Development of ionic liquid-based in situ solvent formation microextraction for iron speciation and determination in water and food samples

In the present work, a novel, simple, and efficient method for the iron (Fe) speciation and determination in different water and food samples was developed using in situ solvent formation microextraction (ISFME) technique followed by spectrophotometric analysis. The procedure is based on the complexation of Fe (II) with 1, 10-phenanthroline. A hydrophilic ionic liquid (IL), 1-Hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF4]), was added to the aqueous media and then ion-pairing agent, sodium hexafluorophosphate (NaPF6), was added in order to obtain a hydrophobic IL ([Hmim][PF6]) as the extraction solvent. The hydrophobic extraction solvent formed under these conditions was completely dispersed into the sample solution. After centrifugation, the fine droplets of the extractant phase settled to the bottom of the conical-bottom glass centrifuge tube. The absorbance of the enriched analyte in the final solution was determined by UV-Vis spectrophotometer against a reagent blank. Total iron was determined after the reduction of Fe (III) to Fe (II) by using ascorbic acid as reducing agent. To obtain the best extraction results, some experimental parameters affecting the extraction efficiency were optimized. Under optimum conditions, the calibration curve was linear in the concentration range of 1.0-60.0 μg L¯1, with the square correlation coefficient (r) equal to 0.998. The limit of detection and the enrichment factor were 0.3 μg L¯1 and 80, respectively. The method was successfully applied to the analysis of iron in water and food samples.