Electrochemical Oxidation of Nortriptyline and Its Voltammetric Sensing at a Carbon Ionic Liquid Electrode

The electrochemical oxidation of nortriptyline at a carbon ionic liquid electrode (CILE) was investigated. Nortriptyline is electrochemically inactive on conventional electrodes but CILE exhibited excellent electrocatalytic activity toward oxidation of nortriptyline with the well-defined anodic peak at 860 mV. This characteristic was attributed to the outstanding conductivity and electrocatalytic effect of the ionic liquid, 1-octylpyridinum hexaflourophosphate, used as a binder in the construction of the electrode. The influence of experimental parameters such as pH and sweep rate was also studied. The quantitative determination of nortriptyline was performed using differential pulse voltammetry technique. Under selected conditions the anodic peak current was linear to nortriptyline concentration in the ranges of 4.8 × 10^–6 to 2.4 × 10^–5 M and 2.4 × 10^–5 to 6.4 × 10^–5 M, with correlation coefficients of 0.9992 and 09949, respectively. The detection limit was 3 × 10^–7 M.     

Efficient highly diastereoselective synthesis of 1,8a-dihydro-7H-imidazo[2,1-b][1,3]oxazines

1-Alkyl imidazoles react smoothly with dialkyl acetylenedicarboxylates in the presence of pyridine carboxaldehydes to diastereoselectively produce 1,8a-dihydro-7H-imidazo[2,1-b][1,3]oxazine derivatives in excellent yields.     

A novel, one-pot and three-component synthesis of α-quinoxalinyl triphenylphosphoranes

The reactive 1:1 zwitterionic intermediate formed by the addition of triphenylphosphine to diaroylacetylenes was trapped with 1,2-benzenediamines to produce triphenylphosphorane intermediates. Intramolecular cyclization and subsequent oxidation of the intermediate afforded functionalized α-quinoxalinyl triphenylphosphoranes in good to excellent yields.     

Simple Synthesis of Stable Phosphorus Ylides Derived from Imidazolidine-2-Thione. Efficient One-Pot Synthesis of α-Amino Esters with β-Phosphorus Substituents

Crystalline phosphorus ylides are obtained in nearly quantitative yields from the addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylates, and imidazolidine-2-thione. A dynamic NMR effect is observed in the ¹ H NMR spectrum of the stabilized ylide obtained from dimethyl acetylenedicarboxylate (Δ G ^≠ = 66.6 kJmol^?1 ) and is attributed to restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.     

Combinatorial Algorithms for Some Variants of Inverse Obnoxious Median Location Problem on Tree Networks

This paper concerns with some variants of the inverse obnoxious median location problem on tree networks, where the aim is either to augment or to reduce the edge lengths at the minimum total cost such that a prespecified subset of vertices becomes an obnoxious multi-facility median location with respect to the perturbed edge lengths. For both augmentation and reduction models, under the rectilinear norm and the sum-type Hamming distance, we develop novel combinatorial algorithms with polynomial time complexities. Particularly, if the underlying tree is an extended star graph, then the problems can be solved in linear time.     

A sol-gel-based amino functionalized fiber for immersed solid-phase microextraction of organophosphorus pesticides from environmental samples

A method based on immersed solid-phase microextraction (SPME) and gas chromatography mass spectrometry detection (GC-MS) for the determination of organophosphorous pesticides (OPPs) in aqueous samples was developed. A sol-gel based coating fiber was prepared using 3-(trimethoxysilylpropyl) amine as precursor. The synthesized fiber was prepared in a way to impart polar moiety into the coating network and would be more suitable for extracting polar and semi-polar organic pollutants. Important parameters influencing the extraction process were optimized and an extraction time of 40 min at 30 °C gave maximum peak area, when NaCl (20% w/v) was added to the aqueous sample. The linearity for disulfoton, phorate and sulfotep was in the concentration range of 0.01 to 5 ng mL^− 1 and for parathion and O,O,O-triethylthiphosphate was in the range of 0.01 to 50 ng mL^− 1. Limits of detection ranged from 1 ng L^− 1, for parathion, to 0.05 ng L^− 1, for disulfoton using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values were all below 10.5% at the 1 ng mL^− 1 level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 80 to 115%.     

Novel thin film nanocomposite membranes incorporated with polyoxovanadate nanocluster for high water flux and antibacterial properties

Using interfacial polymerization (IP) of m-phenylenediamine aqueous solution containing polyoxovanadate nanoclusters (POV) and trimesoyl chloride (TMC) in organic solution, we fabricated a novel polyamide (PA)- polyoxovanadate nanocluster (POV) nanocomposite membranes (PA-POV TFN). The chemical structures and morphologies of the synthesized membranes were characterized by Fourier transform infrared (FTIR) spectroscopy, atomic force microscope (AFM), scanning electron microscopy (SEM) and water contact angle measurements. Experimental results showed that the performances of PA-POV TFN membranes are remarkably dependent on POV incorporation in the membranes, which could be controlled by using different amounts of POV particles. Moreover, the PA-POV TFN membranes illustrated outstanding antibacterial properties against Gram-negative E. coli. On the other hand, the incorporation of various amounts of POV in the membranes improved the membrane separation performances (water flux and salt rejection) as well as the antibacterial activity in FO process as compared to the original thin-film composite (TFC) polyamide membrane.     

New Grafted Nanosilica-Based Sorbent for Needle Trap Extraction of Polycyclic Aromatic Hydrocarbons from Water Samples Followed by GC/MS

In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes from aqueous samples, the prepared needle trap device (NTD) was placed in the headspace of the sample and another needle was also inserted into the sample solution to purge the circulating headspace into the sample. For increasing the extraction efficiency, influencing parameters including extraction time and temperature, flow rate of analyte through the needle trap, the ionic strength, desorption temperature, and time were optimized. The limit of detection (LOD) and relative standard deviation (RSD) values of the method under optimized conditions were 2?C5 ng L^?1 and 1.1?C4.8%, respectively. The RSD% for fluorene was somewhat higher and a value of 16.8% at 40 ng L^?1 was achieved. Finally the developed method was applied to the analysis of tap water and Zayandeh-roud river samples and the relative recovery (RR %) values were found to be in the range of 77?C109%, under the optimized conditions.     

Electrocatalytic Oxidation of Cysteine at a CoSalophen/ n‐(butyl)4SiW12O40 Carbon Paste Electrode

In the present study, a novel mixture consisting of N,N′‐bis(salicylidene)‐1,2‐phenylenediamino cobalt (CoSalophen, CoSal) complex and (n‐butyl)₄SiW₁₂O₄₀ (SiW₁₂), have been used to chemically modify a carbon paste electrode (CPE) for sensitive determination of cysteine (CySH). The electrocatalytic effect of the newly developed modified CPE towards oxidation of CySH was evaluated by comparing cyclic and differential pulse voltammograms in the presence of cysteine at bare, CoSal, SiW₁₂ and CoSal/SiW₁₂ modified CPE. The differential pulse voltammetry method was applied as a sensitive method for quantitative detection of CySH trace amounts, the experimental conditions being optimized in order to evaluate the best analytical parameters of the sensor. Reproducibility and stability studies were also performed and the sensor was applied for the determination of CySH in a pharmaceutical sample and in human blood serum and urine samples.