Mehdi Karimi's research while affiliated with Yazd University and other places

A sorbent with high selectivity and capacity for cadmium ions was prepared through immobilization of deep eutectic solvent (DES) of ChCl- glycerol containing the ligand 2-(3-hydroxy-1-methylbut-2-enylideneamino)pyridine-3-ol (acacapyrH2) on the magnetic graphene oxide. A dispersive micro-solid phase extraction was designed, and the separated/preconcentrated cadmium ion was determined by flow injection flame atomic absorption spectrometry. After the optimization of effective parameters, the method showed linearity in the concentration range of 0.25–15 µg L−1 with the coefficient of determination (r2) of 0.9991 and enhancement factor of 195 for cadmium. The method was very sensitive with the detection limit (defined as 3Sb/m) of 0.06 µg L−1. The method was successfully applied to the determination of Cd(II) in water (drinking and river), fruit (lemon, apricot, and peach) and meat (fish, chicken, and cow meat) samples.

A deep eutectic solvent (DES) of choline chloride and thiourea was synthesised, immobilised on the surface of graphene oxide (GO) nanosheets and reinforced inside the pores of the hollow fibre (DES-GO-HF). Then, solid-phase microextraction flame atomic absorption spectrometry was designed for separation, preconcentration and determination of trace amounts of silver. Various parameters affecting the extraction recovery of the analyte, such as pH, sample volume, type of DES, extraction time, length of the hollow fiber, nature, as well as the volume and concentration of the eluent, were investigated and optimised. Under optimum conditions, the method showed good linearity in the concentration range of 1.0–40.0 µg L⁻¹ with the determination coefficient of (r²) 0.9990 for silver. The method was very sensitive and has limits of detection and quantification (defined as 3Sb/m and 10Sb/m) of 0.2 and 0.7 µg L⁻¹, respectively. The method was successfully applied for the determination of Ag(I) in water, wastewater, ore and hair samples. The accuracy of the method was evaluated through the recovery experiments and the analysis of certified reference materials.

Deep eutectic solvent (DES) was used as the extractant to improve the extraction properties of cotton. DES of choline chloride-urea (ChCl-urea) was prepared and immobilized on the surface of cotton fibers. The resulting sorbent was packed on a microcolumn, and a flow injection flame atomic absorption spectrometry was designed for the online separation and determination of trace amounts of copper and nickel. Various parameters affecting the extraction recovery of analytes such as pH, sample volume, sample loading rate, nature, volume, concentration, and flow rate of eluent were investigated and optimized. Under the optimum conditions, the method showed good linearity in the concentration range of 0.25–50.0 and 4.0–125.0 μg L−1 with the coefficient of determination (r2) of 0.9991 and 0.9990 for copper and nickel, respectively. The method was very sensitive with the detection limits (defined as 3Sb/m) of 0.05 and 0.60 μg L−1 for Cu and Ni, respectively. It was successfully applied for the determination of Cu and Ni in water and biological samples. The accuracy of the method was evaluated through the recovery experiments and independent analysis by electrothermal atomic absorption spectrometry.

A simple, rapid and eco-friendly deep eutectic solvent-modified magnetic nanoparticles extraction method has been reported for ligand-less separation/preconcentration of lead(II) and cadmium(II) for the first time. The metal ions interact with the deep eutectic solvent adhering to the magnetic nanoparticles. Trapped analytes can be easily desorbed with 1.0 M nitric acid and determined by flame atomic absorption spectrometry. The effects of pH value, type of deep eutectic solvent, sample volume, nature and concentration of desorbing solution, ionic strength and extraction time on the extraction were optimized. Under the optimized experimental conditions, the detection limits (defined as 3Sb/m) were 0.4 and 0.1 μg L−1 and the linear dynamic ranges were 2 to 250 μg L−1 and 0.5 to 30 μg L−1 for lead and cadmium, respectively. The relative standard deviations for six replicate measurements at 150 and 20 μg L−1 levels of lead and cadmium were 1.8 and 2.1 %, respectively. A sample volume of 60 mL resulted in a preconcentration factor of 100. The sorbent showed high capacity for lead (25.0 mg g−1) and cadmium (23.7 mg g−1). The method was successfully applied to the determination of lead and cadmium in soil, hair and several water samples. Graphical Abstract Deep eutectic solvent (DES) and Fe3O4 nanoparticles were added to the sample solution, and the DES containing the target ions was trapped on the sorbent and separated by means of a strong magnet. The analytes were desorbed by nitric acid, and the extracted metal ions were then directly submitted to FAAS for quantification

A simple, sensitive and reliable method for the separation, preconcentration and determination of ultra trace amounts of chromium species has been developed. Chromium(VI) in aqueous sample was reacted with 9-phenyl-2,3,7-trihydroxy-6-fluorone to produce a chelate at pH of 5.0 and extracted onto the magnetic nanoparticles coated with the ionic liquid 1-hexadecyl-3-methylimidazolium bromide. The trapped analyte was back extracted using 350 μL of nitric acid solution (2 mol L-1) and was determined by electrothermal atomic absorption spectrometry. Total chromium was determined by oxidizing CrIII to CrVI using KMnO4 in acidic media. Under the optimum conditions, the method exhibited a linear dynamic range of 0.01-0.50 μg L-1 with an enhancement factor of 112 and a detection limit of 0.003 μg L-1 for CrVI. The coefficient of variation (n = 6) at 0.3 μg L-1 concentration level of CrVI was 3.2%.