Application of DSC as a tool for honey floral species characterization and adulteration detection

The thermal behaviour of authentic honeys and sugar syrups (industrial and homemade) was investigated by DSC. To confirm the first previous results concerning the effect of adulteration on the thermal behaviour of authentic honeys, 30 honey samples (Robinia, Lavender, Chestnut and Fir) were analyzed by DSC and their T _g were measured following a suited experimental protocol. The results indicated that this parameter was useful to characterize and to distinguish significantly these varieties between them. Applied to honey samples artificially adulterated with different industrial syrups, DSC showed a detection level of 5–10% depending on the type of syrup. An endothermic phenomenon occurring between 40–90°C during the heating was studied by TMDSC and a new thermal transition similar to a glass-transition was highlighted.This revised version was published online in November 2005 with corrections to the Cover Date.     

Direct determination of phosphate esters in concentrated nitrate media by capillary zone electrophoresis

The potential of capillary zone electrophoresis (CZE) for the determination of dibutyl phosphate (DBP) and monobutyl phosphate (MBP), two degradation products of the tributyl phosphate extractant used in the nuclear fuel reprocessing industry, was evaluated. Analysis conditions were optimised, taking particularly into account that many determinations had to be performed in concentrated aqueous nitrate or nitric acid solutions. Separations were therefore carried out using the counter-electroosmotic mode with cathodic detection in a pH 8.3 electrolyte containing a suitably selected chromophore, salicylate, to ensure the indirect UV detection of the analytes. Various aspects of the method, including its sensitivity, working range, repeatability, and rapidity, were examined. Quantification of both phosphate esters was achieved in less than 3 min at concentrations ranging from 2 x 10(-6) to 10(-3) mol l(-1) in samples containing no macro-component. The lower end of this range increased to 5 x 10(-6) mol l(-1) for MBP and 1.5 x 10(-5) mol l(-1) for DBP in samples containing 5 x 10(-2) mol l(-1) of sodium nitrate, thus enabling their determination in solutions containing nitrate or nitric acid at concentrations up to, respectively, 10,000 and 3000 times higher than the target analyte concentration. This simple, fast and reliable method is routinely applicable to aqueous samples with no other preliminary treatment than a proper dilution; analysis was also performed in organic matrices after a prior extraction. The method was validated by an excellent correlation with the standard DBP analysis technique, gas chromatography (GC). In order to develop appropriate chemical treatments to destroy these compounds, the method was applied to the monitoring of DBP and MBP degradation by hydrogen peroxide in 1 mol l(-1) nitric acid solutions.     

Influence of gamma irradiation on hydrophobic room-temperature ionic liquids [BuMeIm]PF6 and [BuMeIm](CF3SO2)2N

Stability of neat hydrophobic Room-Temperature Ionic Liquids (RTIL) [BuMeIm]X, where [BuMeIm]+ is 1-butyl-3-methylimidazolium and X- is PF6-, and (CF3SO2)2N-, was studied under gamma radiolysis (137Cs) in an argon atmosphere and in air. It was found that the density, surface tension, and refraction index of RTILs are unchanged even by an absorbed dose of approximately 600 kGy. Studied RTILs exhibit considerable darkening when subjected to gamma irradiation. The light absorbance of ionic liquids increases linearly with the irradiation dose. Water has no influence on radiolytic darkening. A comparative study of [BuMeIm]X and [Bu4N][Tf2N] leads to the conclusion that the formation of colored products is related to gamma radiolysis of the [BuMeIm]+ cation. The radiolytic darkening kinetics of RTILs is influenced by the anions as follows: Cl- < (CF3SO2)2N- < PF6-. Electrospray ionization mass spectrometry and NMR analysis reveal the presence of nonvolatile radiolysis products at concentrations below 1 mol% for an absorbed dose exceeding 1200 kGy. Initial step of BuMeIm+ cation radiolysis is the loss of the Bu* group, the H* atom from the 2 position on the imidazolium ring, and the H* atom from the butyl chain. Radiolysis of ionic liquid anions yields F* and CF3* from PF6- and [Tf2N]-, respectively. Recombinations of these primary products of radiolysis lead to various polymeric and acidic species.     

Assay of lipids in dog myocardium using capillary gas chromatography and derivatization with boron trifluoride and methanol

The fatty acids of three lipid classes (free fatty acids, triglycerides, and cholesteryl esters) from dog heart were analysed by gas chromatography. Samples of the left ventricle were homogenized and total lipids were extracted. After separation by thin-layer chromatography, the bands of the lipid classes studied were scraped off, transmethylated according to the boron trifluoride-methanol procedure, and the fatty acid methyl esters were extracted and analysed. The problems related to the quantitation of fatty acids were investigated, namely transmethylation procedure, thin-layer chromatography, and gas chromatographic conditions. Fatty acid methyl esters were separated on capillary columns coated in the laboratory with SP 2340 stationary phase. The high performance of the separation ensured the reliability and the precision of the analysis.     

Determination of 6-mercaptopurine and its metabolites in plasma or serum by high performance liquid chromatography

A sensitive and accurate reversed phase liquid chromatographic assay was developed for the determination of 6-mercaptopurine (6MP) (the active metabolite of azathioprine) in human plasma. The assay involved extraction into acetonitrile and dichloromethane from plasma pretreated with 0.038 M of dithiothreitol solution. The residue was analyzed by isocratic chromatography on a C18 analytical column with UV detection at 326 nm. The average extraction recovery of 6MP was 85%. The method has been applied successfully to the determination of 6MP and its metabolites in pharmacokinetic studies.     

X-ray microfocussing combined with microfluidics for on-chip X-ray scattering measurements

This work describes the fabrication of thin microfluidic devices in Kapton (polyimide). These chips are well-suited to perform X-ray scattering experiments using intense microfocussed beams, as Kapton is both relatively resistant to the high intensities generated by a synchrotron, and almost transparent to X-rays. We show networks of microchannels obtained using laser ablation of Kapton films, and we also present a simple way to perform fusion bonding between two Kapton films. The possibilities offered using such devices are illustrated with X-ray scattering experiments. These experiments demonstrate that structural measurements in the 1 A-20 nm range can be obtained with spatial resolutions of a few microns in a microchannel.