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Functional group monitoring in atmospheric particulate organic matter using tandem mass spectrometry: principles and applications N. Marchand, J. Dron, I. El Haddad and H. Wortham Laboratoire Chimie Provence (UMR 6264), équipe Instrumentation et Réactivité Atmosphérique, Universités d'Aix-Marseille I,II et III- CNRS, 3 place Victor Hugo, 13331 Marseille Cedex 3 Particulate organic matter (POM) in atmospheric under study (figure 1) (ii) a high accuracy aerosols results from primary emissions as well as in quantification of the functional groups (iii) low situ formation through oxidative processes of gas- detection limits allowing applications to phase organic compounds, and contributes in environmental measurements. approximately 20 to 50% of the total fine aerosol Results obtained by this new approach for a wide mass at continental mid-latitude. It has been well panel of atmospheric samples including primary established that this class of particulate material has a sources (vehicular exhaust, wood combustions), SOA high potential impact on both human health and (photo oxidation of xylene), and urban background climate change. In order to better estimate the aerosols collected during winter and summer will be influence of organic aerosols, a good knowledge of presented and compared in terms of functionalisation their composition and reactivity is required. degree. However, considering the degree of complexity of Arbitrary Units (kCps) POM, conventional analytical methods lead to its 75 62 (394 kCps) a) Precursor ions of NO2- incomplete characterization. -NO2 C= 10,7 pmol/µgPM10 Functional group determination is a complementary 50 RfOC ~ 2300 approach between molecular identification and 194 organic carbon measurements which enables the 25 134 154 204 120 168 232 246 262 182 characterization of a larger fraction of the aerosol mass and provides valuable information on its 100 200 300 400 500 m/z 600 Arbitrary Units (kCps) chemical composition. This analytical technique 244 b) Precursor ions of NO3- being besides the best suited for modelling purposes, 150 -ONO2 250 125 it appears imperative to improve its performances. 100 Also, Fourier Transform Infrared spectroscopy (FT- 255 479 359 75 436 194 297 IR) suffers from poor robustness (Blando, 2001), 379 396 278 322 50 531 551 proton nuclear magnetic resonance (H-NMR) 218 558 25 (Tagliavini, 2006) requires heavy instrumentation, 100 200 300 400 500 600 and both have a relatively low sensibility. m/z Intensity (arb. units 40 c) 307 335 C= 30,3 pmol/µgPM10 The aim of the work presented here is to propose a C=O 319 449 RfOC ~ 500 new method for the analysis of functional groups and 30 407 421 to highlight its relevance for atmospheric chemistry 365 379 393 403 purposes. This new atmospheric pressure chemical 20 309 325 363 435 351 ionization-tandem mass spectrometry (APCI- 279 297 364 405 MS/MS) methodology is based either on neutral loss 10 269 291 344 387 477 505 463 mode for carboxylic acid and carbonyl functional 251 519 561 group (Dron et al, 2007, 2008a) either on precursor 0 200 300 400 500 m/z 6 0 0 ion scanning mode for nitro functional group (Dron Dron el al, JMS, 2008 et al, 2008b). These approaches enable to group chemical compounds by their ability to loose a Figure 1. Mass spectra obtained for –NO2 (PAR 46), - known neutral molecular fragment for neutral loss ONO2 (PAR 62) and C=O (NL 181) of a sample collected mode (NL mode) or to produce a characteristic ion in at an urban background site (Chamonix, France) during the collision cell for the precursor ion scanning mode summer. RfOC represents the functionalisation of the (PAR mode). For example, after having been organic carbon (=nOC/nfunct.) derivatized to methyl esters, carboxylic acids are identified by their ability to loose a HOCH3 fragment Blando, J. D., Porcja R. J. & Turpin B. J. (2001). Aerosol Sci. (Dron et al, 2007) while the nitro compounds are Technol., 35, 899-908. Tagliavini, E., Moretti F., Decesari S., Facchini M. C., Fuzzi S., analysed according to their ability to produce NO2- Maenhaut W. (2006). Atmos. Chem. Phys., 6, 1003-1019. (m/z=46 amu) in the collision cell (Dron et al, Dron. J., Eyglunent G., Temime-Roussel B., Marchand N., 2008b). Compared to FT-IR and H-NMR Wortham H. (2007). Caboxylic., Analytica Chimica Acta , spectroscopy, this analytical strategy offers major 605(1), 61-69. Dron. J., Zheng W., Marchand N., Wortham H. 2008a. Journal of benefits, it provides (i) an apparent molecular weight Mass Spectrometry, in press. distribution of the compounds bearing the function Dron. J., Abidi E., El Haddad, I., Marchand N., Wortham H. 2008b.. Submitted to Analytical Chemistry (Fev 2008).
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