The GC-MS detection and characterization of neopine resulting from opium use and codeine metabolism and its potential as an opiate-product-use marker

Neopine, a minor opium alkaloid and an isomer of codeine (also known as -codeine), has been detected in both the urine of opium users and pharmaceutical codeine users. The characterization of neopine was achieved by comparison of the mass spectra and GC retention times of the trimethylsilyl derivative. The presence of neopine in the urine of pharmaceutical codeine users was attributed to the metabolism of codeine through a double bond migration in ring C, from the 7–8 to the 8–14 position. The potential use of the alkaloid as a confirmation marker of opium and/or pharmaceutical codeine use and the ability to differentiate these from heroin use has been discussed.     

Electron impact ionization in helium nanodroplets: controlling fragmentation by active cooling of molecular ions

Reported here is a study of the effects of liquid helium cooling on the fragmentation of ions formed by electron impact mass ionization. The molecules of interest are picked up by the helium nanodroplets as they pass through a low pressure oven. Electron impact ionization of a helium atom in the droplet is followed by resonant charge transfer to neighboring helium atoms. When the charge is transferred to the target molecule, the difference in the ionization potentials between helium and the molecule results in the formation of a vibrationally hot ion. In isolation, the hot parent ion would undergo subsequent fragmentation. On the other hand, if the cooling due to the helium is fast enough, the parent ion will be actively cooled before fragmentation occurs. The target molecule used in the present study is triphenylmethanol (TPM), an important species in synthetic chemistry, used to sterically protect hydroxyl groups. Threshold PhotoElectron PhotoIon COincidence (TPEPICO) experiments are also reported for gas-phase TPM to help quantify the ion energetics resulting from the cooling effects of the helium droplets.     

The design and synthesis of a family of multimolecular host-guest inclusion complexes

The discovery thatexo-2,exo-6-dihydroxy-2,6-dimethylbicyclo [3.3.1]nonane (2) forms novel multimolecular canal-type inclusion complexes has led to a systematic study of related molecular structures. This synthetic programme has shown that diol (2) is the prototype of a family of host diols all with the same crystallographic space groupP3₁21, but with distinctly different canal shapes and dimensions. The structures of the first four members of this new family of hosts are described and contrasted.     

The use of symmetry in direct Møller-Plesset second-order calculations

Summary An algorithm for utilising abelian point group symmetry in direct MP2 energy calculations is presented. This is based upon the direct MP2 method of Head-Gordon, Pople and Frisch. The method uses the petite atomic orbital integral list as in conventional transformations coupled with a symmetry adaption of the three quarter transformed integrals. Representative calculations for ethylene and benzene are presented which demonstrate the potential of the method.     

Development of microspot multi-analyte ratiometric immunoassay using dual fluorescent-labelled antibodies

Radioisotopes are progressively being replaced by non-isotopic labels as reagent markers for immunoassay purposes. The reasons for this development include an avoidance of the practical and environmental disadvantages associated with the use of radioisotopes and the need for higher assay sensitivity. A further stimulus is the increasing requirement to measure multiple analytes simultaneously in the same sample. This paper outlines the general principles underlying multi-analyte “microspot” immunoassay methodology. It relies on the measurement of the ratio of fluorescent signals from individual antibody “microspots” forming a microspot array on a suitable plastic surface. In principle, the methodology is capable of measuring 10⁶ different substances in a sample volume of 100 μl.     

Structural and electronic evolution of the As(OH)3 molecule in high temperature aqueous solutions: an x-ray absorption investigation

The geometrical and electronic structure of the arsenious acid molecule As(OH)(3) in aqueous solutions has been investigated by x-ray absorption spectroscopy (XAS) within extended x-ray absorption spectroscopy (EXAFS) and x-ray absorption near edge structure (XANES), using realistic first-principle calculations in the latter case. This investigation was performed on aqueous solutions of arsenious acid from ambient to supercritical conditions (P = 250 and 600 bars, T 相似文献   

High-performance liquid chromatographic analysis of secoisolariciresinol diglucoside and hydroxycinnamic acid glucosides in flaxseed by alkaline extraction

A HPLC method was developed for the analysis of secoisolariciresinol diglucoside (SDG) and hydroxycinnamic acid glucosides in milled defatted flaxseed flour. Direct extraction by 1 M NaOH for 1 h at 20 degrees C resulted in a higher yield than that obtained by hydrolysis of alcoholic extracts. An internal standard, o-coumaric acid, was used and the method was found to be easy, fast, and with good repeatability. On dry matter basis, different samples of flaxseeds varied considerably in their content of (+)-SDG (11.9-25.9 mg/g), (-)-SDG (2.2-5.0 mg/g), p-coumaric acid glucoside (1.2-8.5 mg/g), and ferulic acid glucoside (1.6-5.0 mg/g).     

Homolytic reactions of polyfluoroaromatic compounds. Part XII. Aryldehydrogenation and aryldefluorination in polyfluorobenzenes

The thermal decomposition of benzoyl peroxide in a range of polyfluorobenzenes at 80° gives biaryls arising from both the displacement of fluorine and hydrogen. Phenyldefluorination predominated only in the attack of 1,2,3,4-tetrafluorobenzene and of pentafluorobenzene, but was evident even in the attack of $\text{o}$-difluorobenzene. The relative rates of displacement, as shown by the isomer distributions, were generally well reflected by the application of partial rate factors found in the phenylation of fluorobenzene; however, phenyldefluorination was not so easily amenable to this treatment, a possible consequence of complex formation between radical precursor and substrate.     

Wavelength dependence of HCO formation in the photolysis of acetaldehyde

The wavelength dependence of HCO(0,0,0) formation in the photodissociation of acetaldehyde was measured using narrow (0.1 nm) bandwidth laser excitation and time-resolved intracavity laser detection (TRILD). A sharp energetic onset at 320 ± 1 nm (89.3 ± 0.3 kcal) for HCO(0,0,0) formation was found. The maximum concentration of HCO(0,0,0) occurs between 100 and 250 μs after excitation depending on the wavelength of excitation