Selective solid phase extraction of trace cadmium(II) and lead(II) from biological and natural water samples by ofloxacin-modified-silica gel

Ofloxacin was successfully used as a chemical modifier to improve the reactivity of silica gel in terms of selective binding and extraction of heavy metal ions. This new functionalised silica gel (SG-ofloxacin) was as an effective sorbent for the solid-phase extraction (SPE) of Cd(II) and Pb(II) in biological and natural water samples and their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Experimental conditions for effective adsorption of trace levels of Cd(II) and Pb(II) were optimised with respect to different experimental parameters using the batch and column procedures. The time for 70% sorption for Cd(II) and Pb(II) was less than 2 min. Complete elution of the adsorbed metal ions from the SG-ofloxacin 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 39.17 and 48.69 mg g^?1 for Cd(II) and Pb(II), respectively. The detection limits of the method were found to be 0.29 and 0.13 ng mL^?1 for Cd(II) and Pb(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was lower than 3.0% (n = 5). The method was applied to the recovery of Cd(II) and Pb(II) from the certified reference material (GBW 08301, river sediment) and to the simultaneous determination of these cations in different water and biological samples with satisfactory results and yielding 100-folds enrichment factor.     

Selective solid-phase extraction of lead(II) from biological and natural water samples using surface-grafted lead(II)-imprinted polymers

A new Pb(II)-imprinted amino-functionalized silica gel sorbent was synthesized by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction of trace Pb(II) prior to its determination by inductively coupled plasma optical emission spectrometry. The Pb(II)-imprinted amino-functionalized silica gel sorbent was characterized by Fourier transform infrared spectroscopy. Compared to non-imprinted polymer particles, the ion-imprinted polymers had higher selectivity and adsorption capacity for Pb(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Pb(II) was 19.66 and 6.20 mg g^?1, respectively. The largest selectivity coefficient of the Pb(II)-imprinted sorbent for Pb(II) in the presence of Cd(II) was over 450. The relative selectivity (α _r) values of Pb(II)/Cd(II) were 49.3 and 46.3, which were greater than 1. The distribution ratio (D) values of Pb(II)-imprinted polymers for Pb(II) were much larger than that for Cd(II). The detection limit (3σ) was 0.20 μg L^?1. The relative standard deviation was 2.0% for 11 replicate determinations. The method was validated for the analysis three certified reference materials (GBW 08301, GBW 08504, GBW 08511), and the results are in good agreement with standard values. The method was also successfully applied to the determination of trace lead in plants and water samples with satisfactory results.     

A magnetic copper(II)-imprinted polymer for the selective enrichment of trace copper(II) ions in environmental water

We have developed a convenient, selective and reliable method for the rapid enrichment of trace quantities of Cu(II) by using a magnetic Cu(II) ion-imprinted polymer. This is followed by their determination by FAAS. The imprints were prepared by using (a) Cu(II) ions as the template, (b) 3-aminopropyltriethoxysilane as both the functional monomer and the crosslinking agent, and (c) Fe₃O₄ as the magnetic component. Enrichment is carried out in a single step, and adsorbed copper ions can be separated from the sample solution by applying a strong magnet. The effects of pH, elution condition, amount of imprint, and of potentially interfering ions were evaluated. Under the optimal conditions, the detection limit and enrichment factor are 0.3?μg L^?1 and 100, respectively, and the recovery is >95?%. The procedure was successfully applied in the enrichment and detection of trace copper ions in environmental water.

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     

Synthesis,characterization and using a new terpyridine moiety-based ion-imprinted polymer nanoparticle: sub-nanomolar detection of Pb(II) in biological and water samples

A highly selective lead-imprinted polymer was synthesized via a thermal precipitation polymerization technique based on a terpyridine-based ligand as the complexing agent. The synthesized polymer was successfully incorporated in a graphite paste electrode (GPE) as the recognition element for lead ion (Pb²⁺). Differential pulse anodic stripping voltammetry (DPASV) technique was used to transduce the binding events at the modified electrode. The imprinted polymer nanoparticles (IP-NPs) were synthesized by precipitation polymerization of ethylene glycol dimethacrylate as the cross-linker, 2,2′-azobisisobutyronitrile as the free radical initiator and 2,2′:6′,6″-terpyridine (terpy) as the recognition element. The sensing procedure is based on the accumulation of lead ions at ??1.0 V vs. Ag/AgCl. Afterward, the DPV was recorded by the sweeping potential in a positive direction to oxidize the accumulated ions, leading to the appearance of a significant anodic peak. The constructed IIP–GPE revealed a linear response toward Pb²⁺ over the concentration range from 0.4 to 10 nM (with the sensitivity of 693.95 nA nM^?1 cm^?2) and 10 nM to 1.0 µM (with the sensitivity of 580.25 µA µM^?1 cm^?2). The limit of detection (LOD) was evaluated to be 0.11 nM (for S/N?=?3). The accuracy of the sensor was explored by analysis of a quality control material (QCMs, Seronorm? urine REF NO 1011645) and different water samples. Selectivity studies showed no particular interference for detection of Pb(II).     

Selective flotation-spectrophotometric determination of trace copper(II) in natural waters, human blood and drug samples using phenanthraquinone monophenylthiosemicarbazone.

Copper(II) forms 1:1 and 1:2 intense red complexes with phenanthraquinone monophenylthiosemicarbazone (PPT) at pH 3-3.5 and > or =6.5, respectively. These complexes exhibit maximal absorbance at 545 and 517 nm, the molar absorptivity being 2.3 x 10(4) and 4.8 x 10(4) l mol(-1) cm(-1), respectively. However, the 1:1 complex was quantitatively floated with oleic acid (HOL) surfactant in the pH range 4.5-5.5, providing a highly selective and sensitive procedure for the spectrophotometric determination of CuII. The molar absorptivity of the floated Cu-PPT complex was 1.5 x 10(5) l mol)(-1) cm(-1). Beer's law was obeyed over the range 3-400 ppb at 545 nm. The analytical parameters affecting the flotation process and hence the determination of copper traces were reported. Also, the structure of the isolated solid complex and the mechanism of flotation were suggested. Moreover, the procedure was successfully applied to the analysis of CuII in natural waters, serum blood and some drug samples.     

Solid-phase extraction of trace Cu(II) Fe(III) and Zn(II) with silica gel modified with curcumin from biological and natural water samples by ICP-OES

Silica gel was firstly functionalized with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with curcumin yielding curcumin-bonded silica gel (curcumin-APSG). This new bonded silica gel was used for separation, pre-concentration and determination of Cu(II), Fe(III), Zn(II) in biological and natural water samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Experimental conditions for effective adsorption of trace levels of metal ions were optimized with respect to different experimental parameters using batch and column procedures in detail. The optimum pH value for the separation of metal ions simultaneously on the newly sorbent was 4.0. Complete elution of the adsorbed metal ions from the sorbent surface was carried out using 2.0 mL of 0.1 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 0.63, 0.46 and 0.37 mmol g^− 1 for Cu(II), Fe(III) and Zn(II) respectively. The time for 95% sorption for Cu(II) Fe(III) and Zn(II) was less than 2 min. The detection limits of the method defined by IUPAC was found to be 0.12, 0.15 and 0.40 ng mL^− 1 for Cu(II), Fe(III) and Zn(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was lower 3.0% (n = 5). 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. This sorbent was successfully employed in the separation and pre-concentration of trace Cu(II), Fe(III) and Zn(II) from the biological and natural water samples yielding 75-fold concentration factor.     

Selective enrichment of anti-inflammatory drugs from river water samples by solid-phase extraction with a molecularly imprinted polymer

A molecularly imprinted polymer (MIP) is synthesised by a noncovalent protocol in which ibuprofen was used as a template molecule. The polymer was evaluated chromatographically and it was seen that the MIP showed cross-reactivity. Subsequently, when this polymer was used as sorbent in SPE it was possible to selectively extract a mixture of nonsteroidal anti-inflammatory drugs from aqueous samples when a cleanup step with dichloromethane was performed. The performance of the MIP was evaluated with river water and water from a wastewater treatment plant, and compared with the performance of a commercial Isolute ENV+ sorbent.     

Spectrophotometric determination of trace copper(II) in biological samples with 2,4-bis(4-phenylazophenylaminodiazo)phenol

A highly sensitive and selective chromogenic reagent 2,4-bis(4-phenylazophenylaminodiazo)phenol (BPPAAP) reacted with copper(II) to form a highly stable complex in the ethanolic solution at pH range of 9.0–12.0. The Cu(II)-BPPAAP complex showed maximum absorbance at 540 nm, with molar absorptivity being 1.86 × 10⁵ L/mol cm. Beer’s law was obeyed over the range 0–0.2 μg/100 mL of copper(II) and variation coefficient is found to be 2.4–4.8%. The detection and quantification limit of the method are 2.0 and 6.5 ng/mL, respectively. To eliminate the interference of foreign ions, a convenient and efficient method using a column packed with sulfhydryl dextrose gel as a solid-phase extractant was utilized with satifactory reults. The developed method has been successfully employed for the determination of copper(II) in the biological samples.     

Preparation of a new Cu(II)-imprinted polymer and its application for the determination of trace copper in water samples by flame atomic absorption spectrometry

A new Cu(II)-imprinted polymer has been prepared for selective solid-phase extraction of Cu(II) prior to its determination by flame atomic absorption spectrometry. Two functional monomers, 4-(methacryloylamino)benzamide and 4-vinylpyridine, formed a complex with Cu(II) ion through coordination interactions. The self-assembled Cu(II)-monomer complex was copolymerised via bulk polymerisation method in the presence of ethyleneglycoldimethacrylate cross-linker. In order to remove Cu(II) ions, the resulting polymer was washed with 1.0 M HNO₃ and then with water until obtaining a neutral pH. The ion imprinted polymer was characterised by Fourier transform infrared. The experimental conditions were optimised for solid-phase extraction of Cu(II) using a column of ion-imprinted polymer (IIP). Quantitative retention was achieved between pH 5.0 and 7.0, whereas the maximum recovery for the non-imprinted polymer (NIP) was about 74% at pH 7.0. The IIP showed higher selectivity to Cu(II) in comparison to the NIP. The IIP also exhibited excellent selectivity for Cu(II) in the presence of other metal ions. The relative standard deviation and limit of detection (3s) of the method were 1.6% and 1.8 µg L^?1, respectively. The method was verified by analysis of two certified reference materials (CWW-TM-D and SRM 3280) and then applied to the determination of Cu(II) in seawater and lake water samples and haemodialysis concentrates.     

Sensitive trace enrichment of environmental andiandrogen vinclozolin from natural waters and sediment samples using hollow-fiber liquid-phase microextraction

The presence of vinclozolin in the environment as far as the endocrine disruption effects in biota are concerned has raised interest in the environmental fate of this compound. In this respect, the present study attempts to investigate the feasibility of applying a novel quantitative method, liquid-phase microextraction (LPME), so as to determine this environmental andiandrogen in environmental samples such as water and sediment samples. The technique involved the use of a small amount (3 microL) of organic solvent impregnated in a hollow fiber membrane, which was attached to the needle of a conventional GC syringe. The extracted samples were analyzed by gas chromatography coupled with electron-capture detection. Experimental LPME conditions such as extraction solvent, stirring rate, content of NaCl and pH were tested. Once LPME was optimized, the performance of the proposed technique was evaluated for the determination of vinclozolin in different types of natural water samples. The recovery of spiked water samples was from 80 to 99%. The procedure was adequate for quantification of vinclozolin in waters at levels of 0.010 to 50 microg/L (r> 0.994) with a detection limit of 0.001 microg/L (S/N= 3). Natural sediment samples from the Aliakmonas River area (Macedonia, Greece) spiked with the target andiandrogen compound were liquid-liquid extracted and analyzed by the methodology developed in this work. No significant interferences from the samples matrix were noticed, indicating that the reported methodology is an innovative tactic for sample preparation in sediment analysis, with a considerable improvement in the achieved detection limits. The results demonstrated that apart from analyte enrichment, the proposed LPME procedure also serves as clean-up method and could be successfully performed to determine trace amounts of vinclozolin in water and sediment samples.     

Determination of copper(II) in wastewater by electroplating samples using a PVC-membrane copper(II)-selective electrode

A PVC membrane containing 4-amino-6-methyl-1,2,4-triazin-3,5-dithione (AMTD) as a suitable ionophore, exhibits a Nernstian response for Cu²⁺ ions over a wide concentration range up to 1 × 10⁻¹ and 1 × 10⁻⁶ M, with a detection limit of 7.5 × 10⁻⁷ M in the pH range 3.0–7.5. It has a fast response time (<15 s) and can be used for at least 12 weeks without any major deviation in the potential. The electrode revealed a very good selectivity with respect to all common alkali, alkaline-earth, transition, and heavy-metal ions. It was successfully applied to the recovery of copper ions from wastewater. The electrode was also used as an indicator electrode in the potentiometric titration of Cu(II) ions with EDTA. The text was submitted by the authors in English.     

Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment

Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 g 1^–1 and 20 l^–1 and limits of determination between 0.5 g l^–1 and 1 g l^–1 are obtained.     

Selective adsorption and separation of Cs(I) from salt lake brine by a novel surface magnetic ion-imprinted polymer

A new Cs(I) magnetic ion-imprinted polymer (Cs(I)-MIIP) aimed at the selective adsorption and separation of Cs(I) from salt lake brine was prepared. The Fe₃O₄@SiO₂ was used as supporter, Cs(I) as template ion, and carboxymethyl chitosan as functional monomer. The product was characterized by Fourier transform infrared spectra, XRD, energy-dispersive spectrometry, scanning electron microcopy, thermogravimetric analysis, and vibrating sample magnetometer. The adsorption of the Cs(I)-MIIP in solution was investigated, which indicated the maximum adsorption capacity was 36.15?mg·g^?1 under the optimum conditions. The pseudo-first-order kinetic model and the Freundlich isotherm model were applied to predict the adsorption process of Cs(I) onto Cs(I)-MIIP. Selectivity experiments showed that the relative selectivity coefficient (k′) were 24.995, 1.73, 1.43, 4.83, and 1.63 to Cs(I)/Li(I), Cs(I)/Na(I), Cs(I)/K(I), Cs(I)/Rb(I), and Cs(I)/Sr(II) binary solutions, higher than those of NIP, respectively. Furthermore, the Cs(I)-MIIP was successfully applied to the enrichment and separation of Cs(I) from the salt lake brine of Qinghai, with satisfactory Cs(I) recovery rates.     

Selective trace enrichment of acidic pharmaceuticals in real water and sediment samples based on solid-phase extraction using multi-templates molecularly imprinted polymers

A novel multi-templates molecularly imprinted polymer (MIP), using acidic pharmaceuticals mixture (ibuprofen (IBP), naproxen (NPX), ketoprofen (KEP), diclofenac (DFC), and clofibric acid (CA)) as the template, was prepared as solid-phase extraction (SPE) material for the quantitative enrichment of acidic pharmaceuticals in environmental samples and off-line coupled with liquid chromatography–mass spectrometry (LC/MS/MS). Washing solvent was optimized in terms of kind and volume for removing the matrix constituents nonspecifically adsorbed on the MIP. When 1 L of water sample spiked at 1 μg/L was loaded onto the cartridge, the binding capacity of the MIP cartridge were 48.7 μg/g for KEP, 60.7 μg/g for NPX, 52 μg/g for CA, 61.3 μg/g for DFC and 60.7 μg/g for IBP, respectively, which are higher than those of the commercial single template MIP in organic medium (e.g. toluene) reported in the literature. Recoveries of the five acidic pharmaceuticals extracted from 1 L of real water samples such as lake water and wastewater spiked at 1 μg/L were more than 95%. The recoveries of acidic pharmaceuticals extracted from 10-g sediment sample spiked at the 10 ng/g level were in the range of 77.4–90.6%. To demonstrate the potential of the MIP obtained, a comparison with commercial C18 SPE cartridge was performed. Molecularly imprinted solid-phase extraction (MISPE) cartridge showed higher recoveries than commercial C18 SPE cartridge for acidic pharmaceuticals. These results showed the suitability of the MISPE method for the selective extraction of a group of structurally related compounds such as acidic pharmaceuticals.     

Cu(II) removal enhancement from aqueous solutions using ion-imprinted membrane technique

In this study, Cu(II)-ion-imprinted membrane adsorbents were prepared via cross-linking of blended chitosan/poly(vinyl alcohol) using glutaraldehyde as cross-linker and copper ions as template. The ability of IIMs to adsorb copper ions from aqueous solutions was assessed using a batch of experiments under different conditions by changing cross-linking density (0.05 mass %, 0.1 mass %, and 0.2 mass %), template content (0.2 mass %, 0.5 mass %, and 0.9 mass %), initial analyte concentration (50 mg L^?1, 100 mg L^?1, and 150 mg L^?1), and adsorbent concentration (0.5 g L^?1, 1.0 g L^?1, and 2.0 g L^?1). The Taguchi method was used to plan a minimum number of experiments. The following optimal levels were thus determined for the four factors: cross-linking density: 0.1 mass %; template content: 0.5 mass %; initial analyte concentration: 150 mg L^?1; and adsorbent concentration: 0.3 g L^?1.     

Determination of radiocesium in environmental water samples using copper ferro(II)cyanide and sodium tetraphenylborate

Summary A procedure for the radiochemical separation and radiochemical purification of radiocesium (¹³⁴Cs and ¹³⁷Cs) in bulk environmental water samples is proposed. Radiocesium was removed from the water by cation-exchange with copper ferro(II)cyanide and was purified by precipitation with sodium tetraphenylborate. The influence of the concentration of potassium in the water sample on the chemical yield was investigated. The validation of the proposed method was carried out by analyzing reference materials. The application of the method was demonstrated with the determination of the concentration of radiocesium in water samples from rivers around NPP “Kozloduy”, Bulgaria, Danube and Ogosta.     

Selective preconcentration of ultra trace copper(II) using octadecyl silica membrane disks modified by a recently synthesized glyoxime derivative

A new simple and reliable method has been developed to selectively separate and concentrate ultra trace amounts of copper ion in aqueous samples for subsequent measurement by atomic absorption spectrometry (AAS). The Cu²⁺ ions are adsorbed selectively and quantitatively during passage of aqueous solutions through octadecyl silica membrane disks modified with bis(2-hydroxyphenylamino) glyoxime. The retained copper ions then stripped from the disk with a minimal amount of 0.2 M nitric acid solution as eluent, and determined by AAS. The proposed method permitted large enrichment factors of about 100 or higher.The limit of detection of the proposed method is 0.004 ng ml⁻¹. The maximum capacity of the membrane disks modified with 25 mg of ligand was found to be 280±32 μg of copper(II). The effects of various cationic interferences on the percent recovery of copper in binary mixtures were studied.The method was successfully applied to the recovery and determination of copper in several water samples.     

Selective separation of silver(I) and mercury(II) ions in natural water samples using alumina modified thiouracil derivatives as new solid phase extractors

A simple and reliable solid-phase extraction (SPE) method has been developed to synthesise two new sorbents: 6-propyl-2-thiouracil and 5,6-diamino-2-thiouracil physically loaded onto alumina surface, phases I and II, respectively. The synthesis of these new phases has been confirmed by IR-spectroscopy. The surface concentrations of the organic moieties were determined to be 0.182 and 0.562 mmol g^?1 for phases I and II, respectively. The evaluation of the selectivity and metal uptake properties incorporated in these two alumina phases were also studied and discussed for 10 different metal ions: Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pb(II) and Ag(I) under different controlling factors. The data obtained clearly indicated that the new SP-extractors have the highest affinity for retention of Hg(II) ions. Selective separation of Hg(II) from Ag(I) as one of the most interfering ion, in addition to the other eight coexisting metal ions under investigation, was achieved successfully using the new sorbents at pH = 9.0 under static conditions. Therefore, Hg(II) exhibits major retention percentage (100.0%) using phase I or II. However, Ag(I) exhibits minor retention percentage equal to 1.33% using phase I and 0.67% using phase II. On the other hand, the retention percentage of the other eight metal ions ranged (0.0–3.08%) using phase I and (0.0–1.54%) using phase II at the same pH. The new phases were applied for separation and determination of trace amounts of Hg(II) and Ag(I) spiked natural water samples using cold vapour atomic absorption spectroscopy and atomic absorption spectroscopy with no matrix interference. The high recovery values of Hg(II) and Ag(I) obtained using phases I and II were ranged 98.9 ± 0.1–99.2 ± 0.05% along with a good precision (RSD% 0.01–0.502%, N = 3) demonstrate the accuracy and validity of the new sorbents for separation and determination of Hg(II) and Ag(I).     

Novel separation and preconcentration of trace amounts of copper(II) in water samples based on neocuproine modified magnetic microparticles

A novel, simple method based on magnetically assisted chemical separation (MACS) has been developed for analytical purposes. In this method, neocuproine modified magnetic microparticles was used for selective extraction and preconcentration of copper(II) ions from aqueous solutions. The advantages of this method include consumption of organic solvents almost eliminated and applications on unclear (containing suspended particles) samples without any preliminary filtration step. This method combines simplicity and selectivity of solvent extraction with easy separation of magnetic microparticles from solution with magnet. In addition, it can be considered as a simple method for determination of partition coefficient. The influence of different parameters, such as presence of extractant, amount of extractant loaded on the microparticles, reducing agent, pH, equilibrium time, ionic strength, type and least amount of stripping solution and limit of detection, were evaluated. Also, the effects of various cationic and anionic interferences on the percent recovery of copper were studied. Copper ions were extracted from solution at pH 6 and were stripped from microparticles with 0.5 M HNO₃. Extraction efficiencies for solutions with volumes up to 100 ml were >99%. Limit of detection was 1.5 μg/l. The method was applied to the recovery and determination of copper in different water samples.