Magnetic nanomaterials for the removal,separation and preconcentration of organic and inorganic pollutants at trace levels and their practical applications: A review

The presence of organic and inorganic pollutants in nature even in very small concentrations threatens human and other living bodies health and makes it significant to remove, separate and preconcentrate these pollutants. Recently magnetic nano sorbents has been used frequently in the separation and preconcentration of these pollutants. The use of magnetic nano sorbents modified with inorganic and organic species has widespread applications in the solid phase extraction (SPE) studies due to its many unique properties. These modified nano sorbents are preferred due to their advantages such as high adsorption capacities and large surface areas. This review examined different types of magnetic materials such as magnetic carbon-based nano sorbents, inorganic nano sorbents with magnetic properties, magnetized biosorbents, magnetic metal-organic frameworks, and magnetized ionic liquids used in SPE studies. In this study, a comprehensive and systematic review of the separation and preconcentration of analytes such as heavy metal ions, drug active substances, pesticides, dyes, hormone disruptors, etc with SPE methods using magnetic nanomaterials has been revealed. Future aspects and challenges that may be encountered are discussed.     

A low-cost and high-throughput benchtop cell sorter for isolating white blood cells from whole blood

The ability to isolate and purify white blood cells (WBCs) from mixed ensembles such as blood would benefit autologous cell-based therapeutics as well as diagnosis of WBC disorders. Current WBCs isolation methods have the limitations of low purity or requiring complex and expensive equipment. In addition, due to the overlap in size distribution between lymphocytes (i.e., a sub-population of WBCs) and red blood cells (RBCs), it is challenging to achieve isolation of entire WBCs populations. In this work, we developed an inertial microfluidics-based cell sorter, which enables size-based, high-throughput isolation, and enrichment of WBCs from RBC-lysed whole blood. Using the developed inertial microfluidic chip, the sorting resolution is sharpened within 2 μm, which achieved separation between 3 and 5 μm diameter particles. Thus, with the present cell sorter, a full population of WBCs can be isolated from RBC-lysed blood samples with recovery ratio of 92%, and merely 5% difference in the composition percentage of the three subpopulations of granulocytes, monocytes, and lymphocytes compared to the original sample. Furthermore, our cell sorter is designed to enable broad application of size-based inertial cell sorting by supplying a series of microchips with different sorting cutoff size. This strategy allows us to further enrich the lymphocytes population by twofold using another microchip with a cutoff size between 10 and 15 μm. With simplicity and efficiency, our cell sorter provides a powerful platform for isolating and sorting of WBCs and also envisions broad potential sorting applications for other cell types.     

微色谱柱分离-光度法测定高稀土铁矿石中的微量钍

采用HD-8微色谱柱对高稀土铁矿石样品(白云鄂博矿)中的钍进行分离富集,探讨了影响其分离富集的条件。实验表明,在4 mol/L HCl介质中钍可被树脂完全吸附,用3 mL 40 g/L草酸铵溶液可以从吸附柱上完全解吸钍,并结合偶氮胂Ⅲ分光光度法进行测定。所建立的方法适合于含铁、稀土量高的矿石样品中微量钍的分离与测定。     

Flame atomic absorption spectrometry determination of trace amount of gold after separation and preconcentration onto ion-exchange polyethylenimine coated on Al2O3

The object of this work is to develop a simple and selective method for efficient extraction of Au(III) ions in aqueous solution using a new solid-phase extraction sorbent. Polyethylenimine (PEI) ion-exchange polymer was coated on alumina in the presence of NaNO₃. The method is based on sorption of Au³⁺ ions on 50 mg PEI/Al₂O₃. A solution of 0.5 M thiourea, then 1.0 M HCl effectively eluted the gold ion and then aspirated into flame atomic absorption spectroscopy (FAAS). The influence of flow rate of sample solution and eluent, the pH effect, eluent type and sorption capacity was investigated. The effects of various diverse ions for preconcentration and separation of the gold ion were investigated. Relative standard deviation of 4.0 μg mL⁻¹ of gold was 1.46% (n = 10). The detection limit was 26.2 ng L⁻¹ in original solution. The method has been applied successfully for the recovery of trace amount of Au(III) ions from water samples.     

Preconcentration and separation of Cr(III) and Cr(VI) using sawdust as a sorbent

A simple, inexpensive method based on solid-phase extraction (SPE) on sawdust from Cedrus deodera has been developed for speciation of Cr(III) and Cr(VI) in environmental water samples. Because different exchange capacities were observed for the two forms of chromium at different pH—Cr(III) was selectively retained at pH 3 to 4 whereas Cr(VI) was retained at pH 1—complete separation of the two forms of chromium is possible. Retained species were eluted with 2.5 mL 0.1 mol L⁻¹ HCl and 0.1 mol L⁻¹ NaOH. Detection limits of 0.05 and 0.04 μg mL⁻¹ were achieved for Cr(III) and Cr(VI), respectively, with enrichment factors of 100 and 80. Recovery was quantitative using 250 mL sample volume for Cr(III) and 200 mL for Cr(VI). Different kinetic and thermodynamic properties that affect sorption of the chromium species on the sawdust were also determined. Metal ion concentration was measured as the Cr(VI)–diphenylcarbazide complex by UV–visible spectroscopy. The method was successfully applied for speciation of chromium in environmental and industrial water samples.     

Preconcentration and separation of some organic water pollutants with polyurethane foam and activated carbon

Summary Although pesticides and phenols, cause reproductive failure in many areas of the world, there is a no effective means of treating waste water containing these compounds. This work deals with the adsorption of insecticides and phenols from aqueous solution by untreated porous polyurethane foam and activated carbon. Static experiments showed that in comparison with activated carbon a reasonable percentage of the compounds was adsorbed by the foam. Attempts were therefore made to extract these species from aqueous solution by foam column chromatography.The results showed that the adsorption of the compounds was brought about by a mechanism similar to that of solvent extraction. The effect of various experimental conditions such as temperature, extracting medium, pH, contact time, volume of sample flow rate, compound concentration, and eluting solvents on the retention and separation of the compounds has been determined. The height equivalent to a theoretical plate (HETP) was calculated from breakthrough capacity curves and from chromatograms obtained from polyurethane foam columns for the insecticide Dyfonate; values were in the range 2.1–2.3 mm at 10–15 ml min^–1. Extraction of the compounds from natural water, and subsequent recovery, were both found to be complete. The high capacity of polyurethane provides advantages over activated carbon; in particular, large sample volumes can be analyzed at high flow rates.     

Separation and determination of trace amounts of zinc, lead, cadmium and mercury in tap and Qaroun lake water using polyurethane foam functionalized with 4-hydroxytoluene and 4-hydroxyacetophenone

A stable chelating sorbent was synthesized by covalently linking 4-hydroxytoluene or 4-hydroxyacetophenone with the polyurethane foam (PUF) through -NN- group. The synthesized chelating sorbents were characterized by IR and UV/vis measurements. The modified foams show excellent stability towards various solvents. Factors influencing the extraction process of Zn(II), Pb(II), Cd(II) and Hg(II) were studied and evaluated as a function of pH of metal ion solution and equilibration shaking time. The values of sorption capacity of metal ions (μg g⁻¹) were determined with the two types of bonded foams. The two phenolic bonded foams were studied comparatively. The potential applications of the two newly synthesized foams for the removal and separation of the examined metal ions from two natural water samples (drinking tap water and Qaroun lake water at Fayoum City, Egypt) were investigated. Precision (assessed as a relative standard deviation, R.S.D.) was also evaluated and found to be ≤7.3% (N = 5) with a detection limit under 0.46 μg L⁻¹.     

Application of modified multiwalled carbon nanotubes as solid sorbent for separation and preconcentration of trace amounts of manganese ions

In this work, the potential of modified multiwalled carbon nanotubes for separation and preconcentration of trace amounts of manganese ion is studied. Multiwalled carbon nanotubes were oxidized with concentrated HNO₃ and then modified with loading 1-(2-pyridylazo)-2-naphtol. Mn(II) ions could be quantitatively retained by modified multiwalled carbon nanotubes in the pH range of 8–9.5. Elution of the adsorbed manganese was carried out with 5.0 mL of 0.1 mol L^?1 HNO₃. Detection limit is 0.058 ng mL^?1 and analytical curve is linear in the range of 0.1 ng mL^?1–5.0 μg mL^?1 in the initial solution with a correlation coefficient 0.9977 and the preconcentration factor is 100. Relative standard deviation for eight replicate determination of 0.5 μg mL^?1 of manganese in the final solution is 0.41%. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions, were studied for preconcentration of Mn(II) ions in detail to optimize the conditions. The method was successfully applied for separation, preconcentration and determination of manganese in different samples.     

Using micellar electrokinetic chromatography for the highly efficient preconcentration and separation of gold nanoparticles

In this paper, we report the use of micellar electrokinetic chromatography (MEKC) for the highly efficient preconcentration and separation of gold nanoparticles (Au NPs). We used the reversed electrode polarity stacking mode (REPSM) of the MEKC system for the on-line enhancement and separation of the Au NPs. Several parameters had dramatic effects on the systems’ performance, including the concentration of sodium dodecylsulfate (SDS) surfactant, the presence of salts in the NP solution, the pH of the running electrolyte, and the temperature of the capillary. Under the optimized conditions [buffer: SDS (70 mM) and 3-cyclohexylamino-1-propanesulfonic acid (CAPS; 10 mM) at pH 10.0; applied voltage: 20 kV; operating temperature: 25 °C; additive: sodium dihydrogenphosphate (NaH₂PO₄, 10 mM); REPSM strategy for sample preconcentration], the number of theoretical plates for the 5.3- and 40.1-nm-diameter Au NPs were 3000 and (an ultrahigh) 2.1 × 10⁶, respectively; in addition, the detection sensitivities toward the Au NPs were enhanced ca. 20- and 380-fold, respectively, relative to those obtained using standard MEKC analysis conditions. Furthermore, monitoring the electropherograms using diode-array detection allowed us to identify and characterize the sizes of the separated NPs from their UV–vis spectra. Our findings suggest that MEKC is a highly efficient tool for both the preconcentration and separation of NPs.     

Improvement of size-based particle separation throughput in slanted spiral microchannel by modifying outlet geometry

The inertial microfluidic technique, as a powerful new tool for accurate cell/particle separation based on the hydrodynamic phenomenon, has drawn considerable interest in recent years. Despite numerous microfluidic techniques of particle separation, there are few articles in the literature on separation techniques addressing external outlet geometry to increase the throughput efficiency and purity. In this work, we report on a spiral inertial microfluidic device with high efficiency (>98%). Herein, we demonstrate how changing the outlet geometry can improve the particle separation throughput. We present a complete separation of 4 and 6 μm from 10 μm particles potentially applicable to separate microalgae (Tetraselmis suecica from Phaeodactylum tricornutum). Two spiral microchannels with the same cross section dimension but different outlet geometry were considered and tested to investigate the particle focusing behavior and separation efficiency. As compared with particle focusing observed in channels with a simple outlet, the particle focusing in a modified outlet geometry appears in a more successful focusing manner with complete separation. This simple approach of particle separation makes it attractive for lab-on-a-chip devices for continuous extraction and filtration of a wide range of cell/particle sizes.     

Synthesis of imprinted polymer material with palladium ion nanopores and its analytical application

Ion imprinted polymer (IIP) materials with nanopores were prepared by formation of ternary complex of palladium imprint ion with dimethylglyoxime (DMG) and 4-vinylpyridine (VP, functional monomer) and thermally copolymerizing with styrene (crosslinking monomer) and divinylbenzene (cross linker) and 2,2′-azobisisobutyronitrile as initiator. The synthesis was carried out with cyclohexanol as porogen and subsequently leached with 50% (v/v) HCl to obtain leached IIP particles. These leached IIP particles can now pick up palladium ions from dilute aqueous solutions. The optimal acidity for quantitative enrichment was 0.2-0.4N HCl and eluted completely by stirring for 15 min with 2×10 ml of 50% (v/v) HCl. The palladium ion imprinting polymer gave 100 times higher distribution ratio than ion recognition (blank) polymer (IRP). Further, percent extraction, distribution ratio and selectivity coefficients of palladium and other selected inorganic ions using IRP and IIP particles were determined and compared. Five replicate determinations of 50 μg of palladium in 1 l of solution gave a mean absorbance of 0.200 with a relative standard deviation of 2.12%. The detection limit corresponding to three times the standard deviation of the blank was 2.5 μg of palladium/l.     

负载α-巯基苯并噻唑聚酰胺树脂富集分离水中汞

提出以合成的纤维状负载α－巯基苯并噻唑聚酰胺树脂为吸附剂,在表态和动态操作条件下,对环境水体中汞的选择性吸附分离方法。实验表明,树脂在pH9的弱碱至2mol/L的强酸介质中,对汞的吸附性能很好,饱和吸附容量为38．74mg/g。树脂中的汞用5％硫脲溶液解脱,再以冷原子吸收分光光度法测定,可对不同水样进行分析,结果满意。     

Determination of inorganic arsenic species in natural waters—Benefits of separation and preconcentration on ion exchange and hybrid resins

A simple method for the separation and determination of inorganic arsenic (iAs) species in natural and drinking water was developed. Procedures for sample preparation, separation of As(III) and As(V) species and preconcentration of the total iAs on fixed bed columns were defined. Two resins, a strong base anion exchange (SBAE) resin and a hybrid (HY) resin were utilized. The inductively-coupled plasma-mass spectrometry method was applied as the analytical method for the determination of the arsenic concentration in water. The governing factors for the ion exchange/sorption of arsenic on resins in a batch and a fixed bed flow system were analyzed and compared. Acidity of the water, which plays an important role in the control of the ionic or molecular forms of arsenic species, was beneficial for the separation; by adjusting the pH values to less than 8.00, the SBAE resin separated As(V) from As(III) in water by retaining As(V) and allowing As(III) to pass through. The sorption activity of the hydrated iron oxide particles integrated into the HY resin was beneficial for bonding of all iAs species over a wide range of pH values from 5.00 to 11.00. The resin capacities were calculated according to the breakthrough points in a fixed bed flow system. At pH 7.50, the SBAE resin bound more than 370 μg g⁻¹ of As(V) while the HY resin bound more than 4150 μg g⁻¹ of As(III) and more than 3500 μg g⁻¹ of As(V). The high capacities and selectivity of the resins were considered as advantageous for the development and application of two procedures, one for the separation and determination of As(III) (with SBAE) and the other for the preconcentration and determination of the total arsenic (with HY resin). Methods were established through basic analytical procedures (with external standards, certified reference materials and the standard addition method) and by the parallel analysis of some samples using the atomic absorption spectrometry-hydride generation technique. The analytical properties of both procedures were similar: the limit of detection was 0.24 μg L⁻¹, the limit of quantification was 0.80 μg L⁻¹ and the relative standard deviations for samples with a content of arsenic from 10.00 to 300.0 μg L⁻¹ ranged from 1.1 to 5.8%. The interference effects of anions commonly found in water and some organic species which can be present in water were found to be negligible. Verification with certified reference materials proved that the experimental concentrations found for model solutions and real samples were in agreement with the certified values.     

CE determination of small ions: methods and techniques

This paper provides an overview on the current status of capillary electrophoresis (CE) in the analysis of inorganic and charged small organic species. The various CE strategies used to improve the separation of ionic analytes are summarized. Technical developments in the design of improved detection systems are described. A brief account of their advantages and limitations is given. The potential use of these devices for miniaturized CE systems is also described. Finally, special attention is focused on the on-capillary preconcentration techniques developed in attempts to overcome the poor detectability of CE. Recent review articles are frequently cited to provide readers with a source of information about pioneering work, theoretical treatments, and specific applications.     

Graphene/graphene oxide and their derivatives in the separation/isolation and preconcentration of protein species: A review

The distinctive/unique electrical, chemical and optical properties make graphene/graphene oxide-based materials popular in the field of analytical chemistry. Its large surface offers excellent capacity to anchor target analyte, making it an powerful sorbent in the adsorption and preconcentration of trace level analyte of interest in the field of sample preparation. The large delocalized π-electron system of graphene framework provides strong affinity to species containing aromatic rings, such as proteins, and the abundant active sites on its surface offers the chance to modulate adsorption tendency towards specific protein via functional modification/decoration. This review provides an overview of the current research on graphene/graphene oxide-based materials as attractive and powerful adsorption media in the separation/isolation and preconcentration of protein species from biological sample matrixes. These practices are aiming at providing protein sample of high purity for further investigations and applications, or to achieve certain extent of enrichment prior to quantitative assay. In addition, the challenges and future perspectives in the related research fields have been discussed.     

Development of an MSFIA-MPFS pre-treatment method for radium determination in water samples

A new automatic method for preconcentration and separation of radium in water samples has been developed. Such method combines both multisyringe (MSFIA) and multi-pumping (MPFS) flow analysis techniques allowing to analyze larger sample volumes with a higher throughput than other previous methodologies. Ra adsorbed on MnO₂, deposited on cotton fiber, is eluted with hydroxylamine and subsequently coprecipitated with BaSO₄. ²²⁶Ra activity is determined off-line by using a low background proportional counter. The procedure yield is (90 ± 3)% and its lower limit of detection 0.05 Bq L⁻¹. This method has been applied satisfactorily to different types of spiked water (tap, mineral and seawater).     

Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II)

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1 ± 0.1 mmol g⁻¹ of alumina. Hg(II) uptake was 1.90 mmol g⁻¹(distribution coefficient log K_d = 5.658) at pH 1.0 or 2.0, 1.68 mmol g⁻¹ (log K_d = 4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g⁻¹ (log K_d < 3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values ≤ 3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2 l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100 mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5 ± 0.5, 98.5 ± 0.5 and 103.0 ± 1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N = 3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.     

The use of solid-phase extraction and direct injection of a copolymer sorbent as slurry into the graphite furnace prior to determination of cadmium by ETAAS

Abstract

Several aquatic heterogeneous humic-solute fractions with known molecular-size ranges were fractionated further by coupled size-exclusion chromatography (SEC) and polyacrylamide gel electrophoresis (PAGE). The results of SEC-PAGE, obtained for several humic-solute fractions, corresponded reasonably well to the known molecular-size distributions of the dissolved organic matter (DOM). Despite the limited resolving power PAGE appears to offer an alternative coarse method, beside SEC, for fractionation of the heterogeneous humic matter (HM).