A highly selective magnetic solid-phase extraction method for preconcentration of Cd(II) using N,N′-bis(salicylidene)ethylenediamine in water and food samples

The application of deep eutectic solvent-based magnetic nanofluid in analytical sample preparation

The pursuit of green analytical chemistry has led to the exploration of deep eutectic solvents (DESs) as green solvents in sample preparation processes. DESs, formed by hydrogen bond donor and acceptor components, exhibit unique properties such as low toxicity, biodegradability, and designable structures that make them ideal for extraction technologies. However, no comprehensive assessment of the utilization of DES-based magnetic nanofluid for analytical sample pretreatment has been performed. This review summarized the preparation methods of DES-based magnetic nanofluids and their application in various microextraction technologies, including vortex-assisted, ultrasonic-assisted, dispersive, and microfluidic device-based approaches, highlighting their role in enhancing the efficiency and sustainability of analytical methods. The paper underscored the importance of the stability of magnetic nanofluids in sample pretreatment and the advantages of using DESs, such as reduced organic solvent usage and compatibility with green chemistry principles. Key findings from recent research on the application of DES-based magnetic nanofluids in microextraction were presented, demonstrating their high extraction recoveries, low detection limits, and applicability to a wide range of analytes and matrices. The outlook suggests potential directions for future research, including the refinement of DES-based magnetic nanofluids for improved performance in analytical sample preparation. This review provides a valuable reference for researchers and practitioners in the field of analytical chemistry, showcasing the potential of DES-based magnetic nanofluids as a sustainable and efficient tool for sample preparation and microextraction.

An alginate-based eutectogel impregnated with polyvinylpyrrolidone/benzoic acid deep eutectic solvent and magnetic carboxylated multiwalled carbon nanotubes: Evaluated as sorbent in green microextraction of pesticides

This article presents the synthesis and application of a novel magnetic eutectogel constituting a polymeric deep eutectic solvent (PDES), carboxylated multiwall carbon nanotube (MWCNT-COOH), and super-dispersible/super-paramagnetic polyvinylpyrrolidone coated-Fe3O4 nanocrystals incorporated in alginate gel. Different methods were used for the characterization of novel polymeric based DES gel including FT-NMR, ATR-FTIR, and SEM were used. The novel DES eutectogel was used for the extraction of pesticides from honey. The modified eutectogel with PDES, MWCNT, and PDES-MWCNT showed 1.8-, 1.4-, and 2.5-fold enhancement in the sorption efficiency under green magnetic micro-solid-phase extraction (MSPE) method before GC-MS analysis. Important factors including the acidity of the samples, adsorption and desorption conditions, and the ionic strength of the preparation solution were investigated. The matrix effect, specificity, the quantification limits (0.023-1.023 μg kg-1), linear dynamic range (0.023-500 µg kg-1 with R2 of 0.9845-0.9986), relative standard deviations (<8.4%), were evaluated. In addition, the method was used to analyze 12 pesticides in four samples of honey. In the spiked concentration range of 0.1 to 10 μg kg-, the obtained recoveries were between 73.2 and 110.8% (RSD% = 8.1%, n = 3).

Comparison Studies on Several Ligands Used in Determination of Cd(II) in Rice by Flame Atomic Absorption Spectrometry after Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction

Ligands plays an important role in the extraction procedures for the determination of cadmium in rice samples by using flame atomic absorption spectrometry (FAAS). In the present study, comparative evaluation of 10 commercially available ligands for formation of Cd(II)-ligand complex and determination of cadmium in rice samples by ultrasound-assisted dispersive liquid–liquid microextraction (UADLLME) combined with FAAS was developed. Sodium diethyldithiocarbamate (DDTC) provided a high distribution coefficient as well as a good absorbance signal, therefore DDTC was used as a ligand in UADLLME. A low density and less toxic solvent, 1-heptanol, was used as the extraction solvent and ethanol was used as the disperser solvent. In addition, the experimental conditions of UADLLME were optimized in standard solution first and then applied in rice, such as the type and volume of extractant and dispersant, pH, extraction time, and temperature. Under the optimal experimental conditions, the detection limit (3σ) was 0.69 μg/L for Cd(II). The proposed method was applied for the determination of Cd(II) in three different rice samples (polished rice, brown rice, and glutinous rice), the recovery test was carried out, and the results ranged between 96.7 to 113.6%. The proposed method has the advantages of simplicity, low cost, and accurate and was successfully applied to analyze Cd(II) in rice.

Developing a highly selective method for preconcentration and determination of cobalt in water and nut samples using 1-(2-pyridylazo)-2-naphthol and UV-visible spectroscopy

BACKGROUND

Heavy metal contamination in water and agricultural products is a major concern that causes risks for human health. This article describes a highly selective approach to preconcentrate cobalt(II) (Co(II)) ions based on the standard UV-visible measurement of Co(II)-1-(2-pyridylazo)-2-naphthol complex at λ = 628 nm in water and nut samples. In this method, magnetic silica (mSiO₂ ) was utilized as a practical sorbent and 1-(2-pyridylazo)-2-naphthol was employed as a complexing agent in the elution step. The adsorbent was characterized via X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. The effects of the main variables (pH, adsorption time, sorbent amount, pH of eluent, ligand volume, and desorption time) were investigated and established.

RESULTS

The maximum recovery was achieved at pH 7 ± 0.3, adsorption time of 60 min, sorbent amount of 40 mg, eluent pH 8 ± 0.2, ligand volume of 2 mL (16.95 × 10^-4  mol L^-1 ) and desorption time of 30 min. The linearity of dynamic range (10-500 μg L^-1 ), limit of detection (0.32 μg L^-1 ), relative standard deviation (3.04%), and preconcentration factor (25) show the reliability of the method. The sorbent was reusable 12 times. Selectivity and the effect of interference ions were successfully examined. The adsorption process of Co(II) ions on mSiO₂ was investigated based on Langmuir and Freundlich isotherms. The Freundlich model was fitted with the system and the maximum capacity adsorption of mSiO₂ for Co(II) adsorption is 2.35 mg g^-1 . Then, the kinetics study revealed that the adsorption process of Co(II) ions on the mSiO₂ follows the pseudo-first-order model. The thermodynamics parameters ΔG, ΔS, and ΔH were calculated.

CONCLUSION

The method was fruitfully applied to preconcentrate Co(II) ions in water and nut samples. This method offers high selectivity and precision for determining Co(II) ions. © 2020 Society of Chemical Industry.