Valérie Leroy

Determination of Polycyclic Aromatic Hydrocarbons in kerosene and bio-kerosene soot

Here we report a new, efficient and reliable analytical methodology for sensitive and selective quantification of Polycyclic Aromatic Hydrocarbons (PAHs) in soot samples. The methodology developed is based on ultrasonic extraction of the soot-bound PAHs into small volumes of acetonitrile, purification of the extracts through C(18) Solid Phase Extraction (SPE) cartridges and analysis by Reverse Phase Liquid Chromatography (RPLC) with UV and fluorimetric detection. For the first time, we report the convenience of adapting the SPE procedure to the nature of the soot samples. As a matter of fact, extracts containing high percentage of unpolar material are recommended to be cleaned with acetone, whereas extracts poor in unpolar compounds can be efficiently cleaned with methanol. The method was satisfactorily applied to kerosene and bio-kerosene soot from atmospheric open diffusion flames (pool fires) and premixed flames achieving Quantification and Detection limits in the range ng mg(-1) soot and recoveries about 90% for most of the PAHs studied.

Advances in PAHs/nitro-PAHs fractioning

The aim of this work was to develop an efficient methodology for the reliable fractioning of nitrated-polycyclic aromatic hydrocarbons (nitro-PAHs) and polycyclic aromatic hydrocarbons (PAHs). Unlike what usually occurs under pressures developed by HPLC (high performance liquid chromatography) systems (above 11 bar) we observed that when normal phase chromatographic fractioning procedures are accomplished under very low pressures (about 1 bar), dipole molecules (nitro-PAHs) elute much faster than non-polar organic molecules (PAHs). This finding allowed developing an original and very efficient methodology for fractioning nitro-PAHs and PAHs. This method is based on normal-phase liquid chromatography through a home-made phenyl column by using hexane as mobile phase at very low speed flow (0.05 ml min−1). Unlike typical HPLC methodology, the fractioning of nitro-PAHs and PAHs was accomplished as a function of their polarity (first the polar compounds as a unique peak and further, the non-polar compounds, PAHs) rather than as a function of their medium polarizability.

Thermal Degradation of Lignocellulosic Fuels: Biopolymers Contribution

Every year, thousands hectares of forest do burn in southern Europe. The Mediterranean area is especially affected during the dry season. Nevertheless, in spite of considerable efforts in fire research, our ability to predict the impact of a fire is still limited, and this is partly due to the great variability of fire behaviour in different plant communities (De Luis et al., 2005). The combustion of forest fuels is partially governed by their thermal behaviour since this step produces a flammable gas mixture. Therefore, the analysis of the thermal degradation of lignocellulosic fuels is decisive for wildland fire modelling and fuel hazard studies (Dimitrakopoulos, 2001; Balbi et al., 2000; Stenseng et al., 2001). We propose in this work to focus on the thermal degradation of different forest fuels and their main components. Following a literature survey, we noticed that there is a lack in the description of the thermal degradation of forest fuels concerned by wildland fires (Grishin et al., 1983; Larini et al., 1998; Sero-Guillaume & Margerit, 2002; Linn & Cunningham, 2005). Even if these models are very different, it’s well known that the energy emitted remains a crucial data. Classic approaches are based on the consideration of the low heat content value obtained by bomb calorimeter (Rothermel, 1983; Andrews, 1986; Nunez-Regueira et al., 2005). The experiments are led in constant volume what bring about a strong temperature raising, and with an excess of pure oxygen. These conditions are far from those met during a wildfire at atmospheric pressure in the air. DSC seems to be a convenient tool in order to follow the thermal degradation at the laboratory (Liodakis et al., 2002). The degradation of forest fuels begins with the pyrolysis process from 373K to 773K (Simeoni et al., 2001; Shanmukharadhya & Sudhakar, 2007; Tonbul, 2008; Yuan & Liu, 2007). Non-combustible products, such as carbon dioxide, traces of organic compounds and water vapour, are emitted between 373K and 473K. Above 473K, the pyrolysis breaks down the fuels components into low molecular mass gases (volatiles), and carbonaceous char. Around 773K all the volatiles are gone; the remaining char is oxidized in a glowing combustion (Beall & Eickner, 1970). Wood is a complex organic material, composed of cellulose (40 to 45% for coniferous trees and 38 to 50% for leafy trees), lignin (26 to 34% for coniferous trees and 23 to 30% for leafy trees), hemicellulose (7 to 15% for coniferous trees and 19 to 26% for leafy trees), extractives (<15%), ashes (< 1%) water and mineral matter (Orfao et al., 1999; Weiland et al., 1998). The chemical composition varies from species to species and within the same variety it varies with the botanical origin, age and location in the tree (trunk, branches, crown and roots). In