MNPs-Nylon 6 composite as a new sorbent for microextraction

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In 2014 a new method for the synthesis of magnetic nanoparticles (MNPs)-nylon 6 composite was proposed. This method is simple and quick since only one step is needed. It is based on a solvent changeover, taking advantage of the different solubility of nylon 6 in formic acid and water. In Figure 1, it can be observed how this synthesis is carried out. The solution of MNPs and nylon-6 in formic acid is added to a beaker with water using a plastic syringe, inducing the precipitation of the polymer around the MNPs. To collect the composite after the synthesis, a magnet is used.
Figure 1. Scheme of the synthesis

When MNPs are combined with a polymer, the resulting composite has the properties of both materials, combining the high extraction capabilities of the polymer and the magnetic behaviour due to the nanoparticles. Moreover, another advantage of using polymers is their wide versatility since they can be tailored-synthesized and different functional groups can be added, to react with different kind of analytes.

Figure 2. SEM pictures of nylon-6 (upper panel) 
and MNPs-nylon-6 composite (lower panel).
The synthesized composite was characterized in terms of infrared spectroscopy, electron microscopy, porosimetry, magnetization curves and elemental analysis. Scanning electron micrographs are shown in Figure 2. It is easy to observe how the MNPs are homogeneously distributed around the polymeric network, giving rise to a rougher surface.

 This new sorbent was employed for the resolution of two different analytical problems. The first one was the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples (1), obtaining a limit of detection (LOD) between 0.05 μg/L for benzo(b)fluoranthene and 0.58 μg/L for phenanthrene. The relative standard deviations (RSD) were in the range from 3.4% (fluoranthene) to 6.8% (benzo(b)fluoranthene). The enrichment factors were in the range from 18.1 (phenanthrene) to 43.5 (benzo(b)fluoranthene), and the absolute extraction recoveries between 36.2 to 87.0%. The recovery study was performed spiking water samples with the analytes (5 µg/L), obtaining extraction recoveries from 80 to 111.
After that, bisphenol A (BPA) was determined in milk samples (2), obtaining a LOD of 3 µg/L and a RSD of 9%. The analysis of different kinds of milk samples verified the applicability of the method, with extraction recoveries of 86, 98 and 99 for whole, semi-skimmed and skimmed milk, respectively.

REFERENCES
(1) E.M. Reyes-Gallardo, R. Lucena, S. Cárdenas, M. Valcárcel. Magnetic nanoparticles-nylon 6 composite for the dispersive micro solid phase extraction of selected polycyclic aromatic hydrocarbons from water samples. Journal of Chromatography A, 1345 (2014) 43-49. Link to the article.

(2) E.M. Reyes-Gallardo, R. Lucena, S. Cárdenas, M. Valcárcel. Dispersive micro-solid phase extraction of bisphenol A from milk using magnetic nylon 6 composite and its final determination by HPLC-UV. Microchemical Journal, 124 (2016) 751-756. Link to the article


Emilia Mª Reyes Gallardo studied Chemistry at the University of Córdoba, finishing them in 2011 with extraordinary end-of-studies award. Since 2009, she was a collaborator student in the department of Analytical Chemistry of this University. After that, she did a Master in Fine Advanced Chemistry and obtained a research grant.  Nowadays she is developing her PhD Thesis focused on the microextraction context using novel material which combines different properties.
You can visit her profiles at Linkedin and Researchgate

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