A preconcentration system for determination of copper and nickel in water and food samples employing flame atomic absorption spectrometry

A green reaction-based turn-off fluorescence sensor for determination of copper ions: DFT calculations, quenching mechanism, green chemistry metrics, and application in environmental samples

When Cu(II) reacts with ascorbic acid (AA) to form Cu(I), Cu(I) can combine with eosin Y (EY) to form ionic associations, resulting in significant fluorescence quenching of the EY. Based on the turn-off of fluorescence in the chemosensor EY, a green reaction is proposed herein for the detection of Cu(II). The novel detection method for Cu(II) demonstrates simplicity, high sensitivity, and excellent selectivity, rendering it suitable for analyzing environmental samples. A static fluorescence quenching mechanism is validated through the Stern-Volmer relationship, and the thermodynamic parameters of the reaction are explored using a van 't Hoff plot. The reaction mechanism is investigated via fluorescence spectra, absorption spectra, and density-functional theory (DFT) calculations. The probe's green nature is confirmed by applying four green analytical chemistry metrics.

Digital image determination of copper in food and water after preconcentration and magnetic tip separation for in-cavity desorption/color development

A new analytical method for measuring copper in food and water was developed and validated, employing a solid-phase extraction (SPE) technique combined with digital-image-based (DIB) detection. A novel magnetic adsorbent of zinc ferrite/Citrullus colocynthis biochar (ZF@C.BC) was used to preconcentrate copper. A magnetic tip was used to separate the copper-loaded adsorbent from the extraction medium and to dispense it to the DIB plate. In-situ desorption and development of the spot color with iodide-starch reagent were carried out, and a digital image of the developed spots was captured using a smartphone and processed using ImageJ software. The copper adsorption capacity was 91.3 mg g-1. Desorption was effected using a 0.3 mol L-1 hydrochloric acid. The preconcentration factor was 300, the limit of detection was 4.8 μg L-1, the linearity was 16-600 μg L-1 and the sample throughput was 12 h-1. The developed approach was validated by analyzing food and water samples, confirming recoveries ≥ 91 % and 88 %, respectively, with RSD ≤ 8.4 %, n = 3.

Development of cysteine-doped MnO2 quantum dots for spectrofluorimetric estimation of copper: applications in different matrices

Copper (Cu) plays a role in maintaining healthy nerve cells and the immune system. Osteoporosis is a high-risk factor for Cu deficiency. In the proposed research, unique green, fluorescent cysteine-doped MnO2 quantum dots (Cys@MnO2 QDs) were synthesized and assessed for the determination of Cu in different food and hair samples. The developed quantum dots were synthesized with the help of cysteine using a straightforward ultrasonic approach to create 3D fluorescent Cys@MnO2 QDs. The resulting QDs' morphological and optical characteristics were carefully characterized. By adding Cu ions, the intensity of fluorescence for the produced Cys@MnO2 QDs was found to be dramatically reduced. Additionally, the applicability of Cys@MnO2 QDs as a new luminous nanoprobe was found to be strengthened by the quenching effect grounded on the Cu-S bonding. The concentrations of Cu2+ ions were estimated within the range of 0.06 to 7.00 µg mL-1, with limit of quantitation equal to 33.33 ng mL-1 and detection limit equal to 10.97 ng mL-1. The Cys@MnO2 QD technique was applied successfully for the quantification of Cu in a variety of foods, including chicken meat, turkey, and tinned fish, as well as in human hair samples. The chance that this novel technique could be a useful tool for figuring out the amount of cysteine in bio-samples is increased by the sensing system's remarkable advantages, which include being rapid, simple, and economical.

Highly selective recovery of Ni(II) in neutral and acidic media using a novel Ni(II)-ion imprinted polymer

In this work, an original ion-imprinted polymer (IIP) was synthetized for the highly selective removal of Ni(II) ions in neutral and acidic media. First a novel functional monomer (AMP-MMA) was synthetized through the amidation of 2-(aminomethyl)pyridine (AMP) with methacryloylchloride. Following Ni(II)/AMP-MMA complex formation study, the Ni(II)-IIP was produced via inverse suspension polymerization (DMSO in mineral oil) and characterized with solid state ¹³C CPMAS NMR, FT-IR, SEM and nitrogen adsorption/desorption experiments. The Ni(II)-IIP was then used in solid-phase extraction of Ni(II) exploring a wide range of pH (from neutral to strongly acidic solution), several initial concentrations of Ni(II) (from 0.02 to 1 g/L), and the presence of competitive ions (Co(II), Cu(II), Cd(II), Mn(II), and Mg(II)). The maximum Ni(II) adsorption capacity at pH 2 and pH 7 reached values of 138.9 mg/g and 169.5 mg/g, that are among the best reported in literature. The selectivity coefficients toward Cd(II), Mn(II), Co(II), Mg(II) and Cu(II) are also very high, with values up to 38.6, 32.9, 25.2, 23.1 and 15.0, respectively. The Ni(II)-IIP showed good reusability of up to 5 cycles both with acidic and basic Ni(II) eluents.

Colorimetric detection of heavy metal ions with various chromogenic materials: Strategies and applications

Detection of heavy metal ions has drawn significant attention in environmental and food area due to their threats to the human health and ecosystem. Colorimetry is one of the most frequently-used methods for the detection of heavy metal ions owing to its simplicity, easy operation and rapid on-site detection. The development of chromogenic materials and their sensing mechanisms are the key research direction in the area of colorimetric method. Since each chromogenic material has their unique optical and chemical properties, they have totally different colorimetric sensing mechanisms. This review focuses on the chromogenic materials and their sensing strategies for the colorimetric detection of heavy metal ions. We divide the chromogenic materials into three types, including organic materials, inorganic materials, and other materials. As for each type of chromogenic material, we discuss their detailed sensing strategies, sensing performance, and real sample applications. Moreover, current challenges and perspectives related to the colorimetry of heavy metal ions are also discussed in this review. The aim of this review is to help readers to better understand the principles of colorimetric methods for heavy metal ions and push the development of rapid detection of heavy metal ions.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

Carboxyl-functionalized hollow polymer microspheres for detection of trace metal elements in complex food matrixes by ICP-MS assisted with solid-phase extraction

In this work, carboxyl-functionalized hollow polymer microspheres (CHPMs) was successfully fabricated using poly (styrene-itaconic anhydride) particles as the core template and itaconic anhydride and trans-anethole cross-linked with divinylbenzene as the shell. The desirable microspheres and hollow structure of CHPMs were demonstrated by scanning and transmission electron microscopies, respectively. The characterized CHPMs as an adsorbent was packed into a solid phase extraction column to simultaneously detect the V(V), Cr(III), Cu(II), Cd(II), and Pb(II) in digested food samples by inductively coupled plasma-mass spectrometry (ICP-MS). A series of experimental parameters of solid-phase extraction (SPE) were investigated through vast experiments to improve sensitivity of the proposed method in metal ions detection. The detection limits of the method reached 0.8-3.2 ng L^-1 for the target elements, and the relative standard deviations (RSDs) ranging from 1.2% to 3.5% were obtained from eleven parallel experiments using a 1.0 μg L^-1 sample solution. The stability allowed the material to withstand more than 15 cycling while the recoveries remained above 88%. In food samples, the detection limits were at 0.20-0.80 μg kg^-1, and satisfactory recoveries of 85-104% were obtained in spike tests of laver, fish as well as chicken.

An environment-friendly and rapid liquid-liquid microextraction based on new synthesized hydrophobic deep eutectic solvent for separation and preconcentration of erythrosine (E127) in biological and pharmaceutical samples

In this study, a new deep eutectic solvent (DES) consist of tetrabuthylammonium bromide (TBABr) and 1-octanol at 1:2 M ratio was prepared for the first time and characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹H NMR) and carbon nuclear magnetic resonance (¹³C NMR) techniques. The new DES was used as an extraction solvent in the ultrasound assisted liquid-liquid microextraction (UA-LLME) of Erythrosine (E127) in blood, urine, pharmaceutical tablet and syrup samples. Accurate and sensitive determination of erythrosine was accomplished with the combination use of DES-UA-LLME and UV-Vis spectrophotometric detection. Before applying UA-LLME, while protein precipitation was applied to blood samples, pharmaceutical tablets were homogenized and dissolved in methanol. The proposed DES-UA-LLME/UV-VIS procedure was applied directly to urine, syrup sample and supernatant of blood and tablet samples with high recoveries in range of 90% and 100%. Erythrosine in the aqueous sample phase was extracted into 200 μL hydrophobic DES phase at pH 7.0. The effect of important analytical variables such as pH of sample solution, mol ratio of DES components, volume of DES, ultrasonic-based extraction time, sample volume and salt effect were optimized. The preconcentration factor (PF), limit of detection (LOD), intra-day and inter-day relative standard deviations (RSD, %) for the developed procedure were found as 40, 3.75 μg·L^-1, 2.6% and 4.6%, respectively.

An environmentally friendly and novel amine-based liquid phase microextraction of quercetin in food samples prior to its determination by UV-vis spectrophotometry

A novel and environmentally-friendly method, which includes determination of trace amounts of quercetin in samples by using UV-vis spectrophotometry after enrichment with amine-based liquid phase microextraction (LPME), has been developed. As extraction solvent, N,N-dimethyl-n-octylamine has been used and the quercetin concentration in extraction phase was determined by UV-vis spectrophotometry at 382.5 nm. Important analytical parameters such as pH, extraction solvent type and volume, sample volume, extraction time were optimized by the method. Quercetin in the sample solution was extracted to 200 μL of N,N-dimethyl-n-octylamine phase at pH 4.0. The detection limit (LOD) and the quantitation limit (LOQ) values for quercetin were calculated as 0.07 μg·mL^-1 and 0.24 μg·mL^-1, respectively. Accuracy studies for the food samples was carried out by addition and recovery experiments. The developed method has been successfully applied to different food samples including spinach, green pepper, red onion and dill weed.

Deep Eutectic Solvent-Based Microextraction of Lead(II) Traces from Water and Aqueous Extracts before FAAS Measurements

Microextraction procedures for the separation of Pb(II) from water and food samples extracts were developed. A deep eutectic solvent composed of α-benzoin oxime and iron(III) chloride dissolved in phenol was applied as a phase separator support. In addition, this deep eutectic mixture worked as an efficient extractor of Pb(II). The developed microextraction process showed a high ability to tolerate the common coexisting ions in the real samples. The optimum conditions for quantitative recoveries of Pb(II) from aqueous extracts were at pH 2.0, conducted by adding 150 µL from the deep eutectic solvent. The quantitative recoveries were obtained with various initial sample volumes up to 30 mL. Limits of detection and limits of quantification of 0.008 and 0.025 µg L^-1 were achieved with a relative standard deviation (RSD%) of 2.9, which indicates the accuracy and sensitivity of the developed procedure. Recoveries from the reference materials, including TMDA 64.2, TMDA 53.3, and NCSDC-73349, were 100%, 97%, and 102%, respectively. Real samples, such as tap, lake, and river water, as well as food samples, including salted peanuts, chickpeas, roasted yellow corn, pistachios, and almonds, were successfully applied for Pb(II) analysis by atomic absorption spectroscopy (AAS) after applying the developed deep eutectic solvent-based microextraction procedures.

One-step preparation of red-emitting carbon dots for visual and quantitative detection of copper ions

A one-step solvothermal method for the preparation of carbon dots with red fluorescence (R-CDs) was put forward, in which sodium citrate and formamide were chosen as precursors, while formamide was adopted as the solvent. The fluorescence emission peak of the as-prepared R-CDs remained the same (600 nm) when the excitation wavelength increased from 490 nm to 560 nm, and the fluorescence quantum yield is 35.3%. Furthermore, the fluorescence intensity of the as-prepared R-CDs could be selectively quenched by copper ions, and the mechanism of Cu²⁺ quenching R-CDs is the combination of static and dynamic quenching. As a result, the R-CDs were applied for the construction of a fluorescent sensor without any modification for the quantitative and visual detection of copper ions, which is a typical contaminant in water. The limit of detection for the fluorescent sensor was as low as 5 nmol/L, and it can be used to fast and directly confirm whether the content of copper ions in drinking water meets the criteria of the United States Environmental Protection Agency and the World Health Organization.

Using PVA/CA/Au NPs electrospun nanofibers as a green nanosorbent to preconcentrate and determine Pb2+and Cu2+in rice samples, water sources and cosmetics

Polyvinyl alcohol (PVA)/citric acid (CA)/Au NPs electrospun nanofibers was synthesized and applied as a green and efficient sorbent to extract and preconcentrate Pb²⁺and Cu²⁺from water sources, rice samples and cosmetics before FAAS.

The impact of strain and feed intake on egg toxic trace elements deposition in laying hens and its health risk assessment

The impact of strain or feed intake on food trace elements and its health risk assessment is still ambiguous, and therefore, available facts are rare. Therefore, this study aimed to assess the effects of both strains and feed intake on trace elements depositions to egg, toxic heavy metals concentration, and health risk assessment of egg consumption. In the current cross-sectional study, the selected strains, including Shaver White, Hy-Line W36, Bovanse White, Lohman LSL-Lite, and Native laying hens of Khorasan Razavi province, were examined. A total number of 50 samples of eggs and 15 samples of their feed was purchased from poultry farms. Yolk and white were separately analyzed. Sample preparation was performed by wet digestion followed by Inductively Coupled Plasma Mass Spectrometry. Trace metals Pb, As, Cd, Hg, Cr, and Ni were detected. Statistical analysis was performed in Stata11.2 portable software. Although there was a significant difference in strains and feed, no significant difference was observed in trace elements in egg contents (weight of egg white and egg yolk). Mercury concentration in all the samples was below the instrument detection limit. In this study, the target hazardous quotients were below one for all trace elements. Therefore, Iranian does not experience the adverse health effects due to the consumption of egg.

Ionic liquid mediated extraction, assisted by ultrasound energy, of available/mobilizable metals from sediment samples

A new extraction method for metals from sediment samples was developed. In this procedure, the chelating agent EDTA was combined with a minimal amount of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim[BF₄]), assisted by ultrasound energy. The available analytes -Cd, Cr, Cu, Ni, Pb and Zn- were extracted under optimal conditions for a 12.5 ratio (extractant volume/sample mass) with 0.005molL^-1 EDTA solution, 0.1molL^-1 NaHCO₃, 5.0mmolL^-1 Bmim[BF₄] and 7.0min of sonication time, using an ultrasonic bath (output power of 160W). The best extractions were obtained with 100W (power dissipated in the liquid). These conditions were obtained applying the univariate method. It is important to highlight that the conventional method (extraction with 0.05molL^-1 EDTA solution only) consumes 6h to extract available metals from sediment samples selectively, and with the proposed procedure the extraction time is noticeable reduced to 7.0min. Extractable metal concentrations obtained were measured by flame atomic absorption spectrometry. The results showed good agreement with those obtained by the conventional method using a Student's paired t-test.

Synthesis, characterization and application of ion imprinted polymeric nanobeads for highly selective preconcentration and spectrophotometric determination of Ni²⁺ ion in water samples

Here, the researchers report on the synthesis of ion imprinted polymeric (IIP) nanoparticles using a thermal polymerization strategy, and their usage for the separation of Ni(2+) ion from water samples. The prepared Ni-IIP was characterized by colorimetry, FT-IR spectroscopy, and scanning electron microscopy. It was found that the particle size of the prepared particle to be 50-70 nm in diameter with the highly selective binding capability for Ni(2+) ion, with reasonable adsorption and desorption process. After preconcentration, bound ions can be eluted with an aqueous solution of hydrochloric acid, after their complexation with dimethylglyoxime, these ions can be quantified by UV-Vis absorption spectrophotometry. The effect of various parameters on the extraction efficiency including pH of sample solution, adsorption and leaching times, initial sample volume, concentration and volume of eluent were investigated. In selectivity study, it was found that imprinting causes increased affinity of the prepared IIP toward Ni(2+) ion over other ions such as Na(+), K(+), Ag(+), Co(2+), Cu(2+), Cd(2+), Hg(2+), Pb(2+), Zn(2+), Mn(2+), Mg(2+), Cr(3+), and Fe(3+). The prepared IIP can be used and regenerated for at least eight times without any significant decrease in binding affinities. The prepared IIP is considered to be promising and selective sorbent for solid-phase extraction and preconcentration of Ni(2+) ion from different water samples.

Analysis of Some Trace Metals in Fish Species after Preconcentration with Congo Red on Amberlite XAD-7 Resin by Flame Atomic Absorption Spectrometry

A new procedure for separation and preconcentration of trace amounts of Cu(II), Ni(II), Fe(III), Zn(II), Cr(III), Cd(II), and Pb(II) in fish samples was proposed. The procedure is based on the adsorption of these metal ions on the column of Amberlite XAD-7 as congo red complexes prior to their determination by flame atomic absorption spectrometry (FAAS). Several factors that can affect the sorption and elution efficiency of the metal ions were investigated and optimized. The sorption was quantitative in the pH range of 6.0–9.0 for Cu(II) and Ni(II), 5.5–8.0 for Fe(III), 6.0–8.5 for Zn(II) and Cd(II), and 7.0–8.5 for Cr(III) and Pb(II). The optimum pH for simultaneous retention was 7.5. The sorption capacity of the resin was found to be 0.89, 0.72, 0.82, 0.61, 0.53, 0.84, and 0.78 mg/g for Cu(II), Ni(II), Fe(III), Zn(II), Cr(III), Cd(II), and Pb(II), respectively. The precision of the method was evaluated as the relative standard deviation obtained by analyzing a series of six replicates and below 6% for all seven elements. The validation of the method was performed by the analysis of certified reference materials. The proposed method was successfully applied to separation/preconcentration and determination of these metals in fish samples.

A novel polyvinyl chloride-membrane optical sensor for the determination of Cu(2+) ion based on synthesized (N'(1)E,N'(2)E)-N'(1),N'(2)-bis(pyridine-2-ylmethylene)oxalohydrazide: experimental design and optimization

A copper (Cu(2+)) ion-selective bulk optode was constructed by using (N'(1)E,N'(2)E)-N'(1),N'(2)-bis(pyridine-2-ylmethylene)oxalohydrazide as ionophore and NaTPB in DBP matrices. Central composite design under response surface methodology was applied for the optimization of variables including pH, amount of ligand, amount of additive and response time which significantly affect the response of proposed sensor. At optimum specified conditions, the high stability, reproducibility and relatively long lifetime of the optical sensor suggest its ability for accurate and precise monitoring of Cu(2+) ion content in various real samples over a concentration range of 1.6×10(-6) to 3.17×10(-5)molL(-1) with a limit of detection of 8.1×10(-7)molL(-1) during response time 6.9min. The proposed optical sensor was successfully applied for the determination of Cu(2+) ion in tap water and different samples.

Efficient and selective extraction and determination of ultra trace amounts of Hg2+ using solid phase extraction combined with ion pair based surfactant-assisted dispersive liquid–liquid microextraction

Solid phase extraction coupled with ion pair based surfactant-assisted dispersive liquid–liquid microextraction based on the solidification of the floating organic drop method was applied for determination of Hg²⁺ in different samples.

Ligandless ultrasonic-assisted and ionic liquid-based dispersive liquid-liquid microextraction of copper, nickel and lead in different food samples

A simple and rapid ultrasonic assisted-ionic liquid based-liquid-liquid microextraction (UA-IL-DLLME) method has been developed for the enrichment and separation of Cu(II), Ni(II) and Pb(II). A two level factorial design was used to determine the effect of key factors such as pH, volume of ionic liquid (IL), carbon tetra chloride (CCl4) and sonication time (St). 1-Butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) and CCl4 were used as an extractant and dispersant solvent, respectively. The accuracy of the proposed method was evaluated by analysing of SRM Apple Leaves 1515 certified reference material. The limits of detections (LODs) were 0.17 μg/L, 0.49 μg/L and 0.95 μg/L for Cu, Ni and Pb, respectively. The enrichment factor (EF) was 100. The method has been successfully applied for the analysis of the content of Cu, Ni and Pb in spice, vegetable and fruit samples by flame atomic absorption spectrometry (FAAS).

Ligandless surfactant mediated solid phase extraction combined with Fe₃O₄ nano-particle for the preconcentration and determination of cadmium and lead in water and soil samples followed by flame atomic absorption spectrometry: multivariate strategy

In the present study, a microextraction technique combining Fe3O4 nano-particle with surfactant mediated solid phase extraction ((SM-SPE)) was successfully developed for the preconcentration/separation of Cd(II) and Pb(II) in water and soil samples. The analytes were determined by flame atomic absorption spectrometry (FAAS). The effective variables such as the amount of adsorbent (NPs), the pH, concentration of non-ionic (TX-114) and centrifugation time (min) were investigated by Plackett-Burman (PBD) design. The important variables were further optimized by central composite design (CCD). Under the optimized conditions, the detection limits (LODs) of Cd(II) and Pb(II) were 0.15 and 0.74 µg/L, respectively. The validation of the proposed procedure was checked by the analysis of certified reference materials of TMDA 53.3 fortified water and GBW07425 soil. The method was successfully applied for the determination of Cd(II) and Pb(II) in water and soil samples.