Ultrasound‐assisted emulsification microextraction coupled with high‐performance liquid chromatography for the simultaneous determination of fragrance allergens in cosmetics and water

A simple, inexpensive, and environmentally friendly method based on ultrasound‐assisted emulsification microextraction followed by solidification of floating organic drop and high‐performance liquid chromatography coupled to diode array detection was developed for the simultaneous determination of 18 potentially allergenic fragrance substances. Several parameters affecting the microextraction process were investigated in detail by the “one‐variable‐at‐a‐time” approach. Optimal conditions were the following: 50 μL of 2‐dodecanol as extraction solvent, 10 mL of sample containing 150 g/L of salt, and 5 min of sonication at 35°C. Under the optimized conditions, method showed good linearity in the selected ranges, with squared correlation coefficients ranging from 0.948 to 0.999. Limits of detection ranged from 0.001 to 0.154 μg/mL and enrichment factors from 9 to 237. Precision of the method, expressed as relative standard deviation, was checked at two levels obtaining good results (3.3–14.4%). Recovery studies were made in baby bath water and in eau de cologne showing acceptable accuracy. Finally, the developed method was successfully applied to different commercial cosmetic and water samples. The most commonly found analyte was linalool followed by cinnamal and lilial. Most of the analyzed samples contained at least one of the target compounds.     

Vortex‐assisted liquid–liquid microextraction using a low‐toxicity solvent for the determination of five organophosphorus pesticides in water samples by high‐performance liquid chromatography

Vortex‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with UV detection was applied to determine Isocarbophos, Parathion‐methyl, Triazophos, Phoxim and Chlorpyrifos‐methyl in water samples. 1‐Bromobutane was used as the extraction solvent, which has a higher density than water and low toxicity. Centrifugation and disperser solvent were not required in this microextraction procedure. The optimum extraction conditions for 15 mL water sample were: pH of the sample solution, 5; volume of the extraction solvent, 80 μL; vortex time, 2 min; salt addition, 0.5 g. Under the optimum conditions, enrichment factors ranging from 196 to 237 and limits of detection below 0.38 μg/L were obtained for the determination of target pesticides in water. Good linearities (r > 0.9992) were obtained within the range of 1–500 μg/L for all the compounds. The relative standard deviations were in the range of 1.62–2.86% and the recoveries of spiked samples ranged from 89.80 to 104.20%. The whole proposed methodology is simple, rapid, sensitive and environmentally friendly for determining traces of organophosphorus pesticides in the water samples.     

Dialkyl phosphates determination by gas chromatography: Evaluation of a microwave‐assisted derivatization†

Dialkyl phosphates are organophosphate insecticide metabolites and their urinary analysis is useful for assessing human exposure to these compounds. This study presents a sample preparation method with microwave‐assisted derivatization for two dialkyl phosphates to make the process faster before gas chromatographic analysis. The optimized conditions for derivatization procedure were: 250 μL of 2,3,4,5,6‐pentafluorobenzyl bromide 3% in acetonitrile for derivative; microwave for 5 min with intensity of 160 W. The electron ionization mass spectrometric analysis was performed using a gas chromatography with mass spectrometry QP‐2010 from the Shimadzu^® equipped with RTx^®‐5MS capillary column. Ions were monitored at selected‐ion monitoring mode at m/z 350 for diethyl thiophosphate and m/z 366 for diethyl dithiophosphate. The developed method was linear for both metabolites. The intra‐assay precision was the values ranged between 1.1 and 9.1%, for diethyl thiophosphate, and between 4.06 and 6.9%, for diethyl dithiophosphate. The interassay precision showed relative standard deviation between 10.3 and 15.1%, for diethyl thiophosphate and between 4.9 and 11.9%, for diethyl dithiophosphate. The results obtained suggests that derivatization assisted by microwave, before gas chromatography with mass spectrometry analysis, can be applied to monitoring of exposure to organophosphates once is fast, sensible, and precise method to determinate dialkyl phosphates.     

Dicyclohexylammonium bromoacetate: a low molecular mass organogelator with a one‐dimensional secondary ammonium monocarboxylate (SAM) synthon

The asymmetric unit of the title salt, C₁₂H₂₄N⁺·C₂H₂BrO₂⁻, contains a dicyclohexylammonium cation connected to a bromoacetate anion by means of an N—H...O hydrogen bond. In the crystal, the ion pairs assemble via N—H...O interactions, forming zigzag infinite chains parallel to the c axis with the (...H—N—H...O—C—O...)_n motif that is considered to be a prerequisite for ensuring gelation properties of secondary ammonium monocarboxylate salts. The title salt was characterized by FT–IR, X‐ray powder diffraction (XRPD), TG–DTA and ¹H NMR spectroscopy in solution. Gelation experiments revealed that dicyclohexylammonium bromoacetate forms molecular gels with dimethylformamide and dimethyl sulfoxide. Scanning electron microscopy (SEM) was used to reveal morphological features of dried gels.     

Synthesis of organosilyl compounds-containing 1,2,4,5-tetraaryl imidazoles sonocatalyzed by M/SAPO-34 (M = Fe,Co, Mn,and Cu) nanostructures

The one-step synthesis of silylated 1,2,4,5-tetraaryl imidazoles by use of a series of M/SAPO-34 (M: Fe, Co, Mn, and Cu) nanocatalysts and subsequent silylation reactions is described. Cu/SAPO-34 catalyst has the highest activity in improving the efficiency of the heterogeneous cyclo-condensation of an aldehyde, benzil, ammonium acetate and a primary aromatic amine in water under ultrasonic irradiation. Some of imidazole derivatives are studied with a view to the synthesis of a series of new, multi-substituted imidazoles containing organosilyl groups including carbosilanes (Si–C) and silyl ethers (Si–O).     

Two novel organic–inorganic hybrid materials from tetrachloridometallate(II) salts and 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium

Two organic–inorganic hybrid compounds have been prepared by the combination of the 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium cation with perhalometallate anions to give 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium tetrachloridocobaltate(II), (C₁₂H₁₂N₂)[CoCl₄], (I), and 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium tetrachloridozincate(II), (C₁₂H₁₂N₂)[ZnCl₄], (II). The compounds have been structurally characterized by single‐crystal X‐ray diffraction analysis, showing the formation of a three‐dimensional network through X—H...Cl_nM⁻ (X = C, N⁺; n = 1, 2; M = Co^II, Zn^II) hydrogen‐bonding interactions and π–π stacking interactions. The title compounds were also characterized by FT–IR spectroscopy and thermogravimetric analysis (TGA).     

非均匀流体介质内部散射声场重建的逐层计算方法*

入射声波激励下非均匀流体介质内部散射声场的重建方法对超声层析成像具有重要意义。以往采用矩量法求解,但该方法全域离散形成的复数满秩矩阵规模随着分辨率与计算精度的提高而急剧增大,对算力具有很高的要求,一定程度上限制了其在实际中的应用。为克服上述缺陷,本文以逐层离散、逐层计算为核心思想,以声散射基本公式与近场声全息理论为基础,推导出逐层计算非均匀流体介质内部散射声场的理论公式并给出对应的几何离散模型。为验证该方法的可行性,以矩量法为参照,对同样的介质模型进行介质内部声场重构仿真。结果表明,逐层算法不仅可以有效地重建非均匀流体介质内部散射声场,且大幅度减小了求解规模。     

Dual effects of ultrasound on fabrication of anodic aluminum oxide

Ultrasound has been proven to enhance the mass transfer process and impact the fabrication of anodic aluminum oxide (AAO). However, the different effects of ultrasound propagating in different media make the specific target and process of ultrasound in AAO remain unclear, and the effects of ultrasound on AAO reported in previous studies are contradictory. These uncertainties have greatly limited the application of ultrasonic-assisted anodization (UAA) in practice. In this study, the bubble desorption and mass transfer enhancement effects were decoupled based on an anodizing system with focused ultrasound, such that the dual effects of ultrasound on different targets were distinguished. The results showed that ultrasound has the dual effects on AAO fabrication. Specifically, ultrasound focused on the anode has a nanopore-expansion effect on AAO, leading to a 12.24 % improvement in fabrication efficiency. This was attributed to the promotion of interfacial ion migration through ultrasonic-induced high-frequency vibrational bubble desorption. However, AAO nanopores were observed to shrink when ultrasound was focused on the electrolyte, accompanied by a 25.85 % reduction in fabrication efficiency. The effects of ultrasound on mass transfer through jet cavitation appeared to be the reason for this phenomenon. This study resolved the paradoxical phenomena of UAA in previous studies and is expected to guide AAO application in electrochemistry and surface treatments.     

Adsorption of Cr(Ⅵ) polluted water by Fe3O4@SiO2-APTMS nanocomposites prepared in the presence of ultrasonic irradiation for sustainable water resources utilization

The research on developing a purification technology for Cr(Ⅵ) polluted water with high efficiency and the low energy consumption is crucial for achieving several Sustainable Development Goals (SDGs). In order to achieve these goals, Fe₃O₄@SiO₂-APTMS nanocomposites were prepared by Fe₃O₄ nanoparticles modified with silica and 3-aminopropyltrimethoxysilane in the presence of ultrasonic irradiation. The nanocomposites were characterized by TEM, FT-IR, VSM, TGA, BET, XRD, XPS and these analytic results proved that the nanocomposites were successfully prepared. The influential factors of Fe₃O₄@SiO₂-APTMS on Cr(Ⅵ) adsorption have been explored and better experimental conditions have been obtained. The adsorption isotherm conformed to the Freundlich model. Pseudo-second-order kinetic model provided a better correlation for the experimental data compared to other kinetic models. Thermodynamic parameters for adsorption indicated that the adsorption of Cr(Ⅵ) was a spontaneous process. It was speculated that the adsorption mechanism of this adsorbent includes redox, electrostatic adsorption and physical adsorption. In summary, the Fe₃O₄@SiO₂-APTMS nanocomposites were of great significance to human health and the remediation of heavy ion pollution, contributing to achievement of the Sustainable Development Goals (SDGs), including SDG-3, SDG-6.     

Investigations into wetting and spreading behaviors of impacting metal droplet under ultrasonic vibration control

Ultrasonic-assisted metal droplet deposition (UAMDD) is currently considered a promising technology in droplet-based 3D printing due to its capability to change the wetting and spreading behaviors at the droplet-substrate interface. However, the involved contact dynamics during impacting droplet deposition, particularly the complex physical interaction and metallurgical reaction of induced wetting-spreading-solidification by the external energy, remain unclear to date, which hinders the quantitative prediction and regulation of the microstructures and bonding property of the UAMDD bumps. Here, the wettability of the impacting metal droplet ejected by a piezoelectric micro-jet device (PMJD) on non-wetting and wetting ultrasonic vibration substrates is studied, and the corresponding spreading diameter, contact angle, and bonding strength are also discussed. For the non-wetting substrate, the wettability of the droplet can be significantly increased due to the extrusion of the vibration substrate and the momentum transfer layer at the droplet-substrate interface. And the wettability of the droplet on a wetting substrate is increased at a lower vibration amplitude, which is driven by the momentum transfer layer and the capillary waves at the liquid–vapor interface. Moreover, the effects of the ultrasonic amplitude on the droplet spreading are studied under the resonant frequency of 18.2–18.4 kHz. Compared to deposit droplets on a static substrate, such UAMDD has 31% and 2.1% increments in the spreading diameters for the non-wetting and wetting systems, and the corresponding adhesion tangential forces are increased by 3.85 and 5.59 times.