A selective spectrophotometric method for determination of rosoxacin antibiotic using sodium nitroprusside as a chromogenic reagent

A selective spectrophotometric method for the determination of rosoxacin (ROS), a 4-quinolone antimicrobial agent, has been developed and validated. The method was based on the reaction of ROS with alkaline sodium nitroprusside (SNP) reagent at room temperature forming a red colored chromogen measured at 455 nm. The conditions affecting the reaction (SNP concentration, pH, color-developing time, temperature, diluting solvent and chromogen stability time) were optimized. Under the optimum conditions, good linear relationship (r=0.9987) was obtained between the absorbance and the concentration of ROS in the range of 20-50 microg ml(-1). The assay limits of detection and quantitation were 2.5 and 8.4 microg ml(-1), respectively. The method was successfully applied to the analysis of bulk drug and laboratory-prepared tablets; the mean percentage recoveries were 100.1+/-0.33 and 101.24+/-1.28%, respectively. The results were compared favourably with those obtained by the reported method; no significant difference in the accuracy and precision as revealed by the accepted values of t- and F-tests, respectively. The robustness and ruggedness of the method was checked and satisfactory results were obtained. The proposed method was found to be highly selective for ROS among the fluoroquinolone antibiotics. The reaction mechanism was proposed and it proceeded in two steps; the formation of nitroferrocyanide by the action of sodium hydroxide alkalinity on SNP and the subsequent formation of the colored nitrosyl-ROS derivative by the attack at position 6 of ROS.     

LC–MS/MS method for the quantification of masitinib in RLMs matrix and rat urine: application to metabolic stability and excretion rate

Masitinib (MST) is a selective tyrosine kinase inhibitor. Validated liquid chromatography tandem mass spectrometric method (LC–MS/MS) was developed for the quantification of MST in rat liver microsomes (RLMs) matrix. The developed method was applied to metabolic stability and excretion rate studies. Reversed phase liquid chromatography was used for resolution of MST and bosutinib (IS) using C₁₈ (50 mm × 2.1 mm, 1.8 μm). Binary solvent system consisted of 35% solvent A (0.1% formic acid in H₂O, pH: 3.2) and 65% solvent B (acetonitrile) used as mobile phase at flow rate of 0.25 mL with a total run time of 5 min. Injection volume was 5 µL. Generation of ions was done in positive ESI source and quantification of MST and IS were done using MRM mode. The developed method showed a linearity in the range of 5–200 ng/mL (r² ≥ 0.9992) with LOQ and LOD of 0.25 and 0.76 ng/mL in RLMs. The intra- and inter-day precision and accuracy ranged from 0.95 to 1.49 and ? 5.22 to 1.13%, respectively in RLMs. Rate of disappearance of MST during incubation with RLMs was almost linear allover incubation time. In vitro t_1/2 was 50.38 min and CL_in was 3.11 ± 0.2. The developed method was applied also to measure the rate of masitinib excretion in rat urine. The method can used for further pharmacokinetic studies of MST.     

Development of Two Innovative 96-Microwell-Based Spectrophotometric Assays with High Throughput for Determination of Fluoroquinolone Antibiotics in their Pharmaceutical Formulations

Journal of Applied Spectroscopy - Fluoroquinolone antibiotics (FQAs) have broad-spectrum antibacterial activity, high potency, variable indications, and excellent pharmacokinetic profi les. Many...     

Development of a novel 96-microwell assay with high throughput for determination of olmesartan medoxomil in its tablets

A novel 96-microwell-based spectrophotometric assay has been developed and validated for determination of olmesartan medoxomil (OLM) in tablets. The formation of a colored charge-transfer (CT) complex between OLM as a n-electron donor and 2, 5-dichloro-3, 6-dihydroxy-1, 4-benzoquinone (p-chloranilic acid, pCA) as a π-electron acceptor was investigated, for the first time, and employed as a basis in the development of the proposed assay. The proposed assay was carried out in 96-microwell plates. The absorbance of the colored-CT complex was measured at 490 nm by microwell-plate absorbance reader. The optimum conditions of the reaction and the analytical procedures of the assay were established. Under the optimum conditions, linear relationship with good correlation coefficient was found between the absorbance and the concentration of OLM in the range of 1-200 μg ml^-1. The limits of detection and quantitation were 0.3 and 1 μg ml^-1, respectively. No interference was observed from the additives that are present in the pharmaceutical formulation or from hydrochlorothiazide and amlodipine that are co-formulated with OLM in some formulations. The assay was successfully applied to the analysis of OLM in tablets with good accuracy and precision. The assay described herein has great practical value in the routine analysis of OLM in quality control laboratories, as it has high throughput property, consumes minimum volume of organic solvent thus it offers the reduction in the exposures of the analysts to the toxic effects of organic solvents, and reduction in the analysis cost by 50-fold. Although the proposed assay was validated for OLM, however, the same methodology could be used for any electron-donating analyte for which a CT reaction can be performed.     

Economic selection of process mean for single-vendor single-buyer supply chain

Process mean selection for a container-filling process is an important decision in a single-vendor single-buyer supply chain. Since the process mean determines the vendor’s conforming and yield rates, it influences the vendor–buyer decisions regarding the production lot size and number of shipments delivered from the vendor to buyer. It follows, therefore, that these decisions should be determined simultaneously in order to control the supply chain total cost. In this paper, we develop a model that integrates the single-vendor single-buyer problem with the process mean selection problem. This integrated model allows the vendor to deliver the produced lot to buyer in number of unequal-sized shipments. Moreover, every outgoing item is inspected, and each item failing to meet a lower specification limit is reprocessed. Further, in order to study the benefits of using this integrated model, two baseline cases are developed. The first of which considers a hierarchical model where the vendor determines the process mean and schedules of production and shipment separately. This hierarchical model is used to show the impact of integrating the process mean selection with production/inventory decisions. The other baseline case is studied in the sensitivity analysis where the optimal solution for a given process is compared to the optimal solution when the variation in the process output is negligible. The integrated model is expected to lead to reduction in reprocessing cost, minimal loss to customer due to the deviation from the optimum target value, and consequently, providing better products at reduced cost for customers. Also, a solution procedure is devised to find the optimal solution for the proposed model and sensitivity analysis is conducted to investigate the effect of the model key parameters on the optimal solution.     

Tunable intramolecular multicenter H-bonding interactions in first-row metal complexes bearing bidentate redox-active ligands

Abstract

In this research article, we report the synthesis and structural characterization of a family of first-row metal complexes bearing redox-active ligands with tunable H-bonding donors. We observed that these coordination complexes can adopt three different geometries and that they are stabilized by intramolecular multicenter H-bonding interactions, which are systematically modified by changing the metal ion (Co, Ni, Cu, Zn), the ligand scaffold (variations in the diamine and ureanyl substituents used) and the solvent of crystallization.     

Construction of a TiO2–Fe3O4‐decorated molecularly imprinted polymer nanocomposite for tartrazine degradation: Response surface methodology modeling and optimization

We synthesized a novel recoverable and reusable photocatalyst system for tartrazine degradation by one‐step incorporation of Fe₃O₄ and TiO₂ nanoparticles into a molecularly imprinted polymer through a facile precipitation polymerization method. The as‐prepared samples were systematically characterized using X‐ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and vibrating sample magnetometry. Benefiting from the positive synergistic effect, tartrazine was almost completely degraded under UV‐C within 180 min by the multicomponent photocatalyst (Fe₃O₄ + TiO₂ + MIP) in comparison with far fewer activities by the corresponding NIP system and the nonmagnetic and bare structures. On the other hand, the central composite design in response surface methodology was applied to optimize the tartrazine photocatalytic degradation process. Twenty experiments were conducted by adjusting three parameters (nanocomposite dosage, initial pH of the reaction solution, and initial dye concentration) in the multiple variable analysis method. A satisfactory correlation between the experimental and predicted values was obtained (R² = 0.956). Additionally, ANOVA analysis with a p value of 1.15 × 10^–5 indicated that the model terms are highly significant. Under the determined optimum conditions, a verification experiment was conducted and shown the adequately approximate value between the predicted (99%) and the experimental (97%) results, which confirmed the validity of the model.     

Structure and sensory equipment of the ovipositor of Habrobracon hebetor (Say) (Hymenoptera: Braconidae)

The microsculpture of various structures of the ovipositor of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is described from scanning and transmission electron microscopy. These include: the ovipositor egg canal, valvillus, seal of the first valvulae, interlocking mechanism (olistheter) connecting the first and second valvulae, an olistheter-like interlocking mechanism connecting the two pieces of the first valvulae, annulation, microtrichia of the third valvulae, and the ovipositor sensory equipment. Better understanding of the microsculpture of these components may make their roles in stinging, oviposition, and the host selection process more clear.     

Unusual addition patterns in trifluoromethylation of [60]fullerene

From pyrolytic trifluoromethylation of [60]fullerene with CF3CO2Ag at 300 degrees C we have isolated ca. sixty C60(CF3)n isomers (numbers in parentheses) as follows: n = 2(1), 4(8), 6(13), 8(21), 10(11), 12(5), 14(4), twenty-one of which have been characterised by 19F NMR. Compounds with addition levels up to n = 20 have also been identified. With increasing value of n, yields decrease and the separation of compounds of similar HPLC retention time but different addend levels becomes more difficult. Many of the 19F NMR spectra show combinations of quartets and septets (the latter tending to be more downfield) due to 'linear' addend arrays. The spectra are consistent with addition across both 6:6- and 5:6-ring junctions [double (1.2) and single (1.6) bonds, respectively], giving corresponding coupling constants for adjacent addends of ca. 14.5 and 12.0 Hz respectively, the differences being attributable to the different 1.2- and 1.6-bond lengths. The 13C NMR spectrum of C60(CF3)2 shows the CF3 groups are in either a 1.4- or 1.6-relationship; the UV-vis band appears at 442 nm. Other unsymmetrical tetra-adducts are comprised of isolated pairs of CF3 groups. The exceptionally large number of derivatives and isomers, (much greater than in any other fullerene reaction), no dominant product, and unusual addition pattern indicates that thermodynamic stability is not of primary importance in governing product formation. EI mass spectrometry of trifluoromethylfullerenes is characterised by loss of CF3 groups, the more highly addended compounds also showing fragmentation by CF2 loss, attributable to steric compression. The CF3 group shows strong IR bands at ca. 1260 and 1190 cm-1. The compounds are stable to aq. acetone, which contrasts to the behaviour of fluorofullerenes. Trifluoromethylation by the Scherer radical (C9F19.) gave addition of up to eight CF3 groups, together with hydrogen in some products. During EI mass spectrometry of some of these, loss of HF attributable to CF3 and H adjacency can occur, giving CF2-containing derivatives.     

Isolation and characterisation of both the first fluoroxyfluorofullerene C60F17OF and oxahomofluorofullerenol C60F17O.OH

The first fluoroxyfluorofullerene C₆₀F₁₇OF (A) has been isolated from the fluorination of [60]fullerene with a mixture of MnF₃ and K₂NiF₆ at 480 °C. This compound has a shorter HPLC retention time than the isomeric fluorofullerene ethers (oxahomofullerenes) and is less stable towards EI mass spectrometry. It fragments by losing OF as a single entity and shows no formation of C₆₀O as a fragment ion. By contrast, the ethers fragment by first losing a number of F atoms and then CO, and ultimately show also the presence of C₆₀O, whilst epoxides lose CO as a main fragmentation step and do not give C₆₀O. The first oxahomofluorofullerenol C₆₀F₁₇O.OH (B) has been isolated from the UV-irradiation of a toluene solution of C₆₀F₁₈ in air during 65 h and readily eliminates HF due to adjacent F and OH groups during EI mass spectrometry. The structures of both the compounds have been deduced from 1D and 2D NMR spectroscopy. Just as oxygen inserts into FCCF bonds of C₆₀F₁₈ to give ethers, so insertion into a CF bond gives A. The oxahomofluorofullerenol B is produced by S_N2′ substitution of F by OH, followed by oxygen insertion into a 6:5-bond (αβ to the OH group) giving a motif not seen previously in fluorofullerenes.