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Environmental Applications of Pyrolysis
Published in Karen D. Sam, Thomas P. Wampler, Analytical Pyrolysis Handbook, 2021
T. O. Munson, Karen D. Sam, Alexandra ter Halle
Samples of the corrosion layers from six outdoor Italian bronze monuments were examined by Py-GC/MS, leading to the identification of organic compounds deriving from both environmental pollution and from protective organic coatings [66]. In addition to direct pyrolysis, some of the samples were subjected to SPM-Py-GC/MS (described in Section IVE). For SPM, 5 µL of 25% tetramethylammonium hydroxide in methanol was added to the dry sample inside the quartz pyrolysis tube. This methylation procedure was especially useful in improving the chromatographic behavior of fatty acids present in the sample. Analytical results varied considerably among monuments, variously showing the presence of nitrogen compounds (pyridine, benzonitrile, cyanopyridine, dicyanobenzene), oxygenated compounds (phenol, benzoic acid, phthalic anhydride), fatty acids, and alkanes.
Capacitive Silicon Resonators with Narrow Gaps Formed by Metal-Assisted Chemical Etching
Published in Nguyen Van Toan, Takahito Ono, Capacitive Silicon Resonators, 2019
Silicon, one of the most important materials in micro/nano systems, has been used for the fabrication of a wide range of micro/nano devices, including microfabricated resonators [1, 2], power generators [3, 4], and bio/chemical sensors [5, 6]. Wet and dry etching techniques are typically employed for patterning silicon structures. The wet etching of silicon [7] is performed under liquid phase in a container, such as a beaker, consisting of potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). The wet etching of silicon can achieve smooth etched surfaces; however, the aspect-ratio structures are limited due to side etching. Whereas high-aspect-ratio structures can be easily achieved by inductively coupled plasma–reactive ion etching (ICP-RIE) with the Bosch process [8, 9] using SF6 (etching cycle) and C4F8 (passivation cycle) gases. Nevertheless, many disadvantages [10] can be found such as limitation of achievable aspect structures, rough etched surfaces, and defect generation on silicon surfaces. Moreover, all these dry methods require radio frequency (RF) generators, vacuum chambers, and precise mechanical parts, such that the device’s fabrication cost becomes high. Thus, novel methods for high-aspect-ratio silicon structures are still needed for micro/nano systems.
Selected Coating Chemistry for Water-Soluble, Core-Shell–Type Nanoparticles with Cross-Linked Shells
Published in Nikhil Ranjan Jana, Colloidal Nanoparticles, 2019
Take 3 mg hydroxyapatite nanorod and dissolve in 2 mL toluene2 (see Section 3.11). In a separate vial, dissolve 30 μL of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in 2 mL of toluene and mix with nanorod solution. Keep the solution under stirring conditions and raise the temperature to 70°C–80°C. In another vial, mix 15 μL of tetramethylammonium hydroxide solution in 0.5 mL of methanol and add dropwise into the nanorod solution. Continue heating at 70°C–80°C for 20–30 min until all the nanorods precipitate. Wash the precipitate with toluene and ethanol, and finally dissolve in 1–2 mL distilled water.
Potentially toxic elements (PTEs) in coffee: a comprehensive review of toxicity, prevalence, and analytical techniques
Published in International Journal of Environmental Health Research, 2022
Neda Mollakhalili-Meybodi, Sima Tahmouzi, Fardin Javanmardi, Amene Nematollahi, Amin Mousavi Khaneghah
Regarding developing alternative sample preparation methods, food chemists and analysts eagerly seek alternative methodologies that do not require complete decomposition of the sample (Trindade et al. 2020). Researchers propose microwave/ultrasound-assisted acid digestion, slurry sampling, and direct solid sampling as alternatives to conventional sample preparation methods that will postpone adverse effects caused by traditional sample preparation. The use of tetramethylammonium hydroxide, an alkaline solution of tetramethylammonium hydroxide, has been proposed as a simple strategy for the solubilization of instant coffee (Ribeiro et al. 2003). The method is validated for the total quantification of Ca, Cu, Fe, Mg, Mn, Na, P, Se, Sn, and Zn using ICP-OES. The potential of using 0.36 mol L-1 HNO3 solution and the solubilization in aqua regia has also been determined by (Asfaw and Wibetoe 2005) to quantify Se, Ca, Mg, K, P, S, and Zn elements by ICP-OES using a dual-mode sample introduction system (MSIS) in different beverages like instant coffee and also (Szymczycha-Madeja et al. 2015) with accuracy, precision and recovery in the range of 1.9–4.7%, 0.5–0.86%, and 93.5–103% respectively. Besides the solubilization method, dilution and centrifugation have also been used to quantify instant coffee elements (Oliveira et al. 2012). This preparation method is reliable for quantifying Ca, Mg, K, Na, Fe, Mn, Cr, and Ni using high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) and graphite furnace atomic absorption spectrometry (HR-CS-GFAAS).
Ionic liquid-based dispersive liquid–liquid microextraction of succinic acid from aqueous streams: COSMO-RS screening and experimental verification
Published in Environmental Technology, 2023
Huma Warsi Khan, Anis Aina Zailan, Ambavaram Vijaya Bhaskar Reddy, Masahiro Goto, Muhammad Moniruzzaman
As appropriate solvent selection is essential to achieve better selectivity and higher efficiency. In this work, six solvents were examined and the solvent that has yielded highest efficiency was chosen for further experimental analyses. When selecting the series of solvents, we have considered the fact that the disperser solvent must be miscible with the extractant as well as the aqueous phase containing SA [6] and must form a cloudy solution when injected into the aqueous phase along with the extractant solvent (i.e. IL). The nature of emulsifier disperser solvent influences the distribution of drop size, mean drop size and the viscosity of emulsion. Its miscibility in both extractant solvent and the aqueous phase is an essential parameter when choosing disperser solvents. The frequently used solvents include methanol, acetone, acetonitrile, ethanol, isopropanol. Therefore, these solvents have been employed considering their miscibility. Similarly in the current study, we have considered methanol, acetone, acetonitrile, isopropanol, dichloromethane and chloroform, and the extraction results are reported in Figure S5. However, dichloromethane and chloroform were rejected as they are not miscible with the aqueous solution. Likewise, methanol and acetone were eliminated because they did not form a cloudy solution when added to tetramethylammonium hydroxide and SA solution. As only acetonitrile formed cloudy solution when injected into the aqueous solution (possibly due to the higher SA solubility in acetonitrile as described previously [14]), acetonitrile was adopted as disperser solvent when applying the DLLME separation method.
Surface properties and doxorubicin delivery in mixed systems comprising a natural rosin-based ester tertiary amine and an anionic surfactant
Published in Journal of Dispersion Science and Technology, 2019
Chao Tian, Yuanli Liang, Haixia Lin, Jie Song, Qi Li, Rui Li, Chunrui Han
In order to determine the purity of RETAS, we tested the GC-MS of RETAS (A) and rosin acid raw material (B) as contrast as shown in the Figure 2. The molecular weight of RETAS is 739.39 and the molecular weight is not permitted more than 600 in GC-MS test. So, the GC-MS of RETAS was carried out by the method of literature.[9] RETAS was methyl etherified by tetramethylammonium hydroxide (TMAH). The reaction of RETAS with TMAH is shown in Figure 2A. Compounds a-g are the main methyl etherified productions of RETAS. Compounds b-d are the three dimethylesters of maleic rosin (MR) and e-g are the three monomethylesters of MR. The compound h would be reacted to be i [bis (2-(Dimethylamino) ethyl) ether] as shown in Figure 3B at the high temperature process of GC-MS. So, the main productions were a (trimethylester of MR), b-d (dimethylester of MR), e-g (monomethylester of MR) and h [bis (2-(Dimethylamino) ethyl) ether]. The main productions and their percent were shown in Table 1. We showed the mass spectrum (MS) and standard MS spectra of main compounds in Figure 4A and 4B. All MS of a-i compounds and unreacted raw materials (corresponding to peak 1 and 2 in Figure 2) well correspond to the standard MS spectra. The unreacted raw materials (peak1 and 2) are isopimaric acid and dehydroabietic acid. Compounds a-i are the productions of methyl etherified RETAS by TMAH. The most production is a, trimethylester of MR, and its percent is 41.7%. The peak area percent of a-i is 81.2%. So, the purity of RETAS is about 81.2% by analyzing GC-MS in detail.