In-syringe on-line supramolecular dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry for determination of iron species in water and food samples

Iron is an essential element for all living organisms. Due to its essential role as an oxygen carrier, electron transporter, hemoglobin producer and enzymes cofactor, it is important for human, animals, and plants [1,2]. Iron exists in either Fe(II) or Fe(III) oxidation state in natural waters and biological samples. The oxidation state strongly affects the bioavailability of iron as well as the physicochemical and toxicological properties of other elements and organic substrates. Therefore, there is an urgent need to develop a simple, sensitive, selective, and rapid analytical methods distinguish these species [3].In this work, a novel in-syringe on-line supramolecular dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry (FAAS) has been proposed for extraction, preconcentration, and determination of Fe(III). Fe(III) is complexed with 4,5-dihydroxy-1,3-benzendisulfonic acid (tiron), neutralized through the formation of the ion pair with 1-hexadecyl-3-methyl imidazolium bromide and extracted into reverse micelles of decanoic acid (DA) in tetrahydrofuran (THF). Total iron was determined after oxidation of Fe(II) to Fe(III) with hydrogen peroxide. The concentration of Fe(II) was determined from the difference between total iron and Fe(III) concentrations. Different variables affecting the extraction efficiency of the analyte were studied. Under the optimum conditions, the calibration curve was linear up to 45 ng mL-1 of Fe(III). The limit of detection (LOD) and limit of quantification (LOQ) were 1.04 ng mL-1 and 3.45 ng mL-1, respectively. The repeatability expressed as the relative standard deviation for six replicate determinations of Fe(III) at 20 ng mL-1 was 1.8%. The method was successfully applied to the determination of iron species in different water and food samples.