On-line ionic imprinted polymer selective solid-phase extraction of nickel and lead from seawater and their determination by inductively coupled plasma-optical emission spectrometry

High Performance Zinc Oxide Nanorod-Doped Ion Imprinted Polypyrrole for the Selective Electrosensing of Mercury II Ions

A biomimetic, ion-imprinted polymer (IIP) was prepared by electropolymerization of pyrrole at the surface of gold electrodes decorated with vertically grown ZnO nanorods. The vertical growth of the nanorods was achieved via an ultrathin aryl monolayer grafted by reduction of diazonium salt precursor. Pyrrole was polymerized in the presence of L-cysteine as chelating agent and Hg2+ (template). Hg2+-imprinted polypyrrole (PPy) was also prepared on a bare gold electrode in order to compare the two methods of sensor design (Au-ZnO-IIP vs. Au-IIP). Non-imprinted PPy was prepared in the same conditions but in the absence of any Hg2+ template. The strategy combining diazonium salt modification and ZnO nanorod decoration of gold electrodes permitted us to increase considerably the specific surface area and thus improve the sensor performance. The limit of detection (LOD) of the designed sensor was ~1 pM, the lowest value ever reported in the literature for gold electrode sensors. The dissociation constants between PPy and Hg2+ were estimated at [Kd1 = (7.89 ± 3.63) mM and Kd2 = (38.10 ± 9.22) pM]. The sensitivity of the designed sensor was found to be 0.692 ± 0.034 μA.pM-1. The Au-ZnO-IIP was found to be highly selective towards Hg2+ compared to cadmium, lead and copper ions. This sensor design strategy could open up new horizons in monitoring toxic heavy metal ions in water and therefore contribute to enhancing environmental quality.

Sensitive colorimetric detection of Pb2+ by geometric field amplification and surface plasmon resonance visualization

Pb²⁺ is one of the major environmental pollutants, which can be visually detected by surface plasmon resonance of nanoparticles. Paper based analytical device, as a newly developed microfluidic detection platform, is featured in cost-effective and suitable for on-site analysis. In this paper, a sensitive and portable detection method for Pb²⁺ was proposed, in which Pb²⁺ was electrokinetically stacked on the paper fluidic channel by geometric field amplification effect and visualized online by glutathione-modified silver nanoparticles. Colorimetric quantification of the visualized stacking band was conducted by smart phone camera. To avoid unfavorable influence from pH change on the surface plasmon resonance visualization, field amplification effect was introduced by geometric design of the paper fluidic channel. The enriched Pb²⁺ was clearly visible on the paper substrate, and the stacking band intensity was about four orders of magnitude enhanced, comparing to the intensity without stacking. A linear response to Pb²⁺ was observed in the range of 0.3-7.0 μM (R² = 0.997) with a limit of detection of 86 nM and a limit of quantity of 0.28 μM. The established method was used in the detection of Pb²⁺ from river and lake water samples, and the results were confirmed by atomic absorption spectroscopy method.

Determination of Trace Nickel in Water Samples by Graphite Furnace Atomic Absorption Spectrometry after Mixed Micelle-Mediated Cloud Point Extraction

A simple and sensitive cloud point extraction method for the preconcentration of ultra-trace amounts of nickel as a prior step to its determination by graphite furnace atomic absorption spectrometry was proposed. It is based on the reaction of nickel with 2-(5-bromo-2-pyridylazo)-5-dimethylaminoaniline (5-Br-PADMA) in HAc–NaAc buffer media and mixed micelle-mediated extraction of the complex using the anionic surfactant sodium dodecyl sulfate sodium (SDS) and non-ionic surfactant (1,1,3,3-Tetramethylbutyl)phenyl-polyethylene (Triton X-114). The optimal reaction and extraction conditions such as pH, concentration of 5-Br-PADMA, SDS and Triton X-114, equilibrium temperature, incubation, and centrifuge time were evaluated and optimized. Under the optimal conditions, the calibration graph was linear over the range 0.1–5.5 ng/mL of nickel with a correlation coefficient of 0.9942. The detection limit obtained was 0.031 ng/mL, and the relative standard deviation was 2.1% for nickel (c = 2 ng/mL, n = 6). The proposed method was successfully applied to the determination of nickel in water samples.

A simple dispersive-micro-solid phase extraction based on a colloidal silica sorbent for the spectrophotometric determination of Fe(ii) in the presence of tetrabutylammonium bromide

This study demonstrates a simplified dispersive micro-solid phase extraction (d-μ-SPE) using silica sol as the sorbent for the preconcentration of ferrous ions.

Highly efficient and selective removal of trace lead from aqueous solutions by hollow mesoporous silica loaded with molecularly imprinted polymers

A novel type of adsorbent for the selective recognition and adsorption of trace Pb²⁺ from aqueous solutions has been successfully constructed simply by grafting molecularly imprinted polymers (MIPs) onto hollow mesoporous silica (HMS). Attractively, the HMS loaded with MIPs (H-MIPs) exhibits a fast adsorption kinetics, marked adsorption capacity of 40.52mg/g and extremely high selectivity toward Pb²⁺ over Cu²⁺, Zn²⁺, Co²⁺, Mn²⁺ and Ni²⁺, and the selectivity coefficients have been determined to be as high as 50. Moreover, such high adsorptive capability and selectivity were retained for at least 6 runs, indicating the stability and reusability of H-MIPs. Lead ion contaminants in real water samples were successfully concentrated and approximately 100% recovered using H-MIPs. Theoretical analysis shows that the adsorption process of H-MIPs follows the pseudo-second-order kinetic and Langmuir isotherm models. These demonstrate that H-MIPs are greatly potential for the rapid and highly efficient removal of trace Pb²⁺ ions in complicated matrices.

Selective Solid-Phase Extraction of Lead Ions in Water Samples Using Three-Dimensional Ion-Imprinted Polymers

Ion-imprinted polymers (IIPs) have drawn much attention in the selective determination of heavy metals. In this study, 8-hydroxyquinoline-grafted gelatin with different types of functional groups was first introduced as a biomolecular monomer to enhance the selectivity of imprinted cavities. Based on its swelling and film-forming properties, a simple strategy containing formation of the hydrogel film, swelling/folding followed by cross-linking, was proposed to prepare three-dimensional IIPs with high adsorption capacity (235.7 mg g(-1)), strong selectivity (imprinted factor was 2.9), and rapid kinetics. Based on the different swelling container, different morphologies of IIPs could be prepared to satisfy the requirements of practical application. Consequently, the IIPs extraction coupled with a spectrophotometric method was applied for determination of lead ions, and the limit of detection was 0.2 ng mL(-1), which could be used for monitoring of Pb(II) in drinking water and surface water.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Novel Pb2+ ion imprinted polymers based on ionic interaction via synergy of dual functional monomers for selective solid-phase extraction of Pb2+ in water samples

A novel kind of Pb(2+) ion imprinted polymers (IIPs) was prepared based on ionic interactions via the synergy of dual functional monomers of methacrylic acid and vinyl pyridine for selective solid-phase extraction (SPE) of Pb(2+) in water samples. Suspension polymerization was employed for the formation of template Pb(2+)/monomer complex by self-assembly in the presence of ethylene glycol dimethacrylate cross-linker. The resulted Pb(2+) IIPs showed fast kinetics, high binding capacity, and the adsorption processes obeyed intraparticle diffusion kinetics and Langmuir isotherm models. The IIPs displayed excellent selectivity toward Pb(2+) over other metal ions such as Cu(2+), Cd(2+), Zn(2+), and Mn(2+) with selective coefficients above 30, as well as high anti-interference ability for Pb(2+) confronting with common coexisting various ions. Through 10 adsorption-desorption cycles, the reusable IIPs exhibited a good recoverability with the standard error within 5%. These features suggested the IIPs were ideal candidates for extraction and removal of Pb(2+) ions. Consequently, the IIPs were utilized as SPE sorbents and related parameters were optimized. An excellent linearity was presented in the range of 0.2-50 μg L(-1) (R(2) = 0.9998), as well as the limits of detection and quantification were achieved of 0.06 and 0.19 μg L(-1), respectively. A good repeatability was obtained with the relative standard deviation of 2.8%. Furthermore, real water samples were successfully analyzed and satisfactory recoveries varying from 95.5 to 104.6% were attained. The IIPs-SPE demonstrated potential application perspectives for rapid and high-effective cleanup and enrichment of trace Pb(2+) ions in complicated matrices.

Utility of cefixime as a complexing reagent for the determination of Ni(II) in synthetic mixture and water samples

A simple, sensitive, and accurate UV spectrophotometric method has been developed for the determination of nickel in synthetic mixture and water samples. The method is based on the complexation reaction of nickel ion with cefixime, thus leading to the formation of Ni-cefixime complex in ethanol-distilled water medium at room temperature. The complex showed the maximum absorption wavelength at 332 nm. Beer's law is obeyed in the working concentration range of 0.447-4.019 μg mL(-1) with apparent molar absorptivity of 7.314 × 10(3) L mol(-1) cm(-1) and Sandell's sensitivity of 0.008 μg/cm(2)/0.001 absorbance unit. The limits of detection and quantitation for the proposed method are 0.016 and 0.054 μg mL(-1), respectively. The factors such as cefixime concentration and solvent affecting the complexation reaction were carefully studied and optimized. The method is validated as per the International Conference on Harmonisation guideline. The method is successfully applied to the determination of Ni(II) in synthetic mixture and wadi water samples collected from Al Rustaq. The same water samples are also analyzed by atomic absorption spectrophotometry. Both methods determined the amount of Ni(II) in water sample and found to be approximately the same.

Determination of trace copper in food samples by flame atomic absorption spectrometry after solid phase extraction on modified soybean hull

Soybean hull was chemically modified with citric acid and used as a solid phase extraction adsorbent for the determination of trace amounts of Cu(2+) in food samples by flame absorption spectrometry (FAAS). The effect of pH, sample flow rate and volume, elution flow rate and volume and co-existing ions on the recovery of the analyte were investigated. The results showed that Cu(2+) could be adsorbed on the modified soybean hull at pH 8.0 and eluted by 2.0 mL of 1.0 mol L(-1) HCl. Under the optimized conditions, the adsorption capacity of modified soybean hull was found to be 18.0 mg g(-1) for Cu(2+). The detection limit of the proposed method was 0.8 ng mL(-1) for Cu(2+) with an enrichment factor of 18. The analytical result for the certified reference tea sample (GBW07605) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace Cu(2+) in dried sweet potato, lake water and milk powder, the recovery of Cu(2+) for spiked samples was between 91% and 109.6%.