Separation of molecular tracers sorbed onto atmospheric particulate matter by flash chromatography

In to order increase sensitivity and to reduce the background induced by matrix effects, a method was developed that uses flash chromatography to separate various compounds present in atmospheric aerosol samples prior to their analysis with different analytical techniques (GC–MS, GC–FID, HPLC). For this purpose, flash chromatography using a 4 g silica gel column crossed by eluent at a flow rate of 20 mL min⁻¹ was used. An eluent with enhanced polarity is needed to separate nonpolar (linear and branched alkanes), semipolar (PAH, nitro-PAH and cholesterol) and polar (methoxyphenols, alkanoic acids, and levoglucosan) compounds. Three combinations of solvents were used: hexane for the nonpolar fraction (F1), toluene/hexane for the semipolar fraction (F2) and dimethylformamide for the polar fraction (F3). The use of different eluents for each fraction allows separation of the sample to be accomplished with good repeatability and satisfying yields [85 ± 5% for F1, 81 ± 8% (PAHs), 89 ± 6% (nitro-PAHs) and 74 ± 7% (cholesterol) for F2 and 79 ± 7% (n-alkanoic acids), 40 ± 11% (methoxyphenols) and 77 ± 6% (levoglucosan) for F3]. The methoxyphenol yields were low due to losses during the concentration/evaporation step. This method was then applied to analyse the organic composition of particles collected at an urban site in Strasbourg (France).     

Contributions to the Experimental Investigation of the Nascent Polymerisation of Ethylene on Supported Catalysts, 2

A series of experiments in a novel quench flow reactor was used to study the influence of the means of adding TEA to the catalyst, the reaction temperature and the hydrogen concentration on the kinetics and morphology of the nascent phase of the polymerisation of ethylene in heptane slurry. It was shown that regardless of the way in which the alkyl was added, an extremely rapid reaction rate was observed for the first few fractions of a second, but that precontacting the catalyst and the TEA cocatalyst led to a slightly higher initial rate. On the other hand, the nascent morphology of the particle/support complex was strongly influenced by the means of adding the alkyl, with precontacting of the two components leading to a better defined product. The influence of the temperature was found to be less significant; however, this was attributed to the particular catalyst.

     

The non-destructive identification of solid over-the-counter medications using single particle aerosol mass spectrometry

Single over-the-counter medication tablets were analyzed in real time using Single Particle Aerosol Mass Spectrometry (SPAMS). Dual-polarity time-of-flight mass spectra were obtained for micrometer-sized single particles dislodged from a single tablet without destroying the shape or markings of each tablet. The solid tablet was placed in a modified-top glass vial and shaken to dislodge and introduce micrometer-sized particles into the SPAMS system. Unique spectra from these particles were obtained in less than 1 s for single tablets of aspirin, ibuprofen, pseudoephedrine, phenylephrine, loratadine, or diphenhydramine. The signals obtained allowed the non-destructive identification of an individual tablet in seconds. SPAMS presents an ideal system for high-throughput analysis of solid drugs.     

Interactions between poloxamers in aqueous solutions: micellization and gelation studied by differential scanning calorimetry, small angle X-ray scattering, and rheology

Poloxamers F88 (EO97PO39EO97) and P85 (EO27PO39EO27) are triblock copolymers of ethylene oxide (EO) and propylene oxide (PO), which have the same hydrophobic PO block. We studied aqueous solutions of these two copolymers by the conjoint use of differential scanning calorimetry (DSC), rheology, and small-angle X-ray scattering (SAXS). The results showed that the temperature-induced micellization of aqueous solutions of F88 and P85 was a progressive process followed by gelation for sufficiently concentrated samples. Gelation was due to the ordered packing of micelles under a hexagonal compact (HC) structure for P85 and a body-centered cubic (BCC) phase for F88. Importantly, the phase diagram of F88/P85 mixtures in water was elucidated and showed the destabilization of the HC phase upon addition of small amounts of F88.     

A new bio-based nanocomposite: fibrillated TEMPO-oxidized celluloses in hydroxypropylcellulose matrix

Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6 °C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at “high” (~5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.     

New electrochemiluminescent biosensors combining polyluminol and an enzymatic matrix

Performant reagentless electrochemiluminescent (ECL) (bio)sensors have been developed using polymeric luminol as the luminophore. The polyluminol film is obtained by cyclic voltammetry (CV) on a screen-printed electrode either in a commonly used H₂SO₄ medium or under more original near-neutral buffered conditions. ECL responses obtained after performing polymerization either at acidic pH or at pH 6 have been compared. It appears that polyluminol formed in near-neutral medium gives the best responses for hydrogen peroxide detection. Polymerization at pH 6 by cyclic voltammetry gives a linear range extending from 8 × 10⁻⁸ to 1.3 × 10⁻⁴ M H₂O₂ concentrations. Based on this performant sensor for hydrogen peroxide detection, an enzymatic biosensor has been developed by associating the polyluminol film with an H₂O₂-producing oxidase. Here, choline oxidase (ChOD) has been chosen as a model enzyme. To develop the biosensor, luminol has been polymerized at pH 6 by CV, and then an enzyme-entrapping matrix has been formed on the above modified working electrode. Different biological (chitosan, agarose, and alginate) and chemical (silica gels, photopolymers, or reticulated matrices) gels have been tested. Best performances have been obtained by associating a ChOD-immobilizing photopolymer with the polyluminol film. In this case, choline can be detected with a linear range extending from 8 × 10⁻⁸ to 1.3 × 10⁻⁴ M. This paper is based on the results presented in a poster that received a Poster Award on the occasion of XIII International Symposium on Luminescence Spectrometry in Bologna, Italy, on September, 7th-11th, 2008.     

Stereoselective preparation of a cyclopentane-based NK1 receptor antagonist bearing an unsymmetrically substituted sec-sec ether

A highly efficient synthesis of the potent and selective NK-1 receptor antagonist 1 is described. The key transformation involved the etherification reaction between cyclopentanol 12 and chiral imidate 30 which was catalyzed by HBF4 to initially give ether 14 as a 17:1 mixture of diastereomers and in 75% combined yield. The diastereoselectivity was upgraded to 109:1 by crystallization of the triethylamine solvate 44 which was isolated in 54% yield from 12. Mechanistic studies confirmed that the etherification reaction proceeds through an unprecedented S(N)2 reaction pathway under typical S(N)1 reaction conditions.     

PEO‐Covered Nanoparticles by Emulsion Inversion Point (EIP) Method

This study reports the first PEO‐coated polymer nanoparticles synthesis by miniemulsion polymerization of nano‐emulsions prepared by the low‐energy emulsification method called EIP. The surfactant used was Brij 98, a PEO based non ionic commercial surfactant. The partial phase diagram of the system water/Brij 98/styrene was first determined. The Emulsion Inversion Point technique was then used on the water/Brij 98/styrene system to the formation of styrene‐in‐water nano‐emulsions. After miniemulsion polymerization, particle sizes as low as 36 nm were obtained. To the best of our knowledge, this method had not been used for polymerizable system up to now.

     

Search for EPR markers of the history and origin of the insoluble organic matter in extraterrestrial and terrestrial rocks

The insoluble organic matter (IOM) of three carbonaceous meteorites (Orgueil, Murchison and Tagish Lake meteorites) and three samples of cherts (microcrystalline SiO2 rock) containing microfossils with age ranging between 45 million years and 3.5 billion years is studied by electron paramagnetic resonance (EPR). The age of the meteorites is that of the solar system (4.6 billion years). The purpose of this work was to determine the EPR parameters, which allow us to discriminate between biogenic and extra terrestrial origin for the organic matter. Such indicators should be relevant for the controversy regarding the biogenicity of the organic matter in the oldest cheroot (3.5 billion years) and in Martian meteorites containing microbe-like microstructures. The organic matter of meteorites contains a high concentration of diradicaloid moieties characterised by a diamagnetic ground state S = 0 and a thermally accessible triplet state S = 1. The three meteorites exhibit the same singlet-triplet gap (ST gap) DeltaE approximately 0.1 eV. To the best of our knowledge, such diradicaloids are unknown in insoluble organic matter of terrestrial origin. We have also shown that the EPR linewidth of insoluble organic matter in cherts and coals decrease logarithmically with the age of the organic matter. We conclude from this result that the organic matter in the oldest cherts (3.5 billion years) has the same age as their SiO2 matrix, and is not due to a latter contamination by bacteria, as was recently found in meteoritic samples.     

Synchrotron FTIR microscopy of Langmuir-Blodgett monolayers and polyelectrolyte multilayers at the solid-solid interface

Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer.