Cloud-point extraction, preconcentration and spectrophotometric determination of trace quantities of copper in food, water and biological samples

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.

Selective adsorption of iron(III) ions based on nickel(II) oxide-copper(II) oxide nanoparticles

Background:

Water contamination and its remediation are currently considered a major concern worldwide. Design of effective methods for water purification is highly demanded for adsorption and removal of such pollutants.

Objective:

This study depicts the effectiveness of nickel oxide-copper oxide nanoparticles (NiO-CuO), which can extract and remediate ferric ions, Fe (III), from aqueous solutions.

Methods:

The NiO-CuO nanoparticles were simply prepared by the co-precipitation method and then used as adsorbent with respectable advantages of high uptake capacity and surface area.

Results:

Adsorption of Fe(III) onto NiO-CuO nanoparticles showed an uptake capacity of 85.86 mgg−1 at pH 5.0. The obtained data from the carried-out experiment of Fe (III) adsorption onto NiO-CuO nanoparticles were well suited to the Langmuir isotherm and pseudo-second-order kinetic models. Moreover, different coexisting ions did not influence the adsorption of Fe(III) onto NiO-CuO nanoparticles. The recommended methodology was implemented on the adsorption and removal of several environmental water samples with high efficiency.

Conclusion:

The design method displayed that NiO-CuO nanoparticles can be used as promising material for the adsorptive removal of heavy metals from water.

Selective separation of uranyl ions from some lanthanide elements using a promising β-enaminoester ligand by cloud point extraction

For uranyl extraction, a distinctive chelating ligand, namely ethyl 2-amino-6-hydroxy-5-(4-methoxyphenyldiazenyl)-4-phenyl-4H-benzo[f]chromene-3-carboxylate, has been synthesized and characterized using FT-IR, NMR, and ESI-MS.

A centrifuge-less cloud point extraction-spectrophotometric determination of copper(II) using 6-hexyl-4-(2-thiazolylazo)resorcinol

A simple, cheap, and environmentally friendly centrifuge-less cloud point extraction procedure was developed for the preconcentration of traces of Cu(II) before its spectrophotometric determination. It is based on a complexation reaction with the hydrophobic azo reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR), in which a complex with a stoichiometric ratio of 1:1 and an absorption maximum at 535 nm is formed. The experimental conditions for Cu(II) determination were found: HTAR concentration (8 × 10^-6 mol mL^-1), mass fraction of the surfactant Triton X-114 (2.2%), pH (5.9, ammonium acetate buffer), and incubation time (10 min at 60 °C). The linear range, limit of detection, molar absorption coefficient and preconcentration factor were calculated to be 4.5-254 ng mL^-1, 1.34 ng mL^-1, 2.54 × 10⁵ L mol^-1 cm^-1, and 10, respectively. The effect of foreign ions was studied, and the proposed procedure was applied to the analysis of water samples and a saline solution for intravenous infusion.

Review of the distribution and detection methods of heavy metals in the environment

Heavy metals can be enriched in living organisms and seriously endanger human health and the ecological environment, which has evolved into a significant global environmental problem. Based on summarizing the spatial distribution of heavy metals in the environment, this review introduces heavy metal detection technologies such as inductively coupled plasma mass spectrometry/atomic emission spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, and laser-induced breakdown spectrometry. It summarizes their respective advantages, characteristics, and applicability. Besides, atmospheric pressure discharge plasma as a potential heavy metal detection technology is also introduced and discussed in this review. The current research mainly focuses on improving the analytical performance and optimizing the practical application. Furthermore, this review not only summarizes the advantages of atmospheric pressure discharge plasma in the field of element analysis but also summarizes the principal scientific and technical problems to be solved urgently.

Spectrophotometric Determination of Trace Concentrations of Copper in Waters Using the Chromogenic Reagent 4-Amino-3-Mercapto-6-[2-(2-Thienyl)Vinyl]-1,2,4-Triazin-5(4H)-One: Synthesis, Characterization, and Analytical Applications

A simple, selective, and inexpensive spectrophotometric method is described in the present study for estimation of trace concentrations of Cu2+ in water based on its reaction with chromogenic reagent namely 4-amino-3-mercapto-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one (AMT). The reaction between copper(II) ions and AMT reagent gives [Cu(L)(NO3)(H2O)2]•H2O complex, where L represents AMT molecule with NH group. The formed complex exhibits a sharp, and well-defined peak at λmax = 434 nm with a molar absorptivity (ε) of 1.90 × 104 L mol−1 cm−1, and Sandell’s factor of 0.003 μg mL−2. Absorbance of the [Cu(L)(NO3)(H2O)2]•H2O follows Beer’s law over a 0.7–25 μg mL−1 range with a detection limit of 0.011 μg mL−1. Validation of the submitted method was established by estimating Cu2+ in certified reference materials and actual sea and tap water samples. The results are compared with data obtained from copper concentration measurements using ICP-OES. The chemical structure of the Cu(II)-AMT complex was fully characterized by FT-IR, SEM, EDX, TGA, and ESR techniques.

Extraction and determination of heavy metals in soil and vegetables irrigated with treated municipal wastewater using new mode of dispersive liquid-liquid microextraction based on the solidified deep eutectic solvent followed by GFAAS

BACKGROUND

In this research, a new extraction method based on dispersive liquid-liquid microextraction and the solidification of deep eutectic solvent has been developed for the determination of heavy metals in soil and vegetables prior to their analysis by graphite furnace atomic absorption spectrometry (GFAAS). In this method, a green solvent consisting of 1-decyl-3-methylimidazolium chloride and 1-undecanol was used as an extraction solvent, yielding the advantages of material stability, low density and a suitable freezing point near room temperature.

RESULTS

Under optimal conditions, enrichment factors are in the range of 114-172. The calibration graphs are linear in the range of 0.02-200 µg kg^-1 and limits of detection are in the range of 0.01-0.03 µg kg^-1 . Repeatability and reproducibility of the method based on seven replicate measurements of 0.80 µg kg^-1 of Hg and 0.20 µg kg^-1 of Pb and Cd in analyzed samples were in the range of 2.3-4.1% and 3.7-6.6%, respectively.

CONCLUSION

A new deep eutectic solvent consists of two parts: 1-decyl-3-methylimidazolium chloride and 1-undecanol in a molar ratio of 1:2. The accuracy of the proposed procedure was also assessed by determining the concentration of the studied metal ions in a polluted farmland soil standard reference material. © 2018 Society of Chemical Industry.

Selective and sensitive spectrophotometric method to determine trace amounts of copper metal ions using Amaranth food dye

Copper is an essential element in some biological processes in organisms, so it was important to find ways to identify trace amounts of it. Minimal amounts of copper ions can be determined in aqueous solutions in the spectrophotometric method suggested in this study. The method depends on the reaction between Cu(II) and Amaranth dye at the pH 6.0. The gradual disappearance of Amaranth colour at 520 nm occurring with an increase of Cu(II) concentration from 0.13 up to 2.0 μg cm^-3. The molar absorptivity coefficient and Sandell's sensitivity of the complex are found to be 0.94 × 10⁴ L mol^-1 cm^-1, 6.8 ng cm^-2 respectively. The advantages of this method are simple, selective, and highly sensitive. The method was used for determination of copper ions in aqueous solutions containing several metal ions, where excellent agreements between reported and obtained results were achieved in aqueous solutions containing copper metal ions only. The postulated method is in an excellent agreement with the determination of Cu(II) ion concentrations by atomic absorption spectroscopy (AAS). The interference was studied to determine the copper metal ions concentration, and do not interfere with eleven of other metal ions.

A new three-dimensional bis(benzimidazole)-based cadmium(II) coordination polymer

A new coordination polymer (CP), formulated as [Cd(L)(DCTP)]_n (1) (L=1,1'-(1,4-butanediyl)bis(2-methylbenzimidazole), H₂DCTP=2,5-dichloroterephthalic acid), was synthesized under hydrothermal conditions and the performance as luminescent probe was also investigated. Single-crystal X-ray diffraction reveals CP 1 is a 3D 3-fold interpenetrated dia network with large well-defined pores. It is found that CP 1 revealed highly sensitive luminescence sensing for Fe³⁺ ions in acetonitrile solution with a high quenching efficiency of K_SV=2541.238L·mol^-1 and a low detection limit of 3.2μM (S/N=3). Moreover, the photocatalytic efficiency of 1 for degradation of methylene blue could reach 82.8% after 135min. Therefore, this coordination polymer could be viewed as multifunctional material for selectively sensing Fe³⁺ ions and effectively degrading dyes.

Spectrophotometric determination of Cu(II) in soil and vegetable samples collected from Abraha Atsbeha, Tigray, Ethiopia using heterocyclic thiosemicarbazone

Two selective and sensitive reagents, 2-acetylpyridine thiosemicarbazone (2-APT) and 3-acetylpyridine thiosemicarbazone (3-APT) were used for the spectrophotometric determination of Cu(II). Both reagents gave yellowish Cu(II) complex at a pH range of 8.0-10.0. Beer's law was obeyed for Cu(II)-2-APT and Cu(II)-3-APT in the concentration range of 0.16-1.3 and 0.44-1.05 µg/mL, respectively. The molar absorptivity and of Cu(II)-2-APT and Cu(II)-3-APT were 2.14 × 10(4) at 370 nm, and 6.7 × 10(3) L/mol cm at 350 nm, respectively, while the Sandell's sensitivity were 0.009 and 0.029 µg/cm(2) in that order. The correlation coefficient of the standard curves of Cu(II)-2-APT and Cu(II)-3-APT were 0.999 and 0.998, respectively. The detection limit of the Cu(II)-2-APT and Cu(II)-3-APT methods were 0.053 and 0.147 µg/mL, respectively. The results demonstrated that the procedure is precise (relative standard deviation <2 %, n = 10). The method was tested for Cu(II) determination in soil and vegetable samples. Comparisons of the results with those obtained using a flame atomic absorption spectrophotometer for Cu(II) determination also tested the validity of the method using paired sample t test at the 0.05 level showing a good agreement between them.

Dispersive liquid-liquid microextraction based on the solidification of floating organic drop followed by ICP-MS for the simultaneous determination of heavy metals in wastewaters

In the present work, a dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of Pb, Co, Cu, Ni, Zn. The influences of analytical parameters, including pH, extraction solvent volume, disperser solvent volume, concentration of chelating agent on the quantitative recoveries of Pb, Co, Cu, Ni, Zn were investigated. The effect of the interfering ions on the analytes recovery was also investigated. Under the optimized conditions, the limits of detection were 0.97-2.18 ng L(-1). The relative standard deviations (RSDs) were 2.62-4.51% (n=7, C=20 ng L(-1)). The proposed method was successfully applied for the analysis of ultra trace metals in wastewater samples.

Mixed micelle cloud point-magnetic dispersive μ-solid phase extraction of doxazosin and alfuzosin

Mixed micelle cloud point extraction (MM-CPE) combined with magnetic dispersive μ-solid phase extraction (MD-μ-SPE) has been developed as a new approach for the extraction of doxazosin (DOX) and alfuzosin (ALF) prior to fluorescence analysis. The mixed micelle anionic surfactant sodium dodecyl sulfate and non-ionic polyoxyethylene(7.5)nonylphenylether was used as the extraction solvent in MM-CPE, and diatomite bonding Fe₃O₄ magnetic nanoparticles were used as the adsorbent in MD-μ-SPE. The method was based on MM-CPE of DOX and ALF in the surfactant-rich phase. Magnetic materials were used to retrieve the surfactant-rich phase, which easily separated from the aqueous phase under magnetic field. At optimum conditions, a linear relationship between DOX and ALF was obtained in the range of 5-300 ng mL(-1), and the limits of detection were 0.21 and 0.16 ng mL(-1), respectively. The proposed method was successfully applied for the determination of the drugs in pharmaceutical preparations, urine samples, and plasma samples.

A highly sensitive and selective assay of doxycycline by dualwavelength overlapping resonance Rayleigh scattering

A dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was developed and validated for highly sensitive and selective assay of doxycycline residues in several meat samples. The response signals were dependent on the specific multi-site coordination between lanthanum(III) and doxycycline (DOTC). And La(III)-DOTC complex would further aggregate to form [La(III)-DOTC]n nanoparticles, resulting in the occurrence of two new scattering peaks. Notably, with the addition of DOTC, the increments of both of these two wavelengths were proportional to the concentration of DOTC over the ranges of 3.9-4.0×10(3) nmol L(-1) (1.7-1.8×10(3) μg/kg). The detection limit of DWO-RRS was 1.1 nmol L(-1) (0.5 μg/kg), which was lower than or comparable to most of the published methods. Additionally, the generating mechanisms of multi-response RRS signals were discussed and a semi-empirical principle was established for better design of multi-response RRS probes.