Deep eutectic solvent decomposition-based microextraction for chromium determination in aqueous environments by atomic absorption spectrometry with electrothermal atomization

Colorimetric detection of chromium (VI) via its instigation of oxidase-mimic activity of CuO

Extensive use of chromium makes it one of the major pollutants of water resources. Chromium (VI) in particular is toxic and has detrimental health effects. Because of its high toxicity a tolerable concentration limit of chromium (VI) in drinking water has been recommended. Here we report a colorimetric method for determination of chromium (VI) in water based on the oxidase-like activity of solvothermal synthesized copper oxide. The particles have been characterized by X- ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Using 3, 3', 5, 5'- tetramethylbenzidine (TMB) as a chromogenic substrate, CuO exhibited a pronounced oxidase-like activity in the presence of chromium (VI). This method enables successful colorimetric detection of chromium (VI). It demonstrated excellent selectivity for detection of chromium (VI) ions against potentially interfering ions. The method's feasibility to real sample analysis has been proven by testing tap water. Hence, we anticipate that the method can be successfully applied for analysis of chromium (VI) in environmental samples.

A novel ratiometric fluorescent probe for the detection of nickel ions in the environment and living organisms

Nickel resources are abundant in the world, and the application of nickel in production and life is more and more extensive. However, excessive nickel entering the environment will not only cause environmental pollution but also seriously endanger plants, animals and human health. Nickel compounds are carcinogenic and have been classified as a class 1 carcinogen. Nickel mainly exists in the form of divalent ions in the environment. However, there are few simple and effective methods for the detection of nickel ions, and these methods still have certain limitations. At present, the mechanisms of nickel influence in organisms are also unclear. Therefore, we constructed a ratiometric fluorescent probe Ra-Ni, which can achieve its own self-calibration and avoid the interference of other factors, thereby realizing the specific identification of nickel ions. The probe can detect nickel ions sensitively with a detection limit as low as 26.2 nM and can respond in a short time (< 2 min), which proves the great potential of the probe in the detection of nickel ions. At the same time, Ra-Ni has also been successfully used for imaging nickel ions in living cells and zebrafish, providing an effective tool for the study of physiological and pathological processes. The detection effect of nickel ions in actual water sample is also satisfactory, which further demonstrates the practicability of Ra-Ni in environmental applications.

A comparative study on selectivity and sensitivity of new chromium and copper electrodes

4-Methylcoumarin-7-yloxy-N-phenyl acetamide and 4-methylcoumarin-7-yloxy-N-4-nitrophenyl acetamide were synthesized and used as new ionophores in the carbon paste matrix to produce two novel potentiometric modified electrodes. The selectivity of the electrode changed from copper (II) to chromium (III) with the addition of a nitro group to the phenyl ring of the ionophore. The ionophores’ tendency to ions was confirmed by UV–visible spectrophotometry. Both electrodes were modified by multi-walled carbon nanotubes (MWCNTs) as an excellent modifier of carbon paste electrode (CPE). The best sensor response in the case of copper (II) selective CPE was obtained by 5% ionophore, 65% graphite powder, 5% MWCNT, and 25% paraffin oil. In addition, in the case of chromium (III) selective CPE, these conditions are 20% ionophore, 50% graphite powder, 5% MWCNT, and 25% paraffin oil. The copper (II) selective CPE showed a Nernstian slope of 32.15 mV/decade within the concentration range of 1.0 × 10^–10–1.0 × 10^–1 mol L⁻¹, while chromium (III) selective CPE showed a Nernstian slope of 19.28 mV/decade over the concentration range of 1.0 × 10^–10–7.0 × 10^–3 mol L⁻¹. The electrodes have short response time of less than 5 s and were used successfully to determine copper (II) in wastewater and to speciation of chromium (III) and chromium (VI).

Air assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets-liquid-liquid microextraction method for extraction of azole antifungal drugs in biological samples prior to high-performance liquid chromatography

A free dispersive method, air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets liquid-liquid microextraction was indicated in this study. This technique was utilized to simultaneously ascertain some azole antifungal drugs prior to high-performance liquid chromatography. In this research, a quasi-hydrophobic deep eutectic solvent was formed from tetrabutylammonium bromide and 1-dodecanol as an organic solvent at a 1:2 molar ratio. The synthesized deep decomposition in the sample solution caused in situ dispersion of extraction solvent and analytes. Air-assisted enhanced a dispersion condition in the sample solution. 1-dodecanol as a green option was replaced with typical extraction solvents providing the advantages of a suitable freezing point near room temperature and low density. The effect of important analytical parameters on the extraction recovery of analytes was assessed. Under these optimal conditions, the limits of detection and limits of quantitation determined were in the range of 0.5-2.8 μg L^-1 and 1.5-9 μg L^-1 , for water, urine and plasma samples, respectively. The Intra-day and inter-day relative standard deviations (RSD% n = 5) were calculated to be 2.9-4.6 % and 4.2-8.9 %, respectively. The results represented the effectiveness of the developed method for the extraction and determination of analytes in biological samples. This article is protected by copyright. All rights reserved.