Solid Phase Extraction Of Trace Amounts Research Articles

Selective aptamer conjugation to silver-coated magnetite nanoparticles for magnetic solid-phase extraction of trace amounts of Pb2+ ions.

Herein, a novel aptamer-functionalized magnetic adsorbent was developed and combined with magnetic solid-phase extraction (MSPE) for the specific enrichment of Pb2+ ions prior to flame atomic absorption spectrometric detection. First, silver-coated magnetite core–shell nanoparticles (Fe3O4@Ag MNPs) were synthesized by the chemical reduction of silver ions on the surface of magnetite nanoparticles. After that, the selective DNA aptamer against Pb2+ was conjugated on the surface of the synthesized nanoparticles to form aptamer-modified magnetic nanoparticles (Fe3O4@Ag-APT). The characterization of the prepared adsorbent was performed through SEM imaging, XRD, FT-IR, EDX, and DRS instruments. The influence of the various experimental parameters on the adsorption and desorption steps in MSPE was investigated via Taguchi experimental design to optimize different parameters. Under the optimized conditions, the Pb2+ calibration graph was linear in the range of 33–1000 μg L−1. The relative standard deviation (RSD%) of the method for six replicates containing 100 μg L−1 of Pb2+ ions was 0.34%. Furthermore, the limit of detection (LOD) and the limit of quantification (LOQ) were 10 μg L−1 and 33.3 μg L−1, respectively. Finally, the applicability of the proposed method was successfully confirmed by preconcentration and determination of trace amounts of Pb2+ ions in tap and seawater samples. We showed a proof of concept for Fe3O4@Ag-APT as an efficient bio-adsorbent, offering a promising strategy for the specific binding/removal of toxic heavy metal ions.

Solid-phase extraction using octadecyl-bonded silica modified with photosynthetic pigments from Spinacia oleracea L. for the preconcentration of lead(II) ions from aqueous samples.

Spinacia oleracea L. extract was immobilized on an octadecyl-bonded silica surface to produce a new sorbent for the solid-phase extraction of trace amounts of metal ions from aqueous neutral samples. A measurement of the metal content has been performed by using graphite furnace atomic absorption spectroscopy. The affinity of the investigated bivalent metal cations for the modified sorbent are in the order: Pb(II)>Cu(II)>Ni(II)>Zn(II) ≈ Cd(II) ≈ Co(II). The quantum-chemically calculated chlorophyll-a-metal ion binding energies were consistent with the measured affinities of the corresponding metal ions to the investigated sorbent. The maximum sorption capacity obtained for Pb(II) was equal to 1.44μmol/g. The value of lead uptake was significantly higher in comparison to the one reported for other sorbents and biosorbents. Immobilized chlorophyll a is responsible for a chelation process with stoichiometry 1:1 owing to the porphyrin rings, which was confirmed by the quantitative analysis performed by reversed-phase high-performance liquid chromatography with diode array detection. The Toth adsorption isotherm model was applicable to the description of the adsorption process of either chlorophyll a or Pb(II). The structural analysis of sorbent was done using Fourier-transform Raman spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector.

Magnetic solid-phase extraction to preconcentrate trace amounts of gold (III) using nickel ferrite magnetic nanoparticles

ABSTRACTIn this research, nickel ferrite (NiFe2O4) magnetic nanoparticles were synthesised by a simple method and applied as sorbent for magnetic solid-phase extraction of trace amounts of Au(III) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The effects of sample pH, amount of sorbent, extraction time, desorption solvent and its volume on the extraction process were optimised. The effects of interfering ions on the recovery of the analyte were also evaluated in model solutions. The best results were obtained at pH 6.5 with 5 mL of eluent solution (0.1 mol L−1 sodium thiosulphate) and an extraction time of 30 min. Under optimal conditions, the sorption capacity was 34.6 mg g−1. Also, enhancement factor (for 100 mL of sample solution) was found to be 19.3. The calibration graph was linear in the range of 4.4–800.0 µg L−1 gold concentration and the limit of detection was 1.32 µg L−1. The relative standard deviation of the method (for n = 8) was 1.57%. The method was successfully applied to the extraction of Au(III) from water samples.

Trace determination of lead(II) ions by using a magnetic nanocomposite of the type Fe3O4/TiO2/PPy as a sorbent, and FAAS for quantitation

The authors describe a magnetic nanoadsorbent consisting of magnetite nanoparticles coated first with titanium dioxide and then with polypyrrole (PPy). It is shown to be a viable material for magnetic solid-phase extraction of trace amount of Pb(II). The magnetic titanium dioxide nanoparticles were synthesized first and then modified with PPy via in-situ electropolymerization. The properties, morphology, and composition of the sorbent were characterized by FTIR, scanning electron microscopy, energy-dispersive X-ray analysis and vibrating sample magnetometry. The effects of pH value, extraction time, type and concentration of eluent, and of sample volume were optimized. Under the optimum conditions, the limit of detection (for S/N = 3) is 0.28 μg⋅L−1. The maximum adsorption capacity of the adsorbent is 126 mg⋅g−1 of Pb(II). The accuracy of the method was investigated by analysis of a Certified Reference Material and the obtained value (0.119 μg⋅g−1) was in good agreement with the certified value (0.120 μg⋅g−1). The method was successfully applied to the determination of Pb(II) in a gastropod and spiked environmental and marine water samples. It gave recoveries in the range from 94.4 to 103.1%.

Rattle-type Fe3O4@SnO2 core-shell nanoparticles for dispersive solid-phase extraction of mercury ions

The synthesis of rattle-type nanostructured Fe3O4@SnO2 is described along with their application to dispersive solid-phase extraction of trace amounts of mercury(II) ions prior to their determination by continuous-flow cold vapor atomic absorption spectrometry. The voids present in rattle-type structures make the material an effective substrate for adsorption of Hg(II), and also warrant high loading capacity. The unique morphology, large specific surface, magnetism property and the synergistic effect of magnetic cores and SnO2 shells render these magnetic nanorattles an attractive candidate for solid-phase extraction of heavy metal ions.The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FTIR, energy-dispersive X-ray spectroscopy and by the Brunnauer-Emmett-Teller technique. The effects of pH value, adsorption time, amount of sorbent, volume of sample solutions, concentration and volume of eluent on extraction efficiencies were evaluated. The calibration plot is linear in the 0.1 to 40 μg·L−1 concentration range, and the preconcentration factor is 49. The detection limit is 28 ng·L−1. The sorbent was applied to the analysis of (spiked) river and sea water samples. Recoveries ranged from 97.2 to 100.5%.

Aspartic acid-modified magnetic nanoparticles as an ideal sorbent for solid phase extraction of Pb in water samples prior to ICP-OES determination

The present study will consider the application of aspartic acid-coated Fe3O4 as a sorbent for solid-phase extraction of trace amounts of Pb using inductively coupled plasma optical emission spectrometry. Magnetic nanoparticles (MNPs) of Fe3O4 possess a high potential for modification with different organic and inorganic compounds. Using an amino acid (in this case, aspartic acid) as a nontoxic modifier, without an organic solvent, could provide a number of environmentally friendly applications in the field of green chemistry. By using modified MNPs as a sorbent, the separation of metal ions from an aqueous sample solution was easily performed by an external magnet without centrifuging or filtering. An elution step was accomplished by using a 2 mol L−1 nitric acid solution for introducing the desorbed analyte to ICP-OES. Different parameters influencing on the extraction efficiency, such as pH, volume of the modifier, extraction and elution time, types and concentrations of eluent were investigated and optimized. Under the optimized conditions, the detection limit for Pb was 0.6 μg L−1 and the calibration curve showed linearity in the range of 1–600 μg L−1. The relative standard deviation (RSD, C = 300 μg L−1, n = 5) was 2.8%. The sorption capacity of the sorbent was found to be 19.9 mg g−1. The sorbent exhibited good stability and high adsorption capacity for lead ions. The applicability of the sorbent was examined by a real sample and the results were satisfactory.

Application of copolymer coated frits for solid-phase extraction of poly cyclic aromatic hydrocarbons in water samples

A conducting copolymer of pyrrole and phenol was electrochemically synthesized on steel frits as a sorbent. The applicability of the frit was assessed for the solid-phase extraction of trace amounts of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples followed by HPLC–UV. The coating produced was very adherent and the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and FTIR spectrum for the coated frit were studied. The effects of various parameters on the efficiency of the solid-phase extraction process, such as the sample loading rate, elution solvent type, salt effect, volume and flow rate of sample and elution solvent were investigated. Under the optimal conditions, the calibration curves were obtained in the range of 0.1–500ngmL−1 (r2>0.98) and the LODs (S/N=3) were obtained in the range of 0.01–0.08ngmL−1. Relative standard deviations (RSDs) for intra- and inter-day precision were 2.7–10.2% and 3.6–11.4%, respectively. The recoveries (8 and 40ngmL−1) ranged from 79% to 115%. The simplicity of experimental procedure, short sample analysis, high extraction efficiency, and the use of low-cost adsorbent show the potential of this method for routine analysis of PAHs in real samples.

Copper, iron, and lead levels in fertilizer and water samples: separation and preconcentration on multiwaled carbon nanotubes

ABSTRACTAn enrichment-separation method using solid-phase extraction of trace amounts of Fe(III), Cu(II), and Pb(II) as their pyrocatechol violet chelates on multiwaled carbon nanotube column has been established. Analytes were desorbed from the column by using 5 mL of 2.0 M HNO3. Influences of some analytical parameters like pH and sample volume on the recoveries of the analyte ions were investigated. Effects of matrix ions were also evaluated. The presented procedure was validated by using additional recovery test and analyzing the certified reference materials (SRM 1570a—Trace Elements in Spinach Leaves and TMDA-70 fortified lake water). The application of this method was successfully performed for the determination of copper, iron, and lead levels in various fertilizer samples marketed in Kayseri–Turkey and some water samples.

Solid-phase extraction of trace metal ions with magnetic nanoparticles modified with 2,6-diaminopyridine

We have modified silica-coated Fe3O4 nanoparticles with 2,6-diaminopyridine and used these for selective magnetic solid-phase extraction of trace amounts of metal ions. The nanoparticles were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Quantitative extraction of trace amounts of Cu(II) and Zn(II) from mixed-ion solutions was accomplished at an optimal pH value of 6 within less than 10 min. The metal ions were eluted from the sorbent with hydrochloric acid. Common electrolytes and chemically related metal ions do not interfere. The relative standard deviations of the method are <4 %. It was successfully applied to the separation and preconcentration of trace metal ions from the certified reference materials GBW 08301 (river sediment) and GBW 08607 (water solution), in natural water, and in samples of vegetable with satisfying results.

Ion-pair Solid-Phase Extraction of Trace Amounts of Ionic Liquid Cations in Fresh and Seawater Samples

The usefulness of ion-pair reagents in selective solid reversed-phase extraction of one N-butyl-4-methylpyridinium and four short-chain alkylimidazolium ionic liquid cations from aqueous media was investigated using various concentrations of alkylsulfonates with different alkyl chain lengths. Final recoveries of the two cations with the shortest alkyl residues were poorer than those of the other, more hydrophobic compounds. Moreover, the recovery values were little affected by the different concentrations of the reagents. In nearly all cases, the best recoveries were obtained with the 1-heptanesulfonate reagent. The analytical performance parameters included excellent linearity over four orders of magnitude, with limits of detection ranging from 0.01 to 0.06 ppm, and very good precision and accuracy. The method was successfully used to extract ionic liquids from spiked seawater and freshwater samples. Recoveries and limits of detection were quite similar to those obtained with preconcentrated standard solutions.

Analytical characterization of a silica gel sorbent with thioetheric sites

The sorption behavior of a newly synthesized silica gel sorbent with thioetheric sites (STS) towards microgram levels of Au(III), Pt(IV) and Pd(II) was studied. Au(III) is quantitatively (>95%) sorbed in the pH region of 1–9. The sorption of Pt(IV) starts at pH 1 and does not exceed 25% in the entire pH region examined. The sorption of Pd(II) starts at pH 7 and reaches 80% at pH 9. The sorption of Au(III) on STS at pH 1 is not affected by milligram amounts of Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) or Co(II). Au(III) is quantitatively eluted with a 5% aqueous solution of thiourea. The adsorption capacity of STS towards Au(III) is 195 mg g−1. The detection limit (DL) of Au(III) (3σ, n = 9) is 25 ng mL−1. The RSD at a level of 10 × DL is about 2%. Solid-phase extraction of trace amounts of Au(III) on the STS sorbent, followed by its flame AAS determination in the eluate was applied to the determination of gold in geological samples. The results obtained for the gold content in the samples were in good agreement with those of the ICP-AES analysis.

Solid-Phase Extraction of Copper with Cupron on Octadecyl Silica Cartridge and its Determination with Atomic Absorption Spectrometry

Solid-phase extraction of trace amounts of copper from large volumes of aqueous solutions was studied. The extraction was carried out by means of an octadecyl silica cartridge modified with cupron. The effect of different parameters such as sample matrix, flowrates of sample solution and eluent, pH, breakthrough volume, and potentially interfering ions was examined. Cu2+ was extracted from solution in the pH range of 6–8.5 on a modified cartridge. Elution was accomplished using 2 mL of 0.2 M HNO3. Hence, with a typical preconcentration factor of 1000, a detection limit of 0.02 ng mL−1 was obtained. The method was applied to the determination of copper in natural water samples.

Evaluation of Several Gas Chromatographic Stationary Phases for the Solid-Phase Extraction of Trace Amounts of Copper in Aqueous Samples.

Evaluation of Several Gas Chromatographic Stationary Phases for the Solid-Phase Extraction of Trace Amounts of Copper in Aqueous Samples.

Determination of vitamin D 2 in emulsified nutritional supplements by solid-phase extraction and column-switching high-performance liquid chromatography with UV detection

This paper deals with a method for solid-phase extraction of trace amounts of vitamin D 2 (VD 2, 19 ng/g) from emulsified nutritional supplements, which contain 50 kinds of compounds, followed by column-switching high-performance liquid chromatography (HPLC) with UV detection at 265 nm. VD 2 is present at 1000–20 000 000 times lower concentration than other components. Bond Elut C 18 cartridge was chosen as for the emulsified nutritional supplements after comparison with eight other types. A sample solution was applied to the solid-phase extraction cartridge and VD 2 was eluted by methanol followed by HPLC. The effects of sample pH, eluent composition and eluate volume on the retention and elution of VD 2 on Bond Elut C 18 cartridge were examined. The resulting method was simple, rapid (analysis time: ∼20 min), sensitive (detection limit: ∼0.1 ng per injection (200 μl) at a signal-to-noise ratio 3:1), and reproducible (relative standard deviation: ∼6.2%, n=5). The calibration graph for VD 2 was linear in the range of 0.1–3 ng per injection (200 μl). Recovery of VD 2 was ∼80% by the standard addition method.

Solid-Phase Extraction of Trace Amounts of Selenomethionine

Preconcentration and separation of trace amounts of selenomethionine was investigated using several solid sorbents. The best results were obtained with copper-treated Chelex 100 chelating resin. Selenomethionine from 100 ml of solution adsorbed on 0.2 g of the resin was eluted with 8 ml of 1.5 mol/l ammonia solution and determined by electrothermal atomic absorption spectrometry. The column chromatography with Cu-Chelex and functionalized cellulose sorbent Cellex T was applied to separate organic and inorganic selenium forms.

Solid-phase extraction of trace amounts of beryllium(II) from natural water samples on a glass-fibre filter followed by solid-phase spectrophotometric determination using Chromazurol B

A selective and sensitive method for the determination of beryllium(II) is described, based on the combined use of solid-phase extraction on a glass-fibre filter (GFF) and solid-phase spectrophotometry using Chromazurol B (CAB). In solid-phase spectrophotometry, beryllium(II) is fixed and determined directly on a membrane filter as the BeII–CAB complex formed in the presence of hexadecyltrimethylammonium bromide. The detection limit is 0.4 ng for 30 cm3 of sample solution. Trace amounts of beryllium(II) in aqueous sample solutions are first extracted on a GFF from a solution containing ethylenediaminetetraacetic acid as a masking agent of co-existing ions at pH 9.5, then determined after desorption from the GFF with 30 cm3 of 0.1 mol dm–3 hydrochloric acid. A recovery of 96.3% is achieved. The proposed method was applied to river water and hot spring water samples with pH values in the range 1.6–3.6 using 3.0–50.0 cm3 of sample solution. The concentrations of beryllium(II) found were in the range 0.12–3.52 ppb.