Preparation of a new magnetic nano adsorbent modified with poly ionic liquide for the extraction and preconcentration of fluoride from different samples followed by indirect detection using flame atomic absorption spectrometry

Fluoride is usually present in different natural water samples at low concentrations. In drinking water, fluoride concentration of about 1 mg/L reduces dental caries and has not harmful effects on health. But, at the levels more than this amount, fluorosis may occur [1]. Maximum acceptable fluoride concentration in drinking water is 1.5 mg/L according to World Health Organization (WHO) [2]. The most common methods to determine fluoride concentration is using ion selective electrodes, ion chromatography, Zr SPADNS and other dyes [3]. In this research we have proposed a solid phase extraction method for extraction and enrichment of fluoride from different samples. A new type of poly ionic liquid coated magnetic nanoparticles (MNPs@PIL) was designed and prepared via free radical polymerization. Designing the nano adsorbent and selecting the ionic liquid was so that, to be able to adsorb fluoride anion. The as synthesized MNPs were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA) and elemental analysis (EA). Then, it was successfully used as adsorbent in magnetic solid phase extraction (MSPE) method for the extraction of fluoride from different samples. The effect of several experimental variables (including pH of sample solution, amount of the adsorbent, extraction and desorption time) were studied and the optimum values were determined. The adsorbed ions were eluted from the adsorbent and little volume of high concentration of Ca2+ solution was added to convert fluoride to CaF2 sediment. After filtration, residue of ca2+ was determined using flame atomic absorption spectrometry and so fluride concentration in sample was determined. Under the optimum experimental conditions, detection limit (S/N=3) of the proposed method for fluoride was obtained as 0.1424µg/mL and a preconcentration factor of 225 was achieved. The proposed method was applied for determination of fluoride in different real samples successfully.