Hydrophilic-carbonaceous magnetic nanoparticles coated with chitosan

By R. Lucena -
The term “nanoparticle” (NP) involves a great variety of materials. According to the size, a NP can be defined as a particle that presents one or more dimensions in the nanometer range, considering 100 nm as arbitrary reference. However, the prefix “nano” also refers to the novel physical and chemical properties that appear in the nano-scale. In the microextraction context, NPs are attractive due to their high superficial area which improve the extraction kinetics. Moreover, in most of the cases, NPs are easily synthesized and they can be derivatized in-surface providing different interaction chemistries. However, the management of these NPs is rather complicated in classic SPE since their small particle size and aggregation tendency usually produce back-pressures in the extraction devices.


Magnetic NPs, usually based on a magnetite (Fe304) core, face up this limitation making easier the recovery of the sorptive material after the extraction. In this sense, the magnetic NPs (with a defined interaction chemistry depending on the analytical problem) are dispersed in the sample in order to promote their interaction with the analytes. After that, the NPs are recovered applying an external magnetic field (a simple magnet) to the extraction vessel. In some cases, especially when non-polar coatings (e.g. C18) are employed, the initial dispersion of the NPs is the limiting step of the process. 

In 2010, Zhang et al proposed the synthesis of magnetic NPs coated with hydrophilic carbon in order to enhance this dispersion. In a recent article published in Talanta, Geng et al. have resented the combination of the good dispersion efficiency of hydrophilic carbon and the good extractability of chitosan for the extraction of bisphenol A in aqueous samples. The synthetic procedure is quite simple including three defined steps:
  1. The production of the magnetite based NP.
  2. The production of the carbonaceous coating by a hydrothermal reaction with glucose.
  3. The final bound of chitosan by a cross-link reaction. 
The results demonstrated that the chitosan coating allows the efficient extraction of BPA from water samples in a rapid way (ca. 20 min).

Link to the article

Other links
Link to the article: Nanoparticle-based microextraction techniques in bioanalysis 
Link to the article: Extraction of environmental pollutants using magnetic nanomaterials
Link to the article: Preparation of carbon coated Fe3O4 nanoparticles and their application for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples


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