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Summary A simple quantitative method for the analysis of the residues of sulphadiazine and sulphadimidine in milk is described. The method is based on a simple extraction step and high-performance liquid chromatography (HPLC) with electrochemical detection. The Chromatographic seperation is performed on a reversed phase column (RP-C2) and an aqueous eluent. With this analytical system 10 ng/ml can be detected. Recoveries of sulphonamides from milk are between 94.4% and 110% in the concentration range of 0.01–1.8 g/ml sample.
Bestimmung von Sulfonamidrückständen in Milch mit Hilfe der HPLC und dem elektrochemischen Detektor
Zusammenfassung Es wird eine einfache Methode zum Nachweis von Sulfonamidrückständen in Milch am Beispiel von Sulfadiazin und Sulfadimidin beschrieben, mit der noch Rückstandsmengen von 10 ng/ml erfaßbar sind. Das Verfahren besteht aus einem einfachen Aufreinigungsschritt, der Trennung der Rückstände auf einer Umkehrphase (RP-C2) und der Detektion mit einem elektrochemischen Detektor. Die Wiederfindungsraten liegen zwischen 94,4% und 110% für einen Konzentrationsbereich von 0,01–1,8 g/ml Untersuchungsmaterial.相似文献
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In this paper, we consider second-order evolution equations with unbounded dynamic feedbacks. Under a regularity assumption, we show that observability properties for the undamped problem imply decay estimates for the damped problem. We consider both uniform and non-uniform decay properties. 相似文献
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Ethylene Conversion to Higher Hydrocarbon over Copper Loaded BZSM-5 in the Presence of Oxygen 总被引:1,自引:0,他引:1 下载免费PDF全文
The successful production of higher hydrocarbons from methane depends on the stability or the oxidation rate of the intermediate products. The performances of the BZSM-5 and the modified BZSM-5 catalysts were tested for ethylene conversion into higher hydrocarbons. The catalytic experiments were carried out in a fixed-bed micro reactor at atmospheric pressure. The catalysts were characterized using XRD, NH3-TPD, and IR for their structure and acidity. The result suggests that BZSM-5 is a weak acid. The introduction of copper into BZSM-5 improved the acidity of BZSM-5. The conversion of ethylene toward higher hydrocarbons is dependent on the acidity of the catalyst. Only weaker acid site is required to convert ethylene to higher hydrocarbons. The loading of Cu on BZSM-5 improved the selectivity for higher hydrocarbons especially at low percentage. The reactivity of ethylene is dependent on the amount of acidity as well as the presence of metal on the catalyst surface. Cu1%BZSM-5 is capable of converting ethylene to higher hydrocarbons. The balances between the metal and acid sites influence the performance of ethylene conversion and higher hydrocarbon selectivity. Higher loading of Cu leads to the formation of COx. 相似文献
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Prof. Dr. Antonino Gulino Prof. Dr. Georgia Papanikolaou Prof. Dr. Paola Lanzafame Prof. Dr. Abdellatif Aaliti Prof. Dr. Patrizia Primerano Prof. Dr. Luca Spitaleri Prof. Dr. Claudia Triolo Zainab Dahrouch Amani Khaskhoussi Prof. Dr. Sandra Lo Schiavo 《ChemistryOpen》2021,10(10):1033-1040
We report on the facile synthesis of SiO2@nitrized-TiO2 nanocomposite (NST) by calcination of TiO2 xerogel with OctaAmmonium POSS® (N-POSS; POSS=polyhedral oligomeric silsesquioxanes). The as-obtained nanoporous mixed oxide is constituted by uniformly distributed SiO2 and nitrized-TiO2, where the silica component is present in an amorphous state and TiO2 in an anatase/rutile mixed phase (92.1 % vs. 7.9 %, respectively) with very small anatase crystallites (3.7 nm). The TiO2 lattice is nitrized both at interstitial and substitutional positions. NST features a negatively charged surface with a remarkable surface area (406 m2 g−1), endowed with special adsorption capabilities towards cationic dyes. Its photocatalytic behavior was tested by following the degradation of standard aqueous methylene blue and methyl orange solutions under UV and visible light irradiation, according to ISO 10678:2010. For comparison, analogous investigations were carried out on a silica-free N−TiO2, obtained by using NH4Cl as nitrogen source. 相似文献
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Azizah M. Malebari Rakia Abd Alhameed Zainab Almarhoon Muhammad Farooq Mohammad A. M. Wadaan Anamika Sharma Beatriz G. de la Torre Fernando Albericio Ayman El-Faham 《Molecules (Basel, Switzerland)》2021,26(4)
Several derivatives containing morpholine/piperidine, anilines, and dipeptides as pending moieties were prepared using s-triazine as a scaffold. These compounds were evaluated for their anticancer activity against two human breast cancer cell lines (MCF-7 and MDA-MB-231), a colon cancer cell line (HCT-116), and a non-tumorigenic cell line (HEK 293). Tamoxifen was used as a reference. Animal toxicity tests were carried out in zebrafish embryos. Most of these compounds showed a higher activity against breast cancer than colon cancer. Compound 3a—which contains morpholine, aniline, and glycylglycinate methyl ester—showed a high level of cytotoxicity against MCF-7 cells with IC50 values of less than 1 µM. This compound showed a much lower level of toxicity against the non-tumorigenic HEK-293 cell line, and in the in vivo studies using zebrafish embryos. Furthermore, it induced cell cycle arrest at the G2/M phase, and apoptosis in MCF-7 cells. On the basis of our results, 3a emerges as a potential candidate for further development as a therapeutic drug to treat hormone receptor-positive breast cancer. 相似文献
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Dr. Patrick M. J. Szell Zainab Rehman Ben P. Tatman Dr. Leslie P. Hughes Dr. Helen Blade Prof. Steven P. Brown 《Chemphyschem》2023,24(3):e202200558
Crystallographic disorder, whether static or dynamic, can be detrimental to the physical and chemical stability, ease of crystallization and dissolution rate of an active pharmaceutical ingredient. Disorder can result in a loss of manufacturing control leading to batch-to-batch variability and can lengthen the process of structural characterization. The range of NMR active nuclei makes solid-state NMR a unique technique for gaining nucleus-specific information about crystallographic disorder. Here, we explore the use of high-field 35Cl solid-state NMR at 23.5 T to characterize both static and dynamic crystallographic disorder: specifically, dynamic disorder occurring in duloxetine hydrochloride ( 1 ), static disorder in promethazine hydrochloride ( 2 ), and trifluoperazine dihydrochloride ( 3 ). In all structures, the presence of crystallographic disorder was confirmed by 13C cross-polarization magic-angle spinning (CPMAS) NMR and supported by GIPAW-DFT calculations, and in the case of 3 , 1H solid-state NMR provided additional confirmation. Applying 35Cl solid-state NMR to these compounds, we show that higher magnetic fields are beneficial for resolving the crystallographic disorder in 1 and 3 , while broad spectral features were observed in 2 even at higher fields. Combining the data obtained from 1H, 13C, and 35Cl NMR, we show that 3 exhibits a unique case of disorder involving the +N−H hydrogen positions of the piperazinium ring, driving the chloride anions to occupy three distinct sites. 相似文献
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Chalcone-derived pyrimidine is a well-known heterocyclic compound that is commonly present in ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) bio-isosteres. Pyrimidine derivatives are effective in both the electronic industry and drug industries. This review highlights the synthesis of pyrimidines, namely mono-pyrimidine, bis-pyrimidine, fused pyrimidine, symmetric, and asymmetric pyrimidine via one-pot and two-pot methods. The one-pot method is the direct reaction of amino derivatives with aldehydes and acetophenones, whereas the two-pot method is frequently reported for the synthesis of chalcone before the cyclization to a pyrimidine. This review is important in organic synthesis, particularly in the heterocyclic field, regarding pyrimidines and their significance in therapeutic and electronic industries. 相似文献
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Rizwan Ahmad Niyaz Ahmad Mohd Amir Fatema Aljishi Marwah Hussain Alamer Heba Radhi Al-Shaban Zainab Alawi Alsadah Bayan Mohammed Alsultan Noor Ali Aldawood Shahanas Chathoth Sarah Ameen Almofty 《Biomedical chromatography : BMC》2020,34(3):e4772
Black pepper (Piper nigrum; BP), known as the ‘king of spices’, imported from various countries is widely available in Saudi Arabian markets, as its demand as a food as well as a medicine for minor ailments is increasing in the country. However, there is a lack of appropriate information regarding these samples in terms of quality variation and standardization. We thus aimed to evaluate the quality and standardize the BP sample with respect to its physicochemical characters, active principle variation [i.e. piperine (PPN)], toxicity, and biological activity. The main focus is to validate whether any difference exists in the quality and quantity of active principle in these samples. For this purpose, physicochemical (chemical tests and ash values) and instrumental analyses [accelerated solvent extraction (ASE), ultra-high-pressure liquid chromatography (UHPLC)-diode array detector, infrared (IR), nuclear magnetic resonance (NMR), and inductively coupled plasma-MS (ICP-MS)] and biological evaluation {in vitro antioxidant activity [2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] and cytotoxicity assay} were performed. An extract yield (g) with %recovery of 2.26 ± 4.24 (11.3) was obtained for the Vietnamese sample, using a fast and rapid method of extraction (ASE). These values were 1.22 ± 2.64 (6.1) and 0.75 ± 1.69 (3.75) for the Pakistani and Indian samples. Physicochemical tests revealed the presence of flavonoids and phenolic compounds in all samples; however, in the Vietnamese sample a low amount of total, acid-insoluble, and high water-soluble ash value was noted. IR and NMR was applied to further standardize the samples. Results of ICP-MS analysis showed a high amount of macronutrients and micronutrients in the samples tested while UHPLC analysis revealed a high amount of PPN (ng/mL) in the Pakistani sample (1,362,614.09); these values were 1,051,848.04 and 768,512.81 for the Vietnamese and Indian samples, respectively. In vitro antioxidant and cytotoxicity activities revealed higher potential for the Vietnamese sample. The samples were properly standardized and effectively differentiated in terms of quality and biological activities using a fast and reliable method, however it certainly does not mean that a particular geographical region is more better or productive in terms of herbal products. 相似文献
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Muhammad Ashraf Syed Shaheen Shah Dr. Ibrahim Khan Dr. Md. Abdul Aziz Prof. Nisar Ullah Dr. Mujeeb Khan Dr. Syed Farooq Adil Zainab Liaqat Dr. Muhammad Usman Prof. Wolfgang Tremel Dr. Muhammad Nawaz Tahir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(23):6973-6984
Tungsten oxide/graphene hybrid materials are attractive semiconductors for energy-related applications. Herein, we report an asymmetric supercapacitor (ASC, HRG//m-WO3 ASC), fabricated from monoclinic tungsten oxide (m-WO3) nanoplates as a negative electrode and highly reduced graphene oxide (HRG) as a positive electrode material. The supercapacitor performance of the prepared electrodes was evaluated in an aqueous electrolyte (1 m H2SO4) using three- and two-electrode systems. The HRG//m-WO3 ASC exhibits a maximum specific capacitance of 389 F g−1 at a current density of 0.5 A g−1, with an associated high energy density of 93 Wh kg−1 at a power density of 500 W kg−1 in a wide 1.6 V operating potential window. In addition, the HRG//m-WO3 ASC displays long-term cycling stability, maintaining 92 % of the original specific capacitance after 5000 galvanostatic charge–discharge cycles. The m-WO3 nanoplates were prepared hydrothermally while HRG was synthesized by a modified Hummers method. 相似文献