Comparative gas chromatographic analysis of narcotics. II. Amphetamine sulphate.

Trace impurities in amphetamine sulphate were studied by a highly sensitive gas chromatographic method. The concentration of these impurities varied considerably between batches whereas the variations within the batches were usually very small. The method is used for the assignment of seizures of amphetamine sulphate to common sources, which in turn may permit chains of illicit distribution of this drug to be traced.     

Less common applications of monoliths. III. Gas chromatography

Porous polymer monoliths emerged about two decades ago. Despite this short time, they are finding applications in a variety of fields. In addition to the most common and certainly best known use of this new category of porous media as stationary phases in liquid chromatography, monolithic materials also found their applications in other areas. This review article focuses on monoliths in capillaries designed for separations in gas chromatography.     

Berberis alkaloids. XXIII. Structure of turcberine

Berberine, magnoflorine, palmatine, columbamine, jatrorhizine, epiberberine, berbamine, O-methylisothalicberine, armepavine, corypalline, glaucine, and corydine and the new alkaloid turcberine have been isolated fromBerberis turcomanica Kar., and the structure of turcberine has been established. Apart from berberine, this is the first time that any of these alkaloids have been isolated from this species of barberry, while this is the first time that corydine and armepavine have been isolated from the genusBerberis.Institute of Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences. Tashkent. Andizhan State Medical Institute. Translated from Khimiya Prirodnykh Soedeninii, No. 1, pp. 77–81, January–February, 1993.     

Le Groupe de Recherche du C.R.N.S. Application des Reactions Nucleaires a l'Analyse Chimique G.A.R.N.A.C.

In this article the research topics dealt with at Research Group for Applications of Nuclear Reactions to Chemical Analysis (GARNAC) are described. Particular emphasis is laid on the main contribution of the GARNAC to the development and the evolution of charged particle activation analysis, evolving with the analytical studies performed and with the scientific and technical progress realized in material and semiconductors science.      

Halogenation of polyethylene. I. Bromination of single crystals

It has been demonstrated that the fold surfaces of polymers can be specific towards chemical attack, if the reaction is mild and nondestructive of the fold. Bromination of suspensions of single crystals of polyethylene in carbon tetrachloride has been shown to be such a system. This chemical modification of a fold surface is a powerful means of extending the applications of the physical methods available. Several methods were used, among them DTA, DSC, infrared spectroscopy and small-angle x-ray diffraction. Experimental results from these methods lead to the following conclusions. (a) Bromination takes place preferentially at the folds and is consistent with a regular adjacent reentry fold model. (b) Annealing of these brominated crystals demonstrates the major role played by the crystal surface in this process. (c) The preparation and properties of a novel copolymer system has been demonstrated. It is felt that this copolymer system may prove a useful addition to those systems presently available.     

E.S.R. and D.S.C. investigations of phase transitions in polymorphic 4-n-alkoxybenzylidene-4′-n-alkylanilines

Abstract

It is shown that the McMillan parameter M = T _SAN/T _N1 (where T _SAN and T _NI are respectively the temperatures of the smectic A to nematic (SAN) and the nematic to isotropic (NI) phase transitions) is useful in analysing the crossover between second and first order behaviour of the S_NN transition in the nO.m homologous liquid crystal series (the 4-n-alkoxybenzylidene-4′-n-alkylanilines). Using a phase diagram of orientational ordering versus M for this series, as obtained in this work (from E.S.R. and D.S.C), a symmetric tricritical point with mean field exponent β₂ = 1 is demonstrated. In a preliminary study of E.S.R. linewidth parameters B and C of nitroxide spin probes dissolved in members of the nO.m series exhibiting a first order S_AN transition, critical-type divergences are observed near this transition. In the case where M is closer to 0.959 (the value at the tricritical point), these divergences appear similar to those previously observed in related nO.m members with a second order S_AN transition; however, they are considerably enhanced for an M value closer to unity (i.e. more removed from the tricritical point). This indicates the importance of coupling between orientational and positional order parameters in the observed critical-type divergences.     

Heterocyclic compounds. X. A new synthesis of thiadiazasteroids

The reaction of ν-ketoacids or ν-aldehydo acids with o-amino amides results in the formation of 4-quinazolones. Using this reaction a number of polyheterosteroid analogs were synthesized. Thus, when 2-amino-3-carboxamido-4,5,6,7-tetrahydrobenzothiophene (9) was refluxed with levulinic acid (10) in a high boiling solvent, thiadiazasteroid analog (11) was obtained in 78% yield. It was found that this facile one-step reaction could be used to synthesize a variety of tetra and pentacyclic compounds. Nmr spectroscopy was used to assign stereochemistry to the 17-methyl “steroids” (31) and (32).     

Comparative gas chromatographic analysis of narcotics. III. Phenmetrazine hydrochloride.

Chemical signatures of phenmetrazine hydrochloride were studied by gas chromatography. The inter-batch variations of the signatures were found to be large whereas the intra-batch variations were usually small. The method is used for the tracing of seized phenmetrazine hydrochloride samples to common sources, which in turn may permit further tracing back to chains of illicit distribution of this drug. The applicability of the method to other narcotics is also discussed.     

Carbohydrates of allium IX. Polysaccharides of A. suvorovii

The carbohydrate compositions of all the organs ofAllium suvorovii Rgl have been determined and it has been established that the bulk of the fructose accumulates in its bulbs. The dynamics of the accumulation of glucofructans in the bulbs has been studied and it has been found that this accumulation is a maximum in the dormancy stage.     

Education in analytical chemistry in the U.S.S.R.

Analytical Chemistry is taught at over 600 schools of higher education in the U.S.S.R. Contents of general and special courses are described in this article. The main problems and objectives of education at universities are mentioned.     

The origin of aromatic solvent-induced shifts in 19F n.m.r.

Aromatic solvent-induced shifts (ASIS) in ¹⁹F n.m.r. spectra of several organic fluoro compounds have been determined in several solvents. ¹⁹F n.m.r. signals of unsaturated fluoro compounds in C₆F₆ and C₆H₆ show excess high field shifts corresponding to the term σ_c (solvent shift caused by chemical interactions). The mechanism of this shift is discussed in connection with the presence of an F-π interaction. A thermal study also supports this idea.     

Pneumatochemical impedance spectroscopy. 1. Principles

Pneumatochemical impedance spectroscopy (PIS) is the indirect transposition of electrochemical impedance spectroscopy (EIS) to solid-gas reactions. In PIS analysis, an analogy is made between pressure and electrical potential on one hand and gas flow and electric current on the other hand, and pneumatochemical transfer functions are derived from gas-phase measurements. Potentially, this spectroscopy can be used to analyze the dynamics of any solid-gas system including adsorption (surface) and absorption (bulk) phenomena, gas (H2) permeation across metallic membranes, and electrocatalysis in gaseous fuel cells. Hydrogen absorption by intermetallic compounds (IMCs), a process of great practical interest for hydrogen storage applications, is more specifically considered in this paper, and the kinetic equations derived in this work pertain only to this case. Whereas classical electrochemical impedance measurements are performed using an harmonic analyzer and monochromatic potential (potentiostatic mode) or current (intentiostatic mode) perturbations, PIS investigation of the dynamics of IMC-H2(g) systems is more conveniently performed using Sievert's-type gas distribution apparatus (SGDA) and polychromatic pressure perturbation signals. This is first because monochromatic isothermal pressure modulations cannot be easily obtained experimentally over the frequency domain of interest and, second, because most IMC-H2(g) systems exhibit strongly nonlinear behaviors in two-phase domains (hysteresis), and this proscribes harmonic analysis. A further benefit of using SGDA and nonharmonic perturbations is that kinetic and thermodynamic information are collected simultaneously during the same experiment. The measurement and modeling of the pneumatochemical transfer functions associated with IMC-H2(g) systems, both in solid solution and two-phase domains, are discussed in this paper which is organized in two parts. The principles of PIS analysis, based on the theory of linear and time-invariant systems, are presented in the first part. The dynamics of hydrogen sorption by metals and IMCs is analyzed in the second part, where a detailed analysis of the multistep reaction paths involved in sorption mechanisms is proposed.     

Crystal structures of synthetic analgetics. IV. Dextropropoxyphene.

The molecular and cystal structure of dextropropoxyphene has been determined by X-ray methods. The crystals are monoclinic, space group P21, with unit cell dimensions a=9.257(2) A; b=9.048(3) A; c=12.074(7) A; beta=93.01(4)degrees. The phase problem was solved by direct methods and the model refined to an R-value of 0.038 for 1799 observed reflections. E.s.d's are, in average, 0.004 A and O.3 degrees in interatomic distances and angles, respectively. The propylamine chain in nearly fully extended, the dihedral angel C4-C5-C7-N being -174.2 degrees. The conformation of this side chain is similar to that in the hydrochloride of the title compound. Thus the proposed bioactive conformation is not preferred by propoxyphene in the crystalline state, as was the case for the free base of methadone.     

Polymer deformation. XI. Biaxial deformation of polyethylene single crystals

Uniaxial deformation of polyethylene single crystals has been reported in the previous papers of this series. This paper presents an extension of this study to the simultaneous biaxial deformation of polyethylene single crystals. Diamond-shaped crystals containing {110} fold domains and truncated crystals containing in addition {100} domains were used in these experiments. The results show that these crystals fail at deformations as low as 6%, giving rise to cracks predominantly in the a direction. Electron diffraction patterns suggest that {310} twinning is more favorable than {110} twinning at the lower degrees of deformation. No phase change from orthorhombic to monoclinic unit cell is observed.     

Determination of the vibration amplitude of thickness shear modes using white beam stroboscopic topography at E.S.R.F.

A new topographic method allows a direct mapping of the amplitude of the vibration modes of piezoelectric devices. With this method it is possible to measure the amplitude of the vibration of a thickness shear mode at each point of an AT cut quartz resonator. The principle of this method is based on the use of stroboscopic section topography obtained from the white beam delivered by a third generation synchrotron soure at ESRF.     

Midgap levels of photoexcited conductive polymers. II. Detailed analysis of trans-polyacetylene

We have studied in more detail aspects of the soliton-antisoliton pair in a trans-polyacetylene chain based on our previous study of the midgap levels associated with the photogenerated oppositely charged soliton-antisoliton pair in conductive polymers employing the concept of the molecular orbital interaction (Part I of this study, this issue). The intersoliton distance has been estimated to be about 10 Å from the Pariser–Parr–Pople method. We have found that the energy gap between the midgap levels is estimated to be 0.45 eV, being significantly related to an additional photoinduced absorption.     

The Discovery of Thin-Layer Chromatography by N.A. Izmailov and M.S. Shraiber

JPC – Journal of Planar Chromatography – Modern TLC - The discovery of thin-layer chromatography by N.A. Izmailov and M.S. Shraiber, and their contribution to the development of this...     

Microbial degradation of polymer solids. I. Cellophane

Specimens of regenerated cellulose films (cellophane) have been inoculated with cellulolytic fungi and the resulting degradation monitored through change in physical properties. Investigation of structure–property relationship in cellophane have revealed that surface microfibrils are highly oriented parallel to the manufacturing machine direction, while those in the film interior exist in a somewhat disordered array. Cellulase enzymes have been observed to diffuse appreciable distances from their point of application and to attack disordered regions more readily than the crystallites. Damage to surface microfibrils appears to involve their being cleaved into short segments. The fungus studied in this work forms a network of hyphae that covers much of the specimen surface soon after growth starts; hyphae penetrate into the film and proceed to remove its core more rapidly than surface layers. Tensile strength declines progressively as this degradation occurs, but vapor barrier properties remain essentially unchanged over the period of these studies. The suggests that intrusion of hyphae, in combination with enzymatic digestion of cellulose, rapidly lowers load-bearing characteristics, but moisture permeation rates stay nearly constant owing to the presence of fungal material at sites where cellulose has been removed.     

Monoterpenic and norisoprenoidic glycoconjugates of Vitis vinifera L. cv. Melon B. as precursors of odorants in Muscadet wines.

The volatile monoterpenic and norisoprenoidic compounds released by glycosidase enzyme hydrolysis of C18 reversed-phase isolates from the juice of Vitis vinifera L. cv. Melon B. have been qualitatively and quantitatively determined using GC-MS and GC-FID. The components analyzed were broadly similar to those previously reported for other varieties but the level of bound p-menth-1-en-7,8-diol was higher in this cultivar. Then the monoterpenic and norisoprenoidic volatiles released from the same glycosidic extracts under mild acid conditions, mimicking wine aging conditions, have been analyzed using GC-Olfactometry and GC-MS. The most odorous compounds detected were p-cymene, terpinen-4-ol, cis- and trans-vitispiranes, 1,6,6-trimethyl-1,2-dihydronaphtalene (TDN), beta-damascenone and riesling acetal. To assess their potential levels in corresponding wines after ageing, most of these odorants were generated by harsh acid hydrolysis from the precursors extracts and quantitatively determined using SPME and GC-MS/MS. For the development and application of this analysis, the odorants not commercialy available were synthesized. The total amounts of norisoprenoidic odorants generated by acid hydrolysis of the glycosidic extracts were shown to be proportional to the total amounts of these precursors.     

Kinetics of partly diffusion controlled reactions. III. Competition between physical and chemical kinetics. Experimental results

In a previous paper (II in this series), we showed that the kinetic parameters of a partly diffusion controlled reaction could be calculated when the p Three examples of fluorescence quenching of electronically excited states were studied: pyrene by biacetyl; sulforhodamine G by I^?; and POPOP by fluorescence and fluorescence polarization measurements. They illustrate the kinetic models derived in papers I and II of this series.