid-phase extraction (d-SPE) was demonstrated in the determination of chlorophenols in environmental water. Several parameters, including sample pH, desorption solvent, ionic strength, adsorbent dose and extraction time were optimized. Under the optimal extraction conditions, the proposed d-SPE coupled with high-performance liquid chromatography showed good linearity range and acceptable limits of detection (0.22?0.54 ng/mL) for five chlorophenols. Notably, the higher extraction recoveries (88.7?109.7%) for five chlorophenols were obtained with smaller adsorbent dose (10 mg) and shorter extraction time (15 min) compared with the reported methods. The proposed method might be potentially applied in the determination of trace chlorophenols in real water samples.2. Fabrication of dendrimer-modified boronate affinity material for online selective enrichment of trace nucleosides in healthy human urine:A high binding capacity dendrimer-modified boronate affinity material PBA@PAMAM@SiO2 was synthesized via introducing tris(2-aminoethyl)amine as branching points and using poly(amidoamine) (PAMAM) as the main dendrimeric scaffold before modification by boronate groups. The high density of amino groups on the dendrimer supplied a large number of binding sites for modifying boronate groups. Thus the adsorption capacity (676.8 ?mol/g for catechol, 771.3 ?mol/g for dopamine,770.0 ?mol/g for adrenaline) of PBA@PAMAM@SiO2 was greatly improved. Moreover, when coupled with large-volume injection and online column-switching SPE, PBA@PAMAM@SiO2 was able to capture cis-diols from 10000-fold interference and enrichment factors reached up to 497?514, which was 26- to 51-fold higher than those of analogous non-dendrimer materials. Especially, the proposed method exhibited a striking low limit of detection (0.24 ng/mL?0.67 ng/mL). Finally, the method was successfully applied to online determination of trace nucleosides in healthy human urine. In conclusion, the prepared adsorbent has potential to effectively enrich a large scale of trace cis-diol substances in real samples.3. Fabrication of boronate-decorated polyhedral oligomeric silsesquioxanes-grafted cotton fiber for selective enrichment of nucleosides in urine:A POSS (polyhedral oligomeric silsesquioxanes) modified boronate affinity fibrous material PBA@POSS@SCF was synthesized by introducing cotton fiber as base material and anchoring POSS as a scaffold, followed by reacting with 4-formylphenylboronic acid (PBA). Excellent purification effect was achieved by introducing abundant binding sites because of POSS modification. Therefore, the adsorption capacity was improved and the corresponding selectivity showed special recognition ability towards cis-diols even with 1000-fold interferences. Several important parameters, such as pH, ionic strength, adsorbent amount, pipette times, washing and elution solvent were optimized. Under optimum extraction conditions, the proposed method was successfully used to extract nucleosides in urine sample with good linearity and the limits of detection was 5.1?6.1 ng/mL. The recoveries were in the range of 83?104% with relative standard deviations of less than 10.3%. Combination of the specific adsorption performance of the prepared boronate affinity fibrous material and in-pipette-tip solid-phase extraction provided a potential analytical tool to effectively identify and quantify cis-diols in biological samples.4. Fabrication of boronate-decorated polyethyleneimine-grafted cotton fiber for selective enrichment of nucleosides in urine:Cheaper polyethyleneimine-modified (PEI) boronate affinity fibrous cotton with high selectivity and binding capacity for cis-diols was developed for in-pipette-tip SPE. The introduction of PEI into the modification of fiber cotton provide abundant binding sites for adsorption of cis-diols, resulting in high binding capacities up to 300 ?g/g for catechol,450 ?g/g for dopamine,700 ?g/g for adenosine, repectively. The adsorbent still showed the recognition ability towards cis-diols even with 1000-fold interferences. Several extraction parameters were optimized, including pH, adsorbent amount, pipette times, washing and elution solvent. Under optimum extraction conditions, the proposed in-pipette-tip SPE method couple with reversed phase liquid chromatography was successfully used to extract nucleosides in urine. The limits of detection was 3.5?4.7 ng/mL, the recoveries were in the range of 89?102% with relative standard deviations of less than 9.9%. In conclusion, combination of the specific adsorption performance of the prepared boronate affinity fibrous material and in-pipette-tip SPE provided a fast pretreatment determination of trace cis-diols in complex real samples.