Mixed hemi-micelle solid-phase extraction based on modified magnetic nanoparticles for extraction of cadmium and lead from food and water samples.

A simple and rapid method for the separation and preconcentration of trace amounts of Cd(ll) and Pb(ll) in milk powder and water samples by magnetic SPE has been developed. The application of silica- coated magnetite nanoparticles (SCMNPs), modified with an anionic surfactant as an effective sorbent material for the microextractioh and determination of trace amounts of Cd(ll)and Pb(ll) from food samples was investigated. The synthesized SCMNPs modified with sodium dodecyl sulfate have the ability to adsolubilize the metal ions after complexation with 1-(2-pyridylazo)-2-naphthol. These magnetic nanoparticles which are carrying the target metals can be easily separated from the aqueous solution by applying an external magnetic field, and the complexed metals can be desorbed using a proper eluent. The effect of pH, concentration of complexing agent, eluent, extraction time, capacity, and desorp tion conditions were investigated. Under the optimized conditions, preconcentration of a 50.0 mL sample solution permitted the LODs of 0.147 and 2.02 µg/L; and the RSDs (n = 7) for 0.05 µg/mL of Cd(ll) and 0.2 µg/mL of Pb(ll) were 2.96 and 1.3%, respectively. The maximum sorption capacity was 8.8 and 9.5 mglg for Cd(ll) and Pb(ll), respectively.

Ferrofluid-based dispersive solid phase extraction of palladium.

A new mode of dispersive solid phase extraction based on ferrofluid has been developed. In this method, an appropriate amount of ferrofluid is injected rapidly into the aqueous sample by a syringe. Since the sorbent is highly dispersed in the aqueous phase, extraction can be achieved within a few seconds. The ferrofluid can be attracted by a magnet and no centrifugation step is needed for phase separation. Palladium was used as a model compound in the development and evaluation of the extraction procedure in combination with flame atomic absorption spectrometry. The experimental parameters (pH, DDTC concentration, type and concentration of eluent, the amount of adsorbent, extraction time, and the effect of interfering ions) were investigated in detail. Under the optimized conditions, the calibration graph was linear over the range of 1-100 µg L(-1) and relative standard deviation of 3.3% at 0.1 µg mL(-1) was obtained (n=7). The limit of detection and enrichment factor (EF) was obtained to be 0.35 µg L(-1) and 267, respectively. The maximum adsorption capacity of the adsorbent at optimum conditions was found to be 24.6 mg g(-1) for Pd(II). The method was validated using certified reference material, and has been applied for the determination of trace Pd(II) in actual samples with satisfactory results.

Cold-induced aggregation microextraction based on ionic liquids and fiber optic-linear array detection spectrophotometry of cobalt in water samples.

A new simple and rapid cold-induced aggregation microextraction (CIAME) method was applied to preconcentrate cobalt(II) ions from water samples as a prior step to its determination by fiber optic-linear array detection spectrophotometry (FO-LADS). In this method, very small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF(6)] and 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [Hmim][Tf(2)N] as hydrophobic ionic liquids (ILs) and extractant solvents were dissolved in the sample solution containing Triton X-114 (anti-sticking agent). 1-(2-Pyridylazo)-2-naphthol (PAN) was chosen as the complexing agent. After dissolving, the solution was cooled in the ice bath and a cloudy solution was formed of IL fine droplets due to the decrease of IL solubility. After centrifuging, the fine droplets of extractant phase were settled to the bottom of the conical-bottom centrifuge tube. Analysis was carried out by a fiber optic-linear array detector spectrophotometer at 570 nm. In this method, which is robust against high content of salt and water-miscible organic solvents, various parameters were investigated and optimized. The applicability of the technique was evaluated by the determination of trace amounts of cobalt in several water samples. Under the optimum conditions, the limit of detection (LOD) of the method was 0.14 ng mL(-1) and the relative standard deviation (R.S.D.) for 30 ng mL(-1) cobalt was 2.32%.