Preconcentration Of Nickel Ions Research Articles

Synthesis of ionically imprinted Poly(Alylthiourea) in the presence of 1-(2-Pyridylazo)-2-Napthol (PAN) for preconcentration in magnetic dispersive solid phase of nickel ions in water and food samples

In the present study, a magnetic ion-imprinted polymer based on n-allylthiourea in the presence of 1-(2-pyridylazo)-2-naphthol (MIIP-PAN) was synthesized, characterized, and applied in the preconcentration of nickel ions by dispersive magnetic solid phase extraction (DMSPE) with FAAS detection. For comparison, non-imprinted polymer (MNIP-PAN) and imprinted polymer without PAN were synthesized. The characterization of the polymers was performed by FT-IR, DRX, TEM, TGA, VSM, and BET. Selectivity studies were performed comparing the competitive adsorption of Ni2+ with other cations on MIIP-PAN and MNIP-PAN, achieving higher relative selectivity coefficients for MIIP-PAN than for MNIP-PAN and NIP. Under optimized conditions, the method provided a preconcentration factor of 76.70, detection limit of 0.25 µg/L and intra-day (2.06 – 2.33 %) and inter-day (1.82 – 4.90 %) precision. The developed method was applied to samples of water, teas, and chocolate powder, and its precision was evaluated through tests of recovery and analysis of certified materials.

Preconcentration of nickel in waters by vortex assisted dispersive liquid-liquid microextraction

AbstractThe present work describes the attempt for the preconcentration of nickel ions by using vortex assisted dispersive liquid-liquid microextraction from aqueous samples. In this method, a small amount of chloroform is rapidly injected by syringe into the water sample containing nickel ions complexed by diethyldithiocarbamate (DDTC).This forms a cloudy solution. The cloudy state is the result of chloroform fine droplets formation, which are dispersed in bulk aqueous sample. Therefore, Ni-DDTC complex is extracted into the fine chloroform droplets and vortex agitation takes place during six minutes. After optimization of experimental variables and determination of analytical characteristics, the method is evaluated for application in real samples. HPLC is used as separation and detection system.

Application of Ni(II)-imprinted cross-linked poly(methacrylic acid) synthesised through double-imprinting method for the on-line preconcentration of Ni(II) ions in aqueous media

The present paper describes the feasibility of on-line preconcentration of nickel ions from aqueous medium on Ni(II)-imprinted cross-linked poly(methacrylic acid) (IIP) synthesised through a double-imprinting method and their subsequent determination by FAAS. The proposed method consisted in loading the sample (20.0 mL, pH 7.25) through a mini-column packed with 50 mg of the IIP for 2 min. The elution step was performed with 1.0 mol L−1 HNO3 at a flow rate of 7.0 mL min−1. The following parameters were obtained: quantification limit (QL) – 3.74 µg L−1, preconcentration factor (PF) – 36, consumption index (CI) – 0.55 mL, concentration efficiency (CE) – 18 min−1, and sample throughput – 25 h−1. The precision of the procedure assessed in terms of repeatability for ten determinations was 5.6% and 2.5% for respective concentrations of 5.0 and 110.0 µg L−1. Moreover, the analytical curve was obtained in the range of 5.0–180.0 µg L−1 (r = 0.9973), and a 1.64-fold increase in the method sensitivity was observed when compared with the analytical curve constructed for the NIP (non-imprinted polymer), thus suggesting a synergistic effect of the Ni(II) ions and CTAB on the adsorption properties of the IIP. The practical application of the adsorbent was evaluated from an analysis of tap, mineral, lake and river water. Considering the results of addition and recovery experiments (90.2–100 %), the efficiency of this adsorbent can be ensured for the interference-free preconcentration of the Ni(II) ions.

Electrosynthesis of a new selective chelating agent for solid phase extraction of Ni(II) from water samples: characterisation and analytical applications

A new polymer as a selective chelating agent for separation and preconcentration of nickel ions from water samples was prepared by electropolymerisation of 4-nitrophenol. Electrosynthesis was carried out on the lead cathode in aqueous sodium acetate solution. The electrode-product is a dark-brown powder, insoluble in water but soluble in methanol, N,N-dimethylformamide (DMF) and tetrahydrofuran (THF). The electrode-product was characterised by differential scanning calorimetry (DSC), gel permeation chromatography (GPC), FT-IR, 1H-NMR, cyclic voltammetry (CV) and UV-Vis spectrometry. A proper mechanism and structure of the prepared polymer was suggested. A few drops of methanolic solution of electrode-product formed a blue complex with nickel ions in an aqueous medium in the pH range of 6 to 10. This new chelating reagent was used as a coating material on activated charcoal and applied for solid phase extraction of trace amounts of nickel ions from natural and waste waters. The effect of different parameters such as type of eluent, elution conditions, sample volume and sample flow rate and mass of coating material were studied. In the presence of co-existing ions, no significant interferences were observed. Under the optimal conditions, limits of detection (LOD) and quantification (LOQ) were 0.32 and 1 µg L−1 Ni(II), respectively. The proposed method was used for determination of Ni(II) in some lagoons south of the Caspian Sea and waste waters of factories. The validity of this method was confirmed by the comparison of the obtained results with the results of ICP-OES.

Surfactant modified walnut sawdust as an alternative green support for efficient preconcentration of nickel ions from different real samples

A simple and relatively selective solid phase extraction system has been described and used for determination of trace amounts of Ni(II) ions in water, soil and split peas by sodium dodecyl sulfate (SDS)-coated microparticles of walnut sawdust modified with dimethylglyoxim. Scanning electron microscopy (SEM) and Fourier transformed infrared (FT-IR) techniques were used for characterization of the sorbent. Adsorption experiments were carried out using batch mode under various operating conditions. The effect of pH, contact time, ionic strength, volume and concentration of the eluent on the Ni(II) preconcentration were studied. The equilibrium time was found to be 30 min and the adsorbed ions were stripped from the solid phase by 10 mL of 3 mol L−1 nitric acid. The eluting solution was analyzed for the Ni(II) content by flame atomic absorption spectrometry (FAAS). The adsorption data were measured at room temperature and the yielded Langmuir monolayer capacity was 22.0 mg g−1. The detection limit (LOD) and the relative standard deviation were 0.55 μg L−1 and 3.1% (n = 5, concentration = 0.1 mg L−1), respectively. The accuracy of the method was examined with the determination of nickel ions in a certified reference material (CRM TMDW-500, drinking water).