Application of Crown Ether to Chemical Analysis. III. Extraction of Amines with Crown Ether

Abstract

The protonated amines were extracted with crown ether as the picrate into organic solvent. The overall extraction constants(Kex) for the 1 : 1 : 1 complexes, AHLP, of 18-crown-6 with protonated amines and picrate between 1,2-dichloroethane and water have been determined at 25°C. The extractability of complexes decreased in the sequence: primary amines > secondary amines, which indicated that the type of amine was a most important factor. The log Kex values were determined to be 6.6, 7.6, 7.9, 8.3, 9.6, 2.5 and 3.8 for tert-butylamine, ethylamine, n-butylamine, sec-butylamine, n-hexylamine, diethylamine and di-n-propylamine respectively.     

OBSERVATIONS ON INFEASIBILITY DETECTORS FOR CLASSIFYING CONIC CONVEX PROGRAMS

Abstract

New insights are presented from a convex duality classification theory of over 25 years ago for recent computational complexity results developed for recognizing some of the asymptotic duality states that prevail for an arbitrary convex programming pair.     

Syntheses,structures, and properties of Ni(II) complexes with 5,5′-bis(4-halogenphenyl)diazo-dipyrromethane

Ni(II) complexes with 5,5′-bis(4-halogenphenyl)diazo-dipyrromethane have been synthesized and characterized by X-ray crystallography. All the complexes have similar crystal structures in which Ni(II) is square-planar by coordinating to two pyrrole and two azo nitrogen atoms. The azo-pyrroles of the ligands can be converted to the hydrazone tautomer after complexing nickel. Moreover, the C–H?···?Ni interaction played an important role in directing self-assembly of the complexes. The UV-Vis spectra of the complexes showed great difference with the metal complexes of pyrrol-2-imine.     

Indications of bulk property changes from surface ion implantation

In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures.     

HOW TO USE MAJOR PARTS OF A PAPER PREVIOUSLY PUBLISHED BY OTHERS TO WRITE A NEW ONE. AN ALLEGATION OF PLAGIARISM BY INDIAN AUTHORS

ABSTRACT

In our present communication we prove the allegation that Indian authors plagarized the major parts and conclusions of our paper published in 1997 and used them in their paper published in this journal in 2000.     

Spectrophotometric Study of Catechol Oxidation by Aerial O2 in Alkaline Aqueous Solutions Containing Mg(II) Ions.

Electronic absorption spectroscopy was employed to study the aerial oxidation of catechol (1,2-benzenediol) in alkaline aqueous solution containing an excess of Mg(II) ions. Graphical analysis by the matrix method of UV spectra recorded at regular time intervals gave a good fit for two absorbing species in solution. Based on this result and our earlier ESR spectroscopic investigations we concluded that two main absorbing species in this system are Mg(II)-spin stabilized o-benzosemiquinone anion radical and C-C dimer formed by the nucleophilic attack of catecholate anion on o-benzoquinone. Although the formation of 1,2,4-benzenetriol during the catechol oxidation has been detected in some ESR studies its presence was not indicated by this analysis probably because of the low and/or stable steady state concentration throughout the experiment.     

Simultaneous Derivative Spectrophotometric Quantification of Diethylamine Salicylate and Methyl Nicotinate in Ointments

A direct derivative, D1 i.e. dA/dλ, spectrophotometric procedure for simultaneous determination of diethylamine salicylate and methyl nicotinate in their binary mixtures and in ointments has been investigated. Good percent mean recoveries, 99.68 ± 0.58 & 99.71 ± 0.27 and 100.85 ± 0.21, could be obtained for diethylamine salicylate at 303 nm & 236 nm and methyl nicotinate at 224 nm, in order, added to ointment. The band overlapping in the first order due to the coexisting parabens, main additive, and the water-washable ointment base occurs sufficient away from those wavelengths chosen for the direct D1-measurement of both drug substances.     

Efficient and Green Method for the Synthesis of 1,5‐Benzodiazepine and Quinoxaline Derivatives in Water

Various 1,5‐benzodiazepine and quinoxaline derivatives have been synthesized in water with excellent yields using a catalytic amount of indium chloride at room temperature. This synthetic protocol is nontoxic, safe, and environmentally benign.     

Spectrophotometry Determination Of Boron With 4-(P-Sulfophenylazo)-1, 8-Dihydroxynaphthalene

Abstract

4-(p-Sulfophenylazo)-l, 8-dihydroxynaphthalene (SPADN) was synthesized to study as a new reagent for the spectro-photometric determination of boron, measuring its absorbance on addition of boron present as boric acid at pH 8.6. The procedure involved mixing aliquots of the sample, ammonium buffer, EDTA and SPADN solutions. Various exchange equilibrium constants in the ion-association extraction systems of SPADN with zephiramine were also determined.     

A thionine-based reversible redox sensor in a sequential injection system

According to the current demands of Green Analytical Chemistry and regarding the need for lower reagent consumption with improved analytical performance, an automatic methodology with a flow-through optosensor incorporating solid-phase spectrophotometric detection was developed. The sensor used in this work was based on the redox state of thionine whose oxidized form is blue and reduced form is colorless with monitoring carried out at 621 nm. This redox indicator was immobilized on gel beads and subsequently packed into a flow-through cell. It was then assembled into a sequential injection system and was shown to be an excellent alternative to monitor enzymatic redox reactions automatically as the redox catalysis is performed by glucose dehydrogenase. This enzyme is a representative dehydrogenase enzyme and uses NAD⁺ as cofactor, promoting the oxidation of glucose to glucono-lactone and reduction of NAD⁺ to NADH. The produced NADH promotes color depletion on the surface of the sensor. The calibration graph for glucose was linear between 5.74 × 10⁻⁴ and 2.00 × 10⁻³ mol L⁻¹ and detection limit was 1.72 × 10⁻⁴ mol L⁻¹. Glucose concentration in different samples including sera, salines, perfusion solutions, powder for preparing oral solutions and solutions for hemodialysis was determined. The method proved to be reproducible with a RSD < 5% for glucose determinations.