Selective extraction of Cu+ and Cu2+ ions from mushroom and lichen samples prior to analysis by micro-volume UV-Vis spectrophotometry: Application of a novel poly (SMIm)-Tris-Fe3O4 nanocomposite

Innovative approaches in cloud-point extraction

Cloud-point extraction (CPE) is a pre-treatment technique for the extraction and preconcentration of different chemical compounds, such as metal ions, pesticides, drugs, phenols, vitamins etc., from various samples. CPE is based on the phenomenon of two phases (micellar and aqueous) forming after the heating of an aqueous isotropic solution of a non-ionic or zwitterionic surfactant above the cloud-point temperature. If analytes are added to the surfactant solution under suitable conditions, they should be extracted into the micellar phase, also called the surfactant-rich phase. Recently, the traditional CPE procedure is being increasingly replaced by improved CPE procedures. In this study, recent advances in CPE over the last three years (2020 - 2022), including the application of various innovative approaches, are reviewed. In addition to the basic principle of CPE, alternative extraction media in CPE, CPE supported by various auxiliary energies, a different modified CPE procedure and the use nanomaterials and solid-phase extraction in combination with CPE are presented and discussed. Finally, some future trends for improved CPE are presented.

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.

Cr speciation analysis based on electrokinetic sample pretreatment with a paper based analytical device

This work presents a new method of Cr speciation analysis based on micro sample pretreatment with a paper-based analytical device (PAD). By using electrokinetic separation and stacking on the PAD, Cr (VI) and Cr (III) can be separated and the recovered to achieve speciation analysis without have to be subjected to subtraction treatment. The separation and recovery properties of Cr (VI) and Cr (III) were characterized and optimized by UV-Vis spectrophotometry, with which the LOQ of 19.0 μg L^-1 and 28.7 μg L^-1, and the recoveries of 88-108% and 90-110%, were obtained for Cr (VI) and Cr (III), respectively. In addition, direct analysis of Cr (VI)/Cr (III) from an electroplating wastewater sample was also demonstrated with this method combined with atomic spectroscopy (GF-AAS and ICP-OES). This sample pretreatment method is fast, cheap and easy to be used. Combined with the high sensitivity and elemental selectivity of atomic spectroscopy and mass spectrometry, this PAD sample pretreatment method could be a compensation to their lack in speciation discrimination, and may play an important role in the speciation analysis of Cr.

Application of a novel poly(SMAm)-Tris-Fe3O4 nanocomposite for selective extraction and enrichment of Cu(I) /Cu(II) from beer, soft drinks and wine samples, and speciation analysis by micro-volume UV-Vis spectrophotometry

In this study, a novel functional nanocomposite was synthesized, characterized and selectively used in pH-controlled separation, pre-concentration and speciation analysis of Cu(I) and Cu(II) from sample matrices where extraction is assisted, facilitated and greatly enhanced by ultrasound energy. The hydrophilic composite material functionalized with tris(2-hydroxymethyl)aminomethane (Tris) and Fe₃O₄ NPs was characterized in detail by ATR-FT-IR, ¹H NMR, XRD, EDX peaks and SEM images. After optimization of the main variables influencing extraction efficiency such as pH, volumes of buffer, modified copolymer in acetone, CTAB and Triton X-114 at fixed concentrations including sonication conditions, the Cu(I) and Cu(II) were monitored against a blank at 347 nm by micro-volume UV-vis spectrophotometer. A good linearity was obtained in the range of 2-140 and 5-150 μg L^-1 for Cu(II) and Cu(I) with r² ≥ 0.993. The limits of detection (LODs) of 0.66 and 1.60 μg L^-1 for each analyte, were obtained from a pre-concentration of 70-fold. After validation, the method was applied to speciation of Cu(I), Cu(II), and total Cu in the pre-treated and diluted beverage samples before and after pre-oxidation of Cu(I) to Cu(II) due to be more sensitive of extraction process to Cu(II) at pH 6.0. The results were also compared with those obtained by FAAS analysis to ensure the reliability of the results. It was observed that there was a statistically good agreement between the results of both methods.

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.