Selective solid-phase extraction of trace Fe(III) from biological and natural water samples using nanometer SiO2 modified with acetylsalicylic acid

A new method using acetylsalicylic acid (aspirin) modified SiO₂ nanoparticles (nanometer SiO₂-aspirin) as a solid-phase extractant (SPE) has been developed for the preconcentration of trace amounts of Fe(III) prior to their determination by inductively coupled plasma optical emission spectrometry. The preconcentration conditions of analytes were investigated, including the pH value, the shaking time, the mass of sorbent, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the sorption capacity of nanometer SiO₂-aspirin was found to be 1.28 mmol g⁻¹. The preconcentration factor is 50. The detection limit (3σ) for Fe(III) was 0.49 ng mL⁻¹. The method was validated by analyzing two certified reference materials (GBW 08301, river sediment and GBW 08303, polluted farming soil), and the results obtained are in good agreement with standard values. The method was also applied to the determination of trace Fe(III) in biological and water samples with satisfactory results. Correspondence: Xiangbing Zhu, Department of Chemistry, Lanzhou University, Lanzhou 730000, P.R. China     

Application of mercapto‐silica polymerized high internal phase emulsions for the solid‐phase extraction and preconcentration of trace lead(II)

A new class of solid‐phase extraction column prepared with grafted mercapto‐silica polymerized high internal phase emulsion particles was used for the preconcentration of trace lead. First, mercapto‐silica polymerized high internal phase emulsion particles were synthesized by using high internal phase emulsion polymerization and carefully assembled in a polyethylene syringe column. The influences of various parameters including adsorption pH value, adsorption and desorption solvents, flow rate of the adsorption and desorption procedure were optimized, respectively, and the suitable uploading sample volumes, adsorption capacity, and reusability of solid phase extraction column were also investigated. Under the optimum conditions, Pb²⁺ could be preconcentrated quantitatively over a wide pH range (2.0–5.0). In the presence of foreign ions, such as Na⁺, K⁺, Ca²⁺, Zn²⁺, Mg²⁺, Cu²⁺, Fe²⁺, Cd²⁺, Cl^? and NO₃^?, Pb²⁺ could be recovered successfully. The prepared solid‐phase extraction column performed with high stability and desirable durability, which allowed more than 100 replicate extractions without measurable changes of performance. The feasibility of the developed method was further validated by the extraction of Pb²⁺ in rice samples. At three spiked levels of 40.0, 200 and 800 μg/kg, the average recoveries for Pb²⁺ in rice samples ranged from 87.3 to 105.2%.     

Speciation analysis of selenoproteins in human serum by microbore affinity-HPLC hyphenated to ICP-Sector field-MS using a high efficiency sample introduction system

Silica gel and nanometer SiO₂ modified with 4-(2-aminoethylamino)-N-(2-(2-aminoethyl amino)ethyl)butanamide (SG-AAEB and nanometer SiO₂-AAEB), which were prepared based on chemical immobilization, were used as sorbents for the solid phase extraction of Cu(II), Fe(III), and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry. Adsorption efficiencies of the two sorbents towards metal ions were investigated by batch and column procedures. For both sorbents the preconcentration conditions of analytes including effects of pH, shaking time, sample flow rate and adsorption capacity, were investigated and compared. The differences of silica gel and nanometer SiO₂ in sizes and surface structures resulted in distinct chemical activity and selectivity toward metals. At pH 4, the adsorption capacity of SG-AAEB was found to be 12.2, 14.5 and 9.8 mg g^?1 for Cu(II), Fe(III), and Pb(II), respectively. In comparison, nanometer SiO₂-AAEB showed a high selectivity toward Pb(II) and has a much larger adsorption capacity (22.3 mg g^?1). Furthermore, the application of SG-AAEB and nanometer SiO₂-AAEB for simultaneous preconcentration of trace Cu(II), Fe(III), and Pb(II) from natural samples was performed with satisfactory results.     

ICP-AES determination of trace elements after preconcentrated with p-dimethylaminobenzaldehyde-modified nanometer SiO2 from sample solution

A new method that utilizes p-dimethylaminobenzaldehyde-modified nanometer SiO₂ (SiO₂-p-DMABD) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The preconcentration conditions of analytes were investigated, including the pH value, the shaking time, the mass of sorbent, the sample flow rate and volume, the elution condition and the interfering ions. The adsorption capacity of nanometer SiO₂-p-DMABD was found to be (mg g^− 1) Cr(III): 6.2, Cu(II): 18.6, Fe(III): 4.7 and Pb(II): 6.0 at pH 4. The adsorbed metals were quantitatively eluted with 4 mL of 1.0 mol L^− 1 HCl. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr(III), Cu(II), Fe(III) and Pb(II) were 0.79, 1.27, 0.40 and 1.79 ng mL^− 1, respectively. The proposed method achieved satisfied results when it was applied to the determination of trace Cr(III), Cu(II), Fe(III) and Pb(II) in biological and water samples.     

Application of Dithizone-Modified TiO2 Nanoparticles in the Preconcentration of Trace Chromium and Lead from Sample Solution and Determination by Inductively Coupled Plasma Atomic Emission Spectrometry

A new method using dithizone-modified TiO₂ nanoparticles (nanometer TiO₂-DZ) as solid-phase extractant has been developed for the simultaneous preconcentration of trace amounts of chromium and lead prior to their measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The preconcentration conditions of the analytes, including the effects of pH, sample flow rate and volume, elution conditions and interfering ions on the recovery of the analytes were investigated. At pH 5, the adsorption capacity of the nanometer TiO₂-DZ was found to be 5.8 mg g⁻¹ and 22.5 mg g⁻¹ for Cr and Pb, respectively. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr and Pb were 0.38 and 1.72 ng mL⁻¹, respectively. The proposed method was applied to the determination of trace chromium and lead in foodstuffs, plants and water samples with satisfactory results.     

Solid-phase extraction of antimony using chemically modified SiO2-PAN nanoparticles

A new analytical method using 1-(2-pyridylazo)-2-naphthol (PAN)-modified SiO2 nanoparticles as solid-phase extractant has been developed for the preconcentration of trace amounts of Sb(III) in different water samples. Conditions of the analysis such as preconcentration factor, effect of pH, sample volume, shaking time, elution conditions, and effects of interfering ions for the recovery of the analyte were investigated. The adsorption capacity of nanometer SiO2-PAN was found to be 186.25 micromol/g at optimum pH and the LOD (3sigma) was 0.60 microg/L. The extractant showed rapid kinetic sorption. The adsorption equilibrium of Sb(III) on nanometer SiO2-PAN was achieved in 10 min. Adsorbed Sb(III) was easily eluted with 4 mL 2 M hydrochloric acid. The maximum preconcentration factor was 62.20. The method was applied for the determination of trace amounts of Sb(III) in various water samples (tap, mineral water, and industrial effluents).     

Preparation of morin modified nanometer SiO<Subscript>2</Subscript> as a sorbent for solid-phase extraction of trace heavy metals from biological and natural water samples

Morin was successful as a chemical modifier to improve the reactivity of the nanometer SiO₂ surface in terms of selective binding and extraction of heavy metal ions. This new functionalized nanometer SiO₂ (nanometer SiO₂-morin) was used as an effective sorbent for the solid-phase extraction (SPE) of Cd(II), Cu(II), Ni(II), Pb(II), Zn(II) in solutions prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace levels of metal ions were optimized with respect to different experimental parameters using static and dynamic procedures in detail. The pH 4.0 was chosen as the optimum pH value for the separation of metal ions on the newly sorbent. Complete elution of the adsorbed metal ions from the nanometer SiO₂-morin was carried out using 2.0 mL of 0.5 mol L⁻¹ of HCl. Common coexisting ions did not interfere with the separation and determination at pH 4.0. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 22.36, 36.8, 40.37, 33.21 and 25.99 mg metal/g SiO₂-morin for Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The time for 95% sorption for Cu(II) and Ni(II) and 70% sorption for Cd(II), Pb(II) and Zn(II) was less than 2 min. The relative standard deviation (RSD) of the method under optimum conditions was lower than 5.0% (n = 11). The procedure was validated by analyzing the certified reference river sediment material (GBW 08301, China), the results obtained were in good agreement with standard values. The nanometer SiO₂-morin was successfully employed in the separation and preconcentration of trace Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) from the biological and natural water samples yielding 75-folds concentration factor.     

Nanometer SiO2 modified with 5-sulfosalicylic acid as selective solid-phase extractant for Fe(III) determination by ICP-AES from biological and natural water samples

A new modified nanometer SiO₂ using 5-sulfosalicylic acid (SSA) as a solid-phase extractant was used for separation, preconcentration and determination of Fe(III) in aqueous solutions by inductively coupled plasma atomic emission spectrometry (ICP-AES). Its adsorption and preconcentration behaviour for Fe(III) in aqueous solutions was investigated using static procedures in detail. The optimum pH value for the separation of Fe(III) on the newly designed sorbent was 3.5. Complete elution of the adsorbed Fe(III) from the nanometer SiO₂-SSA was carried out using 2.0 mL of 0.01 mol L^− 1 of HCl. The time of 90% sorption was less than 2 min for Fe(III) at pH 3.5. Common coexisting ions did not interfere with the separation and determination of Fe(III) at pH 3.5. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 44.01 mg of Fe(III) per gram of sorbent. The relative standard deviation (RSD) of the method under optimum conditions was 3% (n = 5). The procedure was validated by analyzing three certified reference materials (GBW 08301, GBW 08504, GBW 08511), the results obtained were in good agreement with standard values. The nanometer SiO₂-SSA was successfully employed in the separation and preconcentration of the investigated Fe(III) from the biological and natural water samples yielding 100-folds concentration factor.     

Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb²⁺, Ni²⁺, Cd²⁺ and Cu²⁺ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L^?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L^?1, respectively. The relative SDs at 10 µg L^?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples.     

Silica-Coated CaF2:Eu3+ Nanoparticles Functionalized with Oxalic Acid for Bio-conjugation to BSA Proteins

A new method for silica‐coated CaF₂:Eu³⁺ core‐shell nanoparticles functionalized with oxalic acid for bio‐conjugation to bovine serum albumin (BSA) proteins has been developed. Moreover, CaF₂:Eu³⁺/SiO₂ core‐shell nanoparticles modified with oxalic acid are biocompatible and can be dispersed in water. As an organic functional molecule, oxalic acid is able to react with hydroxyl groups existed on the surface of SiO₂ layer by esterification reaction to form carboxylic acid for further bio‐conjugation with BSA. The final products were characterized by means of X‐ray diffraction (XRD), transmission electron microscope (TEM), field‐emission scanning electron microscopy (FE‐SEM), ultraviolet (UV) spectrophotometer, infrared (IR) spectrophotometer and photoluminescence (PL) spectra. XRD result confirmed the phase purity of CaF₂:10 mol% Eu³⁺ and CaF₂:10 mol% Eu³⁺/SiO₂ nanoparticles obtained from the quaternary reverse micelles of cetyltrimethylammonium bromide (CTAB), cyclohexane, n‐pentanol and water. Images of TEM and FE‐SEM showed that the average grain sizes of CaF₂:10 mol% Eu³⁺/SiO₂ and bio‐conjugation of CaF₂:10 mol% Eu³⁺/SiO₂ nanoparticles with BSA were about 17 nm. The patterns of UV and IR spectra showed that BSA was linked to CaF₂:10 mol% Eu³⁺/SiO₂ nanoparticles. In the emission spectrum of CaF₂:10 mol% Eu³⁺/SiO₂ conjugated by BSA nanoparticles, characteristic emission peaks of Eu³⁺ within the wavelength ranging from 500 to 700 nm were observed, which is corresponding to the transitions from the excited ⁵D₀ levels to ⁷F_J levels. This confirmed that the Eu³⁺ dopant ion is located in a Ca²⁺ crystal site with T_d symmetry. CaF₂:10 mol% Eu³⁺/SiO₂ conjugated by BSA nanoparticles remain stable in aqueous media within 15 d with pH ranging from 2 to 9. Therefore, these luminescent colloidal nanoparticles can be potentially employed as targeted fluorescent labels in biomedical research applications.     

Competitive heavy metal removal by poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐itaconic acid)

The competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solutions by the copolymer of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and itaconic acid (IA), P(AMPS‐co‐IA), was investigated. Homopolymer of AMPS (PAMPS) was also used to remove these ions from their aqueous solution. In the preparation of AMPS–IA copolymer, the molar percentages of AMPS and IA were 80 and 20, respectively. In order to observe the changes in the structures of polymers due to metal adsorption, FTIR spectra by attenuated total reflectancetechnique and scanning electron microscopy (SEM) pictures of the polymers were taken both before and after adsorption experiments. Total metal ion removal capacities of PAMPS and P(AMPS‐co‐IA) were 1.685 and 1.722 mmol Me²⁺/g_polymer, respectively. Experimental data were evaluated to determine the kinetic characteristics of the adsorption process. Competitive adsorption of Pb²⁺, Cu²⁺, and Cd²⁺ ions onto both PAMPS and P(AMPS‐co‐IA) was found to fit pseudo‐second‐order type kinetics. In addition, the removal orders in the competitive adsorption of these metal ions onto PAMPS and P(AMPS‐co‐IA) were found to be Cd²⁺ > Pb²⁺ > Cu²⁺ and Pb²⁺ > Cd²⁺ > Cu²⁺, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Pre-concentration of trace amounts of manganese in water samples based on (1-(2-pyridylazo)-2-naphthol) modified magnetic nanoparticles

A simple procedure based on magnetic nanoparticles has been developed for analytical purposes. In this method, 1-(2-pyridylazo)-2-naphthol (PAN)-modified magnetic nanoparticles (MNPs) were used for separation and pre-concentration of manganese(II) ions from aqueous samples. This method combines the use of a solution solvent with separation of magnetic nanoparticles from sample solution using a magnet. The influence of different parameters, such as amount of extractant (PAN) loaded on the nanoparticles, pH of solution, adsorption time, amount of modified nanoparticle, type and amount of eluents for desorption of manganese from magnetic nanoparticles were evaluated. The effect of various cationic and anionic interferences on the percentage recovery of manganese was also studied. Manganese ions were adsorped from a solution at pH 9.5 and desorbed from nanoparticles with 10?mL of DMSO?:?HNO₃ (1?:?1, v/v). The detection limit of the proposed method was found to be 0.11?µg?L^?1. The method was employed to recover and determine the level of manganese in different water samples.     

Nanometer titanium dioxide immobilized on silica gel as sorbent for preconcentration of metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry

Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO₂) was prepared by sol-gel method and characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The adsorptive potential of immobilized nanometer TiO₂ for the preconcentration of trace Cd, Cr, Cu and Mn was assessed in this work. The metal ions studied can be quantitative retained at a pH range of 8-9, and 0.5 mol L⁻¹ HNO₃ was sufficient for complete elution. The adsorption capacity of immobilized nanometer TiO₂ for Cd, Cr, Cu and Mn was found to be 2.93, 2.11, 6.69 and 2.47 mg g⁻¹, respectively. A new method using a microcolumn packed with immobilized nanometer TiO₂ as sorbent has been developed for the preconcentration of trace amounts of Cd, Cr, Cu and Mn prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The method has been successfully applied for the determination of trace elements in some environmental samples with satisfactory results.     

On-Line Separation and Preconcentration of Trace Metals in Biological Samples Using a Microcolumn Loaded with PAN-Modified Nanometer-Sized Titanium Dioxide,and Their Determination by ICP-AES

A flow injection analysis system incorporating a microcolumn of nanometer-sized TiO₂ loaded with 1-(2-pyridylazo)-2-naphthol (PAN) has been used for the development of an on-line multi-element method for simultaneous separation and preconcentration and subsequent determination of Cu²⁺, Co²⁺, Cr³⁺, Y³⁺, Yb³⁺ and Bi³⁺ by ICP-AES. Effects of pH, sample flow rate and volume, elution conditions, adsorption capacity and interfering ions on analyte recovery were examined. The adsorption capacity of nanometer-sized TiO₂ loaded with PAN was 4.73, 18.57, 3.81, 6.14, 4.52 and 20.35mgg^–1 for Cu²⁺, Cr³⁺, Y³⁺, Yb³⁺, Co²⁺ and Bi³⁺, respectively. The method has been applied to the analysis of trace elements in standard reference biological samples, and the results are in good agreement with the certified values.     

Separation of trace amounts palladium by SiO2/TiO2/Ce nanoparticles prior to flame atomic absorption spectrometry determination in anodic slime and wastewater samples

In the present work, a new SiO₂/TiO₂/Ce, nanoparticle was synthesed using sol-gel method and evaluated as an adsorbent for preconcentration trace amounts of Pd(II) ions. The characterization of the nanoparticles has been studied by transmission electron microscope and X-ray diffraction. The preconcentration method is based on palladium adsorption onto the surface of nanoparticle at pH 8.5. The main factors affecting Pd(II) adsorption, such as pH of sample solution, concentration and volume of eluent, sample volume, interfering of the coexisting ions and flow rate of sample and eluent were investigated and optimized. At optimum conditions, linearity was maintained between 4.0 to 1000.0 ng mL^?1. Detection limit based on 3S_b/m was 2.3 ng mL^?1. Seven replicate determinations of a solution containing of 12.5 µg palladium gave a relative standard deviation ±1.7%. According to the Langmuir linear model, the maximum adsorption capacity of palladium was found to be 34.5 mg g^?1. Finally, the feasibility of the proposed method for Pd(II) determination was assessed by analysis of certified reference materials, anodic slime and wastewater samples and satisfactory results were obtained.      

Functionalized silica nanoparticles for trapping Pb2+ ions via diazo‐azomethine scaffolds

Diazo‐azomethine coated silica sorbent for the adsorption of Pb²⁺ ions has been fabricated. The sorbent was obtained by one‐pot synthesis of silica nanoparticles in the presence of diazo‐azomethine molecules possessing silatranyl side chains for grafting via covalent bond formation. The functionalized silica nanoparticles exhibited characteristic physicochemical properties of diazo‐azomethine scaffolds as determined using Fourier transform infrared spectroscopy, scanning and transmission electron microscopies and thermogravimetric analysis. Various adsorption parameters such as pH, weight of adsorbent, time taken for equilibration and recovery of lead ions were optimized using a batch method. The sorbent showed high adsorption capacity for lead ions of 460.4 mg g^?1 at pH = 4. The effect of various competing ions on the adsorption of lead ions was studied and interference was removed by using a masking agent. The sorbent can be regenerated and reused, and is compatible for the adsorption of Pb²⁺ ions from green leafy vegetables. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characteristics of novel chelate fiber containing amine and amidine groups

A polyacrylonitrile (PAN) fiber was adopted for the backbone of a chelate polymer and poly(acrylo‐amidino ethylene amine) (PAEA) was prepared through a one‐step reaction between the PAN fiber and ethylenediamine (EDA). The maximum removal capacity and degree of substitution were 7.8 meq per gram of dried PAEA and 98%, respectively. The PAEA was tested as an adsorbent in single and two‐component metal aqueous solutions under changing pH. The Cu²⁺ ion accomplished maximum adsorption amount at pH 3 and the order of maximum adsorbed amounts on PAEA is Cu²⁺ > Ag⁺ > Zn²⁺ > Ni²⁺ > Pb²⁺ in molar basis. FT‐IR spectroscopy was employed to characterize the chemical bonding in metal aqueous solutions and surface morphology was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Copyright © 2004 John Wiley & Sons, Ltd.     

Solid Phase Extraction of Lead(II) by Sorption on Grinded Eucalyptus Stem and Determination with Flame Atomic Absorption Spectrometry

A sensitive and simple solid‐phase preconcentration procedure for the determination of trace amount of lead by flame atomic absorption spectrometry (FAAS) is developed. The method is based on the adsorption of Pb²⁺ on the column of fine grinded eucalyptus stem adsorbent, elution of the column by nitric acid and subsequent determination by FAAS. The effect of different variables such as pH, eluent type, flow rate and interfering ions on the recovery of the analyte was investigated and optimum conditions were established. The adsorption of lead onto fine grinded eucalyptus stem can formally be described by a Langmuir equation with a maximum adsorption capacity of 4.49 mg g^?1. A preconcentration factor of 50 was achieved using the optimum conditions. The calibration graph was linear in the range 10–125 ng mL^?1 of lead in the initial solution with r = 0.9982. The limit of detection based on 3S_b criterion was 4.5 ng mL^?1 and the relative standard deviation for eight replicate measurements of 30 and 80 ng mL^?1 of iron was 3.6 and 2.8%, respectively. The method was successfully applied to the determination of lead added to well, tap and wastewater samples.     

Preconcentration of trace aluminum (III) ion using a nanometer-sized TiO2-silica composite modified with 4-aminophenylarsonic acid, and its determination by ICP-OES

We describe a nanometer sized composite material made from titanium dioxide and silica that was chemically modified with 4-aminophenylarsonic acid and used for selective solid-phase extraction, separation and preconcentration of of aluminum(III) prior to its determination by ICP-OES. Under optimized conditions, the static adsorption capacity is 56.58?mg?g^?1, the enrichment factor is 150, the relative standard deviation is 1.6% (for n?=?11), and the detection limit (3?s) is 60?pg?mL^?1. The method was validated by analyzing the reference materials GBW 09101 (hair) and GBW 10024 (scallop) and successfully applied to the determination of trace Al(III) in spiked water samples and human urine, with recoveries ranging from 96% to 101%.