Ozone measurement in visible region: an optical fibre sensor system

Ozone measurement based on the optical absorption of visible light at 603 nm using polymer optical fibres is investigated and tested. Comparisons with a commercial UV based sensor demonstrate the ability of the visible based sensor to measure high concentrations over a range 27-127 mg/litre. A resolution of 5 mg/litre is also demonstrated for this sensor.     

6-Hydroxyalkylamino-6-deoxy-cyclodextrins: Towards dendrimeric host-molecules

6-Perhydroxyalkylamino-6-perdeoxy--cyclodextrins have been synthesised by treating 6-perbromo-6-perdeoxy-cyclodextrins with hydroxyalkylamines. The products (1, 2) are precursors of dendrimeric cyclodextrins in which the cavity provides access for the guest to interact with the branches. A fluorescence study has demonstrated the effects of the branches on binding of anilinonaphthalene sulfonate probes. The hosts show selectivity towards guests, and pH-dependence of binding, consistent with polar interaction between guest sulfonate anions and the protonated amino groups of the dendrimeric structure.     

A novel sorbent for the determination of clenbuterol in bovine liver.

The use of three C18 sorbents in matrix solid phase dispersion (MSPD) for the determination of clenbuterol in bovine liver fortified at 5 ng g-1 is described. MSPD grade C18 sorbents give rise to more efficient blending and packing of the material for subsequent washing and analyte elution in comparison with a non-MSPD grade C18 sorbent. Following enzymatic deconjugation of the liver extracts, radioimmunoassay is used as the method of determination. The mean recovery of clenbuterol with all sorbents is comparable and within the range 86-96% in two intra-assay studies (n = 3). The liver extracts in each case are highly coloured. The variation in recovery is observed to be lowest with MSPD grade C18 (end-capped). This sorbent was used in further studies to evaluate the use of solid phase extraction (SPE), post MSPD, with normal phase aminopropyl or mixed mode cation exchange columns for extract purification. The mean recovery of clenbuterol (n = 4, inter-assay study) following MSPD and normal phase SPE clean-up was 95 +/- 15% and 89 +/- 9% at fortification levels of 1 and 2.5 ng g-1, respectively.     

Supercritical fluid extraction (SFE) as a multi-residue extraction procedure for beta-agonists in bovine liver tissue

A supercritical fluid extraction procedure has been developed for the extraction of beta-agonists in bovine liver samples. The method is suitable for compounds of different beta-agonist classes: the substituted aniline-type compounds (e.g. clenbuterol) and the phenolic-type compounds (e.g. salbutamol), including conjugated forms of the latter. The developed procedure involves a combination of supercritical fluid extraction with enzyme immunoassay for the determination of clenbuterol and salbutamol residues at the low ppb level. Addition of methanol modifier and removal of sample moisture are necessary for the extraction of more polar analytes such as salbutamol. Method validation incorporating intra- and inter-assays was carried out on fortified liver tissue and showed good recovery and low variation (RSD < 15%). An enzyme hydrolysis procedure was incorporated into the method for the deconjugation of conjugated residues. The developed procedure was shown to be successful for the determination of both clenbuterol and salbutamol in incurred liver tissue.     

Circular polarization of ion fluorescence completing the analysis of resonant Xe* 4d(-1)(5/2)6p Auger decay

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.e., branching ratios and relative phases of the Auger decay amplitudes.     

Cross section for the H+H2O abstraction reaction: experiment and theory

The absolute value of the cross section for the abstraction reaction between fast H atoms and H2O has been determined experimentally at a mean collision energy of 2.46 eV. The OH population distribution at the same mean energy has also been determined. The new measurements are compared with state-of-the-art quantum mechanical and quasiclassical scattering calculations on the most recently developed potential energy surface.