High temperature-high efficiency liquid chromatography using sub-2 μm coupled columns for the analysis of selected non-steroidal anti-inflammatory drugs and veterinary antibiotics in environmental samples

A high efficiency HPLC method was developed by coupling three sub-2 μm columns in series and operating them at high temperature for the separation of selected non-steroidal anti-inflammatory drugs and veterinary antibiotics in environmental samples. The separation was performed at 80 °C to reduce the solvent viscosity, thus reducing the column backpressure. The chromatographic performance of high temperature-extended column length HPLC method was used to determine the most widely used non-steroidal anti-inflammatory drugs and veterinary antibiotics such as sulphonamides in wastewater samples. The method could simultaneously determine 24 pharmaceuticals in short analysis time with high efficiency. The method involved pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction cartridges. It was validated based on linearity, precision, detection and quantification limits, selectivity and accuracy. Good recoveries were obtained for all analytes ranging from 72.7% to 98.2% with standard deviations not higher than 6%, except for acetaminophen and acetyl salicylic acid, for which low recovery was obtained. The detection limits of the studied pharmaceuticals ranged from 2 to 16 μg L⁻¹, while limits of quantification were in the range from 7 to 54 μg L⁻¹ with UV detection.     

Adsorption of Mercury(II) on Amidoxime Chelating Resins with Magnetic Properties

Two amidoxime chelating resins were prepared. The preparation process was carried out through copolymerization of acrylonitrile with N,N′-methylene-bis-acrylamide (MBA) as a crosslinker in the presence and absence of magnetite (Fe₃O₄) particles. The resins obtained were subsequently treated with hydroxylamine to give the corresponding amidoxime chelating resins. The uptake behavior of the resins toward Hg(II) in aqueous solutions using batch and column techniques was studied. The oxide containing resin gave higher uptake capacities relative to oxide free resin confirming the advantage of embedded particles on the uptake capacity. Thermodynamic and kinetic parameters of the uptake process were calculated. Regeneration of the resins was carried out using 0.5 M KI and the desorption ratio was found to be more than 97%.     

Antifungal activity of compounds isolated from Aspergillus niger and their molecular docking studies with tomatinase

Abstract

Using a dual culture antagonism assay, Aspergillus niger exhibited 51.5?±?1.1% growth inhibition against Fusarium oxysporum f.sp. lycopersici, the wilt pathogen of tomato. For enhanced production of antifungal metabolites, nutrient optimization was performed and in vitro well-diffusion antifungal assays demonstrated that crude extract obtained from GPYB culture showed a maximum zone of inhibition (8.8?±?0.4?mm) against the wilt pathogen, which is corroborated by the comparative LCMS profiles of the extracts from all three media i.e. GPYB, YEB and PDB. Two known compounds, Asperazine (m/z 665 [M?+?H]⁺) and Nigerone (m/z 571 [M?+?H]⁺), were isolated from A. niger and their antifungal activity is reported here for the first time. In MIC experiments, Asperazine and Nigerone inhibited the pathogen at 60 and 80?µg·mL^?1 respectively. Molecular docking studies of Nigerone and Asperazine with F. oxysporum tomatinase showed five and six binding interactions respectively.     

The Nash modification and hyperplane sections on surfaces

We prove that the planar components of the tangent cone of a complex analytic surface at a point correspond to the base points of hyperplane sections by the Nash modification. This correspondence is then used to characterize domination relations between the normalized Nash modification and the normalized blow-up of a point.     

负载型铜钴氧化物协同催化 H2O2/HCO3-降解苯酚

近年来,环境污染特别是水的严重污染使其治理成为一个极具挑战性的课题.各种污染物复杂的化学成分和催化剂在处理过程中的浸出、寿命及成本等问题是导致众多氧化催化剂难以实际应用的主要原因.相对而言, H2O2是一种活性氧含量高、清洁并可在温和条件下使用的氧化剂,在各种高级氧化技术中受到广泛关注.而碳酸氢盐是一种弱碱性物质,在自然界及水体系中广泛存在,且无明显毒害.它可活化 H2O2,加快其氧化各种有机物,并在废水处理领域开始受到关注.该体系的明显优势在于处理体系始终处于微碱性环境,可以有效避免金属氧化物催化剂在处理过程中由于体系酸化而带来的催化剂流失,从而延长催化剂寿命,降低催化剂成本.
　　本文采用浸渍法制备了一种双金属铜、钴氧化物催化剂及相关的对照催化剂体系,利用碳酸氢盐活化 H2O2用于降解苯酚模拟废水.通过各种空白实验发现,负载于γ-Al2O3表面的钴、铜氧化物催化剂 CuO?Co3O4@γ-Al2O3具有最好的催化降解活性,而 CuO@γ-Al2O3, Co3O4@γ-Al2O3, CuO?Co3O4及 CuO和 Co3O4的物理混合物均表现出较差的催化性能.由此可见,在 CuO?Co3O4@γ-Al2O3催化剂中,铜、钴离子在苯酚降解过程中存在协同效应,这可能与催化剂中钴、铜金属离子的相互作用相关. X射线衍射和 X射线光电子能谱结果表明,反应前后 CuO?Co3O4@γ-Al2O3催化剂中金属的氧化状态并未发生改变,在使用过程中钴离子的浸出率可以忽略,铜离子的浸岀率也仅有0.6 ppm.荧光分析实验和自由基捕获实验表明,只有添加?O2-和?OH的捕获剂能明显抑制降解反应,因而推测该反应体系对有机物的降解是一个自由基氧化过程,起关键作用的可能是?O2-和?OH.     

Green approach using monolithic column for simultaneous determination of coformulated drugs

Green chemistry and sustainability is now entirely encompassed across the majority of pharmaceutical companies and research labs. Researchers’ attention is careworn toward implementing the green analytical chemistry principles for more eco‐friendly analytical methodologies. Solvents play a dominant role in determining the greenness of the analytical procedure. Using safer solvents, the greenness profile of the methodology could be increased remarkably. In this context, a green chromatographic method has been developed and validated for the simultaneous determination of phenylephrine, paracetamol, and guaifenesin in their ternary pharmaceutical mixture. The chromatographic separation was carried out using monolithic column and green solvents as mobile phase. The use of monolithic column allows efficient separation protocols at higher flow rates, which results in short time of analysis. Two‐factor three‐level experimental design was used to optimize the chromatographic conditions. The greenness profile of the proposed methodology was assessed using eco‐scale as a green metrics and was found to be an excellent green method with regard to the usage and production of hazardous chemicals and solvents, energy consumption, and amount of produced waste. The proposed method improved the environmental impact without compromising the analytical performance criteria and could be used as a safer alternate for the routine analysis of the studied drugs.     

Thermal analysis for radiative flow of magnetized Maxwell fluid over a vertically moving rotating disk

Journal of Thermal Analysis and Calorimetry - In the current framework, we study the chemically reactive Maxwell fluid flow over a vertically moving upward/downward rotating disk during the...     

Effect of Sodium Dodecylbenzenesulfonate on the Association Behavior of Promethazine Hydrochloride in Aqueous/Electrolyte Solutions at Different Temperatures

The interaction between the amphiphilic phenothiazine drug promethazine hydrochloride (PMT) and an anionic surfactant sodium dodecylbenzenesulfonate has been investigated using the conductometric technique in the absence and presence of an inorganic salt (50 mmol·kg^?1 NaCl) at five different compositions and temperatures. PMT is employed for the cure of allergic symptoms. Different physicochemical parameters such as critical micellar concentration (cmc), thermodynamic, and micellar composition are evaluated and discussed in detail using regular solution theory (RST). The addition of salt decreased the surface charge of micelles, lowering the cmc values of the amphiphile. The interaction parameter (β) is negative at all temperatures and compositions indicating attractive interactions. Due to the presence of NaCl in mixed systems the attractive interaction (β) was further increased (β values more negative). The negative values of Gibbs energy (\( \Delta G^{0}_{\text{m}} \)) of mixing revealed the stability of the solution. Owing to the presence of NaCl, the \( \Delta G^{0}_{\text{m}} \) values are found to be more negative suggesting that the driving force for interaction was significantly increased and micellization more thermodynamically favorable.     

Synthesis and spectroscopic characterization of novel 2-amino-4,5,6,7-tetrahydro-3H-cyclopenta[d]pyrimidine and pyrimido[1,2-a]pyrimidine derivatives

2-Aminocyclopenta[d]pyrimidines 3a-c were achieved via a one-pot, three-component reactions of cyclopentanone 1, aromatic aldehyde and guanidine hydrochloride (1:2:1 molar ratio). Also, cyclization of 2,5-bis-(arylmethylidene)cyclopentanones 2 with guanidine hydrochloride (1:1 molar ratio) in methanol in the presence of sodiummethoxide afforded cyclopenta-[d]pyrimidines 3. Compound 3a has been shown to be a useful building block for the synthesis of some novel pyrimido[1,2-a]pyrimidines 5, 7 and 12. The structures of the newly synthesized compounds were confirmed on the basis of analytical and spectral data.