Determination of the Conformational Preference of para-Aminobenzoic Acid on Vanadium Pentoxide Surface: An XPS and DFT Study

Author(s):  
Fabian Dietrich ◽  
Juan Fernandez ◽  
Samuel Hevia ◽  
Eduardo Cisternas ◽  
Marcos Flores
Author(s):  
Hind Hadi ◽  
Gufran Salim

A simple, rapid and sensitive spectrophotmetric method for trace determination of salbutamol (SAL) in aqueous solution and in pharmaceutical preparations is described. The method is based on the diazotization coupling reaction of the intended compound with 4-amino benzoic acid (ABA) in alkaline medium to form an intense orange, water soluble dye that is stable and shows maximum absorption at 410 nm. A graph of absorbance versus concentration indicates that Beer’s law is obeyed over the concentration range of 0.5-30 ppm, with a molar absorbtivity 3.76×104 L.mol-1 .cm-1 depending on the concentration of SAL. The optimum conditions and stability of the colored product have been investigated and the method was applied successfully to the determination of SAL in dosage forms.


2007 ◽  
Vol 847 (2) ◽  
pp. 224-230 ◽  
Author(s):  
Mugunthu R. Dhananjeyan ◽  
Crystal Bykowski ◽  
Jill A. Trendel ◽  
Jeffrey G. Sarver ◽  
Howard Ando ◽  
...  

2018 ◽  
Vol 233 (9-10) ◽  
pp. 615-626
Author(s):  
Stefan Mebs ◽  
Sabrina Imke Kalläne ◽  
Thomas Braun

Abstract Rhodium boryl complexes are valuable catalysts for hydro- or diboration reactions of alkenes, but can also react with ketones (R2C=O) and imines (R2C=NR′) giving rise to insertion products having formally Rh–R2C–O/NR′–B linkages. The resulting molecular structures, however, may show complex metal–ligand and ligand–ligand interaction patterns with often unclear metal–ligand connectivities (hapticities, ηn). In order to assign the correct hapticity in a set of asymmetric rhodium-allyl compounds with molecular structures indicating η1−5 bonding, a comprehensive DFT study was conducted. The study comprises determination of a variety of real-space bonding indicators derived from computed electron and pair densities according to the AIM, ELI-D, NCI, and DORI topological and surface approaches, which uncover the metal–ligand connectivties and suggest an asymmetric ligand–metal donation/metal–ligand back-donation framework according to the Dewar–Chatt–Duncanson model.


2019 ◽  
Vol 97 (2) ◽  
pp. 140-146
Author(s):  
Tian Gan ◽  
Zhikai Wang ◽  
Mengru Chen ◽  
Wanqiu Fu ◽  
Haibo Wang ◽  
...  

In this work, the Ag@Cu particles with yolk–shell nanostructure was prepared by facile solvothermal method, which was modified on glassy carbon electrode (GCE) to fabricate electrochemical sensor for the convenient and fast determination of p-aminobenzoic acid (PABA). The surface morphology and electrochemical properties of the as-prepared Ag@Cu nanocomposite modified electrode were characterized by scanning electron microscopy, transmission electron microscopy, chronocoulometry, and electrochemical impedance spectroscopy. Further, the electrochemical sensing of PABA was performed on the Ag@Cu/GCE using cyclic voltammetry and differential pulse voltammetry techniques, showing high catalytic activity. Under the optimal conditions, the sensor exhibited a wide linear range, high sensitivity, and low detection limit of 0.315 μmol/L for PABA. The developed sensor was also successfully applied for PABA detection in anesthetic and cosmetics with satisfactory results.


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