| Studies on carbon nanotubes (CNT) become a hot topic in the world due to the unique one-dimensional tubular structure, physical and chemical properties. It is well known that chitosan possesses multi-chiral carbon atoms in its molecular structure unit, and has excellent biocompatibility, biodegradability, non toxicity and adsorption capacity of metal ions. It has been applied in the field of biology, medical and chemical analysis. For the development of chitosan/carbon nanotubes composites (CS/CNT), many researchers have exported the possibility of CS/CNT composites as platforms for the development of electrochemical sensors and biosensors. However, based on adsorption for metal ions and chiral properties of CS, we researched CS/CNT applied to preconcentration of metals ions and enantiomeric selectivity, which will broad the applied field of CS/CNT, and provide a new platform for CNT in the field of enrichment metal ions and enantiomeric selectivity.Firstly, a composite was prepared from chitosan and acid functionalized multiwalled carbon nanotubes directly named chitosan-multiwalled carbon nanotubes (CS-MWCNTs). Two novel composites were designed and synthesized via covalently grafting chitosan derivatives onto the surfaces of acid functionalized multiwalled carbon nanotubes. which were namely Schiff base chitosan multiwalled carbon nanotubes (S-CS-MWCNTs) and reduced Schiff base chitosan-multiwalled carbon nanotubes (RS-CS-MWCNTs), respectively. All composites had been characterized by fourier transform infrared spectrometer, scanning electron microscopy, transmission electron microscopy and thermo gravimetric instrument. The results shown S-CS successfully grafted on the surface of MWCNTs. Besides, base on the results of TAG, we calculated the functional group loading on MWCNT, the contents of grated CS, S-CS and RS-CS on CS-MWCNT, S-CS-MWCNT and RS-CS-MWCNT were84.2%,69.5%,68.8%, respectively.Second, compared the adsorption capacity for metal ions in the three CS/CNT composites, the S-CS-MWCNTs was chosen as the adsorbent of solid-phase extraction. A method was developed for determination of heavy metal V (Ⅴ), Cr (Ⅵ), Pb (Ⅱ), Cu (Ⅱ) and As (Ⅴ) in biological and environmental samples by inductively coupled plasma mass spectrometer (ICP-MS) coupled with S-CS-MWCNTs preconcentration. The parameters influencing preconcentration of target ions were investigated, the optimal conditions were follow as:pH of the sample solution was7.0, the flow rate of sample loading was1.0mL min-1, the eluent concentration was2.0mL of0.5mol L-1HNO3. Under the optimal conditions, the enrichment factors of V (Ⅴ), Cr (Ⅵ), Cu (Ⅱ), As (Ⅴ) and Pb (Ⅱ) reached to52-128, with the detection of limits were as low as1.3-3.8ng L-1. The relative standard deviations of11replicate extractions of1.0μg L-1level were1.4-4.6%. The developed method had been successfully applied to the determination of trace metal ions in herring, spinach, river water and tap water with good recoveries ranging from91.0%to105.0%.Lastly, the CS/CNT application for enantiomeric selectivity of D-tryptophan and L-tryptophan were studied. It was shown that three composites had higher recognition selectivity for L-tryptophan than for D-tryptophan. In addition, selectivity capability of RS-CS-MWCNT was better than the other two composites. The differences of the absorbance capacities were obviously enlarged as the concentrations were increased, maximum separated was up to1.5when the concentration was330mg L-1. It provided a basic research for enantiomeric selectivity for amino acid by CS modified MWCNTs. |
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