Preconcentration Of Cu Research Articles

Green dispersive liquid–liquid microextraction of copper and nickel using a dual-function hydrophobic natural deep eutectic solvent for the analysis of water samples

An environmentally friendly and simple dispersive liquid–liquid microextraction method based on a hydrophobic natural deep eutectic solvent (NADES) was developed for the simultaneous preconcentration of Cu and Ni from water samples. The NADES composed of a 1:1 molar ratio of menthol and decanoic acid, presents hydrophobic characteristics and allows to simultaneously extract both analytes avoiding the addition of ligands or emulsifier agents. The extraction was performed in 1.0 min using 0.500 mL of NADES and a sample volume up to 25.0 mL in 0.5 M ammonium chloride-ammonia buffer solution at pH 8.2. The content of Ni and Cu in the NADES phase was determined using Flame Atomic Absorption Spectroscopy. Under optimal conditions, limits of detection of 1.9 µg L−1 for Cu and 4.6 µg L−1 for Ni were obtained, with precision (expressed as RSD% value) better than 5 % for both metals (n = 3). The method was applied to extract and determine Cu and Ni in water samples with different characteristics: tap water, bottled water, river water, dam water, and seawater. The recoveries for spiked water samples ranged between 97 and 110 % for Cu and 92–98 % for Ni, demonstrating the suitability of the method. The environmental impact of the method was assessed using the AGREE, AGREEprep, and ChlorTox metric tools, resulting in scores of 0.58, 0.61, and 0.48 g, respectively.

Preconcentration of Cu2+, Cr3+, Co2+, and Ni2+ by Solid-Phase Extraction Using a Recently Developed Mixed-Mode Sorbent

The enrichment and simultaneous analysis of Cu2+, Cr3+, Co2+, and Ni2+ by solid-phase extraction method were performed using a stationary phase containing amide functional groups, an aromatic benzene ring, and aliphatic groups in a silica-based structure that we had synthesized for HPLC separations in our previous studies. Solid-phase extraction was performed using a column system and the results obtained were analysed by ICP-OES. Effects of pH, amount of sorbent, amount of eluting solvent, sample volume, flow rates of the eluent and the sample, and interfering ions were evaluated in recovery processes for the metals in the sample solutions. Linear range, detection limit, and relative standard deviation (% RSD) values were calculated for each metal. The linear range (ng/mL) was between 0.01 and 0.25 for all ions, while the limit of detection (ng/mL) was found to be 0.64, 1.7, 0.44, and 0.51 and % RSD was 2.8, 2.4, 2.6, and 2.9 for Cu2+, Cr3+, Co2+, ve Ni2+, respectively.

Preconcentration and determination of Cu(II) and Cd(II) ions from wastewaters by using hazelnut shell biosorbent immobilized on Amberlite XAD-4 resin

Hazelnut shell biosorbent immobilized on Amberlite XAD-4 polymer resin as solid phase extraction method was developed and used for preconcentration of Cu(II) and Cd(II) ions from aqueous solutions. Concentrations of analytes in solutions were determined by Flame Atomic Absorption Spectrometry after extraction with column technique. Functional groups of nutshell biosorbent immobilized on resin were characterized by Fourier transform infrared spectrometry. Optimized critical parameters for preconcentration of Cu2+ and Cd2+ ions from sample solutions with nutshell immobilized on the resin were the pH value of solution, type of eluent solutions, the flow rate of sample solution, quantities of nutshell biosorbent, Amberlite XAD-4 resin, and enrichment factors, respectively. Detection limits of Cu2+ and Cd2+ ions found were 0.29 μg L-1 and 0.25 μg L-1, respectively. The method proposed was applied for determinations of Cu2+ and Cd2+ ions in standard reference material (BCR-670 aquatic plant sample) for accuracy and applied to real water samples such as wastewater and Van lake water. At the 95% confidence level, relative standard deviations (RSDs) were found as 1.44% for Cd2+ and 1.21% for Cu2+ ions with three replicate measurements.

Development of Micro-Column Preconcentration Method Using a Restricted-Access Poly(protoporphyrin-co-vinyl pyridine) Adsorbent for Copper Determination in Water and Milk Samples by FIA-FAAS

For years, researchers have focused on the determination of metal ions at trace levels in environmental and food samples using analytical methods that employ techniques with low cost acquisition and maintenance and without microwave-assisted acid digestion procedures or aggressive reagents. Therefore, the present study deals with the synthesis and application of a novel, restricted-access poly(protoporphyrin-co-vinyl pyridine) adsorbent to preconcentrate copper in water samples and bovine milk that have only been subjected to pH adjusting (pH 6.0) and filtration using posterior on-line determination by FAAS. Regarding macromolecules, the restricted-access property of the adsorbent was achieved using the hydrophilic compound 2-hydroxyethyl methacrylate (HEMA). This method is based on the preconcentration of Cu2+ ions using a flow-injection system which is buffered with 0.05 mol L−1 of Britton–Robinson (BR) at a pH of 6.0 and has a flow rate of 14.0 mL min−1 through a mini-column packed with 50.0 mg of adsorbent. The elution was carried out using 0.40 mol L−1 of HCl toward the FAAS detector. The developed method provided a preconcentration factor of 44.7-fold, low limits of detection (LOD) (0.90 µg L−1) and quantification (LOQ) (2.90 µg L−1), tolerance to interfering ions (95.0 and 103.0%), and intra-day and inter-day precision assessed as the RSD (percentage of relative standard deviation), which ranged from 3.08 to 4.80%. The restricted-access poly(protoporphyrin-co-vinyl pyridine) adsorbent demonstrated outstanding features to exclude macromolecules, bovine serum albumin (BSA), and humic acid (HA) from an aqueous medium. Lake water and bovine milk samples were analyzed by the proposed preconcentration method with minimal sample pretreatment (which was based mainly on pH adjusting and filtration using an analytical curve with external calibration), yielding recovery values from addition and recovery tests ranging from 91.7 to 101.9%. The developed method shows great advantages over previously published methods, avoiding the time-consuming use of concentrated acids in a microwave-assisted acid digestion procedure.

Synthesis and Characterization of Mesoporous Silica Modified with Purpald and Its Application in the Preconcentration of Cu2+ and Cd2+ from Aqueous Samples through Solid-Phase Extraction

The synthesis of an organofunctionalized mesoporous silica was accomplished by a two-step process involving (1) the co-condensation of a silylant agent at the surface of silica, followed by (2) the immobilization of Purpald (ligand) at the organic termination of the silytant agent. The characterization of the organofunctionalized material indicated the presence of NH2 groups, and the immobilization of the ligand was confirmed by 29Si- and 13C-nuclear magnetic resonance. The material’s surface area was determined as 370 m2 g−1. Batch adsorption experiments enabled the determination of optimum pH conditions for the adsorption of Cu(II) and Cd(II). Under optimal pH, the pseudo-second-order kinetic model and Langmuir model provided the best correlations to describe the materials adsorption behavior, suggesting a chemisorption mechanism. When tested in continuous-flow preconcentration experiments, the flow rate and eluent concentration demonstrated to affect the removal of Cu(II) and Cd(II), while the buffer concentration had an effect only over the adsorption of Cu(II). Under optimized preconcentration conditions, it was possible both to determine the concentrations of Cu(II) and Cd(II) in samples such as mineral water, ground water, tap water and river water. Ions commonly found in drinking and natural waters (Na+, K+, Ca2+, Mg2+, Fe3+, Ba2+, Cl−, SO42−, HCO3−, and H2PO4−) did not affect the preconcentration of any of the studied analytes. Reutilization experiments indicated that the adsorbent material can withstand at least 40 adsorption/desorption preconcentration cycles with no efficiency loss.

A facile and sensitive coprecipitation method coupled with flame atomic absorption spectrometry for quantification of Cu(II) ions in complex matrices

In the present investigation, the application of an organic coprecipitant, 2-[5,6-dichloro-2-(2-bromobenzyl)-1H-benzimidazole-1-yl]acetohydrazide (DIBBA), for separation and preconcentration of Cu(II) ions in fruit and water samples through a new carrier element free coprecipitation (CEFC) method was researched for the first time. Flame atomic absorption spectrometer (FAAS) was used for the analyses of Cu(II) ions. The main effective experimental factors such as solution pH, DIBBA quantity, waiting time, centrifuge speed and duration and volume of sample on the recovery efficiency of Cu(II) ions were explored in detail. Under the optimized conditions the preconcentration factor (PF), relative standard deviation (RSD), and limits of detection (LOD) was achieved as 50, 3.4 % and 0.44 ?g L-1, respectively. No interference effects were detected by virtue of the presence of various foreign ions. Satisfactory recoveries (in the range of 94.4 to 103.0 %) in the environmental sample matrix were acquired. After being validated the recommended selective, low cost, simple and rapid CEFC method by spike/recovery tests, it was properly implemented for the low levels detection of Cu(II) ions in sour cherry, mulberry, apple, and peach as fruit samples and stream and sea water samples without any significant matrix effects.

Using a cotton thread-based colorimetric sensor modified by carboxymethylcellulose and cuprizone with smartphone detection for quantification of copper.

In the present work, we report the development of a novel cotton thread-based colorimetric sensor modified by carboxymethylcellulose (CMC) and cuprizone (CPZ) with smartphone detection and its application for the quantitative determination of cupric ions in water and cachaça. The cotton thread/smartphone detection-based colorimetric method is an easily affordable, low-cost technique which allows one to perform real-time and on-field determination analyses, especially with limited financial resources. The method involves the complexation of Cu(II) with CPZ, which causes a change in the coloration of the cotton thread from a shade of white to blue in the detection zone of the colorimetric sensor. The immobilization of CPZ on CMC in the cotton thread leads to the pre-concentration of Cu(II) via a complexation mechanism with colorimetric reaction. The application of the colorimetric sensor allows the quantification of copper in the range from 1 to 12 mg L-1, with a low limit of detection of 0.21 mg L-1. In addition, the recovery assays conducted in samples of water and cachaça resulted in recovery percentages ranging from 84.9% to 107%, which is indicative of a precise method. To validate the precision of the proposed colorimetric method, the values obtained from the quantification analysis were compared with those of the flame atomic absorption spectrometry and a good agreement at the 95% confidence level was obtained.

Carbon/Alginate/Chitosan Composite as a Sorbent for Solid-Phase Extraction and Preconcentration of Cu(II)

Carbon/Alginate/Chitosan Composite (CAC) as a sorbent for solid-phase extraction of Cu(II) (pre-concentration) with atomic absorption spectrometry for analysis was successfully prepared. The sorbent was made with a mass ratio of chitosan:alginate:carbon = 1:1:1. CAC sorbents were characterized using FTIR for functional group analysis while SEM-EDX characterization was performed to determine surface morphology and percentage of elements. SPE parameters were optimized for adsorption-desorption efficiency under various conditions, i.e. of pH 5, Cu(II) concentration of 4 mg/L, the flow rate of Cu(II), and Na2EDTA eluent at 5 mL/min, the volume of Cu(II) sample and Na2EDTA eluent 25 mL and 1.0 M of Na2EDTA eluent concentration. Applying CAC-based SPE for Cu(II) analysis in water samples at optimum conditions gave 80.9–83.6% recovery. In bottled drinking water samples, a pre-concentration factor of 2.5–5 times was obtained, and the Cu(II) concentration of 0.017–0.020 mg/L was detected.

Trace determination of Cu(II) in milk samples after preconcentration on Fe3O4@graphene oxide composite based imprinted polymer

AbstractA new tailor‐fitted graphene oxide‐vinyl pyridine ion‐imprinted polymer (mGOVP/IIP), was synthesized using ethylene glycol dimethacrylate as a cross‐linking agent and 2,2′‐azo‐bis‐isobutyronitrile as an initiator to develop dispersive magnetic‐solid‐phase extraction method for the preconcentration of Cu(II) prior to the determination by flame atomic absorption spectrometry. The material was characterized and optimized for various parameters by batch mode, which includes the effect of initial concentration, contact time, temperature, and eluents. Herein, IIP demonstrated a high sorption capacity (63.54 mg g−1) at pH 5.6, with fast kinetics (15 min). The heterogeneity and chemisorption, mechanistic interpretation was explained by the Freundlich isotherm, pseudo‐second‐order kinetic model, respectively. Moreover, the higher selectivity coefficients for Cu(II) in the binary mixturess of concomitant ions signified preferential affinity over similar structural analogues. Additionally, it can be regenerated up to 7 runs and effectively eluted by 1 M HNO3. This developed method exhibited higher accuracy, precision (relative standard deviation <5%), and preconcentration factor (60). The IIP also described potential applications for Cu(II) determination in milk and its by‐products. Overall, the material exhibits ease of access and removal of template ion from the binding sites, cost‐effectiveness, fast mass transfer, promoted competitiveness, reproducibility, reliability, and good regeneration efficiency.

Schiff base functionalized silica gel for simultaneous separation and preconcentration of Cu(II), Ni(II), and Cd(II) in pharmaceuticals and water samples

A method for separation and preconcentration of Cu(II), Ni(II), and Cd(II) using N-N'-bis(5-methoxsalicylidene)-2-hydroxy-1,3-propanediamine modified silica gel was improved for aqueous samples and pharmaceuticals. Determination of the analytes was achieved by inductively coupled plasma optic emission spectrometry. The experimental conditions including pH value, sample volume, eluent type and volume, sorbent mass, sample, and eluent flow rates were optimized with univariate and multivariate optimization tools. The relative standard deviations of the method were 2.9% for Cu(II), 3.0% for Ni(II), and 3.3% for Cd(II) with recovery values between 98.8 ± 3.2-101.5 ± 3.0%. The limits of detection were found to be 62.4, 39.5, and 28.2 ng L-1 for Cu(II), Ni(II), and Cd(II), respectively. The accuracy of the suggested procedure was tested with the certified reference material (Certipur ICP multi-element standard solution IV) and addition-recovery experiments. The method was successfully applied to eye drop, anesthetic, serum, tap water, mineral water, and spring water samples.

Modification of silica nanoparticles by 2,4-dihydroxybenzaldehyde and 5-bromosalicylaldehyde as new nanocomposites for efficient removal and preconcentration of Cu(ii) and Cd(ii) ions from water, blood, and fish muscles.

Herein, silica nanoparticles were modified by 2,4-dihydroxybenzaldehyde and 5-bromosalicylaldehyde to produce new nanocomposites which were abbreviated as N1 and N2, respectively. The synthesized nanocomposites were used for efficient removal and preconcentration of Cu(ii) and Cd(ii) ions from water, blood, and fish muscles. FE-SEM, FT-IR, XRD, CHN elemental analysis, and nitrogen gas sorption analyzer were used to characterize the new nanocomposites. The XRD proved that the synthesized oxide is cristobalite with an average crystallite size of 54.80 nm. Due to the formation of the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N group, the intensity of the XRD peak at 2θ = 21.9° in the N1 and N2 nanocomposites decreased significantly. The FT-IR bands, which appeared at 1603 and 1629 cm−1 in the N1 and N2 nanocomposites, are attributable to the bending vibration of CN and/or OH, respectively. Also, the FE-SEM analysis shows the morphology of the silica nanoparticles which were identified as spherical and rod-like with slight agglomeration while the N1 and N2 nanocomposites have flaky surfaces due to the formation of CN groups. The maximum Cu(ii) ion adsorption capacities of the N1 and N2 nanocomposites are 64.81 and 40.93 mg g−1, respectively. The maximum Cd(ii) ion adsorption capacities of the N1 and N2 nanocomposites are 27.39 and 26.34 mg g−1, respectively. The adsorption of Cu(ii) or Cd(ii) ions using the synthesized nanocomposites is spontaneous, chemical, exothermic, and well-matched with the Langmuir equilibrium isotherm. The recovery findings demonstrate that the preconcentration process is accurate, adaptable, and resulted in quantitative separation because % Recovery is more than 95%. Furthermore, the % RSD was less than 3.5%, indicating good reproducibility.

Acetic acid modified zinc oxide nanoparticles for solid phase extraction of Cu(II) and Cr(III) in water

Water pollution due to toxic metals may pose a significant effect on the environment and the biota indicating necessity of careful management of their concentration in the system. On the other hand, a simplified and useable sample preparation technique is required for their trace analysis. In this report, a simple solid phase extraction procedure was developed for fast extraction and preconcentration of Cu(II) and Cr(III) from waters using acetic acid modified zinc oxide nanoparticles prior to flame atomic absorption spectrometry. The extraction procedure was optimized in respect to sample volume, pH, adsorbent dose, eluent, and extraction time. Ionic strength and co-existing ions did not exhibited any significant effect on the extraction. Under optimum conditions, with an enrichment factor of 40 and recoveries of over 95%, the limits of detection for both analytes were in the low µg L−1 range. Intra-day and inter-day precision were at about 3% to 4%. The method was applied for trace determination of the analytes in real water samples.

Preparation of melon peel biochar/CoFe2O4 as a new adsorbent for the separation and preconcentration of Cu(II), Cd(II), and Pb(II) ions by solid-phase extraction in water and vegetable samples.

The present research describes the successful preparation of melon peel biochar modified with CoFe2O4 (MPBC/CoFe2O4) followed by its usage as a new sorbent to separate, preconcentrate, and determine the toxic heavy metal ions by magnetic solid-phase extraction. The metal ion desorption was performed by 0.1M HCl solution with a volume of 5.0mL. Flame atomic absorption spectrometry (FAAS) was utilized for detection of the analyte levels. SEM-EDX, TEM, XRD, and FTIR techniques were carried out to illuminate the structure of MPBC/CoFe2O4. The fundamental variables affecting the adsorption and elution efficiencies of the analyte ions including solution pH, MPBC/CoFe2O4 amount, type and concentration of eluent, adsorption and desorption equilibrium time, and sample volume were optimized. The detection limits were calculated as 0.41, 1.82, and 3.16µg L-1 for Cu2+, Cd2+, and Pb2+ ions, respectively, with the relative standard deviation of lower than 4.2%. There were no substantial interference effects on the analyte ion recovery due to the presence of foreign ions at high levels. Five minutes of contact time was adequate to attain the adsorption equilibrium. The adsorption capacity of MPBC/CoFe2O4 was obtained as 106.4, 65.4, and 188.7mgg-1 for Cu2+, Cd2+, and Pb2+ ions, respectively, by utilizing Langmuir isotherm model. The pseudo-second order model is favorable to identify the adsorption kinetics. The method was validated by spike/recovery test, and then, it was successfully implemented to determine the aforementioned analyte levels in sea and stream water, pepper, black cabbage, eggplant, and tomato samples.

Multiple objective optimization of air assisted liquid-liquid microextraction combined with solidified floating organic drop microextraction for simultaneous determination of trace copper and nickel

he impact of rising levels of various heavy metals in the environment from multiple industrial, agriculture, domestic, and technological activities is of great concerns, as heavy metals cause serious health effects for both humans and wildlife. An effective and green chemistry procedure was used for simultaneous extraction of ultra-trace copper and nickel ions in natural waters (e.g. river and well waters) by air assisted liquid-liquid microextraction combined with solidified floating organic drop microextraction (AALLME-SFOD). The extraction of metal ions was conducted in a timescale of several minutes by conversion to metal chelates using sodium diethyldithiocarbamate (DDTC) as a chelating agent prior to AALLME-SFOD procedure, and 1-dodecanol as an extraction solvent to initiate the phase separation of the complex. The response surface methodology (RSM) and central composite design (CCD) were used to optimize the large number of experimental variables (i.e. pH, solvent volume, ligand volume, % NaCl). The analysis of variance (ANOVA) has been applied to evaluate all parameters and their mutual interactions on the extraction yields. The desirability function of Derringer and Suich was applied as a metric for optimization of multiple response variables. The optimized AALLME-SFOD technique proved to be highly effective for the pre-concentration of Cu(II) and Ni(II) from a range of aqueous media (i.e. river and well waters) and provides a quick and easy method, while utilizing compact and low cost equipment with micro-volume organic solvent consumption (e.g. ~120 μL for 5 mL water samples). Quantitation of copper and nickel with Graphite furnace atomic absorption spectroscopy (GFAAS) under the optimum conditions, were linear over the range of (20-100) and (20-200) ng L-1 respectively. Limit of detection for Ni(II) was at 4.5 ng L-1 and 10.4 ng L-1 for Cu(II).

Schiff base functionalized silica gel for simultaneous separation and preconcentration of Cu(II), Ni(II), and Cd(II) in pharmaceuticals and water samples.

A method for separation and preconcentration of Cu(II), Ni(II), and Cd(II) using N-N'-bis(5-methoxsalicylidene)-2-hydroxy-1,3-propanediamine modified silica gel was improved for aqueous samples and pharmaceuticals. Determination of the analytes was achieved by inductively coupled plasma optic emission spectrometry. The experimental conditions including pH value, sample volume, eluent type and volume, sorbent mass, sample, and eluent flow rates were optimized with univariate and multivariate optimization tools. The relative standard deviations of the method were 2.9% for Cu(II), 3.0% for Ni(II), and 3.3% for Cd(II) with recovery values between 98.8 ± 3.2-101.5 ± 3.0%. The limits of detection were found to be 62.4, 39.5, and 28.2 ng L-1 for Cu(II), Ni(II), and Cd(II), respectively. The accuracy of the suggested procedure was tested with the certified reference material (Certipur ICP multi-element standard solution IV) and addition-recovery experiments. The method was successfully applied to eye drop, anesthetic, serum, tap water, mineral water, and spring water samples.

Fabrication and characterization of extrinsic electrochemically modified graphite reinforcement carbon paste electrode for selective determination of Cu(II) in trace levels

An electrochemical oxidation of copper species has been successfully performed by using electrochemically modified 8‑hydroxy quinoline graphite reinforcement carbon paste electrode; in other words, quinolyl graphite reinforcement Carbon paste electrode (Q/GRCPE). Scanning electron microscopy (SEM) was used for the morphological characterization of the electrode before the modification and after modification and utilization. Under the optimal conditions of cyclic voltammetry (CV) and square wave adsorptive anodic stripping voltammetry (SWAdASV), the electrochemical oxidation of Cu(II) can be investigated. The performance of the electrochemically modified sensor was systematically studied. The experimental data suggested that the electrochemically modified sensor exhibited excellent catalytic activity for the electrochemical oxidation of Cu(II) with a detection limit (LOD) 2.1 × 10−11 M. The application of the electrochemically modified sensor for the detection of Cu(II) in Tap water (TW), ground water (GW) and Nile River water (NRW) showed good recovery with reproducible results. The peak currents of Cu(II) were evaluated within a wide concentration range, in favor of more durability, sensitivity, and selectivity which suitable for investigation of real samples. It was shown that the proposed electrochemically modified Q/GRCPE proved to be a cheap "pre- alarm" tool for rapid determining of Cu(II) in environmental water samples even in the presence of some interfering ions. The adsorptive accumulation of Cu(8-HQ)2, approaches results in an effective preconcentration of Cu(II) with short adsorption time (30 s).

Atomic-Absorption Determination of Copper(II) in Water Samples after Its Cloud-Point Extraction Preconcentration

We study and optimize the conditions for the cloud-point extraction (CPE) preconcentration of Cu(II) in the form of its complex with 6,7-dihydroxy-4-methyl-2-phenylbenzopyrylium chloride in the micellar phase of the nonionic surfactant Triton X-100. The introduction of ammonium benzoate into the system until a pH of 4.5 is reached at a Triton X-100 concentration of 0.4 vol % leads to the initiation of the formation of a micellar phase at room temperature. We develop a procedure for the atomic absorption determination of Cu(II) after its CPE preconcentration. The calibration dependence is linear in the concentration range of 5.0 to 213 μg/L, and the detection (cmin) and determination (clim) limits are, respectively, 1.5 and 5.0 μg/L. The proposed procedure is tested in the analysis of natural and drinking waters, and the relative standard deviation (RSD) does not exceed 4%.

Doble role of bathocuproine disulfonic acid as multi-walled carbon nanotubes dispersing agent and copper preconcentration ligand: Analytical applications for the development of hydrogen peroxide and glucose electrochemical sensors

We are reporting a new strategy for preparing carbon nanotubes (CNTs)-based hydrogen peroxide and glucose amperometric sensors by taking advantage of the dual role of bathocuproine disulfonic acid (BCS) as dispersing agent of multi-walled carbon nanotubes (MWCNTs) and as ligand for the preconcentration of Cu(II). The platform was obtained by casting glassy carbon electrodes (GCE) with the dispersion of MWCNTs in BCS (MWCNTs-BCS) followed by the preconcentration of Cu(II) by surface complex formation at open circuit potential (GCE/MWCNTs-BCS/Cu). The resulting electrode was used for the sensitive amperometric quantification of hydrogen peroxide at 0.400 V catalyzed by the preconcentrated copper, with a linear range between 5.0 × 10−7 and 7.4 × 10-6 M, a sensitivity of 24.3 mA.M-1, and a detection limit of 0.2 μM. The adsorption of GOx at GCE/MWCNTs-BCS/Cu followed by the immobilization of Nafion (Naf), allowed the construction of a sensitive and selective amperometric glucose biosensor with a linear range between 5.0 × 10-6 M and 4.9 × 10-4 M, a sensitivity of (477 ± 3) μA.M-1 and a detection limit of 2 μM. The proposed (bio)sensors were successfully used for the quantification of hydrogen peroxide in enriched milk samples and glucose in milk and commercial beverages without any pretreatment.

Fabrication of magnetic Fe3O4@metal organic framework@covalent organic framework composite and its selective separation of trace copper

A novel magnetic composite, Fe3O4@metal organic framework@covalent organic framework (Fe3O4@MOF@COF), was first time prepared by solvothermal methods for selectively separation and preconcentration of Cu2+. The prepared Fe3O4@MOF@COF composite was thoroughly characterized with XPS, TEM, XRD and FT-IR et al. With a high density of nitrogen- and oxygen-containing functional groups on the surface, the Fe3O4@MOF@COF composite could efficiently extract and preconcentrate of Cu2+ ions in aqueous solutions, with a maximum Cu2+ adsorption capacity of 37.29 mg g−1 determined by fitting the adsorption curve to the Langmuir isotherm equation. The magnetic composite after adsorption of Cu2+ was readily separated with an external magnet, and the retained copper could be stripped by acetic acid, which can effectively catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 with the detection of UV–vis spectrophotometry. The detection limit of this platform for Cu2+ is 37.6 nM (n = 11), along with a RSD of 4.14% (0.2 μM, n = 13). It was validated by measurement of water samples and the comparison to graphite furnace atomic absorption spectrometry (GFAAS) was accomplished.

Synthesis and characterization of Fe3O4@polythionine-Au for the removal and pre-concentration of Cu(II) from marine samples

The extraction of Cu(II) ions in marine samples was performed by nanocomposite of magnetic polythionine-Au, as an efficient magnetic extraction phase. For characterization of the prepared materials, different methods including FT-IR, SEM, EDX, TEM and VSM were used. The magnetic polythionine-Au nanocomposite exhibited higher adsorption percentage (98%) than the magnetic polythionine (65%) for uptake of Cu(II) ions. The optimized parameters for magnetic solid-phase extraction procedure were as sample pH of 7, sorption time of 10 min, sorbent dosage of 30 mg, elution solvent (2 mL) of HNO3 (0.3 mol L−1)/thiourea (1% w/v) and breakthrough volume of 300 mL. The adsorption kinetic follows a pseudo-second-order kinetic model and well fitted with the Langmuir isotherm model. The adsorption capacity was 120 mg g−1 for Cu(II). Also, the effect of thermodynamics of adsorption process was discussed. The nanocomposite adsorbent can be used for five cycles without significant decrease in adsorption capacity. The calibration curve was linear in the concentration range of 0.7–50 μg L−1 (R2 = 0.9983). The limits of detection and quantification were achieved as 0.097 and 0.32 μg L−1, respectively. The real samples were a gastropod from the Persian Gulf (Trochus erithreus), and muscle tissues of a fish (Trout) and shrimp. Good relative spiked recoveries (95–105%) were obtained for the real samples.