Development of a new FT-IR method for the determination of iron oxide. Optimization of the synthesis of suitable magnetic nanoparticles as sorbent in magnetic solid phase extraction

In the last few years, there is a clear increasing trend in the number of works dealing with magnetic nanomaterials for pre-concentration and/or separation of ions, organic compounds and inorganic compounds, as well as for use as tools for biomedical purposes because of their low toxicity, biocompatibility and biodegradability. The excellent properties of these nanomaterials are strongly influenced by the particle size and the amount of iron or iron oxide present. In order to obtain the appropriate feature of the magnetic nanoparticles (MNPs), in this work the optimization of the synthesis of magnetite MNPs has been developed. Thus, a simple, rapid and inexpensive method is presented to determine the concentration of Fe3O4 in magnetic nanoparticles (MNPs) by Fourier Transform Infrared Spectroscopy (FTIR). The optimization of the synthesis was accomplished using a multiple response surface methodology based on central composite design (CCD). Three independent factors namely the reaction time, volume and concentration of NH3 were investigated using two response variables, the iron concentration (% w/w) and the nanoparticle size (nm). Spherical MNPs with an iron concentration of 70% (w/w) and a size of 13 +/- 1 nm were obtained by the optimized method. This method was validated by comparison with High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR CS GFAAS).