Olivier Delhomme

Comparison of MTBSTFA and BSTFA in derivatization reactions of polar compounds prior to GC/MS analysis

In this study, MTBSTFA and BSTFA, which are among the preferred derivatization reagents for silylation were both tested on derivatization of six different groups of polar chemicals to get information about usefulness in terms of sensitivity and specificity of both reagents. Tested compound groups were nitrophenols and methoxyphenols, sterols and sugars, dicarboxylic acids and hydroxylated polycyclic aromatic hydrocarbons. It was found that MTBSTFA-derivates produce characteristic fragmentation patterns presenting mainly the fragments [M](+), [M-57](+) and [M-131](+), of which [M-57](+) is generally dominant on the mass spectrogram. BSTFA-derivates mainly show the fragments [M](+), [M-15](+) and [M-89](+) whereof the molecular ion [M](+) is generally dominant. It was also found that steric hindrance and molecular mass play a very important role in the choice of the best suited derivatization reagent: compounds with sterically hindered sites derivatized with MTBSTFA produce very small analytical responses or no signal at all, and compounds with high molecular mass produce no characteristic fragmentation pattern when derivatization is performed with BSTFA. It was also found that MTBSTFA-derivatization facilitates separation of isomer analytes, suggesting its choice in combination to semi-polar columns, whilst BSTFA seems better for sterically hindered compounds. Findings were confirmed with applications of both reagents to biological and environmental matrices (urine and atmospheric aerosols).

Determination of oxygenated polycyclic aromatic hydrocarbons in atmospheric aerosol samples by liquid chromatography-tandem mass spectrometry.

In this paper, the development of an analytical method using liquid chromatography-tandem mass spectrometry (LC-MS-MS) with atmospheric pressure chemical ionization (APCI) for the determination of 17 oxygenated polycyclic aromatic hydrocarbons (OPAH) is described. These OPAH include ketones, pyrones and diketones. The APCI interface parameters have been optimized for maximum sensitivity. Positive ion mode was proved to be most sensitive for ketones and pyrones while negative ion mode gave better detection limits for target diketones. The detection limits of the method ranged from less than 1.20microg L(-1) for several OPAH solutions (between 0.10 and 0.70microg L(-1) for positive mode and between of 0.19 and 1.20microg L(-1) for negative mode). The analytical method was applied particulate matter (PM(2.5)) samples collected over 24-48h periods between March 2005 and June 2005 in Tempe (Arizona, USA). Before analysis aerosol samples were solvent extracted and concentrated to a final volume of 1mL of methanol. OPAH concentrations observed for this urban site ranged from 0.22 to 3.60ngm(-3).

Seasonal and diurnal variations of atmospheric PAH concentrations between rural, suburban and urban areas

Abstract Atmospheric sampling (gas and particle‐phases) of 17 polycyclic aromatic hydrocarbons (PAHs) were performed between 2002 and 2004 in Strasbourg (east of France) and its vicinity. Sites were chosen to be representative of urban (Strasbourg), suburban (Schiltigheim) and rural (Erstein) conditions. Field campaigns were undertaken simultaneously in urban/suburban and urban/rural sites during three seasons. Moreover, air sampling has been performed in three 4–h time intervals per day (morning, midday/afternoon, and evening) to assess the diurnal variations in PAH concentrations. Mean total PAH concentrations were 92 ng m‐3 for the rural site, 127 ng m‐3 for the urban site and 149 ng m‐3 for the suburban site. There is a significant difference in concentrations between the three sites, independently of the seasons considered. At the three sites, the most abundant compounds determined were naphthalene followed by phenanthrene and acenaphtene. Moreover, a variation between warm period (spring) and cold period (autumn and winter) for the three sites was observed with higher PAH concentrations during the cold periods. The diurnal variations of PAH concentrations at the three sites, in warm period, have been observed in accordance with the intensity of the vehicle traffic, with highest concentrations during the morning and the evening. In cold period, there was no difference in concentrations between these two time intervals of high vehicle traffic in urban and suburban sites. It seems that the contribution of domestic heating influenced the diurnal variations of some compounds, especially in the rural site.

Snails as indicators of pesticide drift, deposit, transfer and effects in the vineyard.

This paper presents a field-study of real pesticide application conditions in a vineyard. The objective was to measure the exposure, the transfer and the effects of pesticides on a non-target soil invertebrate, the land snail Helix aspersa. There was no drift of the herbicides (glyphosate and glufosinate) whereas the fungicides (cymoxanil, folpet, tebuconazole and pyraclostrobin) were detected up to 20 m from the treated area. For folpet and particularly tebuconazole, spray deposits on soil (corresponding to losses for the intended target i.e. the vine leaves) were high (41.1% and 88.8% loss of applied dose, respectively). For herbicides, the target was the soil and losses (percentage of compounds which did not reach the soil) were of 22% for glufosinate and 52% for glyphosate. In the study plot, glyphosate was transferred to and accumulated in snail tissues (4 mg kg(-1) dry weight, dw), as was its metabolite AMPA (8 mg kg(-1) dw) which could be in relation with the reduced growth observed in snails. No effects on snail survival or growth were found after exposure to the other organic compounds or to copper and sulphur-fungicides, although transfer of tebuconazole, pyraclostrobin and copper occurred. This study brings original field data on the fate of pesticides in a vineyard agro-ecosystem under real conditions of application and shows that transfer and effects of pesticides to a non-target organism occurred.

POLYCYCLIC AROMATIC HYDROCARBONS ANALYZED IN RAINWATER COLLECTED ON TWO SITES IN EAST OF FRANCE (STRASBOURG AND ERSTEIN)

Polycyclic Aromatic Hydrocarbons (naphtalene, acenaphtene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[j]fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylène, indeno[1,2,3-c,d]pyrene and coronene) have been consecutively analyzed in rainwater sampled in Strasbourg (urban site) and Erstein (rural site) between January 2002 and June 2003 and between April 2002 and June 2003 on a weekly basis respectively. For the sampling of rainwater, a wet-only rainwater sampler was used together with an open collector to take the measurements of precipitation. PAHs in rainwater were extracted by using SPE cartridges and analyzed by HPLC-fluorescence following a method developed in the laboratory. Mean concentrations of all PAHs (Σ 16 HAPs) varied between 0.15 and 79.60 ng·L−1 in Erstein, and between 3.70 and 1596.45 ng·L−1 in Strasbourg. Naphtalene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[j]fluoranthne and benzo[a]pyrene were the most concentrated PAHs analyzed. Benzo[a]pyrene was frequently detected. Seasonal effects were observed with a maximum of concentrations of PAHs during cold periods. Some spatial influences were also reported. The calculation of some PAH ratios show that diesel exhaust could be the main source of PAHs in rainwater on the two sites.

COMPARISON OF TWO ANALYTICAL METHODS FOR THE DETERMINATION OF AZAARENES IN ATMOSPHERIC PARTICULATE MATTER

In this paper, the development of an analytical method for the separation and quantification of 20 azaarenes is described. Two methods are compared: high performance liquid chromatography with fluorescence detection (HPLC-fluorescence) and gas chromatography with mass spectrometry detection (GC-MS). Although HPLC-fluorescence was proven to be the most sensitive method, GC-MS was selected in particular for the efficiency of the separation of the 20 azaarenes. The detection limits of the HPLC-fluorescence and GC-MS methods varied between 0.04 μ g.L−1 (dibenz[a,c]acridine) and 1.30 μ g.L −1 (acridine) and between 1.50 μ g.L −1 (benz[c]acridine) and 2.56 μ g.L −1 (dibenz[a,c]acridine) respectively. The GC-MS method was applied to particulate matter (PM 10 ) samples collected over 48–72 h periods between April 2006 and February 2007 in Strasbourg (East of France). Before analysis aerosol samples were Soxhlet extracted and concentrated to a final volume of about 1 mL of hexane. The seasonally mean concentrations of all azaarenes for this urban site have shown a seasonal variation in which the maximum concentration occurred in the winter (6.0 ng.m 3 ) and the minimum in the summer (0.90 ng.m3). For all the seasons the 2 rings species were the predominant azaarenes while the > 4 rings species were the less abundant.

Ultrasound-coupled semi-supervised nonnegative matrix factorisation for speech enhancement

We present an extension to an existing speech enhancement technique, whereby the incorporation of easily obtained Doppler-based ultrasound data, obtained from frequency shifts caused by a talkers mouth movements, is shown to improve speech enhancement results. Noisy speech mixtures were enhanced using semi-supervised nonnegative matrix factorisation (NMF). Ultrasound data recorded alongside the speech is transformed into the spectral domain and used additionally to audio in the mixture to be separated. Speech components are learned from a training set, whilst noise components are estimated from the mixture signal. We show that the ultrasound data can improve source-to-distortion ratios for the enhanced speech, relative to both the non-ultrasound NMF case and an established Wiener filter-based speech enhancement method.